This is why sudden excess or suction pressure inside the silo must be dealt with instantly. Even though ideally a VHS Pressure Relief Valve should never have to go into action, it must be efficient and reliable if needed.
VHS Pressure Relief Valves consist of a cylindrically shaped metal body with clamp connection spigot to the silo, an exhaust outlet spout for duct connection, an elastic diaphragm able to re-establish pressure balance instantaneously, a counterweight kit to keep the Valve closed under normal conditions, and a weather protection cover.
For some time, tighter safety regulations in industrialized countries have ensured stricter enforcement of rules regarding the safeguarding of silos and bins against excess and negative pressure. There is no question that other countries will have to follow this example.
The counterweight-loaded VHS-type Pressure Relief Valve has one decisive advantage over the other type manufactured by WAM®, the VCP. Due to the moment of inertia of the helical springs on the VCP, pressure balance is re-established extremely quickly but not instantaneously.
The VHS, on the other hand, does the job in real time. Through an interplay of pressure on different surface areas on both sides of a diaphragm fitted inside the valve housing, perfect pressure balance is achieved.
In the event of excess pressure this interaction enables air from inside the silo to flow back into the atmosphere; in case of suction pressure the air penetrates from the atmosphere into the silo.
Performance & Technical Features - Benefits of VHS Pressure Relief Valves
- Casing in carbon steel (VHS2731B), painted RAL 7001 (silver-grey) or in 304 stainless steel (VHS2732B)
- Body diameter = 273mm (10 in)
- Air volume up to 5,000m3/h (2,950 cfm)
- Exhaust outlet spout for connection with centralised suction system
- These Valves are preset for a maximum negative pressure of - 0.005 bar (0.07 psi) and a maximum excess pressure of + 0.05 bar (0.72 psi).
- Should customer requirements be different, the Valves can be set at a maximum excess pressure ranging from + 0.02 bar (0.29 psi) to + 0.08 bar (1.16 psi).
- Weight: 22 kg (49 lbs)
- Small overall dimensions
- Short maintenance time
The working principle of the VHS Pressure Relief Valve itself is innovative. Its special double-acting diaphragm pervious to air sees to both excess and suction pressure relief. The special properties of the diaphragm avoid blockage, as well as the formation of material crusts.