API Plan 23

We have many customers that operate equipment in demanding services that need to cool a single mechanical seal. There are several options available. API 21 and 23 are the most popular and reliable. A seal chamber cooling jacket can also be used, especially with hot water, if it is available. If it is not, my preference – if cooling water is available – is always an API Plan 23 [see figure].

Plan 23 basically consists of a single seal with a circulating device, i.e. a pumping ring. The pumping rings come in all shapes and sizes, however, a good basic pumping ring that will circulate the small amount of fluid (let’s call it water), in the seal chamber is all that is needed. If radial space is limited, an axial flow pumping ring is a good option.

A seal cooler or heat exchanger is required. These can also come in many shapes and sizes. Flowserve makes a NX style cooler that has been around for a long time that works very well. It consists of process cooling coils and a cast shell. 316SS tubing is mostly used, but some older models use brass tubing. The shell is a cast iron or cast steel.