Adjustment of the safety valve

• 1 - Nut / screw that must be turned to adjust the set pressure of the safety valve.

Adjustment of the relief valve is carried out at the installation site after completion of installation and flushing of the system. To do this, set the adjustment pressure, check the opening start pressure, full opening pressure, and closing pressure of the relief valve.

The adjustment pressure of the relief valve should be set slightly higher than the maximum operating pressure of the system, which corresponds to the normal operating mode of the protected installation.

The full opening pressure of the relief valve should not exceed the maximum allowable pressure for the weakest element of the system.

The closing pressure of the relief valve should be higher than the minimum allowable pressure that corresponds to the normal operating mode.

Signs of an incorrectly adjusted safety valve:

• The safety valve opens within the normal operating pressure range. The heating system (or other system protected by the valve) must be designed so that the valve opens only when the pressure exceeds the maximum working value. It should operate only in emergency situations when something goes wrong and the pressure goes beyond the allowed limit.
• The pressure has exceeded the maximum allowable value for the weakest component of the system, but the safety valve did not open. This can lead to damage. In this case, the valve’s opening pressure should be lowered by turning the adjustment screw.

Adjustment of the pressure in a spring-loaded relief valve is carried out by rotating the adjusting screw of the compression spring, which presses the disc against the seat, while adjustment of a lever-type relief valve is carried out by determining the required weight.

Pre-adjustment is not required for relief valves, the adjustment pressure of which is fixed by the manufacturer.

The relief valve is considered to be operational if it provides sealing of the closure, full opening and closing of the shutter, and the pressures, adjustments, start of opening, full opening, and closing pressures are within the permissible values indicated in the valve passport.

Example: Adjustment of the relief valve in a heating system of a 10-story building connected to an autonomous boiler house (or to a heat network using an independent scheme). At the installation site of the relief valve at the basement level, the pressure values will be as follows:

Minimum operating pressure is determined as the sum of the static pressure of the heating system, which is 10 floors at 3 meters = 30 m, plus the minimum excess pressure at the upper floor level - let's assume 5 meters, therefore Pmin = 30 + 5 = 35 m = 3.5 bar. The minimum operating pressure in the heating system is set during its filling with cold water. An increase in water temperature leads to an increase in pressure to the maximum working value. See more details in the principle of operation of the expansion tank.

Maximum operating pressure for the heating system is set when calculating a closed expansion tank. The smaller it is, the more necessary the volume of the expansion tank and the higher its cost. For our building, it would be rational to adopt a maximum working pressure of Pр=5.5 bar. The maximum working pressure in the closed circuit of the heating system is achieved at maximum coolant temperature, i.e., in the coldest days of the heating season.

Maximum allowable pressure for the heating system is determined by the strength limit of the weakest element of the circulation circuit, assuming that it is Pmax=8 bar.

For such a heating system, the relief valve must be adjusted to a pressure of Рн=6 bar, with the opening start pressure of approximately Рно=6.2 bar, full opening pressure of Рпо=6.8 bar, and closing pressure of Рз=4.8 bar.

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