Steam Heating Systems Part 8: Parallel-Series Pilot-Operated PRV Stations

By Mark Bingham

In our final brief blog post on pilot operated steam PRVs, we consider systems that have a large pressure drop, highly variable loads and require steam at an intermediate pressure. A parallel-series PRV station is indicated for this type of system.

Since the information presented in the previous blogs for series PRVs and parallel PRVs is also applicable to series-parallel installations, we will not repeat those details here.

Typical Parallel-Series PRV installation

The following drawing illustrates a series-parallel PRV station which consists of two valves in parallel, an intermediate pressure header and another two valves in parallel. Each set of parallel valves has a manual bypass, and relief valves are installed on the intermediate and low-pressure headers. Drip traps are installed on the high, intermediate and low-pressure headers.

Parallel-Series Pilot-Operated PRV Station for use in steam systems that require steam at an intermediate pressure and have a large pressure drop and highly variable loads.