Series 108 - Pressure Relief Valves

In many liquid piping systems, it is vital that line pressure is maintained within relatively narrow limits. This is the function of the 108 Pressure Relief / Back Pressure Series of the OCV control valves. Installed in the main flow line, the standard Model 108-2 acts as a backpressure or pressure sustaining valve. In this configuration, the valve maintains a constant upstream pressure regardless of fluctuating downstream demand. When used in a bypass line, the same model will function as a relief valve, protecting the system against potentially damaging surges.

Features

• Operates automatically off line pressure.
• Heavy-duty, nylon-reinforced diaphragm.
• Rectangular-shaped, soft seat seal provides drip-tight Class VI closure.
• Diaphragm assembly Guided top and bottom.
• Throttling seat retainer for flow and pressure stability.
• Easily maintained without removal from the line.
• Replaceable seat ring.
• Alignment pins assure proper reassembly after maintenance.
• Valves are factory tested.
• Valves are serial numbered and registered to facilitate replacement parts and factory support.

SURGE / RELIEF

Protects system from over pressure by exhausting excess pressure. The valve may only have to operate intermittently to prevent pressure surges that might occur on pump start, pump stop, or sudden downstream valve closure.

BYPASS PRESSURE CONTROL

Valve keeps pumping system at a constant pressure by bypassing back to source. Provides accurate pressure control when system demand varies widely

BACK PRESSURE / SUSTAINING

Valve allows flow when inlet pressure is above the set-point thus preventing inlet pressure from falling too low. Prevents demand from “robbing” the source, or keeps pump “on its curve.”

Valve Operation

RELIEF VALVE – Closed under normal operating pressures. Valve opens when pressure rises to the set point. Valve will close when system pressure drops below set point.

BYPASS PRESSURE CONTROL VALVE – Opens and modulates to maintain the required pressure.

BACKPRESSURE / SUSTAINING VALVE – Open under normal conditions and closes as upstream pressure falls below set point.

The Model 108-2 consists of the following components, arranged as shown on the schematic diagram:

1.) Model 65 Basic Control Valve, a hydraulically-operated, diaphragm-actuated, globe or angle valve which closes with an elastomer-on-metal seal.

2.) Model 1330 Pressure Relief Pilot, a two-way, normally-closed pilot valve which senses upstream pressure under its diaphragm and balances it against an adjustable spring load. An increase in upstream pressure tends to make the pilot open.

3.) Model 126 Ejector, a simple “tee” fitting with a fixed orifice in its inlet port. It provides the proper pressure to the diaphragm chamber of the main valve depending on the position of the pressure relief pilot.

4.) Model 141-3 Flow Control Valve, a needle-type valve which provides adjustable, restricted flow in one direction, and free flow in the opposite direction. On the 108-2, the flow control valve is connected as a closing speed control.

5.) Model 159 Y-Strainer (standard on water service valves) or Model 123 Inline Strainer (standard on fuel service valves). The strainer protects the pilot system from solid contaminants in the line fluid.

6A / 6B.) Two Model 141-4 Ball Valves (standard on water service valves, optional on fuel service valves), useful for isolating the pilot system for maintenance or troubleshooting.

• Model 108-2 Pressure Relief/ Pressure Sustaining Valve
• Model 108-2HP Pressure Relief / Pressure Sustaining Valve
• Model 108-3 Pressure Relief / Pressure Sustaining and Check Valve
• Model 108-4 Pressure Relief/ Pressure Sustaining and Solenoid Shut-Off Valve
• Model 708-2 Reduced Port Pressure Relief/Pressure Sustaining Valve