Fisher 289 Series relief valves are spring-loaded throttling relief valves used as downstream  pressure regulators to protect the system from overpressure.

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 A smooth throttling action minimizes pressure surges in the system during relief operation. 289 Series relief valves are ideal for low-pressure settings due to the increased sensitivity provided by a large diaphragm area. 289 Series relief valves are designed for pressure control; they are not ASME safety relief valves.