Generally, the valves are components that allow you to regulate the flow of fluid in a hydraulic system. The applications, as well as the materials used for their manufacture, are countless. Thus, there are a wide array of these components to select from according to their intended use and function.

Among the variety, the non-return or check valve, within the dispensing systems, are normally installed on the suction hoses connected to the pumps in order to allow the flow to occur in one direction only thus preventing a back-flow.

They are particularly useful for two main reasons:

• they prevent the emptying of the system when the pump stops;
• by maintaining some fluid in the suction hose, when the transfer begins, the flow meter connected to the system can measure a true flow of the fluid and not only air/empty flow.

But, what can happen in these cases?

The installation of a non-return valve may have some disadvantages:

• when some fluid remains in the delivery hose, the liquid – due to the physical property of the fluids – if overheated (for example when the dispenser is placed in a sunny area) increases its pressure because the container in which it is housed has a fixed volume (the hose). The non-return valve stops the fluid within the hose and doesn’t allow dilatation towards the tank (where the fluid can expand itself freely);
• during transfer; if the valve skips suddenly, an over-pressure is created within the hose; the so-called physical phenomenon “water hammer”: the over-pressure is caused by the lack of release of the pressure wave in the system caused by the skip of the valve itself;
• in case of accident; such as crushing the delivery hose with stagnant fluid; in this case damage to the other components of the system may occur due to the increase of the fluid’s pressure (caused by the crushing) that cannot escape from the system because of the non-return valve.
  

To avoid all these situations, PIUSI has developed a special foot valve with a built-in SAFETY mechanism that ensures all the advantages of a non-return valve, thus avoiding all disadvantages: in the PIUSI non-return valve a second mini-safety valve is installed to discharge up to 3.5 bar in the system thus eliminating all the effects caused by a pressure increase in case of over-heating, “water hammer” or accident.

The PIUSI SAFETY VALVE is installed in all the dispensing systems during the production phase. It can also be purchased separately as a spare part or accessory to secure an already active dispenser. Especially when a flow meter is installed in the system to allow a correct measurement of the fluid.

PIUSI non-return valve with integrated SAFETY valve is available with a 1” in/out.