Pressure relief valve
The pressure relief valve in the fire service is a special type of pressure relief valve and is an important component in hydraulic systems. This valve limits the maximum permissible water pressure in order to protect the system against excessive pressure (excess pressure protection) and to avoid damage. If the pressure in the system exceeds a desired (set) value, this valve allows the water to drain out of the conveying line. As a rule, the maximum permissible pump or system pressure is safeguarded against being exceeded with such a valve.
Use by the fire brigade
A pressure relief valve is also used to refer to a valve for water drainage in the fire service , which is supposed to safely absorb sudden pressure surges within 0.2 seconds when extinguishing water is pumped over long distances . Thus it can e.g. B. prevent the hoses from bursting and the water supply being interrupted.
The pressure relief valve consists of a housing with two rotatable fire brigade couplings at the inlet and outlet of the flow chamber, a fixed B coupling on the overflow, a main valve with control element and setting scale, and an overpressure measuring device.
The pressure relief valve must work in both flow directions, whereby the maximum permissible pressure must be adjustable on a scale from 0 to 16 bar. The pressure measuring device must display a measuring range from 0 to 25 bar. The pressure relief valve has a weight of 6 kg and is insensitive to contamination that can be sucked in via a suction strainer or the pump strainer. It must be able to close tightly at a pressure of 25 bar and the pressure loss with free passage must not exceed 0.1 bar with a flow rate of 800 l / min. The fire brigades in Germany and Austria valves are used according to DIN 14 380 for sale.
The valve is set to a corresponding setpoint between 0 and 16 bar with the setting element. At normal pressure, the flow space is separated from a water chamber above the flow space by the main valve (ring piston or membrane); however, it is constantly filled with water via a compensation line. If the target pressure is exceeded, a control valve opens, which means that more water flows out of the water chamber than is fed in through the equalizing line. The resulting negative pressure between the water chamber and the flow chamber opens the main valve and allows part of the flow to flow out into the open via the B-outlet. If the pressure in the line drops again, the control valve closes again, which leads to a pressure equalization between the water chamber and the flow space. Thus, the main valve can be closed again by a spring. The closing process takes place gradually in order to avoid further pressure surges.
The pressure relief valve is installed in front of a distributor or, in the case of extinguishing water pumping over long distances, in front of each booster pump . When pumping extinguishing water over long distances, the target pressure is 2 bar, otherwise between 5 and 8 bar should be set.
literature
- Lutz Rieck: Die Rote Hefte, booklet 06 - fire extinguishing fittings . Kohlhammer, Stuttgart 2000, ISBN 978-3-17-015171-0 , pp. 59-66 .
- Diverse: Hamilton - Handbook for the fire brigade . Boorberg Verlag, 21st edition 2012. ISBN 978-3-415-04560-6