OSV
Oil Safety Valve
Oil Safety Valves (OSVs) are used to prevent tank siphoning, oil leaks in the event of line breaks, and excessive pressure at the burner fuel unit when using a booster pump. Many state and local codes require a device that will automatically shut off the oil supply before it enters a building should the line between the device and the burner be broken. NFPA standards require that the pressure at the burner fuel pumps must not exceed 3 PSI. The Webster OSV satisfies both requirements when properly installed. Check local codes for any special requirements.
Compatibility
Operating principle :
Prevent oil spills :
Webster OSV valves help prevent oil spills by stopping oil flow in the event of line breaks caused by corroded lines or leaky fittings. It is mounted in the supply line as close as possible to the tank. The OSV requires a vacuum on its outlet side to open the valve and allow oil flow.
When the burner is shut down, there is no vacuum from the fuel unit and the OSV valve is closed – oil flow is stopped.
When the burner starts up, vacuum from the fuel unit opens the OSV, allowing oil to flow.
If a corroded broken line or a loose fitting causes a leak to develop between the OSV and burner, air enters the line. Fuel unit vacuum is reduced and the OSV will not open, preventing tank siphoning and a major spill.
Prevent excessive pressure with a supply pump :
The Webster OSV provides important protection in oil burner supply systems with pressurized supply lines. By isolating burner fuel units from supply line pressure sources (a supply pump or overhead tank, for example), the OSV relieves pressure stain on fuel unit inlets and seals.
For this application, the OSV is installed close to the burner assembly. A sustained vacuum at the outlet side of the OSV, generated by fuel unit operation, causes the valve to open.
The OSV operates as a pressure reducer, with supply line pressure on the valve inlet side and fuel pump vacuum on the valve outlet side.
In systems with burners connected for one-pipe operation, GPH flow through the valve is the same as the burner nozzle firing rate. In two-pipe operation, GPH flow through the valve is the same as the fuel unit suction capacity. Refer to fuel unit manufacturer’s specification for inlet suction capacity. Operation of OSVs in parallel is not recommended.
Installation:
The OSV can be mounted in any position.
In environments where dirt or moisture is a particular concern, the preferred position is with the cover facing down. This allows any moisture in the diaphragm area to drain through the manual access hole.
For priming, use the OSV priming tool (9994013). Insert the tool into the breathing hole and depress the diaphragm plate.
Technical sheet OSV