In water-pressure systems on an industrial scale, devices such as control valves, standard pressure regulators, and other butterfly valves are often used as pressure regulating devices. Regulators are different, some control pressure after themselves, others - to themselves. The pressure reducing valve for water is considered a direct acting regulator. He controls the pressure after himself, but under the condition when this pressure is less than half the indicators at the inlet.
Mechanism characteristic
The pressure reducing valve is controlled by the liquid medium that flows through the working pipeline by moving the control device by the force resulting from the dynamic change of the controlled indicator.
Structurally, the pressure reducing valve consists of three main elements: the regulatory body, i.e. plates, a setting element, or a spring, and a comparison element, which is a membrane.
The principle of operation of the valve is to throttle the liquid medium. Water flows from the high-pressure cavity to the low-pressure cavity, which communicate through the gap between the seat and valve plate. The sensitive element is usually soft rubber membranes with two fabric gaskets, but in some models it can be a piston with cuffs for sealing or rings made of rubber-based material. As a locking mechanism, plates of vulcanized rubber and metal alloy are used.
Valve selection
Each pressure reducing valve for water is selected based on the value of Kvs (throughput capacity of pipe fittings). Among other technical characteristics of all pressure reducing valves, the maximum Kvs value must be indicated for all sizes.
The pressure reducing valve is selected so that the desired throughput value is in the interval between its minimum and maximum values. To select the optimal size, the products are checked with tables of known indicators of valve throughput. However, for certain types of valves, the throughput value cannot depend on the nominal diameter (as is the case with sizes DM505, DM510 - 518). It is highly recommended not to use fittings with a nominal diameter two sizes smaller than the working diameter of the pipeline.
Pressure reducing valve settings
The most accurate designation of the output pressure adjustment range can be achieved by approximating the desired pressure setting level as close to the upper threshold of the range as possible. If the desired outlet pressure is, for example, 2.3 bar, then the range should be selected in the range from 0.8 to 2.5 bar, and not as much as 2–5 bar. If it is necessary to use a wider range, special versions of reinforcement can be used.
Valve protection
It is known that the flow rate of water in the valve seat significantly exceeds the speed of its movement in the pipeline. And probably, the solid particles present in the water can damage not only the saddle itself, but also the plunger (cylindrical rod). To protect the pressure reducing valve, as a rule, a coarse filter is installed in front of it.
Valve types
The following valve types are widely used: DM505, DM506, PRW25, KAT40, DM652, DM664, KAT30, RP45, DM604, DM613, DM810, DM814, DM815. They vary in terms of throughput, operating temperature, pressure settings, material used for manufacturing. Each consumer will be able to choose the option that is suitable for cost and characteristics.