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Pressure and Vacuum Relief Valve, In-Line

  • 10% technology for minimum pressure increase up to full lift
  • extreme tightness, resulting in lowest possible product losses and reduced environmental pollution
  • based on 10% technology, set pressure is close to opening pressure for optimum pressure maintenance in the system as compared to conventional 40% or 100% technology
  • high flow capacity reduces costs through the use of smaller valves
  • connection for vent line
  • can be used in explosion hazardous areas
  • sturdy housing design (PN 10)
  • maintenance-friendly design

Function and Description

The PROTEGO® in-line valve DV/ZW is a state-of-the-art pressure and vacuum relief valve with separate flange connections for use in a vent line. Typically, the valve is installed in the in-breathing and out-breathing lines of tanks, vessels, and process equipment to protect against unallowable overpressure and underpressure. The valve prevents emission losses almost up to the set pressure and prevents air intake almost up to set vacuum. It is designed in a way that if the set pressure is exceeded, the vapors are released into an exhaust pipe (e.g., vent header). If the set vacuum is exceeded, atmospheric air is pulled into the system. For structural reasons, the vacuum valve pallet is one size smaller than the pressure valve pallet.

The device will start to open as soon as the set pressure is reached and only requires 10% overpressure to full lift. Continuous investments in and a commitment to research and development have allowed PROTEGO® to develop a low pressure valve which has the same opening characteristic as a high pressure safety relief valve. This “full lift type” technology allows the valve to be set at just 10% below the maximum allowable working pressure or vacuum (MAWP or MAWV) of the tank and still safely vent the required mass flow. The opening characteristic of the pressure and vacuum side is basically the same. However, the in-breathing will start as soon as the differential pressure between the atmospheric pressure and the tank is greater than the set pressure of the vacuum valve pallet. Due to our highly developed manufacturing technology, the tank pressure is maintained up to set pressure with a tightness that is far above the conventional standard. This feature is ensured by valve seats made of high quality stainless steel and with individually lapped valve pallets (1), or with an air cushion seal (2), in conjunction with high quality FEP diaphragm. The valve pallets are also available with a PTFE seal to prevent the valve pallets from sticking when sticky products are used and to enable the use of corrosive fluids. After the over pressure is released or the vacuum is balanced, the valve re-seats and provides a tight seal.

The optimized fluid dynamic design of the valve body and valve pallet is a result of many years of research, resulting in stable operation of the valve pallet, optimized performance, and reduced product losses.


To select the nominal size (DN), please use the flow capacity charts on the following pages

DN40 / 1½“ 50 / 2" 80 / 3" 100 / 4" 150 / 6"
a280 / 11.02280 / 11.02340 / 13.39390 / 15.35520 / 20.47
b230 / 9.06230 / 9.06240 / 9.45290 / 11.42330 / 12.99
c85 / 3.3585 / 3.35125 / 4.92140 / 5.51185 / 7.28
d210 / 8.27210 / 8.27280 / 11.02310 / 12.20390 / 15.35
Dimensions in mm / inches Larger sizes upon request Dimensions for pressure and vacuum relief valve with heating jacket upon request

Material selection for housing

Design AB
HousingSteelStainless Steel
Heating jacket (DV / ZW-H-...)SteelStainless Steel
Valve seatStainless SteelStainless Steel
Option: Housing with ECTFE-lining Special materials upon request

Material selection for pressure valve pallet

Design ABCD
Pressure range [mbar]
[inch W.C.]
+2.0 up to +3.5
+0.8 up to +1.4
>+3.5 up to +14
>+1.4 up to +5.6
>+14 up to +60
>+5.6 up to +24
>+14 up to +60
>+5.6 up to +24
Valve palletAluminiumStainless SteelStainless SteelStainless Steel
SealingFEPFEPMetal to MetalPTFE
Special materials upon request For higher set pressures refer to type DV/ZW-F.

Material selection for vacuum valve pallet

Pressure range [mbar]
[inch W.C.]
-3.5up to -5.0
-1.4up to -2.0
<-5.0 up to -14
<-2.0up to -5.6
<-14up to -35
<-5.6 up to -14
<-35 up to -50
<-14 up to -20
<-14 up to -35
<-5.6 up to -14
<-35 up to -50
<-14 up to -20
Valve palletAluminiumStainless SteelStainless SteelStainless SteelStainless SteelStainless Steel
SealingFEPFEPMetal to MetalMetal to MetalPTFEPTFE
Special materials and lower set vacuum upon request.

Flange connection type

EN 1092-1; Form B1
ASME B16.5 CL 150 R.F.
other types upon request

Design Types and Specifications

The valve pallets are weight loaded. Higher set pressures are achieved by using spring loaded type DV/ZW-F
Two different designs are available:

In-line pressure and vacuum relief valve, standard design

DV/ZW - –

In-line pressure and vacuum relief valve with heating jacket


Additional special devices available upon request
Within piping systems the influence of backpressure has to be considered in deciding the set pressure and opening characteristics. For special design solutions (e.g. partial load operation) the valve can be supplied with standard valve pallets (with proportional opening function).


Pressure: +2.0 mbar +60 mbar
+0.8 inch W.C. +24 inch W.C.
Vacuum: -3.5 mbar -50 mbar
-1.4 inch W.C. -20 inch W.C.
For higher set pressure refer to type DV/ZW-F.
Lower set vacuum upon request.

Flow Capacity Chart

The flow capacity charts have been determined with a calibrated and TÜV certified flow capacity test rig. Volume flow V in (m³/h) and CFH refer to the standard reference conditions of air ISO 6358 (20°C, 1bar). For conversion to other densities and temperatures refer to Sec. 1: “Technical Fundamentals”.