Like Plan 53B, Plan 53C has only piping and an air or water cooled heat exchanger within the closed loop circuit. Plan 53C features a reference line from the seal chamber to a piston accumulator teed into the closed loop system that provides a constant pressure to the loop above the seal chamber pressure.  The basic setup is comprised of two parts: the closed loop circulating system and the piston accumulator.

The barrier pressure for Plan 53C is a function of the piston accumulator design. Typically barrier pressure is about 10% above the reference pressure.  Some piston accumulators include a spring to provide a slightly higher barrier pressure.

The circulation rate in a Plan 53C system is not controlled directly; it depends on the performance of the pumping ring within the particular closed loop system.  The pumping ring, reservoir and piping are selected to produce the desired operating conditions.  Heat soak as well as heat generation must be considered in determining the desired circulation rate.

As with any piping plan using a pumping ring, proper venting is crucial to successful operation.

Because Plan 53C relies on physical movement of a piston within a cylinder, corrosive and solid contaminants can be a problem.   Plan 53C is not frequently used.