he special plug valves doors maintenance, including the The kelly cock doors repair what is kelly cock door? Following valve repair factory Jiangyin Oulei Si tells you: the kelly cock doors is one of the important tools of drilling BOP system, including upper and lower plug valve door on the the plug valves doors ontology is installed in the faucet lower end of the connector and square drill pipe between the upper ends of the lower part of the plug valve door body installed between the kelly and drill string. Its main use is the possible blowout cases faucet hose, or riser stabbed leakage or broken can be used to close within the drill string through holes. Stopcock door to prevent the blowout plays an important role within the drillstring. In the practical application of some plug valves door under poor working load of failure due to fracture, not only directly affect the normal work of drilling wells discontinued, end-of-life, and even causing casualties and cause.
The stopcock door body is the major parts of the stopcock door knob installed generally as a unitary structure, the side wall openings. STXS135 type plug valve door body,
The plug valve door body fracture problem, has been plagued manufacturers and users. Solve this problem in different work load plug valve door body mechanics theory, to explore the body's stress concentration problems, the use of ANSYS software, to establish the finite element model of the valve body, bilinear kinematic hardening model guidelines [4-5], respectively, of the body pulling, twisting, internal pressure and other loads of body strength detailed analysis, nonlinear finite element analysis, summed up the law of the distribution of structural stress, and to create conditions for the further optimization of the design . Identify the main reason of the stress concentration in the valve body, and make recommendations for improvement.
The plug valves doors finite element model of the body
Principles in the valve body modeling
(1) The shape of the model and the actual structure of the body mechanical remains geometrically similar, but the key part of the study no large effect can be simplified or ignored.
(2) to the lower cock, the internal threaded portion is constricting portion, the external threaded portion is a loading portion, the threads of the mesh will be accounted for a large number of meshing main consideration of the strength of the other parts of the stopcock door, so the external thread Some force equivalent processing, two threaded parts are simplified to the cone.
(3) the knob hole part of the body is the focus of the analysis, the structure all the reservations. Chamfer, the central part of the trench and arc transition section omitted.
(4) In order to facilitate accurate analysis calculated, according to the characteristics of the symmetrical structure of the valve, the main body split, half of analysis, impose constraints on the split plane.
Finite element model
Free mesh (Free) divided solid model, in order to obtain a better calculation accuracy, the use of high precision space tetrahedral 10-node element mesh density control Smart (Smart) cell size control. Size level is set to 6. After meshing, finite element mesh model under cock. Section 6614 of 10963 points, the number of units.
Tensile load finite element analysis
Strength analysis and calculation, design structure are generally calculated stress to dangerous parts of the structure of high-stress zone is less than the allowable stress as a design criteria, to determine whether the design of the structure to meet the design requirements. This is always the assumption that the material is elastic stage. However, the structural strength calculation, obtained in accordance with the linear elastic calculated stress beyond the elastic limit to enter the stage of plastic deformation, linear elastic strength calculation method can not meet the requirements of the calculation. The material should be in accordance with the calculation of the elastic-plastic law stress analysis and strength design, to improve the accuracy and precision of the calculated results.
The plug valves doors body material
Plug valve door body material for low-carbon alloy steel 40CrMnMo, material yield limit of 640 MPa, the fracture limit of 750 MPa the shear modulus 1652.5MPa, bear the load reaches the yield limit, the stress and strain no longer maintain a proportional relationship into the nonlinear stage . Using the classic bilinear kinematic hardening (BKIN) guidelines [7], the guidelines for the use of kinematic hardening yield criterion, so contains Bauschinger effect, this option is used in compliance with VonMises yield criterion, initial each the small strain isotropic materials, which includes most of the metal, so the use of this material hardening model. The body suffered tension simplify uniform load load at the right end of the cross-section. Tensile load changes take 2250-4516kN (to different rig of hook DeadWeight for reference stress the nephogram and stress curve derived, respectively, as the tensile load gradually increases, the local stress concentration range gradually expanded , but always in the body due process requirements, the main open the inner wall of the hole and parallel to the X-direction up and down diffusion hole wall the other direction stress, stress in other parts of the body are much less than the Maximum Stress of the hole wall. two different diameters of the stepped hole, to withstand tensile load, the inner wall of the orifice of the stress concentration is more serious when the valve body has been stretched when the load reaches a certain value, the maximum stress near the yield, but with the load increase the maximum stress value slow rising curve, using bilinear kinematic hardening criteria analysis linear elastic stress is greater than the calculated allowable stress, so that the plastic properties of the material can be considered to be correctly calculated structural strength so as to achieve the purpose of full utilization of the material.
Finite element analysis of the body by the internal pressure
When When the drillstring occurred within the blowout, the pressure of the fluid is high, the countries on the the plug valves doors within the BOP pressure must meet certain criteria, different plug valves doors have different requirements, according to the research, combined with the national standards, whichever 70MPa to 130MPa between the pressure values to be analyzed. The chamfer height of the stress cloud 0:00, internal pressure stress the extremum change curve 130MPa intersecting line at the height variation of the chamfer. Stress change curves intersecting lines at 70MPa when the valve body by internal pressure load, stress extremum concentrated Intersecting line in the knob hole big hole with the body through holes, and mainly small area near in XOY plane. Intersecting lines at the chamfer must intersecting line at the chamfer height taken (1 ~ 1.5) mm more appropriate.
To learn more about the application of the principle of the maintenance of the structure of various types of valves and valve, valve grinding machine coupled with high-quality, effective valve repair work
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