CN104392070A - Pipeline valve safety assessment method based on limit external load calculation - Google Patents

Abstract

The invention relates to a pipeline valve safety assessment method based on limit external load calculation. The method comprises steps as follows: S1, establishing a three-dimensional geometrical model of a valve, a pipeline and a connecting piece; S2, performing finite element mesh generation on the three-dimensional geometrical model to establish a finite element mesh model; S3, establishing a limit external load finite element calculation model on the finite element mesh model; S4, performing calculation according to the limit external load finite element calculation model to obtain a limit external load; S5, establishing multiple combined external load finite element calculation models under the combined action of the limit external load and the maximum working pressure on the finite element mesh model; S6, calculating the stress distribution of the pipeline valve through the combined external load finite element calculation models and determining the safety performance of the pipeline valve according to the stress distribution. With the adoption of the method, the effect caused by the external load on the pipeline valve can be considered before prototype production, whether the strength property of the valve meets the design requirement or not can be judged, potential risks can be predicted, and the product development cycle is shortened.

Description

A kind of pipeline valve safety evaluation method based on limit external load calculation

Technical field

The present invention relates to a kind of pipeline valve safety evaluation method based on limit external load calculation, belong to valve design and calculate and structural safety performance prediction field.

Background technology

Pipeline valve mainly refers to and is arranged on the medium such as conveying crude oil, rock gas and valve on remote service.These valves and pipeline are often installed or are laid on field, and environment for use is extremely severe, often suffers the extreme variation of the disasteies such as land subsidence, rubble flow, flood and temperature.Therefore, except the pressure that the valve be arranged on pipeline is produced except pressure-bearing interior media and its mechanical load, also bear the adapter load that external connecting pipe road causes due to self weight of pipeline, alignment error, piping counter-force, and the additional external applied load (mainly external torque load and axial push-pull load) to cause due to above-mentioned disaster and temperature effect, adapter load and these additional external applied loads are referred to as valve external applied load.

Valve external applied load is extremely crucial for the impact of valve gate technology performance.These external applied loads are on the regional area of the impact of valve mainly near adapter and valve body junction; often can produce higher local stress; be superimposed with again because pressure medium load produces other local stress at these regional areas, make the total stress in this region very large.So the main contributor that the synergy of valve external applied load and pressure medium load will make pipeline and valve body join domain become valve to be occurred to destroy.

Due to the limitation of valve design method and specification, the valve body of current pipeline valve can only consider the impact of internal design pressure when designing and calculating, and heavily stressed external applied load can be caused cannot to consider at all, this just makes designed valve often unreasonable and difficult quality guarantee.

In order to ensure the reliability of product, offshore company proposes a kind of anti-external applied load test method of pipeline valve.But this method exist temporarily without exercisable standard schedule, stress data be difficult to obtain and the problem such as how to evaluate of data result.And have high input owing to setting up test platform, the cost carrying out testing is high, is often difficult to carry out in reality.The more important thing is, this test method just can be carried out after needing Development Prototype, namely cannot evaluate the design rationality of valve and reliability in the design phase.

Maximum external applied load data (i.e. limit external applied load) can be born on earth at present for how to carry out calculating or obtain valve at conceptual phase, and how to evaluate the safety of structure of valve body under these external load functions, also do not have suitable method available.

Summary of the invention

The object of the invention is to solve in prior art the problem not having suitable pipeline valve safety evaluation method to evaluate the design rationality of the pipeline valve in the design phase and reliability, thus provide a kind of can in the design phase just to the pipeline valve safety evaluation method based on limit external load calculation that design rationality and the reliability of pipeline valve are evaluated.

For achieving the above object, the invention provides a kind of pipeline valve safety evaluation method based on limit external load calculation, comprise the following steps:

S1: the 3-D geometric model setting up valve body, pipeline and web member;

S2: FEM meshing is carried out to 3-D geometric model and sets up finite element grid model;

S3: set up limit external applied load limited element calculation model on finite element grid model;

S4: calculate limit external applied load by limit external applied load limited element calculation model;

S5: set up on finite element grid model multiple limit external applied load and maximum working pressure (MWP) act on simultaneously under associating external applied load limited element calculation model;

S6: by associating external applied load limited element calculation model calculate pipeline valve stress distribution and according to the security performance of stress distribution determination pipeline valve.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, in described S1 step, utilize 3 d geometric modeling software to set up 1/2 3-D geometric model to valve body, pipeline and web member, the length of pipeline described in described model is greater than more than 2 times of pipe diameter.In the present invention, web member can be welding sleeve or joint flange etc.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, in described S2 step, the method setting up finite element grid model is: carry out stress and strain model to described 3-D geometric model, and the binding relationship arranging surface of contact between valve body, pipeline and web member completes to the dynamic changes process set up between valve body, pipeline and web member and sets up finite element grid model.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, in described S3 step, the method setting up limit external applied load limited element calculation model is: in described finite element grid model, arrange the material properties of valve body, pipeline and web member and symmetrical border, displacement boundary conditions and load boundary condition complete and set up limit external applied load limited element calculation model; Described external applied load comprises bending moment, torsional moment and axial load.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, described load boundary condition is:

During calculating limit bending moment, load boundary condition is act on the bending moment of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity;

During calculating limit torsional moment, load boundary condition is act on the torsional moment of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity;

During calculating limit axial load, load boundary condition is act on the axial load of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, in described S3 step, described material properties comprises elastic modulus, Poisson ratio; Described displacement boundary conditions for valve support zone is defined as staff cultivation, and defines symmetrical border in described S3 step.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, in described S4 step, described limit external applied load value M _{the limit}calculating comprise the following steps:

A1: presetting external applied load value M is initial value M _begin;

A2: the maximum stress value σ of pipeline valve when calculating described external applied load value M by finite element model _max, and to this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination;

A3: according to the maximum stress value σ recalculating the pipeline valve of its correspondence after fine setting external applied load value _maxand for this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination; The result of determination that the result of determination this obtained and last time obtain compares, and if the same circulate this step; If different, then enter next step;

A4: use formula recalculate external applied load value, wherein M _mwith M _nfor different and immediate two the external applied load values of numerical value of result of determination; " the maximum stress value σ of corresponding pipeline valve that recalculates M _maxand for this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination;

A5: if 0<a≤10, wherein M _xfor " the immediate external applied load value that the result of determination calculated is different then thinks ultimate load value from external applied load value M calculate and terminate;

If $\frac{|M^{\&Prime;}-M_x|}{\mathrm{MIN}(M^{\&Prime;},M_x)}\&GreaterEqual;a\%,$ Then repeat A4.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, described in described A3 step pipeline valve produce destroy carry out the method that judges as:

When external applied load is bending moment, as maximum stress value σ _maxmaterial yield strength σ more than 1 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=σ _y;

When external applied load is torsional moment, as maximum stress value σ _maxmaterial yield strength σ more than 1 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=σ _y;

When external applied load is axial load, as maximum stress value σ _maxmaterial yield strength σ more than 0.5 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=0.5 σ _y.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, the method for finely tuning external applied load value in described steps A 3 is:

The relational expression of the external applied load value M' after fine setting and last external applied load value M is, M '=kM;

Wherein k is correction factor, and the result of determination of load value M is pipeline valve when not producing destruction outside, during calculating limit bending moment, and k value 1.5; During calculating limit torsional moment, k value 1.1; During calculating limit axial load, k value 1.2; The result of determination of load value M is pipeline valve when can produce destruction outside, during calculating limit bending moment, and k value 1/1.5; During calculating limit torsional moment, k value 1/1.1; During calculating limit axial load, k value 1/1.2.

Pipeline valve safety evaluation method based on limit external load calculation of the present invention, in described S6 step, described stress assess method is: in described S6 step, and application Stress Linearization method carries out the evaluation of stress;

Following condition need be met when the assessment result of described security performance is safe simultaneously:

A, primary general membrane stress is no more than the material permissible stress of 1.0 times; Or local membrane stress is no more than the material permissible stress of 1.5 times;

B, primary general membrane stress or a local membrane stress add the material permissible stress that primary bending stress is no more than 1.5 times;

C, primary stress adds the material permissible stress that secondary stress is no more than 3 times;

D, parts maximum stress is no more than the material permissible stress of 3 times.

The present invention compared with prior art has the following advantages:

(1) the pipeline valve safety evaluation method based on limit external load calculation of the present invention, before model machine is produced, just can consider that external applied load is on the impact of pipeline valve, eliminate the hidden danger of quality existed in designed product, do not need method by experiment and just can obtain in the layout design stage the maximum external applied load technical data that pipeline valve can bear, and can judge whether the strength character of valve meets design requirement, prediction potential risks, and design can be optimized according to result, so not only can reduce the cost of advanced development cost and saving development test, and the construction cycle of product can also be shortened.

(2) the pipeline valve safety evaluation method based on limit external load calculation of the present invention, by defining symmetrical border and adopting 1/2 model can reduce the calculated amount of half, make the computation process speed of the pipeline valve safety evaluation method based on limit external load calculation of the present invention improve about one times, save computing time.

(3) the pipeline valve safety evaluation method based on limit external load calculation of the present invention, extreme flexion moment, limit torsional moment and limit axial load calculate separately under these three kinds of load boundary conditions of maximum working pressure (MWP) and bending moment or maximum working pressure (MWP) and torsional moment or maximum working pressure (MWP) and axial load, by linear scaling method fine setting external applied load value with the method for mean value convergence is accurate must obtain ultimate load value, computation process rapid and convenient.

(4) the pipeline valve safety evaluation method based on limit external load calculation of the present invention, 4 judge conditions are adopted to carry out counter stress evaluation, all sidedly, comprehensively to the structural strength of valve body whether can meet the demands and evaluate, the pipeline valve safety evaluation method based on limit external load calculation of the present embodiment is matched with real test findings effectively.

Accompanying drawing explanation

In order to make content of the present invention be more likely to be clearly understood, below according to a particular embodiment of the invention and by reference to the accompanying drawings, the present invention is further detailed explanation, wherein

Fig. 1 is the process flow diagram of the pipeline valve safety evaluation method that the present invention is based on limit external load calculation;

Fig. 2 is the stress and strain model figure of the 3-D geometric model figure of the embodiment of the present invention 1;

Fig. 3 is the external applied load schematic diagram of the embodiment of the present invention 1.

In figure, Reference numeral is expressed as: 1-pipeline; 2-valve body; 3-web member; 4-support component.

Embodiment

Below in conjunction with drawings and Examples, the present invention will be described in detail.

Embodiment 1

The present embodiment provides a kind of pipeline valve safety evaluation method based on limit external load calculation, and flow process as shown in Figure 1, comprises the following steps:

S1: the 3-D geometric model setting up valve body 2, pipeline 1 and web member 3

3 d geometric modeling software SolidWorks is utilized to set up 3-D geometric model, model component comprises valve body 2, web member 3 (welding sleeve) and pipeline 1, in model, the length of pipeline 1 is the pipe diameter of 2 times, because model and boundary condition have symmetry, gets 1/2 model.The maximum working pressure (MWP) P=15MPa of this pipeline valve, the following list of material parameter of valve body 2, pipeline 1, web member 3.The external applied load signal of this valve as shown in Figure 3.By defining symmetrical border and adopting 1/2 model can reduce the calculated amount of half, make the computation process speed of the pipeline valve safety evaluation method based on limit external load calculation of the present embodiment improve about one times, saved computing time.Certainly, according to calculating needs, the length of pipeline 1 also can be more than 2 times of pipe diameter, such as 2.5 times, 3 times, 4 times etc.

Table parts material parameter table

Parts title	Title material	Yield strength value σ y(MPa)	Permissible stress value S (MPa)
				Valve body	ASTM A352-LCC	285	138
Web member	ASTM A350-LF6CL.1	360	240
				Pipeline	GB/T 9711L415M	415	276

S2: FEM meshing is carried out to 3-D geometric model and sets up finite element grid model;

3-D geometric model imports finite element pre-processing software and carries out stress and strain model, as shown in Figure 2, the unit divided is mainly based on hexahedron, certainly, for improving counting yield, the grid of non-attached area can be thicker, and the area grid engaged with pipeline at valve body will segment, and the three-dimensional grid model divided as shown in Figure 2.The method setting up finite element grid model is: carry out stress and strain model to described 3-D geometric model, and the binding relationship arranging surface of contact between valve body, pipeline and web member completes to the dynamic changes process set up between valve body, pipeline and web member and sets up finite element grid model.

S3: set up limit external applied load limited element calculation model on finite element grid model;

The method setting up limit external applied load limited element calculation model is: in described finite element grid model, arrange the material properties of valve body, pipeline and web member and symmetrical border, displacement boundary conditions and load boundary condition complete and set up limit external applied load limited element calculation model, described external applied load comprises bending moment, torsional moment and axial load.

Described load boundary condition is:

During calculating limit bending moment, load boundary condition is act on the bending moment of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity;

During calculating limit torsional moment, load boundary condition is act on the torsional moment of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity;

During calculating limit axial load, load boundary condition is act on the axial load of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity.

Concrete, the material properties of valve body 2, pipeline 1, web member 3 is defined in finite element analysis software ANSYS, described material properties comprises elastic modulus, Poisson ratio, the longitudinal section defined in 1/2 model is symmetrical border, definition displacement boundary conditions, is also defined as staff cultivation by valve support zone.Limited element calculation model limit external applied load calculates separately under maximum working pressure (MWP).Bending moment, torsional moment and axial load and maximum working pressure (MWP) individually load as load boundary condition, form following three kinds of independently design conditions (i.e. three limit external applied load limited element calculation models), the load boundary condition of each design condition is:

Design condition 1: the bending moment (being labeled as W in Fig. 3) and the maximum working pressure (MWP) that act on pipe ends;

Design condition 2: the torsional moment (being labeled as N in Fig. 3) and the maximum working pressure (MWP) that act on pipe ends;

Design condition 3: the axial load (being labeled as F in Fig. 3) and the maximum working pressure (MWP) that act on pipe ends;

S4: calculate limit external applied load by limit external applied load limited element calculation model;

Load boundary condition setting two load steps of above-mentioned each limit external applied load limited element calculation model, first apply maximum working pressure (MWP) 15MPa at mould impression, then apply external applied load at pipeline 1 both sides end face.Because external applied load (bending moment W, torsional moment N and axial load F) is unknown quantity, first carry out being applied on model with an initial value during concrete applying.

Described limit external applied load value M _{the limit}calculating comprise the following steps:

A1: presetting external applied load value M is initial value M _begin;

A2: the maximum stress value σ of pipeline valve when calculating described external applied load value M by finite element model _max, and to this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination;

A3: according to the maximum stress value σ recalculating the pipeline valve of its correspondence after fine setting external applied load value _maxand for this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination; The result of determination that the result of determination this obtained and last time obtain compares, and if the same circulate this step; If different, then enter next step;

To pipeline valve produce destroy the method that judges as:

When external applied load is bending moment, as maximum stress value σ _maxmaterial yield strength σ more than 1 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=σ _y;

When external applied load is torsional moment, as maximum stress value σ _maxmaterial yield strength σ more than 1 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=σ _y;

When external applied load is axial load, as maximum stress value σ _maxmaterial yield strength σ more than 0.5 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=0.5 σ _y;

What deserves to be explained is, here the maximum stress value σ of valve body, web member and pipeline _maxneed to calculate respectively, only have the maximum stress value that valve body, web member and pipeline bear all not exceed the maximum stress value σ of respective material _max, under load value effect in addition, whether can produce the result destroying and judge just as " not producing destruction " to pipeline valve; As long as have the arbitrary maximum stress value born of valve body, web member and pipeline beyond the maximum stress value σ of respective material _max, whether can produce pipeline valve under load value effect in addition and destroy the result that judge and be " produce and destroy ".

A4: use formula recalculate external applied load value, wherein M _mwith M _nfor different and immediate two the external applied load values of numerical value of result of determination; " the maximum stress value σ of corresponding pipeline valve that recalculates M _maxand for this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination;

A5: if wherein M _xfor " the immediate external applied load value that the result of determination calculated is different then thinks ultimate load value from external applied load value M calculate and terminate;

If $\frac{|M^{\&Prime;}-M_x|}{\mathrm{MIN}(M^{\&Prime;},M_x)}\&GreaterEqual;1\%,$ Then repeat A4.

It should be noted that, if in A5 step time, then use M and " replace the M in A4 step in this computation process _mor M _none of them, replacement be M _mor M _nin with external applied load value M " that numerical value that the result of determination calculated is identical, such as external applied load value M _mthe result judged as " not producing destruction ", and M _nthe result judged as " produce destroy ", " the result judged as " not producing destruction ", when repeating A4 step, M " and M if M _nbe just result of determination difference and immediate two the external applied load values of numerical value, " upgrade M with M _mcalculate new M " value.If M " the result judged as " produce destroy ", " upgrade M with M _ncalculate new M " value.What deserves to be explained is, the end condition calculating end in A5 step is the present embodiment chooses a=1, in the less demanding situation of computational accuracy, a% can be replaced to larger numerical value, when computational accuracy requires high, a% can be replaced to less numerical value, the value that usual a chooses is 0.01,0.05,0.1,2,5,10 etc.

Specifically calculate with regard to bending moment, torsional moment and axial load below, concrete computation process is as follows:

1) to the computation process (decimal is rounded up) of extreme flexion moment values: first apply initial value M _begin=115000Nm.

M _begin=115000Nm, it is 171.76MPa that maximum stress value is positioned at sleeve place, does not now also reach stress limit value σ _limit=σ _ywhether (the material yield strength value of sleeve is 360MPa), thus can destroy to pipeline valve generation the result judged and be " not producing destruction ".

First time calculates, M ₁=1.5*M=172500, does not produce destruction;

Second time calculates, M ₂=1.5*M ₁=258750, do not produce destruction;

Third time calculates, M ₃=1.5*M ₂=388125, do not produce destruction;

Calculate for 4th time, M ₄=1.5*M ₃=582187, produce and destroy; Due to M ₄with M ₃the judgement of stress limit value different, thus next continue fine setting external applied load value according to mean value convergence method.

$M_5=\frac{M_3+M_4}{2}=485158,$ Do not produce destruction, $\frac{|M_5-M_4|}{\mathrm{MIN}(M_5,M_4)}=\frac{M_4-M_5}{M_5}=20\%\&GreaterEqual;1\%;$

$M_6=\frac{M_4+M_5}{2}=533672,$ Do not produce destruction, $\frac{|M_5-M_6|}{\mathrm{MIN}(M_5,M_6)}=\frac{M_6-M_5}{M_5}=10\%\&GreaterEqual;1\%;$

$M_7=\frac{M_4+M_6}{2}=557930,$ Produce and destroy, $\frac{|M_7-M_6|}{\mathrm{MIN}(M_7,M_6)}=\frac{M_7-M_6}{M_6}=4.5\%\&GreaterEqual;1\%;$

$M_8=\frac{M_7+M_6}{2}=545801,$ Do not produce destruction, $\frac{|M_7-M_8|}{\mathrm{MIN}(M_7,M_8)}=\frac{M_7-M_8}{M_8}=2.2\%\&GreaterEqual;1\%;$

$M_9=\frac{M_7+M_8}{2}=551865,$ Produce and destroy, $\frac{|M_9-M_8|}{\mathrm{MIN}(M_9,M_7)}=\frac{M_9-M_8}{M_8}=1.1\%\&GreaterEqual;1\%;$

$M_{10}=\frac{M_8+M_9}{2}=548833,$ Do not produce destruction, $\frac{|M_{10}-M_9|}{\mathrm{MIN}(M_{10},M_9)}=\frac{M_9-M_{10}}{M_{10}}=0.5\%\&le;1\%;$

Then get for extreme flexion moment values.

2) computation process (decimal is rounded up) of limit torsional moment value: first apply initial value M _begin=1000000Nm.

M _begin=1000000Nm, does not now also produce destruction;

First time calculates, M ₁=1.1*M=1100000, does not produce destruction;

Second time calculates, M ₂=1.1*M ₁=1210000, do not produce destruction;

Third time calculates, M ₃=1.1*M ₂=1331000, do not produce destruction;

Calculate for 4th time, M ₄=1.1*M ₃=1464100, do not produce destruction;

Calculate for 5th time, M ₅=1.1*M ₄=1610510, exceed stress limit value; Due to M ₄with M ₅the judgement of stress limit value different, thus next continue fine setting external applied load value according to mean value convergence method.

$M_6=\frac{M_5+M_4}{2}=1537305,$ Do not produce destruction; $\frac{|M_6-M_5|}{\mathrm{MIN}(M_6,M_5)}=\frac{M_5-M_6}{M_5}=4.7\%\&GreaterEqual;1\%$

$M_7=\frac{M_6+M_5}{2}=1573908,$ Do not produce destruction; $\frac{|M_5-M_7|}{\mathrm{MIN}(M_5,M_7)}=\frac{M_5-M_7}{M_7}=2.3\%\&GreaterEqual;1\%$

$M_8=\frac{M_7+M_5}{2}=1592209,$ Produce and destroy; $\frac{|M_8-M_7|}{\mathrm{MIN}(M_8,M_7)}=\frac{M_8-M_7}{M_7}=1.1\%\&GreaterEqual;1\%$

$M_9=\frac{M_7+M_8}{2}=1583058,$ Do not produce destruction; $\frac{|M_9-M_8|}{\mathrm{MIN}(M_8,M_9)}=\frac{M_8-M_9}{M_9}=0.5\%\&le;1\%$

$M_{10}=\frac{M_9+M_8}{2}=1587633$

Limit torsional moment value M can be determined _{the limit}=1587633Nm.

3) limit shaft is to the computation process (being rounded up by decimal) of load value: first apply initial value M _begin=1000000Nm.

M _begin=150000Nm, does not now also produce destruction;

First time calculates, M ₁=1.2*M=180000, does not produce destruction;

Second time calculates, M ₂=1.2*M ₁=216000, do not produce destruction;

Third time calculates, M ₃=1.2*M ₂=259200, do not produce destruction;

Calculate for 4th time, M ₄=1.2*M ₃=311040, do not produce destruction;

Calculate for 5th time, M ₅=1.2*M ₄=373248, produce and destroy; Due to M ₄with M ₅the judgement of stress limit value different, thus next continue fine setting external applied load value according to mean value convergence method.

$M_6=\frac{M_5+M_4}{2}=342144,$ Produce and destroy $\frac{|M_6-M_4|}{\mathrm{MIN}(M_6,M_4)}=\frac{M_6-M_4}{M_4}=10\%\&GreaterEqual;1\%$

$M_7=\frac{M_6+M_4}{2}=326592,$ Do not produce destruction; $\frac{|M_6-M_7|}{\mathrm{MIN}(M_6,M_7)}=\frac{M_6-M_7}{M_7}=4.8\%\&GreaterEqual;1\%$

$M_8=\frac{M_7+M_6}{2}=334368,$ Produce and destroy; $\frac{|M_7-M_8|}{\mathrm{MIN}(M_7,M_8)}=\frac{M_8-M_7}{M_7}=2.4\%\&GreaterEqual;1\%$

$M_9=\frac{M_7+M_8}{2}=330480,$ Produce and destroy; $\frac{|M_9-M_7|}{\mathrm{MIN}(M_7,M_9)}=\frac{M_9-M_7}{M_7}=1.2\%\&GreaterEqual;1\%$

$M_{10}=\frac{M_9+M_7}{2}=328536,$ Do not produce destruction; $\frac{|M_{10}-M_9|}{\mathrm{MIN}(M_{10},M_9)}=\frac{M_9-M_{10}}{M_{10}}=0.6\%\&le;1\%$

Then get for limit shaft is to load value.

It is to be noted, when calculating extreme flexion moment, limit torsional moment, limit axial load, if initial value is chosen excessive, the result of determination that whether can produce destruction at this initial value underground pipelines valve is made to be when can produce destruction, then respectively by k value 1/1.5 (during calculating limit bending moment); K value 1/1.1 (during calculating limit torsional moment); K value 1/1.2 (during calculating limit axial load), computation process and said process are in like manner.Make, when adopting linear scaling method fine setting external applied load value, can computation process be accelerated, and the degree of accuracy of numerical value can be ensured by arranging k value.

Extreme flexion moment, limit torsional moment and limit axial load are calculated separately under maximum working pressure (MWP), and by linear scaling method fine setting external applied load value with the method for mean value convergence is accurate must obtain ultimate load value, and computation process rapid and convenient.

S5: setting up imposed load on finite element grid model is extreme flexion moment, limit torsional moment and the limit axial load associating external applied load limited element calculation model also simultaneously under maximum working pressure (MWP);

Utilize limited element calculation model and keep displacement boundary conditions constant, the ultimate load (comprising extreme flexion moment, limit torsional moment and limit axial load) S4 step obtained and maximum working pressure (MWP) are applied on model simultaneously.

S6: by associating external applied load limited element calculation model calculate pipeline valve stress distribution and according to the security performance of stress distribution determination pipeline valve.

The associating external applied load limited element calculation model set up is calculated, obtains the stress distribution of valve body.According to result, parts maximum stress (namely whole associating external applied load limited element calculation model calculates the maximal value of the rear stress obtained) is 383.77MPa, produce on valve inner muscle, pipeline (or web member) and valve body join domain produce higher stress, occur that the stress assess line through wall thickness is chosen in position (i.e. pipeline or web member and valve body join domain) at parts maximum stress.

Then classify by the stress of Stress Linearization method to this stress assess line in finite element analysis software ANSYS and extract, therefrom extracting primary bending stress and primary stress and secondary stress and primary general membrane stress or a local membrane stress.Following condition need be met when the assessment result of security performance is safe simultaneously:

(1) primary general membrane stress is no more than the material permissible stress of 1.0 times, i.e. σ _m≤ 1.0S; Or local membrane stress is no more than the material permissible stress of 1.5 times, i.e. σ _l≤ 1.5S;

(2) membrane stresses or a local membrane stress add the material permissible stress that primary bending stress is no more than 1.5 times, i.e. σ _m(or σ _l)+σ _b≤ 1.5S;

(3) primary stress adds the material permissible stress that secondary stress is no more than 3 times, i.e. P _l+ P _b+ Q≤3.0S;

(4) parts maximum stress is no more than the material permissible stress of 3 times, i.e. σ _max≤ 3.0S;

Valve body ultimate load and maximum working stress symphyogenetic stress assess result as follows:

(1) primary general membrane stress σ _m=69.7≤1.0S=138MPa, meets the demands;

(2) primary general membrane stress adds primary bending stress σ _m+ σ _b=90.3≤1.5S=217MPa, meets the demands;

(3) primary stress adds secondary stress P _l+ P _b+ Q=102.9≤3.0S=414MPa, meets the demands;

(4) parts maximum stress σ _max=383.77≤3.0S=414MPa, meets the demands;

Therefore, under ultimate load and maximum working stress synergy, the structural strength of valve body meets the demands completely.4 above-mentioned judge conditions are adopted to carry out counter stress evaluation, all sidedly, comprehensively to the structural strength of valve body whether can meet the demands and evaluate, the pipeline valve safety evaluation method based on limit external load calculation of the present embodiment is matched with real test findings effectively.

It is pointed out that if valve body does not meet the demands in ultimate load and the symphyogenetic stress assess result of maximum working stress, then carry out the optimal design of valve body, more again above calculating and assessment, until meet design requirement.

Through above each step, limit external applied load (extreme flexion moment, limit torsional moment and the limit axial load) data that pipeline valve system can bear can be obtained, and the structural strength security performance of valve (mainly referring to valve body) under these limit external applied loads and maximum working pressure (MWP) acting in conjunction can be predicted.The above-mentioned pipeline valve safety evaluation method based on limit external load calculation, before model machine is produced, just can consider that external applied load is on the impact of pipeline valve, eliminate the hidden danger of quality existed in designed product, thus do not need method by experiment and just can obtain in the layout design stage the maximum external applied load technical data that pipeline valve can bear, and can judge whether the strength character of valve meets design requirement, prediction potential risks, and design can be optimized according to result, so not only can reduce the cost of advanced development cost and saving development test, and the construction cycle of product can also be shortened.Certainly, the pipeline valve that the pipeline valve safety evaluation method based on limit external load calculation of the present embodiment is also applicable to having manufactured product carries out safety assessment, if pipeline valve has completed product manufacturing when so setting up 3-D geometric model, exactly three-dimensional modeling is carried out to valve body 2, pipeline 1, these three entities of web member 3.

Obviously, above-described embodiment is only used to clearly example is described, and the restriction not to embodiment.For the engineering technical personnel in affiliated field; can also make other changes in different forms on the basis of the above description; here exhaustive without the need to also giving all embodiments, and thus the apparent change of extending out or variation be still among the protection domain of the invention.

Claims (10)

1., based on a pipeline valve safety evaluation method for limit external load calculation, it is characterized in that, comprise the following steps:

S1: the 3-D geometric model setting up valve body, pipeline and web member;

S2: FEM meshing is carried out to 3-D geometric model and sets up finite element grid model;

S3: set up limit external applied load limited element calculation model on finite element grid model;

S4: calculate limit external applied load by limit external applied load limited element calculation model;

S5: set up on finite element grid model multiple limit external applied load and maximum working pressure (MWP) act on simultaneously under associating external applied load limited element calculation model;

S6: by associating external applied load limited element calculation model calculate pipeline valve stress distribution and according to the security performance of stress distribution determination pipeline valve.

2. as claimed in claim 1 based on the pipeline valve safety evaluation method of limit external load calculation, it is characterized in that, in described S1 step, utilize 3 d geometric modeling software to set up 1/2 3-D geometric model to valve body, pipeline and web member, the length of pipeline described in described model is greater than more than 2 times of pipe diameter.

3. as claimed in claim 1 or 2 based on the pipeline valve safety evaluation method of limit external load calculation, it is characterized in that, in described S2 step, the method setting up finite element grid model is: carry out stress and strain model to described 3-D geometric model, and the binding relationship arranging surface of contact between valve body, pipeline and web member completes to the dynamic changes process set up between valve body, pipeline and web member and sets up finite element grid model.

4. the pipeline valve safety evaluation method based on limit external load calculation as described in as arbitrary in claim 1-3, it is characterized in that, in described S3 step, the method setting up limit external applied load limited element calculation model is: in described finite element grid model, arrange the material properties of valve body, pipeline and web member and symmetrical border, displacement boundary conditions and load boundary condition complete and set up limit external applied load limited element calculation model; Described external applied load comprises bending moment, torsional moment and axial load.

5., as claimed in claim 4 based on the pipeline valve safety evaluation method of limit external load calculation, it is characterized in that, described load boundary condition is:

During calculating limit bending moment, load boundary condition is act on the bending moment of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity;

During calculating limit torsional moment, load boundary condition is act on the torsional moment of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity;

During calculating limit axial load, load boundary condition is act on the axial load of pipe ends and the maximum working pressure (MWP) be applied on pipeline and valve cavity.

6. the pipeline valve safety evaluation method based on limit external load calculation as described in claim 4 or 5, is characterized in that, in described S3 step, described material properties comprises elastic modulus, Poisson ratio; Described displacement boundary conditions for valve support zone is defined as staff cultivation, and defines symmetrical border in described S3 step.

7. the pipeline valve safety evaluation method based on limit external load calculation as described in as arbitrary in claim 1-6, is characterized in that, in described S4 step, and described limit external applied load value M _{the limit}calculating comprise the following steps:

A1: presetting external applied load value M is initial value M _begin;

A2: the maximum stress value σ of pipeline valve when calculating described external applied load value M by finite element model _max, and to this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination;

A3: according to the maximum stress value σ recalculating the pipeline valve of its correspondence after fine setting external applied load value _maxand for this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination; The result of determination that the result of determination this obtained and last time obtain compares, and if the same circulate this step; If different, then enter next step;

A4: use formula recalculate external applied load value, wherein M _mwith M _nfor different and immediate two the external applied load values of numerical value of result of determination; " the maximum stress value σ of corresponding pipeline valve that recalculates M _maxand for this maximum stress value σ _maxwhether can produce destruction to pipeline valve to judge, obtain result of determination;

A5: if 0<a≤10, wherein M _xfor " the immediate external applied load value that the result of determination calculated is different then thinks ultimate load value from external applied load value M calculate and terminate;

If $\frac{|M^{\&prime;\&prime;}-M_x|}{\mathrm{MIN}(M^{\&prime;\&prime;},M_x)}\&GreaterEqual;a\%,$ Then repeat A4.

8., as claimed in claim 7 based on the pipeline valve safety evaluation method of limit external load calculation, it is characterized in that, described in described A3 step pipeline valve produce destroy the method carrying out judging as:

When external applied load is bending moment, as maximum stress value σ _maxmaterial yield strength σ more than 1 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=σ _y;

When external applied load is torsional moment, as maximum stress value σ _maxmaterial yield strength σ more than 1 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=σ _y;

When external applied load is axial load, as maximum stress value σ _maxmaterial yield strength σ more than 0.5 times _y, namely think that destroying appears in described pipeline valve, now σ _limit=0.5 σ _y.

9., as claimed in claim 7 or 8 based on the pipeline valve safety evaluation method of limit external load calculation, it is characterized in that, the method for finely tuning external applied load value in described steps A 3 is:

The relational expression of the external applied load value M' after fine setting and last external applied load value M is, M'=kM;

Wherein k is correction factor, and the result of determination of load value M is pipeline valve when not producing destruction outside, during calculating limit bending moment, and k value 1.5; During calculating limit torsional moment, k value 1.1; During calculating limit axial load, k value 1.2; The result of determination of load value M is pipeline valve when can produce destruction outside, during calculating limit bending moment, and k value 1/1.5; During calculating limit torsional moment, k value 1/1.1; During calculating limit axial load, k value 1/1.2.

10. the pipeline valve safety evaluation method based on limit external load calculation as described in as arbitrary in claim 1-9, is characterized in that, in described S6 step, application Stress Linearization method carries out the evaluation of stress:

Following condition need be met when the assessment result of described security performance is safe simultaneously:

A, primary general membrane stress is no more than the material permissible stress of 1.0 times; Or local membrane stress is no more than the material permissible stress of 1.5 times;

B, primary general membrane stress or a local membrane stress add the material permissible stress that primary bending stress is no more than 1.5 times;

C, primary stress adds the material permissible stress that secondary stress is no more than 3 times;

D, parts maximum stress is no more than the material permissible stress of 3 times.