Pressure Relief Valve

Pressure Relief Valve VHS-C


UNI EN ISO 4126-4-2006

The standard indicates: the general requirements for safety valves regardless the fluid for which they are designed. It applies to safety valves that have a usable passage diameter equal, greater than 6 mm for set pressures of 0.1 bar, or greater. There is no temperature limitation.

What does Pressure Relief Valve mean?

The suppression systems must be able to let the air pass and, at the same time, retain dust. In the event that the air has difficulty in passing through the filtration system, the silo internal pressure increases, making the use of the filter unnecessary. To solve the problems, it is mandatory to install a pressure control device that intervenes if a risk situation arises. This measure is called Pressure Control Valve, called PRV from the English acronym Pressure Relief Valve. In the event that the silo internal pressure reaches a limit value, both in positive and negative terms, the valve must open and allow the evacuation / introduction of air, with a consequent and connected emission of dusty material into the atmosphere, a verified condition in case of overpressure operation. An adequate powder loading system, therefore, must let the air pass and at the same time retain the material, avoiding the increase in internal pressure of the silo during the loading phase.
Frequent not provided valve openings generate multiple problems: dust emission into the atmosphere, resulting in a violation of environmental protection regulations and loss of product, with a consequent increase in maintenance and cleaning costs of the areas surrounding the emissions. Moreover, increased maintenance of the various components, which must be cleaned of any deposits in order not to decrease the effectiveness of operation.

Technical Features

From a technical point of view, the valve is a device able to restore normal operating conditions and should intervene rarely or only in cases of system anomaly. The pressure control valves represent the last possibility of venting if abnormal pressure conditions inside the silo endanger the structure. For this reason, it is necessary to intervene immediately if a situation of overpressure or depression arises. The valves are installed above the silos and hoppers to avoid pressure values, during loading, or depression, during unloading, which would compromise the silo structure and / or filter. The intervention values can be calibrated with special kits of springs or counterweights.
In general, the term "relief valve" refers to a valve within a pressurized system that is used to control pressure for the system optimal functionality. Relief valves are designed to help the facility avoid system failures, and protect equipment from over pressurized conditions. Relief Valves are designed to control pressure in a system, most often in fluid or compressed air systems. These valves open in proportion to the increase in system pressure. This means they don’t fly all the way open when the system is slightly overpressure. Instead, they open gradually, allowing the system to return to the preset pressure level. When that level is reached, the valve shuts again. The VHS-C Pressure Relief Valve is the last safety net when abnormal pressure conditions endanger the silo structure. This is why sudden excess or suction pressure inside the silo has to be dealt with instantly.

Technical Characteristics 

- Exhaust outlet elbow for connection to centralised suction system
- Mechanical set-up for inductive signalling sensor
- Vertical mild-steel or 304 stainless-steel flange spigot
- Low number of components
- Counterweight system never in contact with dust
- Membrane and exhaust duct with special geometry manufactured from innovative materials
- Polymer casing and weather protection cover
- Special properties of membrane and elbow prevent clogging and formation of material crusts.

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