2700 Series - Process Valve - Pressure Relief Valve

Product Brand: Farris

Designed to provide customers with the widest selection of sizes, orifices, and construction materials, the Series 2700 meets the exact demands of the process industry.


The 2700 Series pressure relief valve, also known as an expansion relief valve, features a superior design that handles air, steam, vapor, and liquid services. In addition, the fixed blowdown design simplifies testing and repair, and the maximum interchangeability of parts allows for easy maintenance.



  • Metal Seat with optional o-ring
  • Balanced design option
  • Flanged option
  • Optional welding nipple and sanitary connections
General Specifications:
Size 1/2” x 1” to 1-1/2” x 2-1/2”
Orifice Areas C (0.068 sq2) to G Orifice (0.573 sq2)
Set Pressure Ranges 15 to 6500 psig (1.0 to 413 barg)
Temperature Ranges -320 to 750°F (-195 to 399°C)
Flange Classes 150# – 2500#
Suitable for Air, Gas, Vapor, Steam & Liquid Service
Materials of Construction Carbon Steel
Stainless Steel
Low/High Temperature Alloy Steels
Hastelloy C
NACE Compliant Materials


  • ASME/NB Section VIII and III for Air, Steam and Water
  • CSA B51 (Canada CRN)
  • ISO 9001- 2008
  • PED 97/23/EC (European Pressure Equipment Directive)
  • ATEX 94/9/EC (European Potentially Explosive Atmospheres)
  • CSQL (China)
  • GOST-R (Russian)
  • US Coast Guard
  • Nuclear – 10 CRF 50 Appendix B, NCA-4000, NQA-1 N285.0
  • First Point Assessment Limited


Expansion relief valves, also referred to as PRV’s, pressure relief valves, or safety valves, are designed to protect system tanks from overpressure, therefore a vital component.  Overpressure can be caused by several things, including failure of an expansion vessel or a pressure-reducing valve. 



Carrying on pressure tests on systems consists of adjusting the valve set pressure, performing a seat l,eakage test and a backpressure test. The set pressure test is always performed first.

For information on how to perform pressure testing, please see the related document here.



Expansion relief valves are used in a range of industry demanding applications where pressure levels are critical for operation. Applications and industries include:

  • Oil and gas
  • Petrochemical
  • Power generation (using steam, air, gas or liquid.)


What does a pressure relief valve do?

Air pressure relief valves, also known as PRVs or safety release valves, are installed to prevent pressure buildup. The valve opens slowly to release pressure when the level becomes too high.

Why do I need a pressure relief valve?

If the pressure within an air compressor system gets too high, one of the components inside could explode. Essentially, pressure relief valves are designed to prevent uncontrolled depressurization events from occurring, protecting surrounding nearby equipment and employees during overpressure events.

How do you perform a backpressure test on an expansion relief valve?

To carry out a backpressure test, follow the following steps:

  1. The backpressure test applies to all valves designed to discharge to a closed system, including valves with plain caps and packed lever assemblies.
  2. Test the secondary pressure zone of all valves exceeding 1" inlet size with air or other suitable gas at a pressure of at least 30 psi. Use a suitable leak detection solution to verify tightness of all gasket joints and vent/drain plugs.
  3. If leakage is detected at any location, rework the valve to eliminate the leak path.

How does a expansion relief valve work?

Expansion relief valves are often known as pressure relief valves and for a good reason. They come with a preset pressure built into their design to ensure once the valve recognizes the pressure limit, it opens to release the pressure-flow (fluid of compressed air) safely.

Where should a pressure relief be located?

It’s advisable to permanently mount pressure relief valves in a vertical position so the spindle sits correctly and can operate effectively. Overtightening the valve can cause damage to the inlet and cause leakage too. For the inlet piping, keep it short and direct, it should have a shorter diameter than the valve, and it should always be far away from turbulence or vibration in the operating system. 

What causes a pressure relief valve to go off?

A pressure relief valve can encounter overpressure or failure for many reasons, but the most common reasons are typically blocked discharge in the system, contaminants like dirt, rust, or sludge, or even valve misalignment can cause the pressure relief valve to fail. Maintenance and proper inspection periodically can help eliminate leakages, allowing a safe environment for operation and the operators.  

2700 Series - Process Valve - Pressure Relief Valve
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