GB2367398A - Corrosion risk analysis - Google Patents

Abstract

This is a system and method for evaluating and analysing corrosion risk and for identifying priorities for the testing and/or maintenance of corrosion susceptible structures. The system and method includes the collection and processing of survey data relating to structures and item parts thereof and evaluates the risk of failure due to external corrosion. Maintenance and replacement scheduling is facilitated as is a reference to the economic viability of a structure as against the ongoing maintenance costs. The user interface allows for the analysis and identification of potential risks and may be used to analyse change due to various influencing factors. An article of manufacture comprising a machine-readable medium has stored thereon sequences of instructions adapted to implement the system and method of the invention.

Description

2367398 A SYSTEM, METHOD AND ARTICLE OF MANUFACTURE FOR CORROSION RISK

ANALYSIS AND FOR IDENTIMNG PRIORITIES FOR THE TESTING AND/OR MAINTENANCE OF CORROSION 10 SUSCEPTIBLE STRUCTURES

FIELD OF THE INVENTION

The present invention relates to corrosion risk analysis of susceptible structures and more particularly relates to using accumulated data and experience to evaluate corrosion susceptibility and to prioritise for testing and/or maintenance of such 15 structures.

The invention is an expert risk-based management system and method for the protection of iron and steel structures from external corrosion. It has a potential use wherever iron and steel structures are at risk from external corrosion. An article of manufacture for said system and method is also proposed.

20 BACKGROUND OF THE INVENTION

Steel and iron structures and plant (also referred to herein as "assets") are usually coated prior to or during construction. Most substrates, be they unprotected steel or iron, will naturally corrode in air. Coatings are chosen to provide the asset with protection from the environment. However, usually these coatings will not be 25 sufficient to protect the substrate from external corrosion for its entire life.

Condition assessment Surveys of asset corrosion protection coatings are either carried out on a timebased schedule (e.g. every 3 years) or on an ad hoe basis. These condition surveys may show that areas of the protective coating have broken down and ceased to be 5 effective in protecting the substrate from external corrosion. These surveys are often not uniform or systematic in format, with the disadvantage that they may not be data based and used to develop trends or properly inform the decision making process.

Decision making / taking 12Locess 10 Generally, decisions relating to external corrosion maintenance will be made in a part subjective way, either on how the Item Part looks (e.g. is it very corroded, or just spot rust) or on a generic assumption of the importance of the Item Part (e.g. a main structural member is assumed to be more important than a stair). Often, decisions for corrosion protection will be made without systematic assessment of 15 the risk (probability x consequence) of failure from external corrosion over the required remaining life of the Item Part. This is because the relevant information (Item Part specification, utilisation, corrosion allowance, corrosion rate, coating breakdown rate, life required etc.) is not available and the relationship not ftilly appreciated. This has the disadvantage that it is difficult to justify how external 20 corrosion management is pnion'tised, and focused where and when it is required.

Coating choice, maintenance or repair Maintenance or replacement of corrosion protection coatings will often be chosen without systematic analysis to determine the most effective coating (cost versus life) for the required remaining life of the Item Part. Without risk assessment, 25 prioritisation and optimum scheduling of maintenance may be inaccurate. The coating may not protect the Item Part from corrosion for the desired period, causing premature failure. Coatings replacement or maintenance may also be deferred without full knowledge of the risk and consequences (or not) of doing so.

Inspectio 30 Where significant corrosion loss is identified, the Item Part is closely inspected to determine the loss of metal due to corrosion. An individual engineering assessment (of the Item Part affected) will be carried out in conjunction with or immediately post inspection if significant metal loss is identified. This will be 5 compared with the specification required for continued fitness for purpose, and a decision will be made for corrosion protection or replacement. This is reactive and not based upon predictive risk assessment. Yv'bere the inspection is scheduled too late, failure can have occurred.

Qther current systems 10 There are management systems on the market that attempt to factor in external corrosion risk with internal corrosion risks to establish a joint risk rating, but they do not integrate coating protective properties or provide for systematic condition data capture and use in predictive analysis. Neither do they offer an integrated external corrosion protection planning system.

15 There are also systems that database surveys, suggest different coatings for different areas and assist planning of coatings maintenance and repair. However, they are not risk based and do not take into account the specification and utilisation of the individual Item Parts.

In summary, existing methodology for managing external corrosion and

20 protection has the following disadvantages:

ò Risk rating is not solely based upon external corrosion risks related to life required.

ò Risk ratings are not used to group and prioritise Item Parts for maintenance of coatings.

25 Condition data on coatings and Item parts is not used systematically to predict maintenance and failure.

ò Consequences of deferment or delay in coatings maintenance are not immediately available to inforin the decision making process.

ò No risk based system to compare choices of plans, timing, coatings life and 30 cost 5 No database of Item Part specifications, utilisation, purpose and criticality

It is an object of the present invention to seek to alleviate the above disadvantages and to provide means for increasing the reliability and consistence of advice tendered to ensure accurate risk analysis and prioritising of corrosion testing and/or corrosion protection maintenance of a structure.

10 It is further an object of the invention to provide an adaptive and interactive advice system enabling professionals within the construction (in the broadest sense), their operations and maintenance counterparts, and civil engineering industries (in the broadest sense), and their customers, to decide on requirements for testing, maintenance, repair or scrappage based on multi-dimensional risk 15 assessments, It is a yet further object of the invention to provide an expert system for deciding on the acceptability of particular maintenance schedules and the requirements for structural integrity testing and investigations, based on multi-dimensional assessments of risk and cost.

20 In the present application, the term "structure" is intended to be directed towards any physical structure which may carry, contain or otherwise bear a load (including itself). Thus, the term is meant to include, for example, ollrig platforms, pipework, plant, rail, road and foot bridges, piers, buildings or building elements (such as reinforcement frameworks) and the like, Other applications are 25 envisaged including corrosion risk to vehicles, particularly ocean- going vessels, which are exposed to highly corrosive conditions, It will be appreciated by the skilled reader that the application of the invention is particularly diverse.

STATEMENTS OF INVENTION

30 Accordingly, the present invention comprises a system for evaluating and analysing corrosion risk and for identifying priorities for the testing and/or maintenance of corrosion susceptible structures, the system including:

5 means for providing relevant information relating to the identification, specification, nature and purpose of Item Parts subject to external corrosion; means for evaluating and quantifying the risk of failure of parts due to external corrosion-, means for quantifying the length of time the Item Part will be fit for 10 purpose (effective lifie); means for factoring for each Item Part the protection from external corrosion by coatings-, means for evaluating and quantifying the effective life and cost of different coatings-, 15 means for identifying and logging the severity of environments within which Item Parts are located; means for factoring corrosion rate for various environments; means for producing systematic condition records for Item Parts; means for logging and quantifying the effect of the various environments on coating deterioration-, means for recording the effect of the substrate surface condition on the life of the coating; and means for establishing the variation in time due to the accessibility and difficulty of maintenance on different types of Item Part.

25 The invention further provides a user interface for a corrosion risk analysis system including means for a user to interactively explore how the risk of failure of a structure or an Item Part thereof may change due to various influencing factors including coating quality, coating thickness, weathering, corrosion nature, depth and degree of degradation.

5 The user interface includes means for generating recommendations for inspection and testing for corrosion and protective coating quality, which recommendations are preferably prioritised according to recognised weighting factors including, for example, maintenance or replacement costs, longevity of Item Part with respect to expected life of structure, failure risk and consequence of failure.

io The invention further provides a method for conducting corrosion risk analysis I and for identifying priorities for the testing and/or maintenance of corrosion susceptible structures, the method including: prioritising Item Parts according to risk of failure relative to required life; initially estimating and subsequently storing the current condition of the Item Part and protective coating; predicting times to maintenance of the protective coating; predicting times to failure of the Itern Part from external corrosion; planning maintenance or replacement of the Item Part or protective coating; 20 estimating and comparing costs of maintenance or replacement of coating or Item Part; and comparing the effective life, costs and resources required for different coatings.

Data is processed within Budget Area, Work Site, Work Area and Survey Area.

25 Data may be grouped by Item or Item Assembly.

5 The invention yet further comprises a method of providing an indication to a user of the probability of corrosion risk to a structure or an Item Part thereof, the method comprising- interactively exploring how the risk of corrosion affecting a structure or Item Part thereof may change according to a number of influencing factors; and 10 generating recommendations for inspection or testing of a structure or Item Part thereof, said recommendations being prioritised according to recognised weighting factors including, for example, maintenance or replacement costs, longevity of an Item Part with respect to expected life of structure, failure risk and consequence of failure.

15 The method preferably includes the steps of concurrently displaying a plurality of input objects, one or more being configured to generate question fields to be compiled by a user; generating a display based on decisions made from the input objects and question field inputs, and

20 determining and displaying a set of recommendations and associated priorities based on the input objects and question field inputs.

For assessing corrosion risk in a structure or Item Part thereof, the method preferably includes assessing protective coating type and thickness levels, including actual type and thickness on application, expected wear and actual wear-, 25 evaluating degree of or thickness of corrosion; calculating potential economic and physical consequences of structure or Item Part failure; applying mathematical functions to estimate corrosion risk or rates to failure devised from information collected from historic structural analysis, corrosion rates of grades of material, attenuation factors of coatings and coating thicknesses, weathering and other 30 environmental factors; and producing recommendations for testing, inspection maintenance, replacement or not, organised by priority selected by the user or a combination thereof from cost, failure risk and physical harm amongst others.

5 A new product has been conceived that formallses and computerises the decisionmaking processes and accesses vast quantities of supporting data from databases. This product is conveniently made available on a machinereadable medium or may be made available on-line to clients As a subscriber service. Databases of supporting information are updated constantly and, because the decision making 10 process is substantially automated, the system can be adjusted as required to take into account emergent information.

The product is conveniently adapted to utilise existing database software and information technology (including Internet technology) and is intended for access via personal computers and the like.

15 Thus, the present invention yet further provides a machine-readable medium having stored thereon data representing sequences of instructions, said sequences of instructions which, when executed by a processor, cause said processor to:

display concurrently a series of default objects in a first portion of a screen and a series of input objects in a second portion of the screen, the input objects being 20 configured to receive one or more input values; display a set of output values in a subsequent screen, the set of output values including a probability of failure of a given Item Part based upon one or more input values and a recommended set of corrosion indicators; determine risk based on said inputs and displaying a set of recommendations and 25 associated priorities for assessing corrosion and failure risks.

Description of the Drawing

The present invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one embodiment of the system, method and article of manufacture for corrosion risk 30 analysis and for the testing and/or maintenance of corrosion susceptible structures according to the invention. In the drawings:

5 Figure I is a screen shot to identify the Criticality Rating of a subject assembly at Item Part, Figure I a is a screen shot of a user interface facilitating the addition of Item Parts to the survey database-, Figure 2 is a screen shot of a chart illustrating ISO Values as a percentage of 10 Work Area; Figure 3 is a screen shot of coating parameters including a breakdown profile thereof, Figures 4 and 5 are screen shots of a Planning Module comprising a scenario screen for a selected Item Part and a Maintenance Plan for Item Parts in a selected 15 Work Area respectively; Figures 4a and 5a are alternative screen shots of a Planning Module comprising a scenario screen for a selected Item Part and a Maintenance Plan for Item Parts in a selected Work Area, respectively; Figure 6 is a diagrammatic representation of an offshore platform survey area 20 drawing; Figure 7 is a diagrammatic representation of a railway bridge survey area drawing-, Figure 8 is a flowchart illustrating the methodology used to establish data for risk probability ratings and consequence ratings for manipulation and presentation to a 25 planning/scheduling module-, Figure 9 is a detailed flowchart illustrating the derivation of parameters for use in the system and method for corrosion risk analysis from standing data; Figure 10 is a detailed flowchart illustrating the accumulation of information for presenting and reporting Condition Survey data fields-,

Figure I I is a detailed flowchart illustrating the arrangement of condition data and tn other collected data for presentation as Survey Data-, Figure 12 is a detailed flowchart of the methddology and for the assessment of risk-, _W 5 Figure 13 is a detailed flowchart of the Planning Module for scheduling repair, maintenance, replacement or otherwise of Item Parts; and Figures 14a to 14c are flowchart overviews of the Criticality, Estimating and Planning calculation engines, respectively.

Coatings are normally applied to steel structures simply to prevent corrosion.

10 Historically, the need for coatings maintenance was gauged by the extent of coating breakdown, and the actual requirement for corrosion protection remained largely un-quantified, lost in the mists of the original design brief. This is especially true of more mature structures. Painting is expensive, and the logic behind spending significant amounts of money on coating structures is not clear to 15 budget managers. Thus, savings on fabric maintenance have generally been achieved by eliminating or deferring painting programnies, often subjectively without informed risk assessment. Current inspection and asset integrity analysis is either not available or not used to inform the decision making process.

To overcome some of the disadvantages associated with the prior art, there is now

20 provided a relatively simple, rational, and auditable system for optimum-cost maintenance planning over the life of the asset. To do this, the system needed to establish risk from corrosion, sift and prioritise asset items requiring maintenance before the end of required life on the basis of their criticality and predicted condition. By using this system and associated methodology a decision as to 25 what maintenance is required, particularly when it is required, and whether it can be deferred or completely eliminated can be made.

External corrosion management can be defined as monitoring, control and mitigation of corrosion - externally focused. When designing the system significant factors were considered which affect the following:

30 - The asset purpose and life - The asset elements, their significance, location, purpose and condition - The current protection (coating) system and condition.

-194- 5 - Performance of coating protection systems within various environments.

- The corrosive severity of various environments - The management of inspection, survey, and work planning.

With current condition information provided (or agreed default values entered), there is designed a system to estimate the probability of coating breakdown and 10 consequent metal loss over time for each element or "Item Part" of the asset. Taking account of the criticality assigned to each item, the location, current protection and condition, it will then predict time to next maintenance, and thereafter time to (theoretical) failure of the item from corrosion.

Planning is then done on the basis of grouping items by criticality, location (Work 15 Area), and other factors into "workable" projects, with estimated costs.

There are five inter-related modules in the system:

e Work Site Inforniation and Definitions o Risk Assessment and Criticality Determination.

o Condition Survey Assessment.

20 e Standing Data.

9 Fabric Maintenance Planning Module.

Each is considered briefly in turn hereinbelow.

Work Site Information The Work Site Information module provides written procedures for the collection 25 of data for developing the computer application and database. The data includes information regarding policy issues, engineering data and current condition data -I_;- 5 specific to a work site. The following Table I describes briefly the sets of data required for the Work Site.

Data set Description:

Company Organisation name, address and contacts Budget Area Financial group, budget holders and administrators, budgeted amount.

Work site Usually an individual asset within the budget area, such as a bridge or offshore installation.

Additional information for the Work Site will include:

Required life Resource constraints for use in Work program planning Loss of Appearance consequence rating (for use where appearance is a major factor).

Work area Division of Work Site into Work areas (logical to efficient maintenance work).

Corrosion rate zoning (establishes the likely corrosion rate for that area) Survey Area Division of Work Areas into efficient Survey Areas (logical to efficient inspection / survey) Collection of data for Condition Item, Item Item part is the smallest piece of the asset to be individually Part, Item maintained, e.g. a pipe or girder. Sometimes these are part of a Assembly larger Item, which in turn comprises part of a complete Item Assembly. This facility provides for Item Parts to be grouped into ftmetional areas.

Information for Item Parts includes:

Name and Identifier Criticality type (e.g. Channel, pipe etc.) Size, specification and surface area

Required life (defaults to required asset life) Last known condition and metal loss (a default is available).

TABLE I

Most of the required data can be obtained from asset registers, drawings and 10 engineering/inspection records. Pro forma hard copy collection sheets can be provided for the client and/or others to capture the necessary infbrmation, or it can be directly entered to the system. An estimation module is included which can use historical data to predict current condition, thus getting more value from previous -14 5 inspections. It is important to mininlise the need for an initial condition survey to populate the database.

A particular emphasis of the present system is on rhinimising the set-up time and cost, however the more client-provided information there is the better the immediate value of the system to the user. However, a range of default values can be used where specific values are not available, and the set-up can be as general or detailed as required.

Risk Assessment and Criticafit3 Determination With reference to Figure 1, the Criticality Rating of the subject provides a mechanism to prioritise maintenance planning according to the amount of risk that can be tolerated. Items are scheduled for maintenance according to their Criticality and condition, and only if required before the end of life. This allows the operator to:

Focus on critical items to tailor maintenance planning.

Review current condition by Criticality.

20 The module provides for a semi-automatic assessment of risk, dependent upon the probability of failure together with the consequences of failure.

Substrate Failure Probability The system assesses the probability of substrate failure relative to the remaining life required, based upon the Item Part service, details, condition (inclusive of 25 coatings) and environment. It is pre-loaded with calculators for Pressure Pipework, Vessels and Structure. Based upon this calculation it sets the following ratings:

HIGH Failure possible within 50% of remaining asset life LOW Failure possible between 50 and 150% of remaining asset life NS (Not significant) Failure unlikely within 150% of remaining asset life 5 Failure is defined as the point when consequences occur.

Substrate Failure Consequences (relative to service) Substrate failure consequence ratings follow a set of defaults that relate to the item service. For instance, consequences for structural items are considered from loss of structural integrity, and for containment piping, for loss of containment.

10 The default rating assignments follow the standard definition of consequence criteria, together with an option to include cost consequences.

Harm.

Harm in this instance is defined as the loss of life or serious injury (one that impairs an individual's quality of life or restricts future employment) 15 HIGH if probable (where it will happen most times when failure occurs) LOW if possible (where it will happen rarely when failure occurs) NS if it never happens (where it will not happen when failure occurs).

Cost.

Cost may also be measured at three levels 20 HIGH is one or more days lost operation or equivalent cost LOW is between cost of one day's lost revenues and E2,000 NS when cost is less than f-2,000.

These rules are brought together in our matrix Table 2 below:

5 CONSEQUENCE OF FAILURE HIGH LOW NS PROBABILITY HIGH 4 2 OF FAILURE LOW 3 1 NS TABLE2

The matrix is weighted in favour of the consequence rating.

A simple override facility is included for clients who wish to use other criteria, either in general or in specific instances.

10 Condition Surve It is recognised that users wish to get more value out of their inspections. The Condition Survey module provides for capture, storage and reporting of condition information for the components of the Work Site. Survey areas are defined within work areas and identified by means of key sketches and component listings.

15 Written procedures for data collection minimise ambiguity. Reference is made to Figure 2 The module contains printable blank survey forms to capture the following data:

Coating type and current condition, assessed to BS 3900: Part H3, 1983, ISO 4628/3 - 1982 20 Current metal loss (pit depth etc.) Current metal thickness (e.g. flange thickness) 5 General substrate condition Difficulty rating and zone Default condition information can be used where general condition is known and a specific detailed survey is thought unnecessary.

The module provides the operator with a means of recording, reviewing and using 10 condition data to aid planning. Written and graphic reports can be produced using a number of different report choices to give, for instance, an overview of the condition of the entire Work Site, or to isolate particular areas of concern by Item Parts.

The information held in this module is used in conjunction with Criticality and 15 Standing Data within the Planning Module.

Standing Data The Standing Data module provides a library of 'stand alone' data for providing information on the following:

- Coating performance 20 - Zones, including an Environment Severity Rating and Corrosion Rate - Substrate Condition rating, including Work Rate factor.

- Difficulty rating based upon substrate arrangement and access Coating performance Substantial historical evidence has been collated from private and public archives 25 and other publications enabling a library of coating types to be compiled. Least, most and mean times to breakdown (using BS 3900 Ri Scale) are plotted and can be displayed, as shown in Figure 3, as a graphic. These are matched to the Item -11 5 Part, adjusted for Criticality Rating and used together with other Standing Data to predict optimum maintenance and theoretical failure. Choice of coatings is usually a trade off between cost, time/resources to apply, and life. Unit costs and productivity for each coating system are used together with other standing data to provide estimates for maintenance, and for comparison of coating and maintenance choices.

Zones, including Environment Seventy Rating and Corrosion Rate The performance of a coating system is dependent upon a number of factors, key to which are:

The environinent (i.e. the location and nature of substrate) 15 The condition of the substrate immediately prior to coating These factors are used to modify the Coating System perfonnance.

Zones are used to define areas within which the environment is similar, and the deterioration of the Coating System and subsequent Corrosion Rate will also be similar. These factors again are used to modify the Coating performance, and 20 subsequent time to theoretical failure.

Unit Cost Cost (excluding access) is also dependent on a number of factors. Primary factors included within standing data relate to:

Difficulty of area 25 Surface condition of area Both of these factors are used to modify the estimated cost of the maintenance activity.

-it 5 Standing Data is not a 'fixed' module and it is recognised that when building a system users may have their own norms and historical data, which could be used to good effect. Hence, the tables within the Standing Data module can be updated to take account of past and future experience to build a 'learnin g database'.

Planning Modul 10 Referring now to Figures 4 and 5 or alternatively to Figures 4a and 5a, the Planning Module uses all relevant Standing Data, Work Site Information, Condition Data (or estimated condition where up-to-date Condition Data is not available) and Criticality Rating to provide:

Next maintenance date 15 Theoretical failure date Based upon this information it allows the user to 'try out' different groupings andscenarios to select the optimum solution, both in terms of timing and coating choice, to suit their needs and constraints. It also shows the user where certain items may be safely deferred or even eliminated. A range of different reports, by 20 criticality, Ri% breakdown and others are available to help planning.

Built into the system, there is the ability to look forward and predict estimated breakdown and failure in the future, and then plan and budget for maintenance. The user/client is able to plan efficient maintenance of whole areas, when the majority of Items require it, and still identify holding activities required for 25 specific Items in the interim.

The system allows the client to build scenarios using different groupings, years and Coating Systems, enabling comparison of costs and scheduling, building into Optimum Life Cycle maintenance plans, together with costs at Net Present and Net Future Value. This will also allow the cost of replacement to be compared 30 with the cost of maintenance.

Work Plans within Budget Area and Work Site can be produced for current and future years to build in to overall Asset Planning systems.

QC -W 5 Accordingly, the invention provides a system that empowers the user/client through the following benefits:

- Auditable risk based approach (complimentary to established Safety Management Systems) - Focuses inspection and maintenance where and when (or if) it's needed 10 - Reduces maintenance cost through more efficient plan-ning - Develops cost estimates for Asset Life Cycle - Enhances the value from condition inspection - Provides work packages based upon substantial coatings experience - Facilitates flexibility and informed decision making 15 - Predicts maintenance and failure Owners and operators are only too aware of the continuing struggle to maintain and increase margins through focused cost reduction and Life Cycle cost management. VAiilst there are plenty of tools available dealing with internal corrosion and painting planning, it is believed that the area of external corrosion 20 management has been neglected for too long. Those involved with the corrosion protection of assets will be aware that a significant part of their budget is allocated to external corrosion inspection and mitigation, and that unforeseen failures are expensive.

Designed is a system to hand control of external corrosion management back to 25 the user/client. Relatively simple and transparent but powerful, the system as implemented will squeeze more value from inspection and survey results, facilitate a risk based rational approach to planning maintenance, and provide the flexibility to design and update an optimum life cycle maintenance package for the Asset. Should circumstances change, the client is able to modify the asset -2,k _M_ 5 maintenance program with full information, and quickly determine what must be done from what could be done. This approach balances both the needs for prudence and safety, and economic efficiency.

Condition Survey Assessment Module This module established cri'teria for the following:

lo The condition assessment which provides paint work condition rating distributions for painting work areas.

Assessments to be performed with key sketches and comporient listings of survey areas providing an integrated, electronic based data recording system.

Defining Survey areas as parts of painting work areas that are physically suited to 15 be a unique area for survey.

Further to the introductory overview provided above the Condition Survey Module contains written procedures for the Condition Survey methodology, for use by the users of the methodology, as well as data definitions and relationships and specification for use in developing the computer application and database.

2o The following describes:

ò The purpose of the module and philosophy of the methodology ò Procedures for the assembly of set-up data required for Condition Surveys ò A formal procedure for the carrying out Condition Surveys ò The data definitions and relationships and process/calculation specification for

25 use in developing the computer application and database.

1121, _2T_ 5 Condition Survey process provides current data on the extent and seventy of the deterioration of surface coatings, as well as the existence of related component defects. This data is used to set up the current state of coating breakdown from which future breakdown can be extrapolated in the Planning Module. In addition, the survey information provides useful input to the Criticality Assessment 10 process.

As a one-time job, painting work areas are broken down into convenient survey areas and the item content of those survey areas is identified. Key sketches of the survey areas are drawn and data collection sheets are customised, The areas and area content are set up in the database.

15 Condition is surveyed and re-surveyed at appropriate intervals. The Planning Module can be used to aid decisions on survey intervals. The Condition Survey provides a coating deterioration distribution for each painting work area. It will also provide input data for estimating coating maintenance costs.

Data is also provided on the distribution of breakdown rating in the work areas so 20 that areas with distributions skewed by a few severely deteriorated items can be identified for 'spot' treatment.

In addition to coating deterioration other visually detectable deterioration matters are addressed as required by the surveyor. These include extent of substrate corrosion, presence of liquid ponding and insulation and bulkhead penetration 25 condition. The surveyor should also make comments regarding access or other restrictions to performing coating maintenance.

Base Input Data is assembled for the Condition Survey. Advantageously, drawings and component listing for Work Site should be sourced from the user/client if not already available. For offshore sites the best source of 30 information is likely to be a Statutory Operations Manual or similar, plus structural and piping plan and elevation drawings. For onshore work sites such as bridges, the "As-Built" general arrangement and finishings specification drawings should provide the bulk of the necessary information. Electronic or paper versions of drawings are both acceptable. Where possible, drawings which show

5 both structural and plant items for given areas should be used to reduce the overall number of survey areas required. Plans and elevations together are preferred.

An appropriate breakdown of Work Areas and convenient survey areas must be decided prior to the survey. Breakdown of Work Areas is ideally be done in conjunction with a Company representative having a good insight on the layout of io the Work Site. Individual Work Areas are generally exposed to only one of the relevant corrosive environments. Due account may need to be taken of the fonnat of reference drawings or images available and the Permit to Work niles relevant to the Work Site. Survey areas typically comprise four elevations and two plans, one viewed up the other viewed down. Survey areas which cover more than one 15 Work Area are not permitted. Each Survey Area is assigned an appropriate ID. Survey Areas in turn contain "Item Parts" which can be the whole item. Individual condition surveys which cover all or only part of the Item Parts within Survey Areas are given a unique Condition Survey I.D. and have a unique Survey Date.

20 For an offshore platform Work Site, as illustrated in Figure 6, an example of the above breakdown could be:

Work Area: Jacket above water up to underside of module support fiame at El +21m Survey Areas: 1) East elevation ofj acket 25 2) West elevation of jacket 3) South elevation of jacket 4) North elevation of jacket 5) Plan of spider deck and CGF 6) Plan on underside of MSF 5 Item parts: In Survey Area 1):

Leg A between MSL and El =2 1 in Leg B between MSL and El =2 1 in Brace members E I, E2, E3 Oil export riser between MSL and El =21m 10 etc, etc for the other Survey Areas.

For a multi-span railway bridge Work Site, as illustrated in Figure 7, an example of the above breakdown could be:

Work Area: Steel superstructure span 3 above main water course Survey Areas: 1) North plate girder north face 15 2) North plate girder south face 3) South plate girder north face 4) South plate girder south face 5) Span I cross beams Item parts: ln Survey Area 1):

20 Top flange upper side Top flange lower side Bottom flange upper side 5 Bottom flange lower side Web Bearing stiffeners etc, etc for the other Survey Areas.

In producing a convenient Survey Data Format the drawings would provide a 10 useful and necessary reference point for the surveyor, however data must be recorded numerically rather than diagrammatically. Thus, the survey data is recorded in an item part listing table associated with each Survey Area.

In addition to the electronic Survey Area drawing other reference material for the surveyor includes:

15 0 Coating breakdown rating scale example chart (RiO --> Ri5) 0 Written procedure for survey (hereinbelow) Ideally, both of the above are stored electronically on the survey data recorder for easy reference.

Prior to the initial Condition Survey for any Work Site, the coatable surface area 20 of each Item Part must be estimated. Calculation of surface areas should be done to the nearest 5m 2 for each Item Part and be a single area figure for the entire Item Part.

Other pre-survey data required are the coating system and the painting complexity rating for each Item Part. These are entered as code numbers, referenced in the 25 survey procedure, which can if appropriate be altered by the surveyor. Any changes made by the surveyor to these fields can be highlighted to ensure verification and traceability.

5 The surveyor enters percentage values of each rating of coating breakdown and the final output data is these percentages multiplied by the total Item Part area to give individual areas for the distribution of breakdown rating.

Where required, an assessment of the substrate condition is given by the surveyor for Item Parts having areas of coating breakdown rating Ri4 or above. Also, 10 where external corrosion has resulted in loss of steel thickness or pitting, these values are measured and recorded, if not already available.

Comments are recorded for any other relevant defects or points of note, including intercoat disbonding, firewall, penetration or insulation defects, leaks or ponding and painting access difficulties.

15 Digital image photographs are normally taken of general Survey Areas and specific coating or corrosion defects to enhance the reference information for future Condition Surveys.

Tables 3 and 4 give examples of what the surveyor would see on a Survey Area data recording sheet for the platform of Figure 6 and the bridge of Figure 7, 20 respectively.

Company: XYZ Oil Ltd Budget Area: LMN Asset Work Site: ABCI Platfonn Condition Survey I.D:

Work Area: Jacket above water (MSL to El +21m) Survey Date:

Survey Area: 1 East elevation Survey Company:

Survey Area Photo Ref-. Areas of Rating/Degrees of Rusting Surveyor:

item Part Area Coat Diffi- RiO R11 Ri2 RU RU 2:R15 Substrate Current WT / Worst Pit Depth Comments & Photo (m2) System culty (0/6) (0/6) Condition History ref.

Leg A 162 1 3 Leg B 162 1 3 ta = 24.8nim Brace E 1 64 1 2 dp - 2.3mm Brace E2 64 1 3 Brace E3 7 1 3 Riser 51 5 3 I t Table 3 Offshore Platform Example Condition Survey Data Recording Sheet Company: EFG Railways Ltd Budget Area: Newtown to Oldtown Line Work Site: Bridge No. 234 Condition Survey I.D:

Work Area: Steel superstructure span 3 above main water course Survey Date:

Survey Area: I North plate girder north face Survey Company:

Survey Area Photo Ref. Areas of Rating/Degrees of Rusting Surveyor:

Item Part Area Coat Diffl- RiO Ril Ri2 Ri3 Ri4 M Substrate Current WT Worst Pit Depth Comments & History Photo (m2) System culty M M Condition ref.

Top flge up 12 3 2 Water drips from deck Top f1ge low 12 3 2 Bot flge up 12 2 Bot flge low 12 3 2 Web 32 3 2 t, 11.5mm Sup 2 stiff 1 3 2 Sup 3 stiff 1 3 2 I -j f9 I Table 4 Railway Bridge Example Condition Survey Data Recording Sheet 5 The object of Condition Survey Procedure referred to hereinabove is to provide guidance to Surveyors to carry out an assessment of the coating condition of the Item Parts contained in individual Survey Areas as input to the Fabric Maintenance Planning system Of the present invention.

All Surveyors shall be qualified to Level 2 standard in paint inspection, or 10 equivalent capability based on experience.

The following equipment shall be used to achieve efficient and satisfactory recording of survey data:

a) Type hand held data recorder complete with stored electronic files containing:

15 0 Survey data record pro-forma for each Survey Area within the Work Site 0 Reference drawings for each Survey Area 0 Sample coating breakdown rating charts 0 This Survey Procedure 2o b) Digital image camera.

C) 35n-im camera or video d) Suitable measuring equipment, typically 30m fabric tape and 5m steel tape.

e) Magnetic and electronic dry film thickness gauges.

25 The survey methodology comprises visiting each designated Work Area and for each Survey Area within that Work Area to carry out the following:

5 a) For each listed Item Part confirm that assigned coating system is correct, making use of all necessary sources of coating information. Refer to Coating System tables in Standing Data Module for coating system numbers. If coating system' for any Item part is deemed by the Surveyor to be different from that shown, amend number to suit relevant system. The 10 amended number will then be displayed in red on data record pro-forma.

b) For each listed Item Part confirm that coating difficulty rating is correct.

Refer to the Difficulty Rating of Area table in the Standing data Module for coating difficulty rating numbers. If the difficulty rating for any Item part is deemed by the Surveyor to be different from that shown, amend 15 number to suit relevant rating. The amended number will then be displayed in red on data record pro-forma.

C) Estimate and record on the survey data pro-forma, for the whole coated area of each listed Item Part within the Survey Area, a percentage value for ALL of the six degrees of coating breakdown i.e. RiO to:RO. Record 20 coating breakdown areas to the nearest 5%. If necessary use the surface area value for the Item Part given on the pro-fornia together with suitable measurements to aid estimation of area percentages. Refer to sample coating breakdown rating charts for guidance. Ensure the calculated sum of percentages for each Item Part equals 100%.

25 d) Make an assessment of the substrate surface condition those for Item Parts having areas of coating breakdown rating Ri4 or above. Refer to the Surface Condition Multiplier table in the Standing Data Module for substrate surface condition assessment ratings. Where heavy existing coating films having a total thickness over 400 microns are applied to an 30 Item Part these shall also be rated as per the Surface Condition Multiplier table.

C) For Item parts which have significant external corrosion which has resulted in section loss or pitting, remaining wall thickness and pit depth values shall be recorded if possible and as required. Alternatively, these 35 values may be sourced ftom elsewhere (e.g., inspection records). Within 5 the "Conu-nents and History" column these values shall be entered in the following formats:

Current wall thickness "tfa=23mm" (subscript 'f refers to e.g., 'flange') Pit depth "dp=2mm" f) Also under the "Comments and History" heading, for each Item Part insert additional relevant information relating to the following:

presence and extent of any topcoat or topcoat and mldcoat loss, intercoat disbonding, or blistering, rated on the Rating 0-5 scale. (BS3900: PtHl, Sectionl, item 5).

specific defects in insulation firewalls or penetrations 15 presence and condition of any signs or markings presence of ponding or trapped liquids or significant leaks onto Item Part potential access problems for painting works.

g) On completion of recording of survey data, take suitable general photographs of Survey Area and specific photographs to illustrate items included in "comments" section. All photographs taken shall be given a consecutive number (1,2,3...) to be entered on to the pro-forma in the appropriate boxes. The general Survey Area photograph(s) shall normally be given the number 1 (2) etc.

-31% 5 As survey data is being logged electronically, pro-forma recording sheet files should be saved regularly during the survey. This shall be done at least on completion of each Survey Area. At the completion of each shift, all survey records held on the hand held data recorder shall be downloaded onto disk. All digital photographs logged on the pro-forma sheets shall also be downloaded to lo disk at the completion of each shift.

The data derived must be formatted in an easily digestible manner and for reporting, data definitions are required. Firstly, Data Fields from Condition Survey must be set out from the Condition Survey data recording pro-forma sheet for each Survey Area the following data fields are generated.

15 HI <Xompany>> H2 <<Budget Area>> H3 <<Work Site>> H4 <<Work Area>> H5 <<Survey Area>> 2o H6 <<Condition Survey I.D.>> H6 <<Survey Area General Photograph Reference>> H7 <<Survey Date >> H8 <<Surveyor>> H9 <<Survey Conipany>> 25 All fields are simple text except H6 which is a whole number and H7 which is a date field. Table 5 comprises a table of Item Parts Coating Breakdown.

-13 5 For each Item Part on each Date of Survey:

TI Surface Area of Item Part (number) (M) T2 Coating System Number (number) - display in red if amended by Surveyor T3 Coating Difficulty Rating (number between I and 14) - display in red if amended by Surveyor T4 Area Rating 0 (number) T5 Area Rating I (number) T6 Area Rating 2 (number) T7 Area Rating 3 (number) 15 T8 Area Rating 4 (number) T9 Area Rating 5 or more (number) T10 Substrate Surface Condition Rating (number between I and 4) T11 Current WT / Worst Pit Depth T12 Comments & History (general text).

20 T13 Photo ref (number) From data generated in the above fields the following simple reports will be required:

For each Work Area for latest Condition Survey date for each Item Part:

-34 5 Al Total surface area of Work Area (in 2) (1 Areas TI for all Survey Areas within the Work Area) A2 Total area of RiO (in 2) (TIT4) for all Survey Areas within the Work Area) A3 Total area of Ri I (in 2) (TIT5) for all Survey Areas within the Work 10 Area) A4 Total area of Ri2 (M) QTlT6) for all Survey Areas within the Work Area) A5 Total area of Ri3 (M) QTIT7) for all Survey Areas within the Work Area) A6 Total area of Ri4 (M) (Y-(TIT8) for all Survey Areas within the Work Area) A7 Total area of Ri5 or more (in 2) (Y-(T I T9) for all Survey Areas within the Work Area) A8 % RiO (=A2/Al expressed as %) 2o A9 % Ri 1 (=A3/Al expressed as%) AlO % R12 (=A4/Al expressed as %) All % Ri3 (=A5/Al expressed as %) A12 % Ri4 (=A6/Al expressed as %) A13 % R15 or more (%) (=A7/Al expressed as %) -3r5 Where the sum of A8 to A13 is less than 100%, this indicates incomplete condition data for the Work Area. In this case a warning to that effect needs to be given in Reporting function.

For each Work Area by Condition Survey I.D.

BI Condition Survey I.D. No.

lo B2 Survey Date B3 Total surface area of Item Parts surveyed during Condition Survey I.D.

Total surface area of Work Area (M) (expressed as %) B5 Total area of RiO (m) for Item Parts surveyed during Condition Survey I.D. / Total surface area of Work Area (M) (expressed as %) 15 B6 Total area of Ril (m) for Item Parts surveyed during Condition Survey I.D. / Total surface area of Work Area (m) (expressed as %) B7 Total area of Ri2 (M) for Item Parts surveyed during Condition Survey I.D. / Total surface area of Work Area (M) (expressed as %) B8 Total area of Ri3 (m) for Item Parts surveyed during Condition Survey 20 I.D. / Total surface area of Work Area (M) (expressed as %) B9 Total area of Ri4 (in 2) for Item Parts surveyed during Condition Survey I.D. / Total surface area of Work Area (M) (expressed as %) BIO Total area of Rj5 or more (in 2) for Item Parts surveyed during Condition Survey I.D. / Total surface area of Work Area (M) (expressed as %) The intention of the report is to summan'se the last condition of all Item Parts within the Work Area grouped by Condition Survey I.D. and summarised by surface area. Condition is expressed as a percentage of the Work Area surface area per Ri value. Where no condition data exists for Item Parts the total surface -4 5 area of these Item Parts is expressed as a percentage of the total surface area of the Work Area (see example Table 6).

Item Parts which have the following ratings are highlighted to bring to the user/client's attention:

T8 > 50% i.e. Area Rating 4 components exceed 50% 10 o T9 > 10% i.e. Area Rating 5 or more components exceed 10% T 10 =2 or 3 i.e. Substrate Surface Condition Ratings T I I containing text Clt=l or "dp=" indicating current WT or pit depth Risk Assessment - Criticality Determination Probability and consequence of failure rules and data are defined hereinafter. For 15 the purposes of data collection failure is defined as the point at which the consequences occur.

Failure by Substrate Corrosion At and around a Ri4 degree of rusting, substrate steel will begin to corrode at the rate appropriate to the zone and conditions. Failure is not, therefore, immediate 20 but occurs as a result of the loss of protection and the time to failure depends on corrosion rate and effective corrosion allowance.

Item Area Coat Diffl- M R11 Ri2 RB R!4 RB Substrate Current WT / Comments& History Photo ref.

Part (m2) System culty (%) (%) (%) (%) (%) (%), Condition Worst Pit Depth Table 5

1 V4 ANO Rk % surface area of Work Area Condition Survey No. of Item Total surface area of RiO Ril Rj2 1113 Ri4:M5 SurveyI.D. Date Parts Item Parts / Work Area surface area (%) 2/l/99 2 6% 1% 3% 0 0 2% 0 14/7/92 43 82% 0 52% 10% 10% 10% 0 NONE 6 12% None None None None None None Table 6 -36 5 Corrosion Rates for localised external corrosion -in temperate climates are assurned to be as shown in Table 7 below.

Zone Corrosion Rate, mmlyr Offshore Oil& Gas Zones Splash Zone 1.0 Below Cellar Deck 0.3 Exterior Lower Decks 0.2 Naturally Ventilated Module Interiors 0.2 Pressurised Module Interiors 0.05 Top Deck 0.1 Onshore Industrial Zones Marine, Rural 0.1 Marine, Industrial 0.2 Uand, Rural 0.05 Inland, Industrial 0.1 Table 7 - Corrosion Rates (Corrosion Rate Table) It will be understood by the skilled reader that the values illustrated in the above tables are by way of example only, and will change. to reflect environmental, geographical and meteorological conditions for the asset.

-3f- 5 Substrate corrosion failure is applicable to the criticality of- Pipework & pressure vessels.

Load bearing structural members.

Enclosures.

Failure is predicted in accordance with the Effective Corrosion Allowance Calculations (ECA Ca1cs) In the calculations the following definitions apply:

ECA = Effective Corrosion Allowance, i.e. metal thickness not required for strength Default value: = 2.5min for pipework DCA = Design Corrosion Allowance, for vessels CR = Predicted external corrosion rate, e.g. from Table 1.

ta = Actual wall thickness (tf, member flange, tw, member web) tc = Design code wall thickness. i.e. thickness required by the code to contain pressure.

ti Installed wall thickness Aa Actual member cross-section area Ai Installed member cross-section area LTD Loss to date, or tj - t,, P = Maximum Operating Pressure.

D = Outside diameter.

W = Member web height F = Member flange width S = Allowable stress for pipes.Published as tables in ANSFASME B31.3, for instance.

(Default value = 20000psi) E = Joint Efficiency. Depends on manufacturing method.

(Default valve 1) Y Coefficient. Published in ANSI/ASME B31.3.

(Default valve = 0.04) U Utilisation ratio for structural items, Allowable load divided by actual load.

(Default valve = 0.8) 5 For all items subject to deterioration by corrosion the objective is to rate a predicted time to failure by comparison with the expected facility life. Therefore the life is calculated:

Time to failure = ECA/CR 5 Vessels Vessels are normally fabricated to exact thickness with a design corrosion allowance. The common values are 1/8" or 3mm, 1/16" or 1.5min and "none". The Effective Corrosion Allowance is therefore the design allowance adjusted for any losses to date:- 10 ECA = DCA - LTD In some cases small vessels are fabricated from standard thickness pipe and plate. In these cases the ECA should be calculated using an appropriate code.

Also it is possible for a vessel to be operating below its design operating pressure. Provided a reduced operating pressure has been formally accepted and 15 documented the ECA can be calculated to the appropriate code.

Where code calculations are used to calculated ECAs separate values will be generated for the shells and ends.

Pipework With appropriate data available pipework ECAs can be calculated from code:- 20 ECA = ta - tc = t,, -PD/(2(SE+PY) Pipework ECAs may be defaulted to 2.5mm (0.1 inch) which is a typical but by no means universal corrosion allowance for oil and gas production pipework. Use of this default will generally underestimate the ECA by up to 100% in original design conditions. Where, as is common in oil and gas production, operating 25 pressures are much less than design this default value will be very conservative.

In some cases the ECA may be subject to reduction by both internal and external corrosion. In this case an adjusted ECA should be used:

Adjusted ECA = ECA - 1.5 x Facility Expected Life x Internal corrosion rate 5 Where the factor of 1.5 allows for an extension of operating life.

If the user/client maintains a corrosion risk assessment for the pipework it may include ECAs and internal corrosion rates. (ECA Adjustment) Structure Time to failure = Time to Ri4 + ECA/CR 10 For major members, subject to structural analysis:

ECA = (1- U) x ti For items not subject to structural analysis, ECA = 0.2 x ti Where, ti has a value depending on the member type:

Member type ti Value Tubular ti I beam (2Ftf+Wtw)/(2F+W) Angle beam (Wtw +Ftf)/(F+W) Plate or Flat ti 15 Enclosures The skin of an enclosure is assumed to have no structural significance, therefore:

ECA = ti -4 3- 5 Prior Corrosion Losses (ECA Adjustment) The actual wall thickness, ta in all cases may be the original wall thickness, ti, less corrosion losses to date. If measured losses are not available then the loss to date can be estimated by the Planning Module:

LTD = (Service to date - Y, times to Re4) x CR 10 The times to Re4, if there is more than one, may vary if different coatings and surface preparation methods have been employed.

Therefore, Time to failure = ECA/CR = (tj - LTD)/CR 15 Substrate Failure Rating (Probability.Rule) Substrate failure probability is rated as follows:

HIGH Failure possible within 50% of remaining asset life LOW Failure possible between 50 and 150% of remaining asset life NS (Not Failure unlikely within 150% of remaining asset life significant) Substrate Failure Consequences (a Cniticality Type) Substrate failure consequence ratings will follow a set of defaults that relate to the item service, where the service largely depends on the fluid contents of vessels 20 and piping and the structural duty of a structural item.

qq -0- 5 The default rating assignments follow the standard definition of consequence criteria Harm. Loss of life or serious injury (one that impairs an individual's quality of life or restricts future employment)HIGH if probable (where it will happen most times failure occurs) 10 LOW if possible (where it happens rarely) NS if it never happens.

Cost. Cost at three levels HIGH is one or more days lost production or equivalent cost LOW is between cost of one day's lost revenues and E2,000 15 NS when cost is less than E2,000.

(Consequence Rule) A Default Substrate Failure Consequences table is shown below as Table 8. (Default Consequence Table) q( -40- Service Group Default Considerations Rating Oil, Gas & Chemicals - Piping & Vessels Toxic Fluids HIGH Flammable Oil & Gas over 2" dia HIGH Includes most hydrocarbon gases and volatile flu-ids Flammable Oil & Gas 2" dia or less LOW Includes most hydrocarbon gases and volatile fluids Combustible Liquids over 2" dia LOW Includes most non-volatile hydrocarbons Combustible Liquids 2" dia or less NS Includes most non-volatile hydrocarbons Non combustible gases under pressure in LOW vessels and pipework of or over 20" dia Non combustible gases under pressure in NS pipework less than 20" dia, Water NS Not water mixed with volatile hydrocarbons Offshore Structures & Enclosures Jacket members, module support frames, HIGH crane pedestals, flare booms & drilling A-Csubstructures Module frames and walkway, access LOW platform and staircases structures Non-load bearing structures NS Fire rated enclosures & enclosures for LOW plant or materials adversely affected by ambient conditions Wind walls and non-rated enclosures NS 5 Table 8 - Default Consequence Ratings Both the hurdle levels for the consequence ratings and the defaults for individual services can be changed to meet the preferences of the client.

Failure from Loss of Function The potential for failure exists as soon as ftmetional performance is lost.

io However, the incidence of failure depends on the probability of other events. In some cases, however, such as where PFEERJDCR standards have been set for safety purposes offshore, failure may be deemed by the client to have occurred when function is lost.

Fireproofing (a Criticality Type) 15 Failure occurs when, following coating breakdown, either 4-r AMa fire causes harm or infrastructure repair cost, or, loss of regulatory compliance leads to rectification cost Generally the first of these would have either a LOW or NS (Not Significant) likelihood but a HIGH consequence. The second would have a HIGH probability and LOW consequence and would generate the higher criticality.

10 Signs & Markings (a Criticality Type) Failure occurs when, following coating breakdown, either ò inappropriate actions cause harm, or, ò loss of regulatory compliance leads to rectification cost Generally the first of these would have either a LOW or NS likelihood but a 15 HIGH consequence. The second would have a HIGH probability but, in the case of most signs and markings an NS consequence and would generate the lower criticality.

q9 5 Special Surfaces (a Criticality Type) Failure occurs when, following coating breakdown, either ò events cause hann or cost, or, ò loss of regulatory compliance leads to rectification cost These require to be examined on a case-by-case basis.

Appearance (a Criticality Type) Failure occurs when, following coating breakdown, either 0 there is a general dissatisfaction amongst those resident or visiting the platform leading to rectification cost, or, there is loss of business at least partly duties the impression given to 15 potential business partners.

Assets that may fall into the latter category will mainly have a LOW or NS probability but a HIGH consequence. The first category will usually have a probability very much related to the client and workforce culture and industrial relations but the consequence will most likely be LOW or NS when applied to 20 particular items. The matrix for Criticality rating as shown at Table 2 above.

Criticality is used in the Planning module to allow for the tolerance afforded to uncertainty. There is no sure way of knowing when, for instance, a coating may break down to a Ri4 degree of rusting allowing substrate corrosion to occur. Where the uncertainty cannot be tolerated a measure of safety is taken by planning 25 to repaint at earlier than the mean time for the appearance of the Ri4 degree of rusting.

A calculation flowchart for the above criticality determinations is shown in Figure 8.

5 Risk Based Fabric Maintenance Metbod The pninciples on which Criticality Processing is conducted firstly relies on the Criticality Rating.

ò The Criticality Rating depends on 10 -calculating a remaining life deterrmining a Probability Rating from the remaining life - judgementally identifying the probable degree of harm or cost - determining a Consequence Rating from the degree of harm or cost - determining a Criticality Rating from the Probability and Consequence 15 Ratings ò The user can change the rule bases on which the Probability and Consequence Ratings are determined.

ò The Criticality Rating is derived ftom a simple 3x3 matrix rule.

ò The user will have the option to use default values to reduce the need to find data for remaining life and to make item by item decisions for harrn and cost.

The basic calculation for ECA and remaining life and probability rating is:

a Input Item Part ID and Item Type Item Types are:

1-0 5 Vessel Pipe Tubular Plate Flat)Structure 10 Angle Channel I Beam x Optionally input item physical dat Item Default Type(s) Value DCA = Design Corrosion Allowance Vessel ta = Actual current wall thickness Pipe Tubular Plate Flat tj = Installed wall thickness Pipe Tubular Plate Flat Tfa = Actual current member flange thickness I-Beam Channel Angle T f, = Installed member flange thickness I-Beam Channel Angle Tw, = Actual current member web thickness I-Beam Channel Angle Tw, = Installed member web thickness I-Beam Channel Angle P = Maximum Operating Pressure. Pipe U = Utilisation ratio All Default Structure value 0.8 D = Outside diameter. Pipe Tubular W = Member web height I-Beam Channel Angle F = Member flange width I-Beam Channel Angle For input the Worksite Information/Items form should be used. If possible entering the Item Type should activate only those attributes relevant to that type.

These could be put in lookup tables of values from the tables in ANSI B31. 3 and made available on drop down lists when inputting on the Items form:S Allowable stress for pipes. Published as tables Pipe in ANSI/ASME B31.3, for instance.

(Default value = 20000psi) E Joint Efficiency. Depends on manufacturing Pipe method. Published in ANSI/ASNM B31.3.

* (Default value = 1) Y = Coefficient. Published in ANSI/ASME B31.3. Pipe (Default value = 0.04) Calculate Effective Corrosion Allowance (ECA) ECA Calculations for Item Types:- Vessel = DCA Pipe = ti-PD/(2(SE+PY) Tubular = (I- U) x tj Plate = (1- U) x tj Flat = (I- q x tj Angle = (I - U) x (Wtwi+Ftfi)/(F+W) Channel = (I - U) x (2Ftfi+Wtwi)/(2F+W) I Beam = (1- U) x (2Ftfi+Wtwi)/(2F+W) Enclosure = ta OR 5 Accept default ECA or U value if data not available. However, the following are required in all cases for the item type:

Vessel DCA or a current calculated ECA value Structural and Enclosure installed wall thicknesses.

Make adjustment to the - ECA for internal corrosion and -12rior external corrosion.

Internal Corrosion - In some cases the ECA may be subject to reduction by both internal and external corrosion. In this case an adjusted ECA should be used:

Adjusted ECA = ECA - 1.5 x Facility Expected Life x Internal corrosion rate 15 Facility Expected Life = Abandonment Date - Current Date Abandonment Date should be entered on the Worksite Information/Work Site form.

Internal Corrosion Rate should be input on the Worksite Information/Items form and should be only active for Item Types Pipe and Vessel.

20 Prior Corrosion Losses - The actual current wall thickness, ta in all cases may be the original wall thickness, ti, less corrosion losses to date. Then:

Adjusted ECA = ECA - (ti, - ta) If measured losses are not available then the loss to date can be estimated.

Adjusted ECA = ECA - (Service to date - Z times to Re4) x CR 25 Z times to Re4 should be input on the Worksite Information/Items form and should be only active for all Item Types.

5 Overall the adjustment is:

Adjusted ECA = ECA - 1.5 x Facility Expected Life x Internal corrosion rate - (ti, - t,,) OR - (Service to date - 7- times to Re4) x CR Input Zone of item location and Look up Corrosion Rate 10 Zone is an entered on the Worksite Information/Item Part fortri for all Item Types from a drop down list. It would be useful if the Item Part Form is offered from the Items form as soon as the data is entered.

See Table 7 - Corrosion Rates Calculate Remaining Life 15 Time to failure = Adjusted ECA/CR Note If the client maintains a corrosion risk assessment for the pipework it may include ECAs and internal corrosion rates.

The calculation should be made when the Criticality Rating form is accessed for 20 the Item Part.

Probability Rating Substrate failure probability is rated as follows:

HIGH Time to Failure ≤ 0.5 Failure possible (Abandom-nent Date - Current Date) within 50% of remaining asset life 40- LOW 0.5 < Time to Failure ≤ 1.5 Failure possible (Abandonment Date - Current Date) between 50 and 150% of remaining asset life NS (Not 1.5 < Time to Failure Failure unlikely signif- (Abandonment Date - Current Date) within 150% of icant) remaining asset life 5 It is necessary to assign NS where appropriate to distinguish it from a value has not been calculated.

The Probability Rating should be calculated when the Criticality Rating Form is accessed and displayed on the form with a notification if the default ECA or U value have been used.

10 Consequence Rating Substrate failure consequence ratings will follow a set of defaults that relate to the item service, where the service largely depends on the fluid contents of vessels and piping and the structural duty of a structural item.

The user will be required to input the Service on the Items form from a list that 15 relates to the Item Type:

Default Failure Consequences are as shown in Table 8.

Both the defined levels for the consequence ratings and the defaults for individual services can be changed to meet the preferences of the client.

-56 5 Criticality Rating The Probability rating - HIGH, LOW and NS in terms of asset expected life - and the Consequence rating - in terms of hazard or cost hurdles - are combined with a simple matrix to give the Criticality Rating:- Probability Consequence Criticality Rating Rating Rating HIGH HIGH 4 HIGH LOW 2 HIGH NS 0 LOW HIGH 3 LOW LOW 3 LOW NS 3 NS HIGH I NS LOW 0 NS NS 0 This should be applied and displayed when the Criticality Form is opened and an 10 item part selected. It should change if the user changes the Consequence Rating.

The form should have an Accept button. On acceptance the Probability, Consequence and Criticality Ratings should be written to a Criticality table along with the users name and the date.

5-3- 4A Consequence Ratings for Criticality Types For Criticality Type Structure Jacket member HIGH Conductor Guide Frame member LOW Module support frame member HIGH Crane pedestal HIGH Crane member (other than pedestal) LOW Helideck member LOW Flare boom member HIGH Drilling substructure or derrick primary HIGH member Module frame member LOW Walkway or access platform member LOW Staircases structure member LOW Ancillary structure member NS Bridge superstructure primary member HIGH Bridge superstructure secondary or LOW transverse member Bridge substructure primary member HIGH f 49- Bridge substructure secondary member LOW Deck plating LOW Parapet or guard-rail member LOW 5 For Criticality Type - Enclosure Fire or blast rated enclosure LOW Insulating or water tight enclosure LOW Wind walls and non-rated enclosure NS Calculation Notes Calculate Effective Corrosion Allowance (ECA) ECA Calculations for Item Part Types:- Vessel = DCA Pipe = ti-PD/(2(SE+PY) CHS,RHS = (I- U) x ti Plate = (I- U) x ti Angle = (I- U) x ((dw x twl)+(B x tfi))/(B+dw) I Beam, Plate Girder, = (I - U) x ((2 x B x tfi)+(dw x twi))/((2 x B)+dw) Column Section & Channel Enclosure 5 Condition Survey inco oration of pit depth, Pit depth, dp, is only valid for Criticality Types: Pipes and Vessels/Tanks Any value of dp recorded at Condition Survey will in effect increase the LTD.

Thus, For Pipes: LTD would become, ti - ta - dp.

i o For Vessels/Tanks: LTD would become the highest of, tsi - tsa - dp, (where dp is recorded on vessel shell or tank wall) thi - tha - dp, (where dp is recorded on vessel head or tank floor) 15 tsi - tsa thi - tha.

AdJusted ECA Calculations - alternative scenarios A. For Criticality Type: PIPES 1.) If value of internal corrosion rate/year is provided (>O) 20 AND Current thickness, ta is provided C9 -kF- 5 THEN RUN:

Adjusted ECA = ECA - (1.5 x Facility Expected Life x internal corrosion rate) - (ti - ta) 2.) If value of internal corrosion rate/year is NOT provided AND 10 Current thickness, ta is provided THEN RUN:

Adjusted ECA = ECA - (ti - ta) 3.) If value of internal corrosion rate/year is provided (>O) AND 15 Current thickness, ta is NOT provided THEN RUN:

Adjusted ECA = ECA - (1.5 x Facility Expected Life x internal corrosion rate) - (E times at Ri4 or worse x CR) 4.) If value of internal corrosion rate/year is NOT provided (>O) 20 AND Current thickness, ta is NOT provided THEN RUN:

Adjusted ECA = ECA - (Y- times at Ri4 or worse x CR) B. For Criticalily Type: VESSELS/TANKS 1.) If value of internal corrosion rate/year is provided (>O) AND Current thickness, tsa AND/OR tha is provided THEN RUN:

10 a) Adjusted ECA = ECA - (1.5 x Facility Expected Life x internal corrosion rate) - (tsi - tsa) ANVOR b) Adjusted ECA = ECA - (1.5 x Facility Expected Life x internal corrosion rate) - (thi - tha) 15 and use the LESSER of a) and b) as the Adjusted ECA 2.) If value of internal corrosion rate/year is NOT provided (>O) AND Current thickness, tsa AND/OR tha is provided THEN RUN:

20 a) Adjusted ECA = ECA - (tsi - tsa) AND/OR b) Adjusted ECA = ECA - (thi - tha) and use the LESSER of a) and b) as the Adjusted ECA 5 3.) lf value of internal corrosion rate/year is provided (>O) AND Current thickness, tsa AND tha are NOT provided THEN RUN:

Adjusted ECA = ECA - (1.5 x Facility Expected Life x internal corrosion 10 rate) - (2: times at Ri4 or worse x CR) 4.) If value of interrial corrosion rate/year is NOT provided (>O) AND Current thickness, tsa AND tha. are NOT provided THEN RLN:

15 Adjusted ECA = ECA - (Y- times at Ri4 or worse x CR) C.- For Criticali1y.Type: STRUCTURE Internal rate of corrosionlyear does not apply to Structures 1.) If current thickness values, ta/tfa/twa are provided (depending on Item Part Type) 20 THEN RUN:

Adjusted ECA = ECA - (Applicable LTD calculation dependent on Item Part Type) 2.) If current thickness values, ta/tfa/twa are NOT provided (depending on Item Part Type) 5 THEN RUN:

Adjusted ECA = ECA - (F, times at Ri4 or worse x CR) NOTE: CR is Corrosion Rate (external) in mmlyr which varies according to zone Adjusted ECA calculations are NOT APPLICABLE to the other Criticality Types, i.e., Enclosures, Signs & Markings and Special Surfaces 10 Standing Data Explanatory Notes Standing data consists of the following groups ci Coating Types Zones (under which there is) & Environmental Seventy Rating 15 External Corrosion Rate Surface Condition (under which there is) Coating Life Cycle Modifier Unit Cost Work Rate Modifier Difficulty Rating of Area 20 Labour multiplier for different areas Access Data The user can view, add, edit and change any of the Standing Data.

tif 44 - 5 The Standing Data is used within the program instructions of the invention to determine criticality, coating and item maintenance, failure and life cycle, cost, time and resource. It is important that the user understands the basis for determining the Standing Data values as they are interrelated within the External Corrosion Management mechanisms.

10 Coating Types Information entered for Coatings should be based upon the expected life cycle of that Coating System in a Zone that has an Environmental Severity Rating of Unity (1). For instance, if Marine, Rural Zone has an Environmental Severity Rating of 1, then the Coating Life Cycle should be described for that area.

15 Two primary factors influence the Life Cycle of a Coating System. They are:

13 The condition of the surface at the time of coating 0 The envirom-nent within which the Coating System is employed Coating Time To Ri Value The Coating System Life Cycle is expressed in terms of the least (0.1 probability), 20 mean and most (0.9probability) time (in years) of the Coating System to reach breakdown values of between Ril - 5 (BS 3900:Part 1-13:1983, ISO 4628/3-1982) inclusive. Practical experience and published data will usually indicate the variation that will be found for Coating System Life Cycle in this area, but care must be taken to ensure that Surface Preparation and the enviromnent are 25 comparable in these cases.

5 Unit Cost The Unit Cost of the Coating System is expressed in terms of f/m2. This figure should be chosen to correlate with the Surface Condition Multiplier and the Difficulty Rating - Labour Multiplier for Different Areas. The system and method of the invention uses the Unit Cost together with the Surface Condition lo Multiplier and the Difficulty Rating - Labour Multiplier for Different Areas to estimate cost and time.

Productivityfigure The Productivity is expressed in m2/man hour. This figure should be chosen to correlate with the Surface Condition Multiplier and the Difficulty Rating - Labour 15 Multiplier for Different Areas. EXCORR uses the Productivity together with the Surface Condition Multiplier and the Difficulty Rating - Labour Multiplier for Different Areas to estimate time.

Zones Zones are defined by the geographical location. They may be general (e.g. Inland, 20 Industrial) or specific locations (e.g. Offshore splash zone). They are defined primarily in order to establish confines for likely External Corrosion Rates in a particular location, and secondly to establish the Environmental Severity Rating (ESR) that will affect Coating Life Cycle.

External Corrosion Rates 25 These define in millimetres the maximum rate of non-aggravated corrosion (metal loss) that can be expected on unprotected steel at this location. This number is used within the calculations for the Criticality Rating, Effective Corrosion Allowance (ECA) and Time to Failure.

-661 5 Environmental Severity Rating (ESR) These numbers represent the effect of the local environment on the Coating Life Cycle, i.e. how long the Coating System will protect the substrate. EXCORR calculates the projected Coating Life Cycle using this number in conjunction with the Surface Condition-Coating Life Cycle Modifier. Hence, initial Coating 10 System Life Cycle information should be based upon a Zone where the ESR and Surface Condition Modifier are both 1.

Surface Condition Surface Condition is a primary factor in the effectiveness and Life Cycle of a Coating System, and will affect the amount of time taken to prepare and coat the 15 substrate effectively. Categories of Surface Condition are defined by reference to the Ri Scale of Rusting prior to preparation and coating, and other special circumstances (e.g. Heavy existing coatings).

Coating Life Cycle Multiplier These numbers represent the effect of the substrate condition on the Life Cycle of 20 the Coating System, i.e. how long the Coating System will protect the substrate.

The projected Coating Life Cycle is calculated using this number in conjunction with the Environmental Severity Rating. Hence, initial Coating System Life Cycle information should be based upon a surface condition at a typical maintenance situation (currently set at Ri4 (8 - 10% surface breakdown and rusting)) where the 25 number is 1 Unit Cost Work Rate Modifier These numbers represent the effect the surface condition has on time to prepare and coat the substrate. This number is used to modify the unit cost of the Coating System, and thus the cost of the selected work. Hence, initial Coating System Life 30 Cycle information should be based upon a surface condition at a typical maintenance situation (currently set at Ri4- 8, 10% surface breakdown and rusting) where the number is 1.

T 5 Difficulty Rating of Area The difficulty in preparing and coating an area of work impacts the efficiency, work rate, materials used, and thus the cost of the work.

Labour multiplierfor different areas These numbers represent the relative difficulty of working on a particular type of substrate, its location and accessibility. This number is used to modify the unit cost and productivity to provide estimates of cost and time for the work. A value of unity (1) should be matched to the basis for the Unit Cost of the Coating System as it is recorded in the Coating System Standing Data. Currently this is set at 1 for the coating of Flat Clean Plate / very simple structure.

Figures 9 to 14c illustrate the foregoing by way of flowcharts to more clearly show how the collation of certain data and information is derived and applied to assess risk and identify priorities for the testing and/or maintenance of corrosion susceptible Item Parts and structures generally. The flowcharts support the detailed descr-iptions hereinbefore and illustrate how the inforniation from the individual modules is manipulated to create Standing Data, Risk Assessment factors, Condition qualifiers and the like to build on Worksite Information for the production of a maintenance plan or schedule.

Figure 9 shows the derivation of Standing Data from quantifiable data such as corTosion rate in mm./annum to more subjectively assessed data such as the labour multiplier, designated "Difficulty Rating". Similarly, Figure I I shows the derivation of Condition Data from various survey on Item Parts and assembled in identified areas. Survey Data again combines imperial data and subjectively assessed data to provide a comprehensive picture of the condition of the asset.

Fisk Assessment includes the use of Condition Data to govern the likelihood of part failure and it is this information together with probability assessments of occurrences and the consequences thereof which provides the risk indicators for the Item Parts, as illustrated in Figure 12. Referring now to Figure 10, the Worksite information database is built on the information derived from the foregoing modules and base input data.

611 zo- 5 The planning module, as detailed in Figure 13, takes work area and item parts data and combines those with Condition data to detail the work area to plan. A planning and estimating engine is then applied to the data to yield a scenario, that is, a schedule for selected Item Parts.

A scenario calculation engine is applied to the options available to develop the 10 final phase as qualified by a plan manager.

As an overview Figures 14a to 14c illustrate the three main processing engines. To establish a criticality rating (measured between 0 and 4) a Risk Assessment 0 Item Part Criticality Engine takes Worksite Information, Condition Data and Standing Data, as shown in Figure 14a, for subsequent use in the maintenance 15 plan, In Figure 14b, Item Part Information, Condition information and Standing Data are combined in the Planning and Estimating Engine to estimate the current condition of Item Parts from the last available known data and predicts the likely condition of the Item over each remaining year of its operative life. In this way each Item Part can be assigned a required maintenance date and a date of failure.

20 Holding Data is then derived.

Finally, with reference to Figure 14c, the Holding Data derived above, Standing Data and Item Part Criticality are brought together for a given activity year in the Scenario engine for choice of scenarios by selection of type and cost of coatings, protective performance life and selected surface area. From the Scenario Engine 25 final choices are made by the user/client to develop the Plan.

Planning Module Addendum The Planning Module provides estimated dates for maintenance and failure based upon the condition, criticality and coating system of the item, item group and 30 work area. Choice of maintenance (coating) scheme will determine the duration of further protection, date to next maintenance, to be repeated until the optimum scheme to achieve desired life is achieved.

5 The Planning Module provides cost and time estimates based upon norms established for the particular scheme chosen, surface area, the difficulty and resources allocated. In certain circumstances, the cost of maintenance will be compared to replacement.

The Planning Module also provides for the consolidation of work items into a 10 maintenance programme by Work Site and Work Area.

It follows that the planning rules to avoid risk must be related to the risk levels inherent in the criticality ratings.

The criticality identifies the risk of failure. The rating is used to determine the point at which maintenance is advisable to avoid the risk of failure. The choice of 15 the maintenance point can be based on two options:

Maximum allowable coating breakdown (i.e. when corrosion loss needs to be contained, and coating is passed the point of recovery) Failure, to occur just in time, The latter can be used in conjunction with expected corrosion rates to identify 20 replacement of item where economically or operationally preferable.

Condition information (actual or estimated from last known) is used in conjunction with the existing Coating System to determine the time to initial coating maintenance and thence to Item Part failure. Environment and surface condition modify the Coating System effective life. The Risk Rating of an Item 25 part determines its tolerance to coating failure and the probability of this determines the point on the coating life cycle at which Maintenance becomes desirable.

The time to maintenance for each Item Part will be calculated from the current (or estimated) condition to the point at which Maintenance is desirable. An elapsed 30 time is determined from current to initial Coating Maintenance and Item Part 5 Failure Points- Failure of Criticality Types 1,2 and 3, is dependent upon metal loss, and therefore a period of corrosion will occur from Coating Maintenance Point (defined. as the point at which corrosion starts to be significant) until Item Part Failure. Failure of Criticality Types 4,5,6 and 7 are wholly dependent upon the Coating purpose itself, and therefore the practical Maintenance Point is 10 considered to be just before Item Part Failure.

In order to predict the maintenance and failure date, we will need to know the Condition information for the area and apply to each Item Part and:

0 ECA = Effective Corrosion Allowance (see Risk Assessment - Criticality Determination) 15 - Failure rules (see Risk Assessment - Criticality Determination) the current condition of the coating will be determined by either:

Current survey - a Current Survey validity envelope will be set by the client.

Units will be years previous to current year (i.e. include Condition Data for current year to current year - <<Condition envelope in years>> 20 Estimated from last known condition report 0 See Condition Survey Module for Condition Data The current condition of the Surface will be determined by either or both of the following:

25 9 Current survey - a Current Survey validity envelope will be set by the client.

Units will be years previous to current year (i.e. include Condition Data for current year to current year - <<Condition envelope in years>> ò Estimated from last known condition report ò Condition will be described for surface (substrate) at the time of application of 30 current coating (if known) and ECA determined from the Risk Assessment - Criticality Determination Module, Surface Condition Rating from the Surface ConditionTable (see Appendix in Standing Data).

5 The estimated current condition is calculated using last condition report and elapsed time to predict estimated condition. Where Condition Data is outside current survey envelope, the current condition will be estimated by the following process:

Calculate elapsed time (CET) from last survey.

10 CET = <<current year>> - <<survey year>> For each item part where CET = > current survey envelope:

Get Coating Scheme No. from Condition Data <<Number>> Modify Coating Performance (CP) by:

<<SCM>> + <<ESM>> x <<CP to Ri <<number>>years >> = CPm2 15 Where:

CP = Coating Performance, a table of Least, Mean and Most years for the coating to breakdown to a defined Ri value <<Ri I to =>Ri5>> in years <<number >>.

SCM = Surface Condition Multiplier at time of Coating Application 20 (SCM-see Standing Data, Table XX if known, otherwise 1) ESM = Environment Severity Multiplier (ESM - see Standing Data, Table XX if known otherwise 1) CPm = Modified Coating Performance Fix position at last survey <<Ri number>> and <<time>> years 25 Advance time by CET and calculate estimated current Ri value.

Display estimated condition data in table TI and insert <<E>> in date field.

Options to display the Condition data in the form of Graphs will be included.

For the selection, Condition Data is presented as a table, Table 9:

Company V >> Budget Area v >> Work gite V >> W6rk,Area fif thogn, V >> overrule&wrVey area).

ifivey A re a V >> Criticality x (% of Item parts) Coating Condition (% of Surface Area) fT Criticality Type No. of Item, 4 3 1 0 RiO Ril Rj 2 Fj 3 W4 M5 Parts, Critical ity T ype selected Pressure systems v Structure v Enclosure v _j - 0% Fireproofing v Signs and markings v Special surfaces v Appearance v Item Assembly(default all v in selection) It&n 1dd1fif6r:(defA It alF V in selection) Item Parts (default all in V selection) :Estimated. % of surface area of selection estimated.

I I \j Surface Area of total number of Item Parts within chosen selection within the Criticality Type expressed as a % of the Total Surface Area of the selection.

Table 9.

5 Determining time to next maintenance and failure is carried out by order of ò Company ò Work Site ò Work Area ò Criticality Type 10 4 Item Part ò Criticality For each Item Part, the type of coating (from Asset Condition Data) will be matched to a Coating Scheme in the Coating Standing Data. Identification will be 15 by:

a Coating Scheme <<Number>> - Required The Coating Scheme life performance data will be modified as follows: Modify Coating Scheme Life by.- <<SCM>> + <<ESM>> x <<Coating Scheme Years to Ri <<value>> >>2 Where.- SCM = Surface Condition Multiplier (SCM-(see Coating Standing Data) if known, otherwise 1) ESM = Environment Severity Multiplier (ESM - (see Coating Standing Data) if known - otherwise 1) The coating maintenance points are then presented in a table Table 10.

Coating Point of Failure Criteria Maintenance Point Pressure systems Ri4 Loss of wall thickness or ANSI B31.3 MAWT, loss of mechanical strength Lesser (Code Non-Compliance) MAWTs for small bore OR Leak pipe.

WT=O Ri4 Point of Failure Criteria Structure Loss of WT (Code NonLoad/Allowable >1 Compliance or loss of Loss of user confidence apparent load bearing capacity OR Collapse Enclosure Ri4 Penetration WT=O Fireproofing RB Loss of rating Ri3, Time expired, Loss of specified thickness Signs & Marking Ri4 Lossof Ri4 visibility/readability Special Surfaces Ri4 Loss of function (e.g. anti- RA, Loss of Special slip) Function Appearance RD Likely to be unacceptable Unacceptable Ri value to the viewer Table 10 - Coating Maintenance Points relative to Criticality Type The Criticality rating will determine the point on the modified coating life cycle at which coating maintenance is desirable. The higher the criticality the smaller the tolerated risk of failure (see Risk Assessment Module). Maintenance points are calculated / plotted on the curve relative to the criticality and time to maintenance 10 measured.

For Calculation of Time to Maintenance (TM), to establish coating life expired:

Rule.- Basefollowing calculations on Mean Coating Life values Select Coating System <<number>> Calculate years of Coating Life Expired (CLE) fi-o7n known (or estimated) current condition.

Current (or estimated) Condition <<Rj>> From Coating Standing Data calculate CLE: Years <<Number>> relative to 20 Current Condition.

Calculate years to C oating Allaintenance Point (CA11P) relative to Criticality Type.

Rule: Appearance - where Appearance is Ticked within Work Site, all selection will default to Appearance Altaintenance and Failure Criteria.

25 Rule: Fire Proofing - If Fire Proofing Tick Box within Item Part is Ticked, these Item Parts will default to Fire Proofing Maintenance and Failure Criteria (OVerrules Appearance):

Maintenance Point <<Rj>> From Coating Standing Data calculate CMP: Years <<Number>> from 0 years 30 7M is (<<CNIP>> - <<CLE>>) + (probability value for Criticality Rating - see below) in years.

5 This calculation is repeated automatically for all Item Parts ivithin the Work Area.

Probability Value for Criticality Rating.

The Criticality Rating will determine the tolerance of failure, and thus the Maintenance Point will be adjusted to reflect this tolerance. For each Coating io Scheme, the Least time and Most Time values determine the probability of coating breakdown at a specific time during the coating life. The Criticality rating will determine the acceptable probability for calculation of the Maintenance and Failure Points.

Values for this adjustment are given in the Risk Assessment - Criticality 15 Determination Module.

Adjustment is calculated as follows:

By:

ò Coating Scheme ò Ri value 20 Least time to Ri value LT <<years>> (i.e. Probability 0. 1) Most time to Ri value MT <<years>> (i.e. Probability 0.9) Probability = Ap (Cr) Values are:

For Criticality.- Ap(Cr) 0 0.75 1 0.5 2 0.4 3 0.3 4 0.2 MT - LT = Maximum Variation (MV) 25 (MV x Ap(Cr)) -MV/2 = Probability adjustment, 5 Calculation of time to failure (TF) Rule: Metal loss starts at Ri4 Coating failure The Criticality of the item is determined by the tolerance to the risk of failure.

Coatings are applied for a particular purpose. Failure conditions for these are given in the Risk assessment Method.

10 Establish coating life expired:

Rule: Base following calculations on Mean Coating Life values Calculate years of Coating Life Expired (CLE) from known (or estimated) current condition. Current (or estimated) Condition <<Ri>> 15 CLE - Years <<Number>> For Criticality Types 1,2 and 3:

Calculate years to start of corrosion (SQ.

From Rule, point at which corrosion starts is R14 <<number>> SC Years <<Number>> 20 Time to Corrosion Start is (<<SC>> - <<CLE>>) + (probability value for Criticality Rating).

Probability Vahiefor Criticality Rating.

The Criticality Rating will determine the tolerance of failure, and thus the estimated Corrosion Start will be adjusted to reflect this tolerance. For each 25 Coating Scheme, the Least Time and Most Time values determine the probability of coating breakdown at a specific time during the coating life. The Criticality rating will determine the acceptable probability for calculation of the Corrosion Start.

Values for this adjustment are given above.

30 Adjustment is calculated as follows- By:

ò Coating Scheme ò Ri value 5 Least time to Ri value LT <<years>> (i.e. Probability 0. 1) Most time to Ri value MT <<years>> (i.e. Probability 0.9) Probability = Ap (Cr) NIT - LT = Maximum Variation (MV) (N4V x Ap(Cr)) - MV/2 = Probability adjustment.

10 Calculation of tinie to Failure (TF) Rule: Metal loss starts at Ri4 CoatingJailure The Criticality of the item is determined by the tolerance to the risk of failure.

Coatings are applied for a particular purpose. Failure conditions for these are 15 given in the Risk assessment Method.

Establish coating life expired.- Rule: Base folloiving calculationsOnMeanCoating Life values Calculate years of Coating Life Expired (CLE) from known (or estimated) current condition.

20 Current (or estimated) Condition <<Ri>> CLE - Years <<Number>> For Criticality Types 1, 2 and 3:

Calculate years to start of corrosion (SQ:

From Rule, point at which corrosion starts is Ri4 <<number>> 25 SC Years <<Number>> Time to Corrosion Start is (<<SC>> - <<CLE>>) + (probability value for Criticality Rating).

For Criticality: Ap(Cr) 0 0.75 1 0.5 2 0.4 3 0.3 4 0,2 5 Probability Valuefor Criticality Rating.

The Criticality Rating will determine the tolerance of failure, and thus the estimated Corrosion Start will be adjusted to reflect this tolerance. For each Coating Scheme, the Least Time and Most Time values determine the probability of coating breakdown at a specific time during the coating life, The Criticality 10 rating will determine the acceptable probability for calculation of the Corrosion Start.

Values for this adjustment are given above.

Adjustment is calculated as follows-.

By -.

15 - Coating Scheme a Ri value Least time to Ri value LT <<years>> (i,e. Probability 0. 1) Most time to Ri value MT <<years>> (i.e. Probability 0. 9) Probability = Ap (Cr) 20 MT - LT = Maximum Variation (MV) (MV x Ap(Cr)) - MV/2 = Probability adjustment.

Calculation of time to Failure from R14 is given for criticality Types 1, 2 and 3 in Risk assessment - Criticality Dele7-Mination Modide.

TF = Dine to RN + (ECAI'CR) 25 7-his calculation can be repeated autoinaticallyfor the whole Work Area For Criticality Ypes 4 6vhe7-e Item Part has Fire Proqfzng ticked),5,6 and 7 (where Work Site has Appearance ticked): Nominal failure occurs at a specific RI value for these Criticality types. Maintenance Points for these items will typically occur just before failure.

30 Therefore, the maintenance Planning Process (above) will be used to define Maintenance and Failure Points.

S -VP- 5 Maintenance will only be necessary to ensure the subject fulfils its purpose over a desired life. From the foregoing it is possible to predict and provide a profile for time to Maintenance and Failure for Work Areas, by Criticality Type, Item parts and Criticality showing:

0 Coating maintenance time by % surface area 10 - Time to Failure by % surface area Remaining life required (RLR) Ride: Yhe remaining life desiredfor an item will be the remaining time required for that itenz to maintain ih Fitnessfor Puipose. Failtire is defined as Loss ofFitnessfor Purpose.

15 RLR will default to the asset RLR. However, for Item Parts, this may be overridden by a specific RLR.

De veloping a plan Rule: Planning will be by Total W07 Area, gTouped or individual Item Parts.

Rule: Maintenance to Total Work Area (Mtvva) becomes due ii'hen a desired % 20 surface area (PSA) of a Work Area becomes duefor Maintenance.

Maintenance and Failure Points for the Work Area will be summed and expressed as a % surface area of the Work Area by calendar year.

Total Work Area maintenance becomes due when the total sum of the surface areas for each successive year from current become => the pre-set % (PSA).

25 Item Parts which fail before this time are identified, saved and processed through the Strategy I planning process to just achieve the Planned Maintenance date set for the % surface area of the Work Area.

The entire work area is then planned using Strategy I or 2 methodology described below.

30 The Work Area plan can then be summarlsed by year, Criticality Type, activity and cost.

Data Pre-set gate % of Surface Area <<number>> Derived data:

Criticality Type (Standing Data) 10 Year I" Calendar year where % surface area ≥ Pre-set gate % Surface Area Sum of % surface area of Criticality Type = Maintenance Point for successive calendar years Sum of % surface area of Work Area = Maintenance Point for successive calendar years.

15 Cumulative sum % of surface areas of Work Area = Maintenance Point per successive calendar years.

Maintenance Point for Total Work Area(Mtwa) = Calendar Year where Cumulative sum % of surface areas of Work Area ≥ PSA.

20 Ideniffication offtenz Partsfailing before Maintenance Point From the Work Area condition report, list all those Item Parts by Criticality Type that Fail< Mtwa.

Sum by Criticality Type, and process through Strategy Ito achieve Mtwa before Failure.

Strategies The planning of a Work Area will be done by analysing the condition report, ZD selecting areas for maintenance, and applying either of 2 base strategies'.

1. Fixed term - lowest cost maintenance to avoid failure or metal loss for 30 specific number of years.

2. Life cycle - plan optimum maintenance for RLR.

Strategy I - specific period Select specific number of years (Yx) Where failure occurs within Yx years from current, Select up to 3 suitable coatings from the Coating data base.

10 For each coatin-:

Modify Coating Performance (CP) by:

<<SCM>> + <<ESM>> x <<CP to Ri <<number>>years >> CPm2 Where:

CP = Coating Performance to defined R1 breakdown <<number >> years 15 SCM = Surface Condition Multiplier (SCM-see Standing Data, Table Xx if known, otherwise 1) ESM Environment Severity Multiplier (EM - see Standing Data, Table XX if known - otherwise 1) CPm. = Modified Performance <<years>> 20 Add Coating Performance to initial Maintenance point (M) or Failure point(F) if initial coating maintenance point is in past.

i.e. If M occurs => current year, add CPrn = M2 Where M = initial Maintenance Point <<calendar year>> CPm. = modified Coating Scheme Life <<years>> 25 M2 = next maintenance point <<calendar year>> Or i.e. If M does not occur, default to current year Myc or specify year Mys, or F.

Add CPrn to (Myc or Mys or F) = M2 Where:

30 Myc = current year Maintenance Point <<calendar year>> Mys = specified Maintenance Point <<calendar year>> CPm. = modified Coating Scheme Life <<years>> M2 = next maintenance point <<calendar year>> 0 46Coiiipai-ingp7-oposediiiai77te7iatice 10 YX 7-equii-ed If M2 + time to failure <<years>> is > Yx, save in table and stop. If M2 + time to failure <<years>> is < Yx, repeat from 'Select a coating... 'choosing appropriate Coating scheme to just achieve desired RLR.

10 The information is then displayed in a form such as that shown in Figure 5a.

Strategy 2 - Life cycle Where failure occurs within remaining life required (RLR), Select a coating from the Coating data base. Modify Coating Performance (CP) by:

15. <<SCM>> + <<ESM>> x <<CP to Ri <<number>>years >> = CPm2 Where:

CP = Coating Performance to defined Ri breakdown <<number >> years SCM = Surface Condition Multiplier (SCM-see Standing Data, Table XX if known, otherwise 1) 20 ESM = Environment Severity Multiplier (EM - see Standing Data, Table XX if known - otherwise 1) CPrn Modified Coating Performance <<years>> Add Coating Performance to initial Maintenance point (M) or Failure point(F) if initial coating maintenance point is in past.

25 i.e. If M occurs => current year, add CPm = M2 Where M = initial Maintenance Point <<calendar year>> CPrn = modified Coating Performance <<years>> M2 = next maintenance point <<calendar year>> Or 30 i.e. If M does not occur, default to current year Myc or specify year Mys, or F.

Add CPm to (Myc or Mys or F) M2 Where:

Myc = current year Maintenance Point <<calendar year>> Mys = specified Maintenance Point <<calendar year>> 35 CPm = modified Coating Performance <<years>> 5 M2 = next maintenance point <<calendar year>> Comparingpi-oposed maintenance to RLR If M2 + time to failure <<years>> is > RLR, save in table and stop. If M2 + time to failure <<years>> is < RLR, repeat from 'Select a coating..' 10 choosing appropriate Coating scheme to just achieve desired RLR. The information is tabulated as in Table 11, for example.

Costs Costs are calculated for work by the following method- Base cost (Cb) = Surface Area x Cost per m2 for the Coating System 15 Costs are then adjusted by the Surface Condition Multiplier and Difficulty Multiplier:

Adjusted Cost (Ca) = Cb x Surface condition multiplier (SCM) x difficulty multiplier (DM).

SCM can be found in Standing Data 20 DM can be found in Standing Data.

Net Future Vahie (NFV) The Net Future Value is the current cost with inflation included. This is calculated by:

NFV = (Ca) x (I +i)' 25 Where i = inflation rate, and n = number of years to activity.

Net Present Vahte (NP V) The Net Present Value is what the NFV is worth today if invested at current interest rates. This is calculated by:

16 5 NPV=NFVxl (I+i)- Where i inflation rate, and n = number of years to activity. N is taken as the number of years to Maintenance activity. i <<%>> is input to Asset Data.

It will of course be understood that the invention is not limited by the specific details described herein, which are given by way of example only and that various modifications and alterations are possible within the scope of the invention.

Claims (1)

1. 5 CLAIMS:

   1. A system for evaluating and analysing corrosion risk and for identifying priorities for the testing and/or maintenance of corrosion susceptible structures, the system including:

   means for providing relevant information relating to the identification, specification, nature and purpose of item parts subject to external corrosion; means for evaluating and quantifying the risk of failure of parts due to external corrosion; means for quantifying the length of time the item part will be fit for purpose (effective life); means for factoring for each item part the protection from external corrosion by coatings; means for evaluating and quantifying the effective life and cost of different coatings; means for identifying and logging the severity of environments within which item parts are located; 30 means for factoring corrosion rate for various environments; means for producing systematic condition records for item parts; means for logging and quantifying the effect of the various environments 35 on coating deterioration;

   5 means for recording the effect of the substrate surface condition on the life of the coating; and means for establishing the variation in time due to the accessibility and difficulty of maintenance on different types of item part.

   2. A system as claimed in claim 1, in which the probability of substrate failure of an item part is assessed with respect to the estimated remaining life of the part and the life required.

   15 3. A system as claimed in claim 2, in which maintenance or replacement priorities are associated with item parts according to risk ratings which are weighted with respect to the consequences of substrate failure.

   4. A user interface for a corrosion risk analysis system including means for a 20 user to interactively explore how the risk of failure of a structure or an item part thereof may change due to various influencing factors including coating quality, coating thickness, weathering, corrosion nature, depth and degree of degradation.

   25 5. A user interface as claimed in claim 4, in which includes means for generating recommendations for inspection and testing for corrosion and protective coating quality, which recommendations are prioritised according to recognised weighting factors including, amongst others, maintenance cost, replacement cost, longevity of item part, longevity or 30 expected life of structure, failure risk and consequence of failure.

   6. A user interface as claimed in claim 4 or claim 5, in which a condition survey is produced for presentation to the user, the survey presenting inspection recommendation rotas, maintenance schedules and replacement 35 priorities for predetermined survey areas.

   7. A user interface as claimed in any one of claims 4 to 6, in which historical data is utilised to present criticality ratings in absence of.input data to present a scheduled maintenance date and a theoretical failure date for an item part or structure.

   8. A method for conducting corrosion risk analysis and for identifying priorities for the testing and/or maintenance of corrosion susceptible structures, the method including:

   15 prioritising item parts according to risk of failure relative to required life; initially estimating and subsequently storing the current condition of the item part and protective coating; 20 predicting times to maintenance of the protective coating; predicting times to failure of the item part from external corrosion; planning actions for maintenance or replacement of the item part or 25 protective coating; estimating and comparing costs of maintenance or replacement of coating or item part; and 30 comparing the effective life, costs and resources required for different planned actions.

   9. A method as claimed in claim 8, in which data is processed according to predetermined parameters including Budget Area, Work Site, Work Area 35 and Survey Area.

   -so- 10. A method as claimed in claim 8 or claim 9, in which data is grouped by item or item assembly.

   11. A method of providing an indication to a user of the probability of 10 corrosion risk to a structure or an item part thereof, the method comprising:

   interactively exploring how the risk of corrosion affecting a structure or item part thereof may change according to a number of influencing 15 factors; and generating recommendations for inspection or testing of a structure or item part thereof, said recommendations being prioritised according to recognised weighting factors including, amongst others, maintenance cost, 20 replacement cost, longevity of an item part, longevity or expected life of structure, failure risk and consequence of failure.

   12. A method as claimed in claim 11, in which includes the steps of.

   25 concurrently displaying a plurality of input objects, one or more being configured to generate question fields to be compiled by a user; generating a display based on decisions made from the input objects and question field inputs; and determining and displaying a set of recommendations and associated priorities based on the input objects and question field inputs.

   13. A method as claimed in claim I I or claim 12, in which the method 35 includes any one or more of assessing protective coating type and 9( _9R_ 5 thickness levels, including actual type and thickness on application, expected wear and actual wear; evaluating degree of or thickness of corrosion; calculating potential economic and physical consequences of structure or item part failure; applying mathematical functions to estimate corrosion risk or rates to failure devised from information collected from 10 historic structural analysis, corrosion rates of grades of material, attenuation factors of coatings and coating thicknesses, weathering and other environmental factors; and producing recommendations for testing, inspection maintenance, replacement or not, organised by priority selected by the user or a combination thereof from time, cost, failure risk and 15 physical harm, amongst others.

   14. A machine-readable medium having stored thereon data representing sequences of instructions, said sequences of instructions which, when executed by a processor, cause said processor to:

   20 display concurrently a series of default objects in a first portion of a screen and a series of input objects in a second portion of the screen, the input objects being configured to receive one or more input values; display a set of output values in a subsequent screen, the set of output values including a probability of failure of a given item part based upon 25 one or more input values and a recommended set of corrosion indicators; determine risk based on said inputs and displaying a set of recommendations and associated priorities for assessing corrosion and failure risks.

   15. A machine-readable medium as claimed in claim 14, in which stored thereon there is included "stand-alone" data representing library facts associated with item parts, structures, coating performances, corrosion rates, amongst others.

   5 16. A machine-readable medium as claimed in claim 14 or claim 15, in which there is included data representing "weighting" data, statistically derived or accumulated from data generated during earlier surveys, including real life and/or experimental data for reviewing failure probability rates and failure consequence ratings.

   10 17. A machine-readable medium as claimed in any one of claims 14 to 16, in which there is included data representing indexed information including pricing data.

   18. A machine-readable medium having stored thereon data representing sequences of instructions for execution by a processor, the instructions 15 causing the processor to implement a method of conducting corrosion risk analysis and for identifying pniorities for the testing and/or maintenance of corrosion susceptible structures as defined in claim 8.

   19. A machine-readable medium having stored thereon data representing sequences of instructions for execution by a processor, the instructions 20 causing the processor to implement a method of providing an indication to a user of the probability of corrosion risk to a structure or item part thereof as defined in claim 11.

   20. A system for evaluating and analysing corrosion risk and for identifying priorities for the testing and/or maintenance of corrosion susceptible 25 structures, substantially as herein described with reference to and as shown in Figures 1 to 5 and 8 to 14c of the accompanying drawings.

   21. A user interface for a corrosion risk analysis system substantially as herein described with reference to and as shown in Figures I to 5.

   93 _W__ 5 22. A method for conducting corrosion risk analysis and for identifying priorities for the testing and/or maintenance of corrosion susceptible structures substantially as herein described with reference to the accompanying drawings.

   23. A method of providing an indication to a user of the probability of 10 corrosion risk of a structure or an item part thereof, substantially as herein described with reference to the accompanying drawings.

   24. A machine-readable medium substantially as herein described with reference to the accompanying drawings.