Check valves are devices placed on systems with a view to controlling the fluid and with the aim of directing the flow in a single direction. Typically, these valves are formed by a shutter, disc or ball, constrained by a guide and pushed by a spring against a seat. If there is insufficient or no fluid pressure, to the extent that it infers on the force of the spring, the valve remains closed. The passage of the fluid takes place when the system pressure increases to the point that it opens the valve, subsequently overcoming the elastic force of the spring.
Check valves can be divided into different types: disc, swing, ball or back pressure. Disc check valves can be inserted between the flanges and the seal, which can be chosen either in plastic or metal. Swing check valves are made from carbon steel or stainless steel and are manufactured in compliance with international standards (DIN, ISO). The Italvalvole® back pressure valves are made of stainless steel: the parts in contact with the fluid are in AISI 316 while the seals are in PTFE and EPDM. They are generally used on pump feed pipes so as to prevent the return of the pumped flow.
The operating principle is very simple: as soon as the pumped fluid reaches the pressure value to the point that it overcomes the spring force, the shutter opens and lets the fluid pass through. When the pressure value drops below the value that counteracts the spring force, the shutter closes. One unusual aspect of these valves is the possibility of being able to adjust the pressure value of the valve opening within a certain range, so as to ensure that the fluid reaches the user with a certain pressure value
Check valves are generally used in hydraulics, installing them on the circulation pumps' feed pipes and thus allowing for the direction of flow to be regulated avoiding the reflux, that is, the return of liquids when the tap is turned off. They are also applied to prevent the system from emptying in the event of the pump stopping and for all the other requirements for controlling the flow of fluid.