CN105404776A - Reliability evaluating method for pipe with corrosion defect - Google Patents

Abstract

The present invention discloses a reliability evaluating method for a pipe with a corrosion defect. The evaluating method comprises: acquiring a minimum operating pressure Pmin and a maximum operating pressure Pmax of a pipe as well as a mean operating pressure P* of the pipe within a first preset time period; selecting P*+/- K1, P*+/- K2,...P*+/- Kq from an interval between Pmax and Pmin, and obtaing 2q+3 pressure interpolation points, wherein q is an integer greater than or equal to 2; according to the pressure interpolation points, calculating a failure probability of each corrosion defect by using the Monte Carlo Method, and obtaining a reliability degree of the pipe according to the failure probability of the corrosion defect; and calculating a pipe reliability degree under a preset pressure by using an interpolation method according to the reliability degree of the pipe. The method provided by the present invention is simple in calculation, short in time consumption, relatively high in accuracy and can relatively well reflect actual results; and within a certain inner detection period, the evaluation personnel can readily and rapidly calculate the reliability degree of the pipe under a random pressure except that calculation of interpolation sample points needs to consume a certain time.

Description

A kind of fiduciary level evaluation method of the pipeline containing corrosion default

Technical field

The present invention relates to oil and gas pipes technical field, particularly relate to a kind of fiduciary level evaluation method of the pipeline containing corrosion default.

Background technology

Oil and gas pipes is related to national Important Economic lifeblood, and its safety problem can not be ignored.For preventing trouble before it happens, with regard to the different failure cause of pipeline and failure mode, relevant evaluation need being carried out to its performance, providing foundation for formulating maintenance maintenance plan.For the evaluation containing defect body residual intensity, initial many deterministic interpretational criterias directly adopted based on interior testing result both at home and abroad, but because the performance parameter and load parameter etc. of tubing in evaluation procedure all has uncertainty, deterministic method is caused to have certain limitation, therefore from last century Mo, there is the method for evaluating reliability based on probability statistics.

For the reliability evaluation of corrosion pipeline, model conventional is at present Stress-Strength Interference Model, available limit state equation Z=P _fthe form of-P=0 is expressed, in formula, and P _frepresent booster failure pressure, P represents operating pressure, and the failure probability F of fault location is and occurs Z≤0 shape probability of state.Then certain fault location fiduciary level R _i=1-F _i, in formula, F _irepresent the failure probability of i-th fault location, R _irepresent the fiduciary level of i-th fault location.If total n place defect on certain segment pipe, then the fiduciary level R=R of this segment pipe ₁r ₂r _ir _n.For Stress-Strength Interference Model, the method solving the body failure probability of fault location the most frequently used is MonteCarlo method, and the method program structure is simple, is easy to realize, can processes the situation of the stochastic variable distributed containing multiple different probability.

When utilizing said method to calculate containing defect natural gas line fiduciary level, when the transportation scheme formulated gas distributing system (or pipeline) under different throughput rate or when formulating reliability based distribution and fiduciary level enhancing plan, need repeatedly to carry out sample calculation with regard to the defective pipeline fiduciary level of different operating mode (different operating pressure).For an actual operation pipeline, several ten thousand even tens0000 place's defects may be had, if the often kind of plan operating mode now proposed for supvr all carries out series of computation, then expenditure of time is large, efficiency is lower, even may there is the phenomenon of low memory for ordinary electronic computing machine, use comparatively inconvenience.

Summary of the invention

The application provides a kind of fiduciary level evaluation method of the pipeline containing corrosion default, solve technical method of the prior art when calculating the defective pipeline fiduciary level under different operating pressure, not only expend man-hour comparatively large, and the technical matters that the internal memory taken is larger.

The application provides a kind of fiduciary level evaluation method of the pipeline containing corrosion default, and described evaluation method comprises:

Obtain the minimum operating pressure P of described pipeline _minwith maximum operating pressure P _max, and the average operating pressure P* in the first Preset Time;

P* ± K is selected in interval Pmax-Pmin ₁, P* ± K ₂... P* ± K _q, obtain 2q+3 pressure interpolation point, described q be more than or equal to 2 integer;

According to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline described in this according to the failure probability of described corrosion default;

The pipeline fiduciary level under interpolation calculation preset pressure is adopted according to the fiduciary level of described pipeline.

Preferably, described according to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, be specially:

Calculate the booster failure pressure of each described corrosion default

$P_f=\left(\frac{2t}{D}\right)(SMYS+68.95)\[\frac{1-0.85\frac{d}{t}}{1-\left(0.85\frac{d}{t}\right)M^{-1}}\],$ Wherein, described SMYS is pipeline SMYS, and d is the corrosion default degree of depth, and t is pipe thickness; D is outer diameter tube, and M is the bulging factor, $M={\[1+\frac{1.255}{2}\frac{L^2}{Dt}-\frac{0.0135}{4}\frac{L^4}{D^2{t}^2}\]}^{1/2},$ ? $\frac{L^2}{Dt}>50,M=0.032\frac{L^2}{Dt}+3.3,$ Wherein L is the length of described corrosion default;

Calculate P _fbe less than or equal to the probability of 0 with the difference of described pressure interpolation point, obtain the failure probability of each described corrosion default.

Preferably, described according to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline described in this according to the failure probability of described corrosion default, be specially:

The fiduciary level R at a described kth corrosion default place _k=1-F _k, wherein, F _krepresent the failure probability at a kth corrosion default place, R _krepresent the fiduciary level of a kth fault location, total corrosion default quantity of described pipeline is the fiduciary level R=R of p, described pipeline ₁r ₂r _kr _p.

Preferably, described K ₁=0.5, described K ₂=1, described K _qit is the multiple of 0.5

The application's beneficial effect is as follows:

The application passes through at the minimum operating pressure P of pipeline _min, average operating pressure P ^*and maximum operating pressure P _maxbetween value, obtain pressure interpolation point, monte carlo method is adopted to calculate the failure probability of each corrosion default again, the fiduciary level of pipeline is obtained according to described failure probability, the pipeline fiduciary level under arbitrary pressure can be calculated again according to the fiduciary level employing method of interpolation of described pipeline, the method calculates simple, consuming time short, accuracy is higher and can reflect the pipeline fiduciary level of actual result preferably, in certain in sense cycle, except calculating interpolated sample point needs to consume except certain hour, evaluation personnel can calculate the fiduciary level of this segment pipe under random pressure at any time fast, solving technical method of the prior art not only expends larger man-hour, and the technical matters that the internal memory taken is larger.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described by the accompanying drawing used required in describing embodiment below, apparently, the accompanying drawing in the following describes is only some embodiments of the present invention.

Fig. 1 is the process flow diagram of the fiduciary level evaluation method of a kind of pipeline containing corrosion default of the application's better embodiment;

Fig. 2 is the fiduciary level evaluation method pressure interpolation point schematic diagram in Fig. 1;

Fig. 3 is the concrete exemplary plot of fiduciary level evaluation method pressure interpolation point in Fig. 1.

Embodiment

The embodiment of the present application is by providing a kind of fiduciary level evaluation method of the pipeline containing corrosion default, solve technical method of the prior art when calculating the defective pipeline fiduciary level under different operating pressure, not only expend man-hour comparatively large, and the technical matters that the internal memory taken is larger.

Technical scheme in the embodiment of the present application is for solving technical matters of the prior art, and general thought is as follows:

Containing a fiduciary level evaluation method for the pipeline of corrosion default, described evaluation method comprises:

Obtain the minimum operating pressure P of described pipeline _minwith maximum operating pressure P _max, and the average operating pressure P* in the first Preset Time;

P* ± K is selected in interval Pmax-Pmin ₁, P* ± K ₂... P* ± K _q, obtain 2q+3 pressure interpolation point, described q be more than or equal to 2 integer;

According to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline described in this according to the failure probability of described corrosion default;

The pipeline fiduciary level under interpolation calculation preset pressure is adopted according to the fiduciary level of described pipeline.

The application passes through at the minimum operating pressure P of pipeline _min, average operating pressure P ^*and maximum operating pressure P _maxbetween value, obtain pressure interpolation point, again according to described pressure interpolation point, monte carlo method is adopted to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline according to described failure probability, then the pipeline fiduciary level under arbitrary pressure can be calculated according to the fiduciary level employing method of interpolation of described pipeline.The method calculate simple, consuming time short, accuracy is higher and can reflect actual result degree preferably, in certain in sense cycle, except calculating interpolated sample point needs to consume except certain hour, evaluation personnel can calculate the fiduciary level of this segment pipe under random pressure at any time fast, solve technical method of the prior art when calculating the defective pipeline fiduciary level under different operating pressure, not only expend man-hour comparatively large, and the technical matters that the internal memory taken is larger.

In order to better understand technique scheme, below in conjunction with Figure of description and concrete embodiment, technique scheme is described in detail.

Not only expend man-hour comparatively large to solve technical method of the prior art, and the technical matters that the internal memory taken is larger, the application provides a kind of fiduciary level evaluation method of the pipeline containing corrosion default.As shown in Figure 1, described evaluation method comprises:

Step S11: the minimum operating pressure P obtaining described pipeline _min(pressure and urban subscriber's demand pressure need be used in suction port of compressor) and maximum operating pressure P _max(the maximum pressure-bearing of pipeline), and the average operating pressure P* in the first Preset Time; In the present embodiment, described first Preset Time can be one month.

Step S12: select P* ± K in interval Pmax-Pmin ₁, P* ± K ₂... P* ± K _q, obtain 2q+3 pressure interpolation point, described q be more than or equal to 2 integer.As, get this pipeline average operating pressure P of nearly month ^*, get P respectively simultaneously ^*± 0.5MPa and P ^*the operating pressure of ± 1MPa, and numbering P ₂=P ^*-1, P ₃=P ^*-0.5, P ₄=P ^*, P ₅=P ^*+ 0.5, P ₆=P ^*+ 1, as shown in Figure 2, certainly, also reconnaissance can be expanded according to the actual requirements to P ^*± 1.5MPa, P ^*± 2MPa ...

Step S13: according to described pressure interpolation point, adopts monte carlo method to calculate the failure probability of each corrosion default, obtains the fiduciary level of pipeline described in this according to the failure probability of described corrosion default.

Step S14: adopt the pipeline fiduciary level under interpolation calculation preset pressure according to the fiduciary level of described pipeline.Described method of interpolation is specially cubic spline interpolation.

Particularly, described according to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, be specially:

Calculate the booster failure pressure of each described corrosion default $P_f=\left(\frac{2t}{D}\right)(SMYS+68.95)\[\frac{1-0.85\frac{d}{t}}{1-\left(0.85\frac{d}{t}\right)M^{-1}}\],$ Wherein, described SMYS is pipeline SMYS, and d is the corrosion default degree of depth, and t is pipe thickness; D is outer diameter tube, and M is the bulging factor, $M={\[1+\frac{1.255}{2}\frac{L^2}{Dt}-\frac{0.0135}{4}\frac{L^4}{D^2{t}^2}\]}^{1/2},$ ? $\frac{L^2}{Dt}>50,M=0.032\frac{L^2}{Dt}+3.3,$ Wherein L is the length of described corrosion default;

Calculate P _fbe less than or equal to the probability of 0 with the difference of described pressure interpolation point, obtain the failure probability of each described corrosion default.

Particularly, described according to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline described in this according to the failure probability of described corrosion default, be specially:

The fiduciary level R at a described kth corrosion default place _k=1-F _k, wherein, F _krepresent the failure probability at a kth corrosion default place, R _krepresent the fiduciary level of a kth fault location, total corrosion default quantity of described pipeline is p, described p be more than or equal to 2 integer, the fiduciary level R=R of described pipeline ₁r ₂r _kr _p.

Be described below by way of citing:

As certain 35.2km natural gas line (wall thickness t=7mm, pipe radius R=213mm), interior examining report shows this segment pipe and has 3923 place's corrosion defaults, the maximum operating pressure 4MPa (design pressure) of this pipeline, minimum operating pressure 0.5MPa (user divides defeated pressure minimum), a nearly monthly average operating pressure 1.6MPa.

When supvr formulates the transportation scheme under different throughput rate at different times to this pipeline or formulates reliability based distribution and fiduciary level enhancing plan, need respectively with regard to 1MPa, 1.2MPa, 1.4MPa, 1.6MPa, 1.8MPa, 2MPa, 2.2MPa, 2.4MPa, 2.6MPa ... pipeline fiduciary level under equal pressure calculates, then take following manner specifically to implement:

According to conduit running code, get the minimum operating pressure P of pipeline _minand maximum operating pressure P _max, and numbering P ₁=P _min=0.5MPa, P ₇=P _max=4MPa.

Get this pipeline average operating pressure P of nearly month ^*=1.6MPa, gets P simultaneously respectively ^*± 0.5MPa and P ^*the operating pressure of ± 1MPa, and numbering P ₂=P ^*-1=0.6MPa, P ₃=P ^*-0.5=1.1MPa, P ₄=P ^*=1.6MPa, P ₅=P ^*+ 0.5=2.1MPa, P ₆=P ^*+ 1=2.6MPa, as shown in Figure 3.

According to pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, particularly, set up limit state equation Z=P _f-P=0, in formula, P _frepresent booster failure pressure, P is pressure interpolation point, and the failure probability F of fault location is and occurs Z≤0 shape probability of state, and the present invention selects RSTRENG0.85dL method in ASMEB31G-2012 to solve P _f.

$P_f=\left(\frac{2t}{D}\right)(SMYS+68.95)\[\frac{1-0.85\frac{d}{t}}{1-\left(0.85\frac{d}{t}\right)M^{-1}}\]$

Wherein,

SMYS: pipe steel nominal SMYS [MPa]

T: pipe thickness [mm]

D: the corrosion default degree of depth [mm]

D: outer diameter tube [mm]

M: the bulging factor (FoliasFactor) [dimensionless]

For $\frac{L^2}{Dt}\≤50,$

$M={\[1+\frac{1.255}{2}\frac{L^2}{Dt}-\frac{0.0135}{4}\frac{L^4}{D^2{t}^2}\]}^{1/2}$

For $\frac{L^2}{Dt}>50,$

$M=0.032\frac{L^2}{Dt}+3.3$

Wherein, L is the length of described corrosion default.

The fiduciary level R at a described kth corrosion default place _k=1-F _k, wherein, F _krepresent the failure probability at a kth corrosion default place, R _krepresent the fiduciary level of a kth fault location, total corrosion default quantity of described pipeline is the fiduciary level R=R of p, described pipeline ₁r ₂r _kr _p.

According to the fiduciary level under 7 pressure interpolation points, cubic spline interpolation is adopted to calculate 1MPa, 1.2MPa, 1.4MPa, 1.6MPa, 1.8MPa, 2MPa, 2.2MPa, 2.4MPa, 2.6MPa ... pipeline fiduciary level under equal pressure.

The application passes through at the minimum operating pressure P of pipeline _min, average operating pressure P ^*and maximum operating pressure P _maxbetween value, obtain pressure interpolation point, monte carlo method is adopted to calculate the failure probability of each corrosion default again, the fiduciary level of pipeline is obtained according to described failure probability, the pipeline fiduciary level under arbitrary pressure can be calculated again according to the fiduciary level employing method of interpolation of described pipeline, the method calculates simple, consuming time short, accuracy is higher and can reflect actual result preferably, in certain in sense cycle, except calculating interpolated sample point needs to consume except certain hour, evaluation personnel can calculate the fiduciary level of this segment pipe under random pressure at any time fast, solve technical method of the prior art when calculating the defective pipeline fiduciary level under different operating pressure, not only expend man-hour larger, and the technical matters that the internal memory taken is larger.

As in above-mentioned example, under arbitrary operating pressure condition, adopt monte carlo method to carry out 50,000 sampled analog respectively to 3923 corrosion defaults, approximately use 4.5 hours.For being in the pipeline that interior sense cycle is 5 years, if when annual supvr formulates the transportation scheme under different throughput rate to gas distributing system (or pipeline) or formulates reliability based distribution and fiduciary level enhancing plan, pipeline fiduciary level under average computation 20 different operating modes (different operating pressure), then accumulative 4.5*20*5=450 hour consuming time in this work inherent in 5 years.And adopt the method in the present invention, sampled analog is carried out to 7 sample points, about 49 hours consuming time, under follow-up method of interpolation solves any operating mode, pipeline fiduciary level spent time is only a few minutes, always consuming timely be about the former 1/10, not only increase work efficiency, and ensure that high accuracy.

Although describe the preferred embodiments of the present invention, those skilled in the art once obtain the basic creative concept of cicada, then can make other change and amendment to these embodiments.So claims are intended to be interpreted as comprising preferred embodiment and falling into all changes and the amendment of the scope of the invention.

Obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.

Claims (4)

1., containing a fiduciary level evaluation method for the pipeline of corrosion default, it is characterized in that, described evaluation method comprises:

Obtain the minimum operating pressure P of described pipeline _minwith maximum operating pressure P _max, and the average operating pressure P* in the first Preset Time;

At interval P _maxp _mininterior selection P* ± K ₁, P* ± K ₂... P* ± K _q, obtain 2q+3 pressure interpolation point, described q be more than or equal to 2 integer;

According to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline described in this according to the failure probability of described corrosion default;

The pipeline fiduciary level under interpolation calculation preset pressure is adopted according to the fiduciary level of described pipeline.

2. evaluation method as claimed in claim 1, is characterized in that, described according to described pressure interpolation point, adopts monte carlo method to calculate the failure probability of each corrosion default, is specially:

Calculate the booster failure pressure of each described corrosion default $P_f=\left(\frac{2t}{D}\right)\left(SMYS+68.95\right)\[\frac{1-0.85\frac{d}{t}}{1-\left(0.85\frac{d}{t}\right)M^{-1}}\],$ Wherein, described SMYS is pipeline SMYS, and d is the corrosion default degree of depth, and t is pipe thickness; D is outer diameter tube, and M is the bulging factor, $M={\[1+\frac{1.255}{2}\frac{L^2}{Dt}-\frac{0.0135}{4}\frac{L^4}{D^2{t}^2}\]}^{1/2},$ ? $\frac{L^2}{Dt}>50,$ $M=0.032\frac{L^2}{Dt}+3.3,$ Wherein L is the length of described corrosion default;

Calculate P _fbe less than or equal to the probability of 0 with the difference of described pressure interpolation point, obtain the failure probability of each described corrosion default.

3. evaluation method as claimed in claim 1, it is characterized in that, described according to described pressure interpolation point, adopt monte carlo method to calculate the failure probability of each corrosion default, obtain the fiduciary level of pipeline described in this according to the failure probability of described corrosion default, be specially:

The fiduciary level R at a described kth corrosion default place _k=1-F _k, wherein, F _krepresent the failure probability at a kth corrosion default place, R _krepresent the fiduciary level of a kth fault location, total corrosion default quantity of described pipeline is the fiduciary level R=R of p, described pipeline ₁r ₂r _kr _p.

4. evaluation method as claimed in claim 1, is characterized in that, described K ₁=0.5, described K ₂=1, described K _qit is the multiple of 0.5.