WO2009112582A1

WO2009112582A1 - Telemetry based data collection method and system for carrying out such method

Info

Publication number: WO2009112582A1
Application number: PCT/EP2009/053018
Authority: WO
Inventors: Michael Anthony Hayward
Original assignee: Single Buoy Moorings Inc.
Priority date: 2008-03-14
Filing date: 2009-03-13
Publication date: 2009-09-17

Abstract

This invention relates to a telemetry based method of determining properties like thickness or deflection for a set of multiple positions on a structure, like the hull of an offshore construction or ship, comprising the steps of placing at least three transmitting devices on three positions on the structure, determining the coordinates of the devices relative to the structure as well as taking measurements of the property at positions on the structure. This can be done via a hand-held measuring device and storing for each measurement the coordinates of the position of measurement in the measuring device, which position of measurement is determined in the measuring device on the basis of receipt by the measuring device of a signal that is transmitted by the transmitting devices.

Description

Telemetry based data collection method and system for carrying out such method.

Field of the invention

The invention relates to a method of determining properties for a set of multiple positions on an offshore structure comprising the steps of:

- placing at least three transmitting devices on three positions on the structure, and

- determining the coordinates of the devices relative to the structure and taking measurements of the property at positions on the structure.

The invention also relates to a system and to a hand-held measuring device for carrying out the method.

Background of the invention

Classification societies require that for offshore constructions and ships, like for example trading tankers, hull inspections are performed on a regular basis. Part of the scope of such an inspection is the taking of, recording and subsequent analysis of Ultrasonic Thickness Measurement (UTM) readings. A trading tanker (with sometimes a length of over 300m, width of over 50 m and a draft of over 30 m), needs for example to be dry docked every 5 years to be inspected with an overall UTM survey. Such a survey can include more than 10,000 local UTM readings and such a survey can take as long as 50 days to complete. For constructions moored offshore like an FPSO, Semi- sub, Spar or TLP, etc, regular dry-docking is not an option due to production requirements. Therefore, hull inspections need to be done offshore.

Currently to take the UTM measurements and readings at least two operators are required; one person to take the reading with a handheld UTM device and another person to record the reading on a sheet of paper and mark the location (very approximately and inaccurate) on a drawing of the piece of steel structure that is being measured. After it is recorded by hand on paper, the data then needs to be entered manually into a computer data sheet and then into a hull monitoring software program to be further processed and evaluated.

There are many systems available in the market that enable UTM measurements of steel structures to be taken i.e. that can measure the thickness of steel structures. There are also many systems on the market that can locate their position by triangulation (mobile phones, GPS-based systems, etc), as is disclosed for example in US6915216.

Patent publications US7076992 and US2005/0099892 are for example both focused on thickness measurements of the hull, but the disclosed methods involve an external survey of a vessels hull using acoustic signals that are bounced off coupons that are permanently placed within the hull at set locations.

The disadvantages of these known methods are the large costs involved for placing large numbers of non acoustic property-changing coupons at many locations on the surface of a ship. Also, the hull would have to be perfect at the points where a coupon is placed which is often not the case as hulls often have been exposed to environmental conditions for a long period of time. These coupons would only work for flat plate steel without obstructing structures in the way (stiffeners for example). In these known methods, a support vessel is needed during the survey as well as an underwater robot that is controlled from the support vessel. This robot passes under the ship 'pinging' the coupons placed within the hull to record the thickness measurements. Support vessel day rates capable of operating a ROV are high and such an operation would be complicated to organise.

Summary of the invention

It therefore is an object of the present invention to provide a method for taking measurement data on a construction and a system and device for carrying out such a method, preferably on an offshore construction, which is relatively simple, easy to operate and which involves relatively low costs. It is another object of the invention to provide a method, system and device which allow accurate successive measurement cycles to be carried out at clearly defined positions.

Hereto the method according to the invention comprises the steps of taking measurements of a property at positions on the structure via a hand-held measuring device and storing for each measurement the coordinates of the position of measurement in the measuring device, which position of measurement is determined in the measuring device on the basis of receipt by the measuring device of a signal that is transmitted by the transmitting devices.

By the use of a hand-held measuring device which at the same time determines its position from three structure-based transmitting devices, properties such as thickness of the structure can be rapidly and easily measured for multiple locations and stored on the device together with the coordinates of the measurement data. This measurement data recorded according to the invention is available immediately for reporting or downloading for instance into a corrosion monitoring database.

The method and system according to the invention is very efficient and involves low costs as only one person is required to locally take the measurements and position readings during for instance an UTM survey of an offshore construction of a vessel. At the same time, the readings are relatively accurate as the telemetrically measured positions are electronically registered in the handheld device at the same time the UTM is completed for each position.

The method according to the invention allows for a flexible inspection survey of the overall offshore construction or vessel, as it can be divided in parts that can each be inspected at any time independently from each other. For example, whenever a crude oil storage tank is empty it can be surveyed while the other crude oil storage tanks of the same tanker remain in operation. This measurement of a part of or the whole offshore structure or vessel can be done with high accuracy, even when the overall structure is subject to large deformations, for example sagging and hogging, torsional deflections, hull deformations due to ballast and stored products, etc., which occur both in offshore situations as well as in dry-dock situations.

The method and system of the present invention can for instance be used for UTM readings, to check the "reality-as-build" dimensions of the vessel, or can be used for ballasting and product storage management or for over time structure fatigue analysis, etc.

The method and system according to the invention can use a 3 point telemetric data collection protocol and can be used for material thickness measurements for measuring multiple points on large offshore constructions, more specifically for measurement material thickness within a vessels hull.

For this case, the handheld measuring device can comprise a standard device that is capable of taking Ultrasonic Thickness Measurements (UTM) readings of a large steel structure with a locating system that is capable of recording by telemetry the exact location in x, y, and z coordinates of the UTM reading that is taken, as well as the thickness of the steel (t,x,y,z). This can be done from internally or externally of the structure, for example when the offshore structure or vessel is in dry-dock. Alternatively, the invention can be used to measure for example hull deflections which can be used for fatigue analysis, to optimize loading and unloading sequences of ballast and product storages tanks in vessels and for "reality-as-build" measurements of realized large offshore constructions and vessels.

The method according to the invention allows for efficient UTM measurements to be taken from within the offshore construction or ship, even when it is sailing or moored offshore and avoids the use any kind of locating devices that are permanently attached to the hull. According to the invention a handheld UTM device is combined with a telemetry system of 3 transmitters or beacons for exact position reading of the hand held UTM device by way of x, y and z coordinates. The data stored in the internal memory of the hand held device may, in one embodiment, be transferred to a central storage device and combined with for instance a 3D computer model of the structure or compared with previous measurement data.

After finalizing a local survey on an offshore structure or vessel part, the transmitting devices can be removed but the places were they were temporarily fixed to the structure can be marked for future inspections or if it is decided that specific repair of certain hull parts needs to be carried out. This ensures a greater level of accuracy in the readings.

In one embodiment according to the invention, one or more target positions are supplied to the measuring device wherein in the measuring device a distance from the target position is determined and a distance indication signal, such as an optical signal, a graphic display, an acoustic signal and/or a vibration signal is provided by the measuring device. The operator thereafter moves the hand- held measuring device to or near the target position, and takes a measurement when he has arrived at or near the target position.

The target positions may for instance be formed by measurement positions of a previously collected set of measurement data.

For this latter case, the memory of the handheld device can therefore be up-loaded again with one or more sets of previously recorded UTM locations.

By way of a positioning indicating tracer on the handheld device, it would be possible to find and locate a previously measured point again, with the help of the telemetric signals of the beacons which are put back again in their originally marketed places or they might still be at their place on that specific part of the vessel. As the user approaches the previously measured point the handheld device would alert the operator, for example by way of a increasing frequency of audible 'beeps' (or alternatively via a screen or color based indicator) that the handheld device is in the vicinity of the previously taken measurement reading. The device can be provided with an onscreen display that would show the distance required to move in an x, y or z direction for the handheld unit to locate the previous reading location again.

This option would be especially useful in tracking the diminution of a ships structure as it would allow the same points within the offshore structure or vessel to be measured again in time.

It is also advantageous to track down the exact locations again which were measured during the inspection and for which material repair or material replacement is needed, resulting from the evaluated measurements.

The properties that are measured according to the invention may comprise a material thickness, the measuring device comprising an ultrasonic thickness measurement unit.

Alternatively, it is possible for the measuring device to comprise a probe for supporting the device against the structure in a defined state. In this case, the position of the measuring device in a defined position relative to the component parts of the structure is recorded at different positions for instance for measuring hull deflections over time; this data can be used for example for further fatigue analysis of the offshore construction or vessel.

Brief description of the drawings

Some embodiments of a method and device according to the invention will be explained in detail with reference to the accompanying drawing. In the drawing:

Fig. 1 shows a sectional side view of a moored vessel with 3 transmitters or beacons placed within a specific storage tank of a vessel,

Fig.2 shows the top view of the vessel of figure 1,

Fig. 3 schematically shows a person with a handheld UTM device in a tank of a vessel that is provided with 3 transmitters or beacons for carrying out the method according to the invention,

Fig. 4 is a schematic view of a system according to the invention, Fig. 5 is a flow chart of a method according to the invention, and Fig. 6 is a flow chart of a method using target locations and a distance indication on the hand-held measuring device.

Detailed description of the invention

Figs. 1 and 2 show a side view and top view of a vessel 1 comprising three transmitting devices A,B,C at positions having coordinates (x,y,z) relative to a central calibration position (0,0,0). The transmitting devices A,B,C are removable transmitting beacons that are temporarily placed during the survey at known, marked locations on the vessel structure. These removable transmitting beacons can be placed at a specific part of the offshore structure, unit or vessel to be inspected, for example in a crude oil storage tank of a trading tanker. The positions of the beacons are known relatively to the central calibration position (0,0,0) which can be a fixed point on the vessel or a virtual point in a 3D computerized representation of the offshore construction or vessel. Due to for example sagging and hogging of the vessel or due to changes in ballast and stored product in the tanker, the relative position of the beacons with regard to this central calibration point can change in time. However, an accurate position of the handheld device with regard to the beacons is still possible as the beacons are placed in or near the part of the vessel to be inspected on marked locations. This allows the location of the handheld device to always be known accurately in relation to the beacons. As the position of the beacons is known in relation to the vessel, ship or structure then the location of the handheld unit can be deduced.

Fig. 3 shows an operator 2 inside a tank 4 of a vessel, holding a hand-held measuring device 3 which determines its position by receiving signals from transmitting devices A,B,C. The handheld device 3 will triangulate its position relative to these 3 beacons A,B,C by a telemetric signal such as an UHF, VHF, wifϊ, Bluetooth or similar signal. As the locations of the beacons are known accurately, it will be then possible for the handheld device, which may for instance be a UTM-device, to calculate its position relative the beacons and therefore to the structure of the ship. The handheld device 3 is provided with an internal memory and records at a local point the thickness measurement of the steel (UTM) and at the same time records the exact location of each individual UTM point reading; it records in an x, y, z format the exact position of the handheld device due to the telemetric signals of the 3 beacons that are received by the handheld unit. All this data regarding the thickness and exact position of the measured point is saved in a memory within the handheld unit. After finalizing the survey and recording of all the UTM points of that specific part of the vessel, the handheld unit can then be plugged into a computer by way of a USB cable or similar connection and the recordings can be downloaded directly into a computer. This would result in a table of results similar to as follows:

This data can then be uploaded into a 3D computer model of the offshore structure or vessel, for example up-loaded directly in the hull maintenance software that classification societies supply for each specific vessel they are responsible for classing. The locations of gaugings within the model are normally already known within the software as the 3-D model is built in an x, y, z format as well.

The collected data, which can be made available in real time, can also be used to optimize loading and unloading procedures and management of ballast and product storages tanks. The measurement points at the hull and tank will also deflect during loading and unloading of the tanks, as well as due to hogging and sagging of the vessel. These deflections of the measuring points with regard to the final calibration point (0,0,0) can be exactly measured and analyzed real time.

Also during construction of the very large offshore construction or vessel, the telemetric system according to the invention allows for an exact "reality-as-build" measurement of realized structure or parts thereof. This data can be collected and compared with the computerized 3D model of the offshore structure or vessel and the 3D model can be up-dated accordingly.

Fig. 4 shows a schematic lay-out of a hand-held measuring device 5 according to the invention comprising a measurement unit 6, such as a UTM-device or a probe for positional measurements, and a memory and display unit 7. The memory and display unit 7 can receive positional signals from transmitting devices A,B and C on the basis of which it calculates and stores its position, and stores the measurement data derived from the measurement unit 6. The coordinates of these positions and the measurement data can be transferred from the device 5 to a central storage unit 8.

From the storage unit 8, data may be uploaded into the memory of the unit 7, for instance coordinates of previous measurements. For checking such previously measured points, repair and/or maintenance purposes, the unit 7 can be provided with a (sound or color based) locator such as a display 9, so that it can track down an earlier measured point using the telemetric signals of the 3 beacons A,B,C to locate itself in relation to such a previously measured point.

Fig. 5 schematically shows the operation of the measuring device 5 wherein in step 10 the position is determined based on the signals from beacons A,B,C and is stored in the memory of the unit 7. In step 11 the measurement data is sampled via unit 6 in fig. 4 and in step 12 this measurement data is stored together with the coordinates in the memory of unit 7. In step 14 the operator moves the device 5 to a new measurement location and the cycle is repeated. In fig. 6, it is shown that in step 15 target positions are uploaded into the memory and display unit 7, for instance from central storage device 8, or, alternatively, via a web- based application. In step 16 the operator 2 moves to a new location at which the unit again determines its coordinates and compares these in step 17 as the current position with the target position. In case the distance from the target position is below a certain threshold value, measurement data are collected in step 19. However, if the distance from the target position is above the threshold value, in step 18 a distance indication is provided (such as a audible and or visible signal) and the operator 2 moves to a new location in step 16. In step 19 the measurement data are collected and stored in the unit 7 in step 20. In step 21, a new target position is set in the memory and display unit 7 and the operator 2 moves to a new location in step 16.

The method and device according to the present invention could be of interest to ship owners, operators, UTM companies and classification societies as a system and method according to the invention clearly saves time and costs in data collection and data processing while at the same time its increases the accuracy of the data recorded during the inspection surveys.

Claims

1. Method of determining properties for a set of multiple positions on a structure comprising the steps of: - placing at least three transmitting devices on three positions on the structure

- determining the coordinates of the devices relative to the structure

- taking measurements of the property at positions on the structure via a hand- held measuring device and storing for each measurement the coordinates of the position of measurement in the measuring device, which position of measurement is determined in the measuring device on the basis of receipt by the measuring device of a signal that is transmitted by the transmitting devices.

2 Method according to claim 1 wherein the measurement data and the corresponding coordinates are transferred from the hand-held device to a central storage device.

3 Method according to claim 1 or 2, further comprising the steps of:

- providing the measuring device with one or more target positions, - determining in the measuring device a distance from the target position and proving a distance indication signal,

- moving the hand-held measuring device to or near the target position, and

- taking a measurement at or near the target position.

4 Method of determining properties for a set of multiple positions on an offshore structure comprising the steps of:

- providing at least three transmitting devices on three positions,

- providing one or more target measurement positions to a hand-held measuring device, - determining in the measuring device the position of said measuring device on the structure on the basis of receipt by the measuring device of a signal that is transmitted by the transmitting devices and determining in the measuring device a distance from the target position and proving a distance indication signal, - moving the hand-held measuring device to or near the target position, and

- taking a measurement at or near the target position.

5 Method according to claim 3 or 4, wherein the target positions are formed by measurement positions of a previous set of measurement data.

6 Method according to claim 3, 4 or 5, wherein the indication signal comprises one or more of the set consisting of an optical signal, a graphic display, an acoustic signal and a vibration signal.

7 Method according to any of the preceding claims, wherein the properties that are measured comprise a material thickness, the measuring device comprising an ultrasonic thickness measurement unit.

8 Method according to any of claims 1 to 6, the measuring device comprising a probe for supporting the device against the structure in a defined state.

9 System for determining properties for a set of multiple positions on a structure comprising

At least three transmitting devices on three positions on the structure and a hand- held measuring device adapted for taking measurements of the property at positions on the structure and storing for each measurement the coordinates of the position of measurement in the measuring device, which position of measurement can be determined in the measuring device on the basis of receipt by the measuring device of a signal that is transmitted by the transmitting devices.

10 System according to claim 9 comprising a central storage device for providing the measuring device with one or more target positions that are formed on the basis of the positions of one or more previous measurements, wherein the measuring device is adapted for determining a distance from the target position and comprises an indicating unit for proving a distance indication signal. Hand- held measuring device for determining properties for a set of multiple positions on a structure comprising a measuring unit adapted for taking measurements of the property at positions on the structure and storing for each measurement the coordinates of the position of measurement in the measuring device, which position of measurement can be determined in the measuring device on the basis of receipt by the measuring device of a signal that is transmitted by at least three spaced-apart transmitting devices.

Measuring device according to claim 11, comprising an input unit for receiving a target position and an indicating unit for proving a distance indication signal on the basis of the distance between the target position and a measured position.

Measuring device according to claim 11 or 12, comprising an ultrasonic thickness measurement unit.