Valve welding standards

Valves are among the most widely used fluid control devices in the petroleum, chemical, metallurgical and energy industries. As an important part of the pipeline system, the valve specifications and types of many, the role is also different. Some used to connect or cut off the media, regulating media pressure or flow, to prevent media pressure exceeds the specified value, to ensure the safe operation of pipelines or equipment. There are also used to separate, mix or distribute media to ensure system conditions. Due to the role of the valve in the pipeline system, the valve manufacturing process will directly affect the safe operation of pipeline equipment. Therefore, the "pressure pipe components manufacturing safety registration and management approach" provides that the valve manufacturing units should be subject to safety registration, only the safety of registered manufacturing units of the valve can be used for the pressure pipe. With the continuous development of working conditions, the performance requirements of the valve are also getting higher and higher, and the related technologies in the manufacture of the products are getting more and more attention. As the valve and pipeline components related to the technical specifications are not complete, such as the valve welding, corrosion resistant surfacing and hardfacing and so there is no clear rule. The valve specificity, whether it can follow the relevant pressure vessel boiler pressure vessel manufacturing technical specifications to be explored, all of these to the valve safety registration review brings some difficulties. This article analyzes the related issues and suggests that new standards should be developed that can be tailored to meet the actual needs so that the technical specifications are more comprehensive and easy to operate. Valve body in the manufacture of large valves generally use the form of welding, and valve body wall thickness is often greater than 38mm. According to the relevant provisions of the pressure vessel at home and abroad, when the thickness of weldment is more than 38mm, it needs to be heat-aged after welding to remove hydrogen and eliminate welding residual stress and restore material plasticity. However, due to the different sealing materials, and thermal aging after welding can lead to the deformation of the valve, the valve is to be heat-treated, or what should be done to ensure the quality of the relevant standards in the country are not provided. At present, foreign large-scale welding valve has entered our market, it should be based on what kind of norms to acceptance or valve welding heat treatment is not required, it is also worth discussing and researching. Therefore, for a particular product, such as a large welded valve, in particular whether or not it is subject to post-weld thermal aging, it is necessary to conduct a comprehensive test which includes evaluation of the weld bevel, joint form, temperature stress distribution or control and elimination of stress deformation Conducted a study to determine the reliability of the welded joint, and to develop appropriate specifications to ensure the quality and reliability of the valve.