Machinery Guards-Environmental Health & Safety - Carnegie Mellon University

Machinery Guards

Machine guards are your first line of defense against injuries caused by the operation of any kind of machinery.  OSHA regulations require guarding anywhere there is a danger of having any body part come in contact with a moving part.

There are five general types of safeguards that are permitted to be used:

(1)    Location - If a piece of equipment is located so that it is impossible to come in contact with it, or for someone to be contacted by any part of the process (e.g., splashing) no physical guarding is necessary.  An example of this would be an exhaust fan mounted in an outside wall 15' above floor level and out of reach of employees.

(2)    Guards - These are physical barriers that prevent contact.  They are the most common type of protection we have at CMU, and we have them in nearly all our mechanical rooms.  Examples of these are guards over pump couplings, motors, belt drives, etc.

(3)    Devices - Devices limit or prevent access to the hazardous area.  Examples of devices are photocells (sometimes called "electric eyes") that stop a machine if your hand enters a sensing field, or an interlock that requires all components to be in assigned positions before a machine will operate.

(4)    Automated feeders and ejectors - These are normally found only in manufacturing operations.  They are designed to automatically feed stock into a machine without requiring the operator to place his hands into a dangerous position.  Punch presses use this type of guarding.

(5)    Miscellaneous aids - Examples of these are shields to prevent sparks or chips from striking people in the immediate area, holding tools that an operator can use to keep his hands out of the way of moving parts, or even a rope barrier (often called an awareness barrier) that keeps you away from the machine.

Guards must be durable and secured or anchored so that they will not move during operation, but they have to be easy to remove for maintenance.  They are not permitted to create a hazard themselves.  An example of such a hazard would be a guard that is so large that it forces anyone walking past to take a more dangerous route.

The moving parts of any machine present a potential for severe injury.  Amputations, fractures, lacerations, or crushing injuries are all too common, and in the presence of large moving parts, not often found here at CMU fortunately, people have been pulled into the machinery and suffered fatal injuries.  Understanding the purpose and importance of machine guarding is important to anyone working around even the smallest of moving parts, such as a belt pulley.

The most common problems we are seeing on campus are missing guards or guards that do not provide complete protection.  Many of our older guards are open in the back, making it very easy for a worker to reach around for something and have his hand pulled into an operating drive pulley.  As we discover these we are getting them fully enclosed.  If you are aware of any, let your foreman know, or call Jim Gindlesperger in EH&S so it can be placed on a repair list.

If you take a guard off a piece of equipment to perform maintenance, be sure to replace it.  Often our inspections find guards sitting on the floor beside the piece of equipment they are meant to guard.  Having them beside the equipment, or even nearby, provides zero protection.  Guards must be in place to be effective.  Always replace guards that you remove to perform a repair or maintenance.  If you run across any guards that have been left off, replace them, also. 

Be sure to understand how guards work, and why we need them.  It could save you from a serious injury.