Internationally Approved Product
ULListed
FMApproved
CEMarkedCLA-VAL
A fire pump main relief valve protects the fire protection system from overpressure by relieving excess pressure to a safe point when the pressure at the pump discharge exceeds the set value. Pump flow, working pressure and discharge line conditions are evaluated together when selecting a pressure relief valve.
Cla-Val Models 50B-4KG1 (globe) and 2050B-4KG1 (angle) are pilot-operated pressure relief valves designed for fire protection systems. The valve holds system pressure at the pump discharge constant within close limits under varying flow demands. Its fast-opening, slow-closing action protects against pressure surges that occur when the pump starts and stops.
The normally closed CRL pilot opens the valve precisely on excess pressure. Pressure is adjusted with the pilot screw while watching a gauge; the adjusting screw is protected by a sealable cap. A double-guided stem, tapered metal seat and replaceable 316 stainless steel seat provide drip-tight closure, and the valve is designed for in-line maintenance.
The valve can be used for pressure relief, pressure sustaining, back pressure and unloading functions. The models are UL certified under UL 1478 (Fire Pump Relief Valves). The manufacturer recommends fitting a WC-1 waste cone at the valve outlet so that relief flow can be monitored visually.
| Specification | Value |
|---|---|
| Model | 50B-4KG1 (globe) / 2050B-4KG1 (angle) |
| Sizes | Flanged 1.5″–8″; grooved 1.5″–8″ (angle 1.5″–6″); threaded 1.5″–3″ |
| Pressure Class | Class 150: 250 psi (ductile) / 285 psi; Class 300: 300 psi |
| Pilot Adjustment Ranges | 10–75 psi, 20–200 psi (Class 150); 100–300 psi (Class 300) |
| Max. Temperature | Water: 180 °F |
| Body / Trim | Epoxy-coated ductile iron ASTM A-536 / stainless steel |
| Pilot / Elastomer | Cast bronze / Buna-N |
| Approvals | UL 1478 (20171110-EX2855); KOL models 3″–8″ FM Class 1361 |
Technical values are based on manufacturer documents; confirm against the current data sheet before ordering.
Pressure regulation and relief at the fire pump discharge
Sprinkler, hydrant and fire hose cabinet systems
Foam fire suppression applications
Seawater and heavy-duty applications (with optional materials)Other equipment considered together with the Fire Pump Main Relief Valve in the fire pump room:
