CN110942156A - Heat exchanger group preventive maintenance method based on operation risk - Google Patents

Heat exchanger group preventive maintenance method based on operation risk Download PDF

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CN110942156A
CN110942156A CN201911035913.6A CN201911035913A CN110942156A CN 110942156 A CN110942156 A CN 110942156A CN 201911035913 A CN201911035913 A CN 201911035913A CN 110942156 A CN110942156 A CN 110942156A
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tube bundle
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corrosion depth
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CN110942156B (en
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李春树
黄卫东
李涛
孙全胜
李洪涛
张中洋
郭拂娟
王艳丽
李梦瑶
高丽岩
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China Petroleum and Chemical Corp
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Abstract

A heat exchanger group preventive maintenance method based on operation risk comprises the following steps: establishing an in-service heat exchanger operation risk evaluation standard, determining the heat exchanger operation risk level, and performing heat exchanger preventive management and control; establishing a tube bundle sampling inspection standard of the heat exchanger; detecting the heat exchange tubes in the selected heat exchanger tube bundle by using rotary ultrasonic equipment, and processing the detection data; estimating the maximum corrosion depth of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger at the operation risk by using an extreme value statistical method; performing prediction analysis on the service life of the heat exchanger tube bundle according to the obtained maximum corrosion depth of the heat exchanger tube bundle; and performing preventive maintenance on the heat exchanger tube bundle according to the prediction analysis result. The heat exchanger group closed-loop risk management and control system is simple and reasonable, is convenient to use, and realizes closed-loop risk management and control of the heat exchanger group. The method and the device can determine the heat exchanger with the risk higher than the medium-high risk, and realize closed-loop risk management and control of the heat exchanger group.

Description

Heat exchanger group preventive maintenance method based on operation risk
Technical Field
The invention relates to a preventive maintenance method for a heat exchanger group. In particular to a heat exchanger group preventive maintenance method based on operation risk
Background
As a strategic and basic industry in China, petrochemical industry forms a complete industrial chain related to the strategic and basic industries, drives the development of a large number of industries, and is closely related to the development of national economy. Meanwhile, the petrochemical industry is also a high-energy-consumption industry, and a little improvement in any production process can bring huge economic benefits. The heat exchanger is one of the most common devices in petrochemical production, not only serves as a widely-used device for ensuring normal operation of a specific process flow, but also is an important device for developing and utilizing industrial secondary energy to realize waste heat recovery.
However, in the operation process of the heat exchanger, the medium passing through the tube and the shell pass has certain corrosivity, so that the heat exchange tube is corroded, and after a corrosion pit appears in the heat exchange tube, if the corrosion pit is not processed, the corrosion degree is rapidly intensified until the heat exchanger leaks, so that the safety production of a petrochemical device is influenced. The traditional heat exchanger maintenance management method is after-maintenance, namely, pipe blockage maintenance is carried out after leakage occurs, at present, heat exchanger maintenance management carried out by most enterprises basically stays between comprehensive periodic maintenance and individual heat exchanger accident treatment and after-emergency repair modes, no measure for solving problems in advance is provided, the after-maintenance mode causes great waste of resources and has huge potential safety hazards, and therefore a heat exchanger preventive maintenance and management strategy based on an operation risk state needs to be introduced, information technology is fully combined, and safe and reliable operation of the heat exchanger is guaranteed. To date, no complete system and method exists for the operation risk-based heat exchanger preventive maintenance management method of large petrochemical plants.
Disclosure of Invention
The invention aims to solve the technical problem of providing a heat exchanger group preventive maintenance method based on operation risk, which can realize closed-loop risk management and control of the heat exchanger group.
The technical scheme adopted by the invention is as follows: a heat exchanger group preventive maintenance method based on operation risks comprises the following steps:
1) establishing an in-service heat exchanger operation risk evaluation standard, determining a heat exchanger operation risk level, and performing heat exchanger preventive management and control according to the risk level;
2) establishing a tube bundle sampling inspection standard of the heat exchanger;
3) detecting the heat exchange tubes in the selected heat exchanger tube bundle by using rotary ultrasonic equipment, and processing the detection data;
4) estimating the maximum corrosion depth of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger at the operation risk by using an extreme value statistical method;
5) performing prediction analysis on the service life of the heat exchanger tube bundle according to the obtained maximum corrosion depth of the heat exchanger tube bundle;
6) and performing preventive maintenance on the heat exchanger tube bundle according to the prediction analysis result.
The heat exchanger group preventive maintenance method based on the operation risk has the following advantages:
1. through analyzing the heat exchanger for the important degree to the device, the corrosion mechanism of the heat exchanger is analyzed, and the historical information of the heat exchanger scaling and blocking resulting in leakage is subjected to statistical analysis and the like, an in-service heat exchanger operation risk evaluation program is formed, and the evaluation program is simple and reasonable and is convenient to use.
2. The detection work of the in-service heat exchanger tube bundle is usually carried out in the maintenance work within one operation period of the device, the rotary ultrasonic detection and extreme value statistical method is adopted, only a tube box of the heat exchanger needs to be opened and only a small number of heat exchange tubes are subjected to spot inspection in the detection process, the maximum corrosion depth is found through statistical calculation, the combined method greatly reduces the maintenance workload, the maximum corrosion depth value of the whole heat exchanger is calculated according to the maximum corrosion depth value of the small number of spot inspection heat exchange tubes, the service life of the heat exchanger tube bundle is predicted according to the value, a corresponding heat exchanger preventive management strategy is formulated according to the prediction result, and a basis is provided for the next maintenance work.
3. The method determines the heat exchangers with higher risk from the first operation risk evaluation of the heat exchangers in service in the whole plant to the last operation risk evaluation of the heat exchangers with higher risk after the heat exchangers with higher risk are subjected to predictive inspection and maintenance, thereby realizing the closed-loop risk management and control of the heat exchanger group.
Drawings
FIG. 1 is a flow chart of a large petrochemical plant heat exchanger operation risk evaluation method;
FIG. 2 is a block diagram of preventive maintenance management of a high operational risk heat exchanger cluster of a large petrochemical plant;
FIG. 3 is a diagram of the result of the rotary ultrasonic testing of the high operational risk heat exchanger;
FIG. 4 is a schematic diagram of a defect detection by rotation ultrasonic of a single heat exchange tube of a high-operation-risk heat exchanger.
Detailed Description
The operation risk based heat exchanger group preventive maintenance method of the present invention will be described in detail with reference to the following embodiments and accompanying drawings.
The invention relates to a heat exchanger group preventive maintenance method based on operation risk,
referring to fig. 1 and 2, the method for performing preventive maintenance on a heat exchanger group based on operation risk according to the present invention includes the following steps:
1) establishing an in-service heat exchanger operation risk evaluation standard, determining a heat exchanger operation risk level, and performing heat exchanger preventive management and control according to the risk level; the evaluation standard for establishing the operating risk of the in-service heat exchanger comprises the following steps:
(1) five influencing factors for determining the failure possibility of the heat exchanger are as follows: production importance, self importance, service state, difficulty of maintenance and inspection, and influence degree of failure consequence;
(2) determining the weight of five influencing factors of the heat exchanger operation risk degree by applying an analytic hierarchy process:
the production importance weight b1 is 0.31,
the self importance weight b2 is 0.16,
the in-service state weight b3 is 0.23,
the repair difficulty level weight b4 is 0.09,
the failure consequence influence degree weight b5 is 0.21;
(3) grading standard for five influence factors of heat exchanger operation risk
(3.1) scoring according to production importance:
after the heat exchanger leaks, the device stops running and other devices are influenced to stably run for 5 minutes;
after the heat exchanger leaks, the local part of the device stops running, and the running speed is 4 minutes;
only the normal production and process operation of the device is affected after the heat exchanger leaks, and the product quality is unqualified and is divided into 3 minutes;
the product quality and the process operation are not influenced after the heat exchanger leaks, but the medium series flow is caused, and the medium on the other side is polluted, so that the long-term running risk of the equipment is increased, and the score is 2;
the product quality, the process operation and other equipment are not affected after the heat exchanger leaks, and the score is 1;
(3.2) grading according to the importance of the score:
when the medium in the heat exchanger is one of hydrogenation reaction products, reforming reaction products, oil gas at the top of a fractionating tower, oil gas at the top of an absorbing tower, oil gas at the top of a resolving tower, circulating oil gas at the top of a normal tower, catalytic slurry oil, acidic water, coking purified water, circulating hydrogen and neutral gas, the medium is 5 minutes;
when the medium in the heat exchanger is one of liquefied gas, normal bottom oil, bottom reducing oil, lean rich amine liquid and sulfolane, the medium is 4 minutes;
when the medium in the heat exchanger is a medium which can generate a wet hydrogen sulfide corrosion environment and is one of oil gas at the top of a stable tower, oil gas at the top of a separation tower, fuel gas, fresh hydrogen and acid gas, the medium is divided into 3 minutes;
the medium in the heat exchanger contains corrosive medium, but the material of the tube bundle is selected to resist corrosion, and the number of the tube bundle is 2;
the medium in the heat exchanger is one of deoxygenated water, softened water, boiler water and steam without corrosiveness and is 1 minute;
(3.3) scoring according to service status
The running time of the heat exchanger is more than 20 years, or more than two times of pipe blockage repair occur in one year, or the maintenance finds that the residual average wall thickness of the pipe bundle is less than 1mm, or finds that the depth of a corrosion pit is more than 1.5mm, or the cumulative repairing pipe blockage rate reaches more than 15 percent and is 5 minutes;
the running time of the heat exchanger is 15-20 years, or once pipe blockage repair happens in one year, or corrosion exists in the last time of maintenance, or the residual wall thickness of the pipe bundle is 1.0-1.6 mm, or the cumulative repairing pipe blockage rate reaches 8% -15%, and is 4 min;
the running time of the heat exchanger is 10-15 years, or one-time pipe blockage repair occurs in one running period, or the cumulative repairing pipe blockage rate reaches 2% -8%, or the heat exchange pipe is thinned for 3 minutes in the last time of maintenance;
the running time of the heat exchanger is 5-10 years, or once pipe blockage repair occurs in two running periods, or the residual wall thickness of the pipe bundle is found to be 2 minutes between 2.0-2.2 mm by maintenance;
the running time is 1-5 years, or the pipe blockage repair never occurs from the time of putting into service, and is 1 minute;
(3.4) grading the difficulty level of heat exchanger maintenance:
during maintenance, the device where the heat exchanger is located needs to be shut down, or the equipment and the unit need to be shut down for more than 15 days, or the equipment and the unit need to be returned to a factory for maintenance, and the maintenance period is more than 11 days and is 5 minutes;
during maintenance, the heat exchanger needs to be shut down for 10-15 days, or the heat exchanger cannot be repaired on the site of the device, and needs to be returned to a factory for maintenance within 5-10 days, wherein the time is 4 minutes;
the heat exchanger is arranged above a 4-layer platform, the dismounting and mounting time is long, a crane of more than 200 tons is needed, obstacles are arranged around the heat exchanger, the auxiliary cost is high, the maintenance can be cut out by one machine, and the equipment outage time is 3-10 days, namely 3 minutes;
the heat exchanger is arranged on a 1-3-layer platform, a crane with the volume of less than 200 tons can be used for operation, obstacles are arranged around the crane and need to be treated, the crane can be cut out singly during maintenance, and the equipment outage time is 2 minutes within 3 days;
the equipment is arranged on the ground, no obstacle exists around the equipment, the equipment can be operated by a crane with less than 200 tons, the overhaul condition is easy to create, the overhaul can be cut out singly, and the equipment outage time is 1 minute within 1 day;
(3.5) scoring the degree of influence of the consequences of failure
The medium in the heat exchanger is inflammable, explosive, highly toxic or severely pollutes the environment, so that the social influence is 5 minutes;
the medium in the heat exchanger is toxic and combustible and is in a position where people often pass; is divided into 4 minutes;
the medium in the heat exchanger is high temperature, can be spontaneously combusted after being leaked, but is nontoxic and unexplosive, and is divided into 3 minutes;
the medium in the heat exchanger leaks, and is nontoxic, non-combustible and non-explosive, but causes peripheral local pollution, 2 minutes;
the medium in the heat exchanger is non-toxic, non-inflammable and non-explosive, and does not affect the product quality, and the number is 1;
(4) calculating the operation risk index of the heat exchanger and whether to perform preventive management and control on the heat exchanger
The comprehensive calculation formula of the heat exchanger operation risk index M is as follows:
m-b 1 × production importance + b2 × self importance + b3 × service status + b4 × ease of repair + b5 × impact degree of failure consequence
Scoring the heat exchangers according to the scoring criteria of the five influencing factors, substituting the scoring criteria into a comprehensive calculation formula of the running risk index M of the heat exchangers to obtain the running risk index M of each heat exchanger, and identifying the running risk of the heat exchangers according to the following criteria;
when the operation risk index M is 4.7-5, the heat exchanger is operated at high risk, and preventive management and control of the heat exchanger are carried out;
when the operation risk index M is 4.2-4.7, the heat exchanger is operated at medium and high risk, and the preventive management and control of the heat exchanger are considered;
when the operation risk degree index M is 2.5-4.2, operating the heat exchanger at a medium risk, not performing preventive management and control on the heat exchanger, but calculating the operation risk degree in each overhaul period;
when the operation risk degree index M is 1-2.5, the heat exchanger is operated at low risk, and the preventive management and control of the heat exchanger are not carried out.
2) Establishing a tube bundle sampling inspection standard of the heat exchanger; when the spot inspection quantity of the heat exchange tubes in the heat exchanger tube bundle is calculated, the error limit e is 7% for the high-risk operation heat exchanger, the error limit e is 10% for the medium-high risk operation heat exchanger, and the standard error S of the heat exchanger tube bundle wall thickness estimator is obtained by performing statistical analysis on the wall thickness detection result of the heat exchanger tube bundle2The value is 0.2 mm.
The establishment of the heat exchanger tube bundle sampling inspection standard comprises the following steps:
(1) determining the sampling quantity of the heat exchanger tube bundles:
the sampling quantity of the heat exchange tube bundle is as follows:
Figure BDA0002251486190000041
in the formula:
n is the sampling number of the heat exchange tubes in the heat exchanger tube bundle;
z is 1.96 when the heat exchanger is operated for high risk and 1.64 when the heat exchanger is operated for medium and high risk;
s is the standard error of the heat exchanger tube bundle wall thickness estimator, and the unit is mm;
for the error limit, the value of the error limit e is 7% for the high risk operation heat exchanger, and the value of the error limit e is 10% for the medium and high risk operation heat exchanger;
n is the total number of the heat exchange tubes in the heat exchanger tube bundle;
thereby obtaining:
the number of tube bundle spot checks of the high-risk operation heat exchanger is as follows:
Figure BDA0002251486190000042
wherein n is an integer after carry;
and (3) determining the sampling inspection quantity of the tube bundles of the heat exchanger in high-risk operation:
Figure BDA0002251486190000051
wherein n is an integer after carry.
3) Detecting the heat exchange tubes in the selected heat exchanger tube bundle by using rotary ultrasonic equipment to obtain a detection result data diagram of each extracted heat exchange tube shown in the figure 3, wherein the corrosion state of each extracted heat exchange tube is as shown in the figure 4, and processing the detection data; the method comprises the following steps:
(1) selecting n heat exchange tubes in the heat exchanger tube bundle according to the spot inspection standard of the heat exchanger tube bundle, inspecting the residual wall thickness of each part of the selected n heat exchange tubes by using rotary ultrasonic equipment, and obtaining the minimum wall thickness of each heat exchange tube as tiAnd n heat exchange tubes form a data set with the minimum wall thickness of t1,t2,...,ti,...,tn}；
(2) Removing abnormal values by adopting an interquartile range (IQR) method, specifically, removing the minimum wall thickness data set { t } t1,t2,...,ti,...,tnDivide into 4 parts at a quartile distance, each part containing 25% of data:
the 1 st quartile Q1 is the 25 th percentile;
the 2 nd quartile Q2 is the 50 th percentile, i.e., the median;
the 3 rd quartile Q3 is the 75 th percentile;
the interquartile range IQR is defined by:
IQR＝Q3-Q1
which may be interpreted as the range covered by the middle 50% of the data, IQR (quartering distance), as a measure of the degree of data dispersion, is more accurate than standard deviation.
The detected data t is determined by the following two formulasiAs outliers:
ti＜Q1-1.5 XIQR or
ti＞Q3+1.5×IQR。
(3) The new data formed after the abnormal values are removed are sequentially arranged from small to large to form a new data set { x1,x2,...,xi,...,xmM is less than or equal to n; the data in the new data set obeys an extremum distribution pattern.
4) Estimating the maximum corrosion depth of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger at the operation risk by using an extreme value statistical method;
the method for estimating the maximum corrosion depth of the tube bundle of the heat exchanger running at the high risk or the tube bundle of the heat exchanger running at the medium and high risk by using the extreme value statistical method is used for calculating a detection data set { x) of the corrosion depth of the tube bundle of the heat exchanger running at the risk above the medium and high risk1,x2,...,xi,...,xmAnd (4) performing parameter estimation on a position parameter lambda and a scale parameter α of the extreme value statistical model of the maximum corrosion depth of the heat exchanger tube bundle with the operation risk higher than the middle-high risk, and calculating the maximum corrosion depth value of the heat exchanger tube bundle with the operation risk higher than the middle-high risk according to the result of the parameter estimation.
Operation risk the maximum corrosion depth of a tube bundle of a high risk operation heat exchanger or a tube bundle of a medium high risk operation heat exchanger is according to the following formula:
Figure BDA0002251486190000052
α＝0.7797×S
λ＝0.577×α-μ
Figure BDA0002251486190000061
Figure BDA0002251486190000062
in the formula:
xmaxthe maximum corrosion depth estimation value of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger is in unit mm;
lambda is a position parameter of a maximum corrosion depth extreme value statistical model of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger, and the unit is mm;
α is a scale parameter of a maximum corrosion depth extreme value statistical model of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger, and the unit is mm;
s is a tube bundle corrosion depth detection data set { x) of a high-risk operation heat exchanger or a tube bundle corrosion depth detection data set of a medium-high risk operation heat exchanger1,x2,...,xi,...,xmStandard deviation in mm;
mu is a tube bundle corrosion depth detection data set { x) of a high risk operation heat exchanger or a tube bundle corrosion depth detection data set of a medium and high risk operation heat exchanger1,x2,...,xi,...,xmMean of } in mm;
n is the total number of the heat exchange tubes in the heat exchanger tube bundle.
5) Performing prediction analysis on the service life of the heat exchanger tube bundle according to the obtained maximum corrosion depth of the heat exchanger tube bundle;
establishing a function according to the relationship between the maximum corrosion depth of the heat exchanger tube bundle and the service life of the heat exchanger to simulate the relationship between the corrosion depth of the tube bundle of the heat exchanger with high risk operation or the heat exchanger with high risk operation and the service life, wherein the relationship is as follows:
Figure BDA0002251486190000063
in the formula (I), the compound is shown in the specification,
r is the service life of the heat exchanger with the operation risk in the middle and high risk operation or the tube bundle of the heat exchanger with the high risk operation;
c is the maximum corrosion depth of the running risk measured at the moment r in the middle-high risk running heat exchanger or the tube bundle of the high risk running heat exchanger, and the unit is mm;
t is a undetermined coefficient.
According to the formula, the time of the heat exchanger running to the current detection is r years, and the predicted maximum corrosion depth of the tube bundle is c-xmaxDetermining undetermined coefficient T, wherein xmaxA maximum corrosion depth estimate for a tube bundle of a high risk operational heat exchanger or a tube bundle of a medium high risk operational heat exchanger; on the basis, under the current use condition of the tube bundle of the heat exchanger, when the tube bundle is supposed to be completely corroded and perforated, the maximum corrosion depth is the wall thickness of the heat exchange tube of the tube bundle, namely c is the original wall thickness of the heat exchange tube of the tube bundle, the coefficient T to be determined and the original wall thickness value of the heat exchange tube of the tube bundle are brought into an r-solving formula, and the maximum corrosion depth of the heat exchange tube of the current tube bundle is xmaxUnder the condition of (1), the time of perforating the heat exchange tube is obtained by prediction and calculation, namely the service life of the heat exchanger tube bundle is obtained.
6) And performing preventive maintenance on the heat exchanger tube bundle according to the prediction analysis result. The specific preventive maintenance standard is as follows:
(1) using 4 years as an equipment overhaul period, subtracting the current service life of the heat exchanger from the predicted service life of the heat exchanger, if the value is more than 4 years and less than 8 years, carrying out emergency overhaul treatment on the heat exchanger in the period, but monitoring the heat exchanger, carrying out comprehensive rotary ultrasonic detection on the heat exchanger during large overhaul of the equipment, and finding out that the maximum corrosion depth of the heat exchanger tube bundle exceeds xmaxThe heat exchange tubes of the heat exchanger tube bundle are subjected to tube plugging treatment, and the operation risk level of the heat exchanger is recalculated;
(2) taking 4 years as an equipment overhaul period, subtracting the current service life of the heat exchanger from the predicted service life of the heat exchanger, and if the value is less than 4 years, carrying out comprehensive rotation ultrasonic detection on the heat exchanger to find out that the maximum corrosion depth of a tube bundle of the heat exchanger is xmaxA heat exchange pipe for plugging treatment if it should be replacedIf the pipe plugging rate of the heat exchanger pipe bundle exceeds 10%, preparing the heat exchanger pipe bundle with the same model, replacing, if the pipe plugging rate of the heat exchanger pipe bundle does not exceed 10%, recalculating the operation risk level of the heat exchanger pipe bundle, and monitoring and operating the heat exchanger.

Claims (7)

1. A heat exchanger group preventive maintenance method based on operation risks is characterized by comprising the following steps:
1) establishing an in-service heat exchanger operation risk evaluation standard, determining a heat exchanger operation risk level, and performing heat exchanger preventive management and control according to the risk level;
2) establishing a tube bundle sampling inspection standard of the heat exchanger;
3) detecting the heat exchange tubes in the selected heat exchanger tube bundle by using rotary ultrasonic equipment, and processing the detection data;
4) estimating the maximum corrosion depth of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger at the operation risk by using an extreme value statistical method;
5) performing prediction analysis on the service life of the heat exchanger tube bundle according to the obtained maximum corrosion depth of the heat exchanger tube bundle;
6) and performing preventive maintenance on the heat exchanger tube bundle according to the prediction analysis result.
2. The operational risk based heat exchanger group preventive maintenance method according to claim 1, wherein the establishment of the operational risk evaluation criteria of the heat exchanger in service in step 1) is as follows:
(1) five influencing factors for determining the failure possibility of the heat exchanger are as follows: production importance, self importance, service state, difficulty of maintenance and inspection, and influence degree of failure consequence;
(2) determining the weight of five influencing factors of the heat exchanger operation risk degree by applying an analytic hierarchy process:
the production importance weight b1 is 0.31,
the self importance weight b2 is 0.16,
the in-service state weight b3 is 0.23,
the repair difficulty level weight b4 is 0.09,
the failure consequence influence degree weight b5 is 0.21;
(3) grading standard for five influence factors of heat exchanger operation risk
(3.1) scoring according to production importance:
after the heat exchanger leaks, the device stops running and other devices are influenced to stably run for 5 minutes;
after the heat exchanger leaks, the local part of the device stops running, and the running speed is 4 minutes;
only the normal production and process operation of the device is affected after the heat exchanger leaks, and the product quality is unqualified and is divided into 3 minutes;
the product quality and the process operation are not influenced after the heat exchanger leaks, but the medium series flow is caused, and the medium on the other side is polluted, so that the long-term running risk of the equipment is increased, and the score is 2;
the product quality, the process operation and other equipment are not affected after the heat exchanger leaks, and the score is 1;
(3.2) grading according to the importance of the score:
when the medium in the heat exchanger is one of hydrogenation reaction products, reforming reaction products, oil gas at the top of a fractionating tower, oil gas at the top of an absorbing tower, oil gas at the top of a resolving tower, circulating oil gas at the top of a normal tower, catalytic slurry oil, acidic water, coking purified water, circulating hydrogen and neutral gas, the medium is 5 minutes;
when the medium in the heat exchanger is one of liquefied gas, normal bottom oil, bottom reducing oil, lean rich amine liquid and sulfolane, the medium is 4 minutes;
when the medium in the heat exchanger is a medium which can generate a wet hydrogen sulfide corrosion environment and is one of oil gas at the top of a stable tower, oil gas at the top of a separation tower, fuel gas, fresh hydrogen and acid gas, the medium is divided into 3 minutes;
the medium in the heat exchanger contains corrosive medium, but the material of the tube bundle is selected to resist corrosion, and the number of the tube bundle is 2;
the medium in the heat exchanger is one of deoxygenated water, softened water, boiler water and steam without corrosiveness and is 1 minute;
(3.3) scoring according to service status
The running time of the heat exchanger is more than 20 years, or more than two times of pipe blockage repair occur in one year, or the maintenance finds that the residual average wall thickness of the pipe bundle is less than 1mm, or finds that the depth of a corrosion pit is more than 1.5mm, or the cumulative repairing pipe blockage rate reaches more than 15 percent and is 5 minutes;
the running time of the heat exchanger is 15-20 years, or once pipe blockage repair happens in one year, or corrosion exists in the last time of maintenance, or the residual wall thickness of the pipe bundle is 1.0-1.6 mm, or the cumulative repairing pipe blockage rate reaches 8% -15%, and is 4 min;
the running time of the heat exchanger is 10-15 years, or one-time pipe blockage repair occurs in one running period, or the cumulative repairing pipe blockage rate reaches 2% -8%, or the heat exchange pipe is thinned for 3 minutes in the last time of maintenance;
the running time of the heat exchanger is 5-10 years, or once pipe blockage repair occurs in two running periods, or the residual wall thickness of the pipe bundle is found to be 2 minutes between 2.0-2.2 mm by maintenance;
the running time is 1-5 years, or the pipe blockage repair never occurs from the time of putting into service, and is 1 minute;
(3.4) grading the difficulty level of heat exchanger maintenance:
during maintenance, the device where the heat exchanger is located needs to be shut down, or the equipment and the unit need to be shut down for more than 15 days, or the equipment and the unit need to be returned to a factory for maintenance, and the maintenance period is more than 11 days and is 5 minutes;
during maintenance, the heat exchanger needs to be shut down for 10-15 days, or the heat exchanger cannot be repaired on the site of the device, and needs to be returned to a factory for maintenance within 5-10 days, wherein the time is 4 minutes;
the heat exchanger is arranged above 4 layers of platforms, the equipment outage time is 3-10 days, and the number of the equipment outage time is 3 minutes;
the heat exchanger is arranged on a platform with 1-3 layers, and the equipment outage time is within 3 days and is 2 minutes;
the equipment is on the ground, and the equipment outage time is within 1 day and is 1 minute;
(3.5) scoring the degree of influence of the consequences of failure
The medium in the heat exchanger is inflammable, explosive, highly toxic or severely pollutes the environment, so that the social influence is 5 minutes;
the medium in the heat exchanger is toxic and combustible and is in a position where people often pass; is divided into 4 minutes;
the medium in the heat exchanger is high temperature, can be spontaneously combusted after being leaked, but is nontoxic and unexplosive, and is divided into 3 minutes;
the medium in the heat exchanger leaks, and is nontoxic, non-combustible and non-explosive, but causes peripheral local pollution, 2 minutes;
the medium in the heat exchanger is non-toxic, non-inflammable and non-explosive, and does not affect the product quality, and the number is 1;
(4) calculating the operation risk index of the heat exchanger and whether to perform preventive management and control on the heat exchanger
The comprehensive calculation formula of the heat exchanger operation risk index M is as follows:
m-b 1 × production importance + b2 × self importance + b3 × service status + b4 × ease of repair + b5 × impact degree of failure consequence
Scoring the heat exchangers according to the scoring criteria of the five influencing factors, substituting the scoring criteria into a comprehensive calculation formula of the running risk index M of the heat exchangers to obtain the running risk index M of each heat exchanger, and identifying the running risk of the heat exchangers according to the following criteria;
when the operation risk index M is 4.7-5, the heat exchanger is operated at high risk, and preventive management and control of the heat exchanger are carried out;
when the operation risk index M is 4.2-4.7, the heat exchanger is operated at medium and high risk, and the preventive management and control of the heat exchanger are considered;
when the operation risk degree index M is 2.5-4.2, operating the heat exchanger at a medium risk, not performing preventive management and control on the heat exchanger, but calculating the operation risk degree in each overhaul period;
when the operation risk degree index M is 1-2.5, the heat exchanger is operated at low risk, and the preventive management and control of the heat exchanger are not carried out.
3. The operational risk based preventative maintenance method for heat exchanger group according to claim 1, wherein the establishing of the heat exchanger tube bundle spot inspection standard in step 2) comprises:
(1) determining the sampling quantity of the heat exchanger tube bundles:
the sampling quantity of the heat exchange tube bundle is as follows:
Figure FDA0002251486180000031
in the formula:
n is the sampling number of the heat exchange tubes in the heat exchanger tube bundle;
z is 1.96 when the heat exchanger is operated for high risk and 1.64 when the heat exchanger is operated for medium and high risk;
s is the standard error of the heat exchanger tube bundle wall thickness estimator, and the unit is mm;
e is an error limit, the value of the error limit e is 7% for the high risk operation heat exchanger, and the value of the error limit e is 10% for the medium and high risk operation heat exchanger;
n is the total number of the heat exchange tubes in the heat exchanger tube bundle;
thereby obtaining:
the number of tube bundle spot checks of the high-risk operation heat exchanger is as follows:
Figure FDA0002251486180000032
wherein n is an integer after carry;
and (3) determining the sampling inspection quantity of the tube bundles of the heat exchanger in high-risk operation:
Figure FDA0002251486180000033
wherein n is an integer after carry.
4. The operational risk based heat exchanger group preventive maintenance method according to claim 1, wherein the step 3) comprises:
(1) selecting n heat exchange tubes in the heat exchanger tube bundle according to the spot inspection standard of the heat exchanger tube bundle, inspecting the residual wall thickness of each part of the selected n heat exchange tubes by using rotary ultrasonic equipment, and obtaining the minimum wall thickness of each heat exchange tube as tiAnd n heat exchange tubes form a data set with the minimum wall thickness of t1,t2,...,ti,...,tn}；
(2) Using a four-bit pitch squareRemoving abnormal values by a method, specifically, using the minimum wall thickness data set { t }1,t2,...,ti,...,tnDivide into 4 parts at a quartile distance, each part containing 25% of data:
the 1 st quartile Q1 is the 25 th percentile;
the 2 nd quartile Q2 is the 50 th percentile, i.e., the median;
the 3 rd quartile Q3 is the 75 th percentile;
the interquartile range IQR is defined by:
IQR＝Q3-Q1
the detected data t is determined by the following two formulasiAs outliers:
ti＜Q1-1.5 XIQR or
ti＞Q3+1.5×IQR。
(3) The new data formed after the abnormal values are removed are sequentially arranged from small to large to form a new data set { x1,x2,...,xi,...,xmM is less than or equal to n; the data in the new data set obeys an extremum distribution pattern.
5. The operational risk based preventive maintenance method for heat exchanger group according to claim 1, wherein the maximum corrosion depth of the operational risk in the tube bundle of the high risk operational heat exchanger or the tube bundle of the medium and high risk operational heat exchanger is estimated by applying extremum statistic method in step 4) according to the following formula:
Figure FDA0002251486180000041
α＝0.7797×S
λ＝0.577×α-μ
Figure FDA0002251486180000042
Figure FDA0002251486180000043
in the formula:
xmaxthe maximum corrosion depth estimation value of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger is in unit mm;
lambda is a position parameter of a maximum corrosion depth extreme value statistical model of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger, and the unit is mm;
α is a scale parameter of a maximum corrosion depth extreme value statistical model of the tube bundle of the high-risk operation heat exchanger or the tube bundle of the medium-high risk operation heat exchanger, and the unit is mm;
s is a tube bundle corrosion depth detection data set { x) of a high-risk operation heat exchanger or a tube bundle corrosion depth detection data set of a medium-high risk operation heat exchanger1,x2,...,xi,...,xmStandard deviation in mm;
mu is a tube bundle corrosion depth detection data set { x) of a high risk operation heat exchanger or a tube bundle corrosion depth detection data set of a medium and high risk operation heat exchanger1,x2,...,xi,...,xmMean of } in mm;
n is the total number of the heat exchange tubes in the heat exchanger tube bundle.
6. The operation risk based heat exchanger group preventive maintenance method according to claim 1, wherein the step 5) is to establish a function according to the relationship between the maximum corrosion depth of the heat exchanger tube bundle and the service life of the heat exchanger to simulate the relationship between the corrosion depth and the service life of the tube bundle of the operation risk in the high risk operation heat exchanger or the high risk operation heat exchanger, and the relationship is as follows:
Figure FDA0002251486180000051
in the formula (I), the compound is shown in the specification,
r is the service life of the heat exchanger with the operation risk in the middle and high risk operation or the tube bundle of the heat exchanger with the high risk operation;
c is the maximum corrosion depth of the running risk measured at the moment r in the middle-high risk running heat exchanger or the tube bundle of the high risk running heat exchanger, and the unit is mm;
t is a undetermined coefficient.
According to the formula, the time of the heat exchanger running to the current detection is r years, and the predicted maximum corrosion depth of the tube bundle is c-xmaxDetermining undetermined coefficient T, wherein xmaxA maximum corrosion depth estimate for a tube bundle of a high risk operational heat exchanger or a tube bundle of a medium high risk operational heat exchanger; on the basis, under the current use condition of the tube bundle of the heat exchanger, when the tube bundle is supposed to be completely corroded and perforated, the maximum corrosion depth is the wall thickness of the heat exchange tube of the tube bundle, namely c is the original wall thickness of the heat exchange tube of the tube bundle, the coefficient T to be determined and the original wall thickness value of the heat exchange tube of the tube bundle are brought into an r-solving formula, and the maximum corrosion depth of the heat exchange tube of the current tube bundle is xmaxUnder the condition of (1), the time of perforating the heat exchange tube is obtained by prediction and calculation, namely the service life of the heat exchanger tube bundle is obtained.
7. The operational risk based heat exchanger group preventive maintenance method according to claim 1, wherein the specific preventive maintenance standard of step 6) is:
(1) using 4 years as an equipment overhaul period, subtracting the current service life of the heat exchanger from the predicted service life of the heat exchanger, if the value is more than 4 years and less than 8 years, carrying out emergency overhaul treatment on the heat exchanger in the period, but monitoring the heat exchanger, carrying out comprehensive rotary ultrasonic detection on the heat exchanger during large overhaul of the equipment, and finding out that the maximum corrosion depth of the heat exchanger tube bundle exceeds xmaxThe heat exchange tubes of the heat exchanger tube bundle are subjected to tube plugging treatment, and the operation risk level of the heat exchanger is recalculated;
(2) taking 4 years as an equipment overhaul period, subtracting the current service life of the heat exchanger from the predicted service life of the heat exchanger, and if the value is less than 4 years, carrying out comprehensive rotation ultrasonic detection on the heat exchanger to find out that the maximum corrosion depth of a tube bundle of the heat exchanger is xmaxThe heat exchange tube is subjected to tube plugging treatment, if the tube plugging rate of the tube bundle of the heat exchanger exceeds the rateAnd if the pipe blockage rate of the heat exchanger pipe bundle does not exceed 10%, recalculating the operation risk level of the heat exchanger pipe bundle and monitoring and operating the heat exchanger.
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