Indirect Acting Pressure Regulating Valves – Testing
Indirect Acting Pressure Regulating Valve – Testing
by Terin Hopkins
The testing requirements for pressure regulating valves (PRV) are often overlooked but vitally important to verify the valves will work as designed and when needed. Closed valves and any failure of a valve is catastrophic and continues to be the leading cause of system failure. They are not only imperative to fire service operations when installed on standpipe systems, but when indirect PRV are installed, they often regulate pressure for multiple fire protection systems, including automatic fire sprinklers.
Direct and Indirect Acting Pressure Regulating Valves
When the term pressure regulating valve is used, most people think of direct acting PRV’s found on fire department hose connection points. Direct acting PRV’s are installed at the hose connection, reducing water pressure flowing into fire department hose-lines, but there are two types of PRV valves. Direct acting and indirect acting pressure regulating valves. Like direct acting valves, indirect can be either factory set or field adjustable; simply meaning they come directly set from the factory and cannot be adjusted in the field or they can be adjusted, within their range, after installation. They are all set for a specific location within the building and operate in the same manner, with one key exception, the location of their installation.
While both direct and indirect are each used to reduce water pressure (both static and residual), they are installed in different locations on the system. The direct acting is installed at the hose connection and has a direct effect on reducing water pressure flowing into hose-lines. The indirect is installed inline within the system, reducing the downstream pressure to one or more hose connections, and can be used to reduce pressure on other systems, like automatic fire sprinklers systems.
When indirect PRV’s are used to supply more than two hose connections, a second PRV must be installed in series for redundancy and be equipped with an equally sized bypass around the PRV’s with a normally closed valve.
Pressure Regulating Valve Testing
Indirect and direct acting PRV’s are subject to the requirements of NFPA 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems and must be in accordance with the manufacturer recommendations. NFPA 25 requires all PRV’s to be fully flow tested every five years. The testing of direct acting pressure regulating valves is fairly straight forward…simply flow test directly from the pressure regulating valve and compare with previous test results.
The indirect gets a bit harder, mostly based on the locations of the valves and having a means capable of independently evaluating each PRV. When indirect PRV’s are used in sprinkler or combined systems they are required by NFPA 13 Standard for the Installation of Sprinkler Systems to have a test connection (valved outlet) downstream of the PRV, with the capability of accommodating the full flow of all systems served from the PRV.
This independent valved outlet allows for a connection point for the testing of each PRV, utilizing the standpipe test riser as the drain. The results are again compared to previous flow tests and adjusted to manufacturer instructions. Each PRV is also required to have a valved outlet installed to accommodate a pressure gauge and signage indicating the purpose of the test connection valve.
This often-overlooked flow test is vital to system performance and must be conducted every five years to verify systems will operate as intended.
About the National Fire Sprinkler Association
If you’re interested in learning more about fire sprinklers and the important role they play in protecting lives and property, consider joining the National Fire Sprinkler Association (NFSA). As a non-profit organization dedicated to promoting the use of fire sprinkler systems, the NFSA offers a wealth of resources and information on fire protection, including training courses, research studies, and industry news. Whether you’re a fire protection professional or simply interested in learning more about fire safety, the NFSA is a valuable resource that can help you stay up-to-date on the latest developments in the field.