What is Machine Guarding?

Most machines have cutting blades or rotating/moving parts that can cause bodily harm if they come in contact with plant workers operating the equipment or working nearby. To protect workers from hazards related to machinery, machine guards are used. Machine guarding is a safety mechanism that typically comprises of a shield or a device covering hazardous locations of the machine to prevent contact with body parts or contain hazards like chips or sparks from coming out of a machine. Machine guards assist in preventing injuries, reducing risks and improving safety.

Types of Machine Guards

Machine guards can be classified into 6 types:

• Fixed guards.
• Automatic guards.
• Interlocked guards.
• Trip guards.
• Positional and distance guards.
• Electro-sensitive safety devices.

Fixed Guards

By nature of their position, these machine guards prevent access to dangerous parts.

Automatic Guards

This type of guards move in advance of each operation or stroke of a machine and sweep or push the operator’s arm or person out of the way before the stroke is made or automatically take up position similar to a fixed guard before the danger can arise. They are sometimes employed in applications where material or blanks are fed by hand into the machine.

Automatic guards are best combined with trip guards; however, they have being replaced by interlocked guards in most plants.

Interlocked Guards

These guards are moveable and their movement is interconnected with the power of control system of the machine. They should be correctly adjusted before any potentially dangerous operation can start.

Trip Guards

Trip guards stop the machine or automatically cause the appropriate action to be taken immediately danger arises. Most often than not, they can be combined to the advantage with automatic guards or with positional and distance guards.

Positional and Distance Guards

These are often a rather a basic form of fixed guard, placed so that to keep an operator or other person at a safe distance from a machine which cannot be enclosed because of the nature of the material being handled or the work being performed.

Electro-Sensitive Safety Devices

Barriers or screens of interlaced light beams are used widely on machines such as power presses, bending brakes and guillotines, where the size and shape of the work pieces prevent complete enclosure with fixed guards.

The risk of failure with such machines can lead to serious injuries so this demands that the design of these guards be a specialized issue with check circuitry and timing requirements to prevent failures to danger as per international Standards that specify the safety integrity for these devices.

Related articles:

• Safety Function in a Machine Control System
• Demand Mode vs. Continuous Mode Safety Function
• What is Safety Related Control System (SRCS)?
• Hazardous Locations Classifications
• Methods of Protecting Instruments from Explosive Atmospheres