Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Relief valves

Relief valves

Relief valves

What is the difference between Adjustable pop off/Inline relief valves and proportional relief valves

RE: Relief valves

It is not totally clear what you are asking, but I'll take a guess. A "pop" relief valve has a "huddling chamber area" that throws the valve open. The pressure must reduce below the set pressure before the valve will close. A proportional relief valve does not have a huddling chamber and it modulates with the incoming pressure, a lot like a control valve.

Good luck,

To a ChE, the glass is always full - 1/2 air and 1/2 water.

RE: Relief valves

From the catalogue data posted I can comments as follows;-
The comments Latexman advised earlier are basically correct - when Pressure Relief Valves are discussed in the API-526/ASME I, VIII sense.
In such cases you get
Safety Valves (pop opening on compressible fluids)
Relief Valves (proportional* opening with rise or reduction in pressure) *theoretical but difficult with spring loaded designs
Safety/Relief Valves - designs that cater for both (also used a general term - as is Pressure Relief Valve/Device)
The above can be spring loaded or pilot operated designs in the case of valves. All are generally right angle pattern.

However, many people (including the subject manufacturers) simply use loose terms such as relief valve for all types. Proportional type can and should only be limited to designs that can actually modulate and then on incompressible fluids, liquids, only. It is mainly prefered that proportional operation is used to prevent system/piping shock etc.

The Fitok open/close chart shows a linear lift and reseating - that is proportional.
The CircleSeal valve is an in-line valve (rather than end of line) with a non API design that allows a pop lift and reclose through a straight through design. These types can also be called, safety valves, relief valves, pop off valves, inline relief valves, air release valves etc., etc. These are also relatively low pressure.

Now. What I have stated is true in the ASME/API sense which most of the world uses besides USA. In the European Union, there is only one name and that is Safety Valve for all designs and applications. However, API/ASME is used and understood.

For further info on Pressure Relief Valves, please see attached Emerson PRV Engineering Handbook (read Anderson Greenwood Crosby). Page 2.1 starts with some definitions.

Hope that helps.

Per ISO, only the term Safety Valve is used regardless of application or design.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


White Paper: Industrial Control Basics: Contactors
A contactor is an electrical device used for switching an electrical circuit on or off. Considered to be a special type of relay, contactors are used in applications with higher current carrying capacity, while relays are used for lower current applications. Download Now
Research Report: State of IoT Adoption in Product Development 2019
This research report, based on a survey of 234 product development professionals, examines the current state of Internet of Things (IoT) adoption by product design teams, its perceived importance, and what features and capabilities teams consider important when making decision about adding IoT functionality to their products. Download Now
Research Report: Augmented Reality for Maintenance, Repair and Overhaul (MRO)
The term Industry 4.0 denotes a cluster of technologies that’s poised to fundamentally reshape manufacturing and bring about a new industrial revolution. These include 3D printing (AM), the Industrial Internet of Things (IIoT), artificial intelligence (AI) and mixed reality technologies, more commonly known as virtual reality (VR) and augmented reality (AR). Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close