Please discuss a practical on-site issue: the effective use of temporary gaskets for pressure testing and purging
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For new projects, flange gaskets are relatively expensive and are used in large quantities. After piping is installed, tasks such as purging and pressure testing are required, and the flanges have to be disassembled and reassembled multiple times. Some gaskets get damaged after just one disassembly – please share the best practices from your own organizations. This post was last edited by lonelyghost_li on 2008-1-27 17:53]
Determine the purging pipe openings in advance, and use temporary gaskets at these locations.
I agree with the opinion above: using temporary gaskets can reduce the need for permanent gaskets. It is also important to take care of and protect the permanent gaskets. If possible, pay attention to disassembling them after each use; depending on their condition after disassembly, they may be used again once, but generally they can only be used twice. Additionally, there are differences among gaskets made of different materials, so it’s best to use them accordingly by categorizing them
First, determine the blowing and removal points; during pipeline installation and blowing, use inexpensive temporary gaskets； For other points, use formal gaskets to avoid damage during repeated removal ； For the selection of temporary gaskets, asbestos boards or rubber ones are commonly used.
Thank you all for your participation. When I was in charge of a project some time ago, I asked the installation team to use asbestos gaskets for temporary piping. This worked fine for pipes with smaller diameters, but when the diameter exceeded DN250, problems arose during pressure testing using spiral gaskets – it was difficult to compress them properly. I’m not sure whether the thickness of the gaskets wasn’t appropriate or if the pipes weren’t aligned correctly during assembly. I hope everyone will share their experiences based on what they have seen on site, so as to improve our engineering skills.
Correction: Change “those who have seen it in person or witnessed it” to “those who have seen it in person or carried it out”
The designated purging ports are usually locations that are easy to disassemble and assemble, making adjustments convenient. What the original poster mentioned might refer to pipes that cannot be adjusted; if it is necessary to have a purging port at that location, then a weld must be made there, after which the flange can be tightened.
The parts that need to be removed for pipeline purging and pressure testing are generally the equipment connection points and instrument connections; blind plates with a thickness equal to that of the gaskets should be used in these areas. This approach not only eliminates the need for gaskets but also protects the equipment and instruments by preventing impurities from entering them. Temporary gaskets can be used during pressure testing. The temporary blind flange can remain in place until after purging is completed, at which point it can be replaced with a proper gasket. Areas with temporary blind plates and gaskets should preferably be marked.
When adding a gasket, align it with the flange’s sealing surface; this way, when the bolts are tightened, there will be no misalignment, which helps to protect the gasket’s sealing surface. Gaskets of this type can be reused multiple times
Recently, the gaskets (asbestos-wrapped gaskets) produced by our factory all have a \"tail\" – about 100 mm remains at the very end after the gasket is wrapped. During installation, this \"tail\" can be held by hand to position the gasket properly, which yields better results.
There’s no other good solution except using temporary pads! !