Machine Guarding

Machines that are not properly safeguarded can cause serious injury, such as crushed or severed fingers, hands and arms, eye injuries, and even blindness.

If you’ve ever seen the gruesome result of a complex machinery accident, then you will appreciate the need for machine safeguards. When we talk about safeguards, we’re talking about simple devices or methods that protect make it difficult for workers from to injuringe themselves while working on a machine, like a shield or guard to protect from sparks, or a grate that keeps them away from the churning part of a rotary blade.

Shortcuts around machine safety features are a frequently cited cause for many machine related accidents, occurring when workers decide to forego the normal protocol of working with a safeguard and bypass it altogether, leaving them with considerable risk of harm and injury. Workers should never ignore the engineered controls or safety features of machinery—these devices exist for a reason.

OSHA requires that one or more methods of machine guarding be provided to protect the operator and other employees in the machine area from hazards created by moving parts, as well as preventing contact with other hazards such as heat, non-ionizing radiation, sharp edges, etc. Additionally, safeguards must remain securely in place, protect against falling objects, create no new hazards or interference, and allow for safe maintenance and lubrication of the machinery. Maintenance of machinery is a situation commonly related to machine accidents, so awareness in those situations is critical to personal safety, as is recognition of safeguards and proper protocol, like shutting down equipment, and locking out operation.

The safeguard must prevent hands, arms, and any other part of a worker's body from making contact with dangerous moving parts. A good safeguarding system physically eliminates the possibility of the operator or another worker placing parts of their bodies near hazardous moving parts. Physical barrier guards are an effective means for providing this protection, but sometimes this is not possible depending on a machine’s point of operation. In those situations a presence- sensing device is used, which stops a hazardous action before contact can be made.

In other instances, restraints such as a sweep or pull-back device are used. This requires physically removing the operator’s hands from the point of operation. Additional means for keeping an operator’s hands away from the point of operation hazard are two-hand constant pressure operating switches, which must be held down in order for the machine to operate. Some systems use combinations of both types of protective devices. If hazards are not within 7 feet of a place where they are accessible, they are considered guarded by location.

How does a safety professional determine which safeguards are necessary for a piece of machinery? They consider the type of operation, the size and shape of material, and the method of handling, placing, and removal of the material at the point of operation. Other considerations involve the physical layout of the work area and the production requirements. It requires both a detailed understanding of the machinery and of the procedure for operation that workers must follow to accomplish the task.

Methods of Machine Safeguarding

• Barrier guards
• Presence-sensing and physical restraint devices
• Guarding by location/distance
• Feeding and ejection methods
• Miscellaneous aids

Guards are barriers which protect against hazards from all sources, including access prevention to danger areas. The danger area, also called the danger zone, is the machine’s point of operation area from which the operator must stay clear during the machine’s operation cycle to prevent injury. There are four general types of barrier guards. These include fixed, interlocked, adjustable, and self-adjusting.

The second method for machine safeguarding is the use of safety devices. A safety device performs one of several functions. It may occupy both of the operator’s hands to keep them from entering the danger zone while the machine is cycling. This forces the operator to keep both hands and his body out of danger.

The safety device may be a presence-sensing kind that detects the presence of anything entering the danger zone and stops the machine in mid-cycle. Another form of device is the physical restraint variety. It is designed to physically withdraw the operator’s hands from the danger area during operation.

The third method for safeguarding is by location or distance. Safeguarding by location or distance means that hazardous moving machine parts must be inaccessible or must not present a hazard to a worker during the normal operation of the machine.

Miscellaneous aids are the last method of machine safeguarding. Miscellaneous aids do not provide complete protection from machine hazards, but they can provide the operator with an extra margin of safety. Some examples include awareness barriers, shields, placement and holding tools, and push sticks or blocks.