Leakage issues after container installation
Thread Content
For a tower-type vessel that passed the pressure test after manufacturing without any leaks, why does leakage occur at the bolted joints of the tube sheet after it is installed on-site? ?
The horizontal plane was not corrected during installation, or there is gas deflection
There are issues with the installation quality; a pressure test must be conducted again after installation before it can be put into use. During testing at the manufacturing plant, the equipment is in a horizontal position, making it easier to tighten the bolts. However, when installing it on-site, the equipment is in an upright position and may even be suspended in the air, which makes it difficult to tighten the bolts properly. Some bolts may not be tightened sufficiently, and if a pressure test is not carried out based on experience, leaks could occur.
After the equipment was manufactured and passed the pressure testing with no leaks, leakage occurred at the bolt connections of the tube sheet after it was installed on site. 1. There are issues with the installation quality; a further pressure test is required before the equipment can be put into use； 2. Vibration during equipment transportation caused some of the bolts to loosen, resulting in leaks ； This is not easy to handle ； During pressure testing in the manufacturing plant, one is in a lying position, which makes it easier to tighten the bolts. However, when installing them on-site, one is in an upright position and may even be in the air, making it more difficult to tighten the bolts. Based on experience, if pressure testing is not carried out for the products we manufacture, there is a risk of leaks.
There are many reasons: transportation, installation, temperature changes, lateral forces on the tower, and so on. Each specific issue needs to be analyzed individually.
Is it possible that the gaskets used during testing at the manufacturing plant are different from those used in the field? To save costs during pressure testing at the factory, soft gaskets might be used, while soft gaskets are not used in actual operation on site
Is it thermal expansion and contraction that cause a decrease in the bolt tightening force?
Loose bolts during transportation and installation can also cause leaks.
1 is a problem with the screw, 2 is a problem with the gasket. The specific reasons are complex and require on-site inspection; each issue must be analyzed individually.
What was said on the 4th floor is correct. Vibrations during equipment transportation caused some of the bolts to loosen, resulting in leaks; a pressure test must be conducted again after installation before the equipment can be put into use.
There are many factors affecting the sealing integrity of bolted connections in pressure vessels; one of them is the bolt tightening procedure； According to ASME-PCC-1, the bolts need to be tightened again a few hours after installation in order to counteract the effect of bolt stress relaxation ； As mentioned on the 3rd floor, construction is inconvenient, and some procedures have been omitted; for example, multiple bolts must not be tightened in a crosswise sequence with torque levels varying. Those who are interested can take a look at the bolt tightening procedures specified in ASME-PCC-1.