How to address hydraulic pressure issues with prefabricated welded groove equipment
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Hello everyone, I have a question. One of our clients needs prefabricated welded sections for their pipelines; they plan to weld these sections onto the main pipeline on site. However, they require that we conduct a hydrostatic test in the factory. How should we carry out this test? Should we weld blind flanges at both ends before testing and then remove them, and if so, how exactly should the pipeline be welded to those blind flanges? I haven’t dealt with this before; please help me out. Thank you in advance.
It is sufficient to weld two steel plates at each end with a thickness that meets the strength requirements; these plates should be slightly larger in diameter than the tube, with fillet welds applied around the entire perimeter
This must be carried out in accordance with the requirements of the contract technical agreement; requests made midway can only result in additional costs. As for pressure testing of the other parts, it is necessary to carry it out before leaving the factory. You can use the flange for pressure testing and obtain the relevant certification, and then cut off the flange for future use. The rest can be done according to the customer’s requirements, I guess. For reference.
The cost of purchasing flanges is high; it would be better to weld blind plates directly, though I’m not sure how to do that.
Thank you, but is the strength of the fillet weld sufficient? It’s a CLASS2500, so I’m a bit worried
Everything else that requires pressure testing must also be done. If it’s just about producing this one piece of equipment, then welding is the only option. Note, this is for the stress testing of other parts.
This post was last edited by Paris on 2021-10-19 07:17. There are basically these two methods for pressure testing the weld joints of high-pressure equipment. The first method involves directly welding a cover; once the water pressure test is successful, the cover is removed and the groove is ground. It’s necessary to leave some margin at the weld joint of the equipment in advance. The second method involves welding a liner made of the same material as the pipe outside the pipe, or applying a weld-on gasket, and then welding a short section or a cover onto it. With this approach, no margin needs to be left at the equipment joint; the groove can be prepared directly. The short section is optional, depending on the length of the equipment pipes. If nitrogen is used to fill the equipment, the cover used for pressure testing can serve as a nitrogen seal, and the end user can simply remove it after the pressure test – but care must be taken with the cutting location to avoid damaging the base material. You need to verify the thickness of the hydraulic head and spools, as well as the strength of the fillet welds.