Pressure and Vacuum Relief Valves
Below the technical fundamentals of the PROTEGO® pressure and vacuum relief valves are summarised. You can find more detailed information under "PROTEGO® Technology" - Volume 1 of the Online-Catalogue.
PROTEGO® pressure and vacuum relief valves have weightloaded or spring-loaded valve pallets. When there is excess pressure in the tank, the pressure valve pallet guided in the housing lifts and thereby releases the flow into the atmosphere (Fig. 3a) until the pressure falls below the set pressure. The valve then recloses. The vacuum side of the valve is tightly sealed by the additional overpressure load. When there is a vacuum in the tank, the overpressure of the atmosphere lifts the vacuum disc and the tank is vented (Fig. 3b).
In principle, the diaphragm valve, which is loaded with liquid (as a weight), and the pilot-valve, which is self-controlled, operate in the same manner.
The weight-loaded valve pallets have different designs. A distinction is made between the full-lift pallet (Fig. 4 and Fig. 5a, b) and the normal pallet (Fig. 6).
The sealing between valve pallet and valve seat is provided by an FEP air cushion seal, a metal to metal sealing, or PTFE flat sealing depending on the set pressure or on the application. The best sealing is obtained with a metal valve disclapped to be seated on the metal valve seat (metal to metal). When the set pressures are low, an FEP air cushion seal provides a tight seal. The tightness of the PROTEGO® valves is far above the normal standard (DIN 3230 leakage rate B0 or API 2526) and hence meets the stringent demands of emission control regulations.
PROTEGO® pressure and vacuum relief valves have weightloaded or spring-loaded valve pallets. When there is excess pressure in the tank, the pressure valve pallet guided in the housing lifts and thereby releases the flow into the atmosphere (Fig. 3a) until the pressure falls below the set pressure. The valve then recloses. The vacuum side of the valve is tightly sealed by the additional overpressure load. When there is a vacuum in the tank, the overpressure of the atmosphere lifts the vacuum disc and the tank is vented (Fig. 3b).
In principle, the diaphragm valve, which is loaded with liquid (as a weight), and the pilot-valve, which is self-controlled, operate in the same manner.
The weight-loaded valve pallets have different designs. A distinction is made between the full-lift pallet (Fig. 4 and Fig. 5a, b) and the normal pallet (Fig. 6).
The sealing between valve pallet and valve seat is provided by an FEP air cushion seal, a metal to metal sealing, or PTFE flat sealing depending on the set pressure or on the application. The best sealing is obtained with a metal valve disclapped to be seated on the metal valve seat (metal to metal). When the set pressures are low, an FEP air cushion seal provides a tight seal. The tightness of the PROTEGO® valves is far above the normal standard (DIN 3230 leakage rate B0 or API 2526) and hence meets the stringent demands of emission control regulations.
PROTEGO® pressure and vacuum relief valves with full-lift pallet discharge the flow within 10% overpressure from the set pressure to a fully opened valve (full-lift).
This is attained by precisely harmonizing the diameter and height of the valve pallet rim with the adapted, machined and lapped valve seat. In addition, the flow-enhancing design reinforces the overall effect on the outflow side. These valve pallets are used in end-of-line and in-line valves.
This is attained by precisely harmonizing the diameter and height of the valve pallet rim with the adapted, machined and lapped valve seat. In addition, the flow-enhancing design reinforces the overall effect on the outflow side. These valve pallets are used in end-of-line and in-line valves.
PROTEGO® pressure and vacuum relief valves with conventional pallets discharge the flow within a 40% pressure rise with a proportional response.
After the initial response, the rise in pressure is proportional to the discharged flow up to a full lift. When the back pressure in the connected pipeline is high or the valve is installed in combination with a pressure control valve, this method provides greater stability for the overall system. However, the overall flow performance is not as good as that of valves with full-lift valve pallets. These valve pallets (Fig. 6) are primarily used in in-line valves when required by operating conditions.
After the initial response, the rise in pressure is proportional to the discharged flow up to a full lift. When the back pressure in the connected pipeline is high or the valve is installed in combination with a pressure control valve, this method provides greater stability for the overall system. However, the overall flow performance is not as good as that of valves with full-lift valve pallets. These valve pallets (Fig. 6) are primarily used in in-line valves when required by operating conditions.
Depending on the design of the valve and the valve pallets, the design pressure and design vacuum (negative pressure) is achieved with different overpressure (Fig. 7). Unless otherwise agreed, the standard PROTEGO® valve design is for 10% technology.
Advantages of PROTEGO® 10%-technology:
Advantages of PROTEGO® 10%-technology:
Pressure conservation very close to the maximum allowable tank pressure
Minimization of product losses
Reduction of vapour emissions
