Application of advanced technology in the domestic large pipeline valve:all welded ball valve

Application of advanced technology in the domestic large pipeline valve

All rely on imports in the year 2000 China’s large-scale all-welded pipeline ball valves. Localization process of digestion, absorption and innovation through the use of modern advanced design techniques, such as reverse engineering, screening engineering, numerical analysis of finite element method, anti-breaking design, the design of anti-corrosion, low torque design and advanced manufacturing technology and technology and equipment, was a success.
Reverse engineering technology and its applications

The key technology of all-welded body pipeline ball valves (Figure 1) is the body welding, welding ball valve assembly is the last step, not heat-treated. Therefore, the development of free weld heat treatment after welding technology research, anti-Sum learn the foreign pipeline valve welding process with technology product localization shortcut.

2.1 welding base metal inverse

(Figure 2) the toughness of the reserve in order to increase the welding joint, the welding base material and the valve body material is in addition to meet the basic requirements ANSIB1634, API6D, ASTMA105 ASTMA350 standard, should be higher than the standard in order to improve the impact toughness of the base material. Comprehensive determination of a comprehensive analysis of the foreign ball valve material and mechanical properties, elected for Free weld heat treatment after welding base metal. Its chemical composition (C, Mn, P, S, etc.) in the steel smelting process control, the more stringent requirements on the mechanical properties of the material and hardness, and to develop the the forgings procurement technology file, as a business standards.

2.2 welding materials inverse
Determined through a comprehensive analysis of the the foreign ball valve weld and heat affected zone material chemical composition, hardness values ​​of the distribution. Chemical composition of domestic wire and imported wire the welded samples as well as the welding residual stress measurement sample to do a comparative analysis to determine the selection of imported flux and low domestic wire matching principle, reduce the welding residual stress, improve weld toughness reserves.

2.3 welding parameters Reverse
Reverse the process parameters from a foreign valve product weld size. Such as from the weld width of 25mm, the height of 3mm, the surface of the Tsim phylloid ichthyosis stripes, Gibbous surface within the weld surface morphology, thrust reversers, and estimating the wire diameter, the welding current, voltage, and line speed, etc., and after repeated The different parameters of the simulation and the sample comparison, the welding parameters is optimized for a low residual stress, and low welding deformation.

The 2.4 welding equipment Reverse
On the basis of comprehensive analysis of foreign welding equipment, to create a low-cost dedicated welder. Such as the use of foreign rotatable torch conductive Tsui structural design to improve the performance of the slag detachability. Anti-string action and anti-beating roller frame design to meet the needs of a narrow gap welding groove. Can be adjustable wire feeder design meet the requirements of different welding processes. Using the Lincoln power, uninterrupted run of semi-automatic submerged arc welding machine can.

3 Screening engineering technology and its applications
In the digestion and absorption of the technology of foreign products by the new theory, advanced technology and technical standards of some of the foreign products technology screening. Enhance the technological innovation capability, with independent intellectual property rights. By screening can improve the technological content of products, improve product quality, which is the key product localization work.

3.1 transitional segment material screening
In some foreign company ASTMA694 F56, F60 as the valves and of X70, X80 pipe the transition weld material, this material is only applicable to the high-pressure liquid pipe (ANSIB314), unsuitable for the valve material and the material of the high-pressure gas pipe (ANSIB318) .
Valve design standard ANSIB1634 this material, nor material pressure – temperature ratings data. Pipeline the standard ANSIB318 in not included in Appendix A reference standard, and included in other publications not referenced in Appendix C. Analysis of this material, and only after a smelting, the chemical composition is not strictly controlled, the impact toughness is not required. Therefore, it can not organizations and the ultrapure smelting, acicular ferrite X70 and X80 grade steel phase soldering, otherwise the welded joints of dissimilar materials organization is not continuous, the chemical composition is not continuous, discontinuous material properties and the stress singularity.
The in the F56 ASTMA694, F60 can not as a valve material has been recognized in the U.S. Engineers reply. And on March 27, 2009 published in the ASMEB1634 explanation.

3.2 fracture toughness tests with Free welding heat treatment after a safety assessment
Weld heat treatment which is the standard provisions of the of ASME relevant standards, API6D, ASTMA105, ASTMA350. The actual situation of the product can not be heat treatment, none of this to make a scientific explanation and evaluation of foreign valve company. Draw on domestic practices in major projects in the subsea pipelines, offshore oil platforms, fracture mechanics theory, according to BS7448 fracture toughness CTOD values ​​test methods and API1104 of Appendix A and DNV assessment standards made the whole thickness of 140mm welded joints CTOD test , as well as the standard test ring circumferential residual stress determination, failure assessment curve FAD, Free post-weld heat treatment of the safety assessment of the test results.

3.3 The use of welded structures in the neck
Foreign company fully welded valve body pipeline ball valves, valve neck and valve body bolts, valve body neck for typical structural discontinuity design, valve body the neck medial produce stress concentration of 25 ~ 3 times, work stress . The role of this part of the material in the inner pressure and the external actuators torque composite load is a hidden structure, but also the external leakage of a seal point. By finite element analysis, to prove the existence of hidden dangers. Therefore, the neck welded structure (Figure 3), to improve the stress state, and eliminate leakage points.

Finite element numerical analysis method and its application

The 4.1 body strength stress analysis

Select a minimum wall thickness of the conventional design of the valve body in accordance with the ASMEB1634 rules. This approach can not be applied to the the neck valve body structure design, also can not analyze the the valve body stress intensity under complex loading conditions. NA pipeline valve for long-distance running in the wild harsh geological conditions and weather conditions, and can only be used for preliminary design. The valve may exist in the long-distance pipeline external bending moments caused by ground subsidence or landslides may exist due to installation, pipeline tension and pressure caused by the temperature difference between day and night or summer and winter temperature difference. In both pressure and external load complex load state, only by a numerical analysis method to simulate actual working conditions (Figure 4). Dynamic mechanical equipment identification in accordance with the ASMEQME-1 nuclear power plant about the end of the load test requirements, the external load is applied (ie the moment through the stem center plane, tension and pressure is applied to the pipe centerline), according to ASMEQME-1 and the ASME nuclear power plant manufacturing standards, external piping material yield bending loads, external tensile load and external compression test load as finite element analysis plus load value, this value is also designed as a composite load analysis based on. Finite element analysis and design of body strength four aspects. The valve body of the valve body 12 times the working pressure stress intensity. External bending loads and pressure valve body under the joint action of the valve body strength analysis. External tensile load pressure and the valve body under the joint action of the body strength. External compressive load pressure and the valve body under the joint action of the body strength.

The external loading analysis calculations and experiments, it is assumed that bending load, tensile load and compressive load is applied to a separate, unrelated.


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