Controlling Seal Chamber’s Environment to Improve Seal Life

The pump’s seal chamber contains a limited volume of liquid to lubricate and cool the seal faces. The seal faces will generate heat based on the speed, pressure, and the lubricating properties of the pump fluid. Unless this fluid is cooled or replaced, the temperature in the seal chamber around the seal will increase, which can make it too hot for reliable long term seal performance. For optimum seal life the maximum temperature rise in the fluid around the seal faces should be maintained at 5-15°F (3 to 9° C).

API 610 & 682, ANSI / ASME B73 and ISO 21049 standards have over the years developed piping plans to improve the environment in the sealing chamber.

The following three product recirculation Piping Plans discussed are just a few of the many plans developed by the above standards.

All three of these plans require simple piping. The main advantage of these plans is that the flush source is the pump fluid so no product contamination occurs, which will cause the need for reprocessing of the finished product. To create flow for these piping plans the fluid must have a differential pressure.

This is the most common flush piping plan used. With this plan the appropriate amount of the pumped fluid is piped from the discharge (high pressure) side of the pump to the seal chamber typically thru a connection in the gland.

The primary purpose of this plan is to create a flow of the fluid by the sealing faces to dissipate the heat generated at the faces. It is also possible to increase the pressure in the seal chamber by using the proper flow along with a close clearance throat bearing/ bushing resulting in improved vapor pressure margin.

It’s recommended that the flush should be directed over the sealing faces at the 12 o’clock position, which also helps to vent the seal chamber.

Plan 13 is similar to Plan 11 except for the recirculation flow is reversed by piping from the seal chamber back to the suction (low pressure) side of the pump. This plan is typically used on vertical pumps, and helps to vent air and vapors out of the seal chamber.

This is a combination of both a Plan 11 recirculation from pump discharge and Plan 13 recirculation to pump suction. On vertical pumps this plan is used when there is a concern that the pumped fluid may flash due to the reduction of pressure in the seal chamber when using a Plan 13. By using a Plan 11 with the Plan 13 it minimizes the reduction of pressure thus maintaining proper vapor pressure margin to insure good seal life. Plan 14 allows for complete venting of the seal chamber provided the flush out (FO) is properly located.

For more information on these piping plans or if you have more specific questions on other piping plans, please feel free to contact us at sales@flexaseal.com.