Likely ⅓ of the problems I encounter in refinery vacuum systems are due to difficulties with the seal drum. For example:
- The seal legs are too short. This causes the bottom portion of the seal leg to be exposed to the vapor, which is then drawn up into the condenser, which no longer drains.
- The seal legs are too long. Many seal drums have the bottom of the seal leg 4” above the bottom of the vessel. Between turnarounds, sludge covers the bottom of the seal leg and the condensers stop draining.
- Poor level control in seal drum. The seal baffle should prevent loss of the liquid seal. However, a high level will cause condensate back-up.
- Corrosion of seal leg inside drum. The corrosion is biological in nature. The holes in the legs above the overflow baffle will then cause the leg to lose its seal and condensate drainage will stop.