Pressure Reducing Valves – stations are designed with a High-Flow and Low-Flow PRV that work in parallel to maintain a constant pressure downstream across the flow load profile of the zone. Low-Flow valves are typically direct-acting (ex. Cla-Val Model CRD-L), and High-Flow valves are pilot-operated (ex. Cla-Val Model 90-01); however actual valve selections depend on the flow and pressure drop of each station.

Pressure Reducing Valve

A minimum volume (10% ~ 20%) is considered in expansion tank at start-up in cold conditions. As heating is started volume expands and tank sizing should be such that expanded volume fills (70% ~ 80%) of tank volume.

Block Valve and Control Panel – The addition of a pressure switch, control panel, and block valve can add additional safety and monitoring to the PRV Station. When a PRV fails, the pressure switch detects the high pressure and sends a signal to the control panel. This triggers the panel alarms (local and BAS output) and closes the block valve to shut down the water supply to the zone.

Water pressure valve

Size an horizontal expansion tank for hot oil system using Therminol VP-1 as thermic fluid. Fluid is heated from 30 °C to 350 °C. System hot oil volume is 7.87 m³. L/D to be used as 2.5. Thermic fluid density is 1056 Kg/m³ at 30 °C and 761 Kg/m³ at 350 °C.

Expansion tank is provided in hot oil system to accommodate for the increased thermic fluid volume due to thermal expansion. It also helps in removal of moisture and non-condensables during start-up. This article will show how to do sizing of an expansion tank.

Water pressureregulator

Piping Components – A Strainer is required upstream of the PRVs to keep them clear of trash. Pressure gauges are required on both the high-pressure and low-pressure sides of the PRVs to see what the pressure drop across the valve is.  Isolation valves on all PRVs and relief valves are required for maintenance.

Pressure Reducing Valve (PRV) Stations are an essential component of a water-distribution system in a commercial building. The 2015 Uniform Plumbing Code Section 608.2 states that PRVs are required at any point where the system static pressure exceeds 80 PSI. Typically, this applies to mid- and high-rise buildings when the pressure boost to serve the upper floors is over 80 PSI. It takes a combination of valves and safety devices to create a Pressure Reducing Station.

Relief Valve – Relief valves are required downstream of the PRVs to prevent over-pressurization when the PRV fails. A pilot-operated valve can be used (ex. Cla-Val Model 50-01), but we recommend a direct-acting valve like the Cla-Val Model 55B.