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Specifications for safety Relief type 121

Safety Relief valve type 121

The Sensus safety Relief valve type 121 is also known as a back-pressure regulator. The safety Relief has a single diaphragm with a balanced valve. This makes the Sensus type 121 very accurate. It is a modulating relief and not a pop-up type. Depending on the operating conditions, a membrane box with a diameter of 8″, 12″ or 16″ can be chosen. The safety relief is available in connection sizes ranging from 3/4″ up to 4″.


121-8, 121-12 and 121-16.

Maximum operating pressure

The maximum inlet pressure depends on the version and the Relief spring.

Operating temperature

-28.9 – +65.5° C (-20° F +150° F).

Spring range

12.0 – 700.0 mbarg (with different springs).

Connection sizes

3/4 “, 1”, 1.1/4 “, 1.1/2”, 2 “, 2.1/2″ NPT.

Flanged in DN50 PN10, 2″ANSI125lbs, 3” ANSI125lbs and 4 “ANSI125lbs.

Applicable gases

Natural gas, propane, butane, air and nitrogen. Various designs are available for special (corrosive) gases.