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Naphtha vapours are observed at manway lid of roof top when its opened . Mild naphtha vapours are also observed at roof drain of the storage tank when its opened. Generally roof drain of the storage tank is kept in open condition only . The storage tank is of Internal Floating Roof type . Tank safe height is 10.75m . Generally tank height is maintained at 9 m or lower. Tank outlet Temperature is between 36 to 42deg. Let me know why naphtha vapours are emanating from roof tanks and roof drains. I dont think there is swivel joint leak .
 
Answers
16/09/2018 A: senthil rajappan, SADARA, senthil.rajappan@sadara.com
Have you seen any high pressure alarm , check the trend and analyze with sequence of operation. Perform validation of mass and pressure flow to the tank to identify along with RCA.
Note the high pressure alarm set point for vessels equipped with PVRVs is usually set at 80% of the PVRV set pressure.
13/09/2018 A: Prakash Pimparkar, Environmental Consulting Services , prakash.pimparkar@yahoo.in
The source is rim seal the manway lid either foulty or not shut properly.If problem persists need to replace with double or mechanical seal.The roof drain can and need to be opened only periodically