Can non-pressure components still be welded after the equipment’s hydrostatic test?
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There is currently a waste heat boiler, whose front tube sheet is made of 15CRMOR, while the cylinder connected to it is made of Q345R. The design requirements specify that after heat treatment and hydrostatic testing, the weld joints between the front tube sheet and the cylinder must be subjected to 20% ultrasonic inspection. However, there is a ring plate on the cylinder, at a distance of 90 mm from the weld, which serves as an outer insulation layer. If welding is carried out before the hydrostatic testing, it becomes impossible to conduct the required 20% ultrasonic inspection. Is it still possible to carry out welding on the cylinder after the hydrostatic testing? I hope the experts can give me some advice. Thank you!
Parts that require heat treatment generally are not allowed to be welded to the main body anymore. Welding is necessary, and on-site heat treatment is also required
Personally, I think water pressure isn’t an issue; heat treatment is the real problem. It is recommended to change the position of the ring plate so as to avoid the weld seam
The hydrostatic test is carried out after stress relief through heat treatment; welding is performed after the hydrostatic test, which in turn causes uneven stress distribution, so this approach is not recommended
Here are two suggestions for reference: 1. Move the insulation support slightly to meet the requirements for weld ultrasonic testing. 2. The thermal insulation support is replaced by several connection plates welded to the cylinder; the thermal insulation support ring is fixed to the connection plates using bolts or is welded in place.