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Pressure or 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
  • can be used as pressure or vacuum relief valve
  • compact, space-saving right-angle design
  • high flow capacity reduces costs through the use of smaller valves
  • non-corrosive
  • weight reduction in comparison to steel/stainless steel
  • high surface quality
  • different plastics can easily be combined
  • maintenance-friendly design

Function and Description

The PROTEGO® in-line valve R/KSM is a state-of-the-art pressure or vacuum relief valve in a right angle design made out of high-grade synthetic material. Typically, the valve is installed in the in-breathing or out-breathing lines of tanks, vessels, and process equipment to protect against unallowable overpressure or underpressure. The valve prevents emission losses almost up to the set pressure and prevents unacceptable product entry. The valve is a perfect solution for corrosive, polymerizing, or sticky substances.

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 for pressure and vacuum side is the same. Due to our highly developed manufacturing technology, the tank pressure is maintained up to the set pressure with a tightness that is far above to the conventional standard. This feature is ensured by special valve seats made of high quality synthetic material or PTFE. After the overpressure 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 chart on the following page

DN50 / 2" 80 / 3" 100 / 4" 150 / 6" 200 / 8"
a200 / 7.87245 / 9.65300 / 11.81370 / 14.57625 / 24.61 (650 / 25.59)*
b376 / 14.80521 / 20.51563 / 22.17 (523 / 20.59)*687 / 27.05 (651 / 25.63)*914 / 35.98 (912 / 35.91)*
c150 / 5.91200 / 7.87225 / 8.86280 / 11.02350 / 13.78
d180 / 7.09250 / 9.84300 / 11.81350 / 13.78 (405 / 15.94)*560 / 22.05 (500 / 19.68)*
Dimensions in mm / inches * Dimensions in brackets only for PVDF

Material selection for housing

Valve seatPEPPPVDF
Valve palletA, C, DB, C, DC, D
Special materials upon request

Material selection for valve pallet

Design A B C D
Pressure range [mbar]
[inch W.C.]
±6,0 up to ±16
±2.4 up to ±6.4
±5,5 up to ±16
±2.2 up to ±6.4
±9,5 up to ±30
±3.8 up to ±12
±30 up to ±100
±12 up to ±40
Valve palletPEPPPVDFHastelloy
Spindle guidePEPPPVDFHastelloy
Special materials and devices with higher set pressure or vacuum are available upon request

Flange connection type

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

Design Types and Specifications

The valve pallet is weight loaded. Highest set pressure range can be reached with metal valve pallets.

In-line pressure or vacuum relief valve, standard design


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.


Pressure or vacuum settings:

±6.0 mbar ±100 mbar (DN 50/2”)
±2.4 inch W.C. ±40 inch W.C.
±4.0 mbar ±100 mbar (DN 80/3”)
±1.6 inch W.C. ±40 inch W.C.
±4.5 mbar ±100 mbar (DN 100/4” - DN 200/8”)
±1.8 inch W.C. ±40 inch W.C.

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”.

Flow direction marked at the housing by ->
Tank connection for pressure relief function
Tank connection for vacuum relief function