Swivel joints are used in the roof drain line of the floating roof tank. In our refinery we usually replace these during repair work on the tank. In that case the life of the joints is about 10-15 years. But I want to use these joints again. There is no testing facility for these joints. There are 20 swivel joints in each tank so a good amount of money is required to replace them. My questions are:
1. Is it a good decision to replace the joints after 10-15 years?
2. How should we test the joints if we wish to use them again?
Answers
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16/10/2020
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A:
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ARNAB GUPTA, Kuwait Oil Company, arnabgupta_2000@yahoo.com
Swivel joints are one of the weak links of roof drains, if not maintained properly. I've experienced roof failures when the entire JKRD assembly stuck up due to swivel joint failure. Presently flexible hoses are a good alternative and this may be contemplated when the tank is taken up for major overhaul.
There are a few tests like assessing swivel joint movement while under external pressurization equivalent to the maximum filling height of the tank. These require special fixtures which are bespoke.
Regarding maintenance, O-Rings at swivel are prone to hardening and seizing; compatibility with the tank product should be checked.
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