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

Pneumatic Tips

Tips, Trends, Resources, News and Information

  • Pneumatics Blog
  • Industry News
  • Air Preparation
  • Engineering Basics
  • Equipment
    • Actuators
    • Cylinders
    • Fittings
    • Gears
    • Grippers
    • Pumps
    • Air Compressors
    • Tubing
    • Vacuums
    • Valves
  • Pressure Sensing
  • Design Guides
    • Design Guide Library
    • Hydraulic Valves
    • Electro-Pneumatic Regulators
    • Hydraulic Cylinders
    • Hydraulic Hose Assembly
    • Hydraulic Pumps
    • Pneumatic Actuators
  • Videos
You are here: Home / Engineering Basics / Critical safety functions within pneumatic systems

Critical safety functions within pneumatic systems

April 24, 2015 By Mike Santora Leave a Comment

Share

pneumatics-safety-emergency stop-buttonAs machine builders become more adept at the science of applying newer safety standards—such as ISO 13849—to their designs, they’ve started to take a deeper look at safety within their systems. Here are five of the most common safety functions within pneumatic systems.

1. Protection against unintended startup

Potentially the most common of all pneumatic safety, and often used in conjunction without pneumatic safety functions, protection from unintended startup is a vitally important safety function on many machines. This function is most often achieved by a purpose-built pneumatic safety valve that has been certified to achieve the required performance level. Simple, solenoid activated valves with a single valve element that are certified to performance level (PL) c are available from several manufactures. Applications requiring PL d or e often require a more sophisticated valve with redundant valve elements to achieve this function. When specifying this component, check to see if an external safe relay or safety PLC is required to comply with the certifying requirements. Some products achieve these performance levels with built-in electronics.

2. Exhausting

The requirements for this function are often very similar to the requirements for protection against unexpected startup, and this function can be realized within the same component that provides your protection against unexpected startup. In this case, because the exhausting device is also the pressure supply valve, care must be taken so that the failure of the device that shuts off incoming pressure doesn’t interfere with the exhausting behavior of the system. In the case of the devices that are certified to PL e, this is often accomplished by allowing much greater flow in the exhaust direction than the supply direction. In this case, the downstream pressure can still quickly decay to a safe level even if incoming flow fails to shut off.

Important note: The exhausting function can be easily defeated by a muffler element that is clogged with foreign material. Ensure that you get a safe muffler with your valve. Specially designed safe mufflers are available that prevent clogging by having a large exhaust path cross-drilled, thus ensuring exhaust capability.

3. Reversing the movement

In simple applications that require a low performance level, this function can be accomplished by applying a simple spring-return solenoid valve. In applications requiring a higher PL, such as “hands in press” applications, a more robust solution is required. This is accomplished using redundant valve elements, plumbed in such a way that they will only extend the cylinder when both valve elements have shifted. By sensing the position of each valve element and feeding these signals back to the safe PLC, Category 4 control architecture can be realized. While it is possible to achieve this performance with discreet components, certified components are available that achieve this function in an integrated package.

4. Stopping, holding, blocking

This safety function is applied in a wide variety of applications with varying performance level requirements. Simple applications can sometimes be satisfied by using a pilot-operated check valve installed in the cylinder port, while more complex applications with higher performance level requirements often require a mechanical rod brake or clamp that uses spring pressure to hold the piston rod in position when applied in combination with an appropriate valve.

5. Reducing speed

Reducing speed is probably the simplest of the common pneumatic safety functions. Simple flow controls can be made tamper resistant after initial validation to ensure that movement parameters are not altered at a later date.

Filed Under: Engineering Basics, Featured, Industry News

Reader Interactions

Leave a Reply

Your email address will not be published. Required fields are marked *

 

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Primary Sidebar

Fluid Power World Digital Edition

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.

RSS Featured White Papers

  • eBook: Practical Guide to Pneumatics
  • Saving energy and service cost with electric linear systems
  • White Paper-How to Design Efficient Pneumatic Systems!
Subscribe Today
Hose Assembly Tips

Follow Paul on Twitter

Tweets by @DW_Editor

Follow Mary on Twitter

Tweets by @DW_MaryGannon

Footer

Pneumatic Tips

Fluid Power World Network

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

PNEUMATIC 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 © 2022 · 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