Parker R Series Relief Valves are unique since they offer both a low pressure valve line (RL4) and a higher pressure valve line (RH4). They are both designed such that when the upstream pressure exceeds the closing force exerted by the spring, the lower stem opens, permitting flow through the valve. Flow through the valve increases proportionately to the increase in upstream pressure. These relief valves work from 1-25 psig crack pressure systems up to 5,000-6,000 psig crack pressure systems. The highly visible color coded labels on the valves indicate the associated crack pressure spring included in the valve.
To assist the installer, these valves are offered with a wide range seal materials. From Ethylene Propylene Rubber at -70F to Fluorocarbon Rubber at 400F, these relief valves meet numerous applications.