liquid seal overpressure protection
liquid seal overpressure protection
(OP)
Hello,
We have several tanks protected for overpressure and vacuum by a liquid seal. The system consists of a small pipe in another pipe with a larger diameter and a closed bottom end. In case of overpressure the liquid will move upwards and at a certain overpressure the gas start flowing through the liquid .
Two questions arise about this particular system of a liquid seal:
1. Is there an engineering standard to calculate the capacity of a liquid seal used for overpressure protection?
2. What is de the maximum allowed accumulated pressure for vessel with 0 psig design pressure? ASME Section VIII Division 1 cannot be used since it is only applicable for pressures above 15 psig.
We have several tanks protected for overpressure and vacuum by a liquid seal. The system consists of a small pipe in another pipe with a larger diameter and a closed bottom end. In case of overpressure the liquid will move upwards and at a certain overpressure the gas start flowing through the liquid .
Two questions arise about this particular system of a liquid seal:
1. Is there an engineering standard to calculate the capacity of a liquid seal used for overpressure protection?
2. What is de the maximum allowed accumulated pressure for vessel with 0 psig design pressure? ASME Section VIII Division 1 cannot be used since it is only applicable for pressures above 15 psig.





RE: liquid seal overpressure protection
Thus said, you should use well established pipe friction calculational methods such as Crane Technical Bulletin 400.
OSHA requires a 100% safety factor for uncalibrated pressure protection devices.
So if the rating calculation result is 1,000 scfm, you can only claim 500 scfm of protection.
Question 2: Low pressure tanks have zero allowable accumulation.
Equipment shall not exceed the MAWP or vacuum.
For your situation, I would pay a mechanical engineer to evaluate the tanks for pressure and vacuum.
Get a documented rating for record files.
This is part of being a responsible equipment owner.
RE: liquid seal overpressure protection
Hopefully, this is an API-620 Low-Pressure tank, but with a design pressure of "0", it is unlikely.