The DHE is used to maintain the barrier fluid pressure for a limited period after the SPA circulating
pump has failed or been switched off. It prevents a loss of pressure on the mechanical seal and stops
it from opening. The seal, however, is no longer cooled and must therefore be brought to an immediate
stop. How long the pressure is maintained will depend on the following two factors: the rate of leakage
of the mechanical seal and the amount of buffered fluid stored in the accumulator.