Forced circulation from the seal chamber through a cooler and back to the seal chamber.
This plan involves the forced circulation of process fluids from the seal chamber through a seal flush heat exchanger and back to the seal chamber.
- Seal has an internal circulating device (pumping ring) that circulates seal chamber fluid through a cooler and back to the seal chamber.
- Provides a cool flush to the seal to improve lubricity, reduce coking, and/or avoid fluid flashing to vapor.
- Commonly used for hot water services above 180°F [80°C] (e.g. boiler feed water) and hot hydrocarbon services.
- Throat bushing is used to isolate product in the seal chamber from product in the pump volute.
- More energy efficient than Plan 21 since only the fluid in the seal chamber is run through the cooler.
- If the cooler duty is high, fouling and clogging on the water side can occur over time.
- Potential for clogging on the process side if the fluid becomes too viscous at reduced temperature.
- Best piping practices must be followed to avoid vapor entrapment and stalled flow in the tubing.
- Improved energy savings compared to Plan 21
- Cool flush improves seal lubricity and reduces coking
- The use of products with a high viscosity can negatively affect fluid circulation
- Maintenance of the Seal Cooler although better than Plan 21