Seal System Plan 53B

Description

In flush Plan 53B barrier fluid circulates to and from a double mechanical seal (Arrangement 3 seal). Pre-pressurized bladder accumulator provides pressure to the circulation system. Flow is maintained by the seal impeller. Heat is removed by a water or air cooled heat exchanger.

 

Plan 53B vs Plan 53A

• Plan 53B is recommended when barrier fluid pressure is above 10 bar to avoid the problem of nitrogen dissolving into the barrier fluid. In Plan 53B barrier fluid and nitrogen are physically separated by the elastomer bladder.
• A Plan 53B system does not require a nitrogen line near the installed pump unit. Nitrogen is injected into the system only once with the required pressure. During operation only fluid make-up is required (Automated top up is recommended for higher pressures).

 

Having said that, we would recommend API Plan 53A more often because:

• A Plan 53A system is many times cheaper.
• A Plan 53A system is easily and cheaply made of chemically resistant components. The elastomer bladder can be damaged, e.g. by solvents which the pump is pumping. How? Doesn't the double mode prevents the pumped product from getting into the seal system? Unfortunately, no, not always, at least not for systems with manual top up. If a double seal fails but the pump has to continue operating for some reason, the pressure in the Plan 53B system may go down and become equal to pressure in the seal chamber. Then the pumped product will migrate into the seal system. If solvents are present they will attack the rubber bladder. Soon the system will start leaking solvents and oil outside. The repair will cost a lot.

 

All in all, a Plan 53B seal support system may be the system of choice for a specific application but the price of a well-designed 53B system with automatic top up (refill) approaches that of a Plan 54 system.