Piping and valve knowledge: [Weekly topic] When welding valves to pipes, should the valves be in an open position? (12.20---12.27)
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This post was last edited by WQC on 2010-12-19 at 19:57. When welding valves to pipes, should the valve be in a closed state or an open state?
The valve should be in the open position, so that the soft seal on the valve stem is not damaged by the valve seat at high temperatures
It needs to be opened; otherwise, the air inside the valve will expand and pores may form in the weld. Also, that sealing surface should be kept as far away as possible from hot spots; once it deforms, the sealing efficiency decreases
The valve should be in the open position. When welding pipelines, if the valves are closed, the gas generated inside the pipeline cannot escape, which affects the formation of the weld.
To turn it on, I have observed it in person – experienced craftsmen do it this way. The reason seems to be that this approach helps prevent weld leaks……
To enable this, keep it open for good air circulation, which facilitates heat dissipation, helps improve welding quality, and protects the valve.
In the on position, it prevents weld slag from damaging the valve plate or seal
To prevent deformation due to heat, the valve should not be closed when connecting it to the pipeline.
If the pipeline can be vented, the valve should be closed to prevent welding slag from splashing onto the sealing surface.