How to conduct a hydrostatic test on large-diameter pipes?
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Please discuss how hydraulic testing is carried out for large-diameter pipes in general For things such as the reboiler return line to the tower, and some of the lines on the tower, are they usually tested under pressure on the ground first and then erected, given their larger diameter? If the construction has already been carried out according to the plans, how should a hydrostatic test be conducted? Should eight-character blind plates or gaskets be added? Since the hydrostatic test pressure is usually 1.5 times the design pressure of the pipeline (this value is greater than 1.5 times for high-temperature and stainless steel pipelines; the exact value must be determined according to the relevant standards), this eight-character blind plate or gasket will be quite thick. What should be done if it isn’t possible to use such a thick plate or gasket? I seek advice from experienced workers! ! !
By large diameter you mention, how large is it? How tall is the tower? As far as I know, submarine pipelines are pressurized as a whole or in sections once their construction is basically complete, and the height of the risers at the platform jacket is even greater than the water depth, reaching eighty or ninety meters in some cases. Generally, the pipeline is filled with water to remove any bubbles, then blind flanges are welded at both ends, followed by pressurization and holding the pressure.
Large pipes refer to those with a diameter of DN600 or more; they are over 70 meters in height
The DN600 pipes aren’t that large either. When we worked on utility tunnels in the past, DN1050 pipes were installed over a length of one kilometer each; they were just horizontal pipes
There should be no problem carrying out a pressure test right after installation.
Pneumatic testing can be considered as an alternative in accordance with the specifications
The specifications also state that when pressure testing is difficult, it is necessary to consult with the designer and use 100% flaw detection as a substitute for pressure testing
Pneumatic testing and 100% flaw detection can both replace hydraulic testing. But I would like to ask: when long-distance crude oil or gas pipelines pass through the Gobi Desert or uninhabited areas where there is a lack of water and electricity, is this same method used?
How is salt corrosion dealt with after seawater pressure testing?
Logically, fresh water should be used. But in reality, it is all seawater, with a certain proportion of chemical agents such as corrosion inhibitors and dyes added. After the pressure testing is complete, the water must be drained and the area dried out (apparently to a dew point of -35 degrees inside the pipes). If it had been set aside and not put into use at that time, it would still need to be inerted with nitrogen. That’s basically it.