Fisher 289L Low Pressure Relief Valve 1" x 1" FNPT
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The 289 Series relief valve is a throttling relief valve used downstream of pressure regulators to protect the downstream system from overpressure. A smooth throttling action minimizes pressure surges in the system during emergency operation. These relief valves are available in 1/4, 3/4, 1 or 2 NPT sizes with spring ranges (relief pressure settings) from 5 in. w.c. to 75 psig / 12 mbar to 5.2 bar.
All sizes above 1/4 NPT feature a pitot tube booster for achieving the highest possible relief capacity with a minimum buildup of system pressure. When the valve is opening, high gas velocity through the orifice creates an area of relatively low pressure near the end of the pitot tube. This pitot tube effect forms a partial vacuum above the diaphragm which helps to open the valve.
- Type 289L-22: 1” x 1” FNPT spring-loaded relief valve for relief pressure settings of 10" to 18” WC
- Type 289L-21: 1” x 1” FNPT spring-loaded relief valve for relief pressure settings of 12" to 40” WC
289 Series Spring-Loaded Relief Valves Bulletin
- 289 Series Spring-Loaded Relief Valves Instruction Manual