• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Mobile Hydraulic Tips

Mobile Hydraulic Tips focuses on pumps, fittings, valves, manifolds and other products and news in the Mobile Hydraulics industry.

  • Hydraulics Blog
  • Industry News
  • Engineering Basics
  • Components
    • Cylinders
    • Fittings / Couplings
    • Pumps / Motors
    • Sensors / Gages
    • Valves / Manifolds
    • Related components
  • Hydraulic Fluids
  • Suppliers
  • FIND A DISTRIBUTOR

What is a relief valve?

June 21, 2019 By Mary Gannon

Share

A relief valve is a device used to limit pressure in one or more locations in a hydraulic circuit. A relief valve uses a spool or poppet engaged to the closed position by a spring. A spool is a cylindrical piece of machined steel that slides within a machined body. A poppet is a flat piece of machined steel attached to a stem, and the face of the poppet rests against a seat to provide superior sealing. A spool often provides better metering characteristics, but has significantly more leakage than a poppet design.

what are relief valves image courtesy of Hydac
Image courtesy of Hydac

When pressure rises in the portion of the circuit where the relief valve is installed, force acts upon the spool end or poppet face; the force applied by the spring opposes the force on the spool end or poppet face to keep the valve closed. Valve spring compression force is often variable — compression height can be reduced by an adjustable screw — although effective range is limited (for example, a spring might be effective between 1,000 and 5,000 psi or 100 and 1,200 psi, but rarely between 100 and 5,000 psi).

As hydraulic pressure continues to rise in the circuit where the valve is installed, force against the spool or poppet starts to overcome the opposing force of the spring, opening a flow path to the tank. As pressurized fluid exits the relief valve, energy is diverted (in the form of heat) until downstream pressure equals the spring value force, which could be drops of flow or all of pump flow, depending on the application and state of the circuit.

In short, a relief valve is a hydraulic component designed to limit pressure in an entire system or subcircuit by diverting pressurized flow to the reservoir. They are most often installed directly downstream of the pump to control system pressure, but can be used in other parts of the circuit to protect isolated components.

You may also like:

  • Hydraulic-Pumps-2
    What is the difference between fixed and variable pumps?

  • What is a flow divider?
  • Sun Hydraulics FLeX_XMD Solenoid-operated relief valves
    Solenoid-operated relief valves reduce system complexity while increasing safety
  • Ross Controls HBB Hydraulic safety Valve Systems 1536071037-2.jpg
    Ross Controls expands into hydraulics with hydraulic safety valve system

  • Directional valve offers best of both worlds

Filed Under: Components, Valves / Manifolds

Primary Sidebar

Design Guides

Pneumatic Actuators Design Guide

Hydraulic Cylinders Design Guide
Subscribe Today

Fluid Power World Digital Editions

Fluid Power World Digital EditionBrowse the most current issue of Fluid Power World and back issues in an easy to use high quality format. Bookmark, share and interact with the leading design engineering magazine today.

Follow us on Twitter

Tweets by @wtwh_paulheney

Follow us on Twitter

Tweets by MHydraulicTips

Follow us on Twitter

Tweets by DW_MaryGannon

Footer

Mobile Hydraulic Tips

FLUID POWER WORLD NETWORK

  • Fluid Power World
  • Hose Assembly Tips
  • Pneumatic Tips
  • Sealing and Contamination Tips
  • Fluid Power Distributor Lookup

MOBILE HYDRAULIC TIPS

  • Subscribe to our newsletter
  • Advertise with us
  • Contact us
  • About us
Follow us on Twitter  Add us on Facebook  Follow us on LinkedIn  Follow us on YouTube  Follow us on Instagram

Copyright © 2021 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy