Lockout-tagout - Hazardous Energy and Its Isolation

Hazardous Energy and Its Isolation

Modern machinery can contain many hazards to workers, from things like electrical, mechanical, pneumatic or hydraulic sources. For example a typical industrial machine may contain things like hot fluids, moving presses, blades, propellers, electrical heaters, conveyor belts with pinch points, moving chains, ultraviolet light, etc.

Disconnecting or making safe the equipment involves the removal of all energy sources and is known as isolation. The steps necessary to isolate equipment are often documented in an isolation procedure or a lockout tagout procedure. The isolation procedure generally includes the following tasks:

1. Identify the energy source(s)
2. Isolate the energy source(s)
3. Lock and Tag the energy source(s)
4. Prove that the equipment isolation is effective

The locking and tagging of the isolation point lets others know not to de-isolate the device.

The National Electric Code states that a safety/service disconnect must be installed within sight of serviceable equipment. The safety disconnect ensures the equipment can be isolated and there is less chance of someone turning the power back on if they can see the work going on. These safety disconnects usually have multiple places for locks so more than one person can work on equipment safely.

In industrial processes it can be difficult to establish where the appropriate danger sources might be. For example, a food processing plant may have input and output tanks and high temperature cleaning systems connected, but not in the same room or area of the factory. It would not be unusual to have to visit several areas of the factory in order to effectively isolate a device for service (e.g. device itself for power, upstream material feeders, downstream feeders and control room).

Modern safety manufacturers provide a range of isolation devices specifically designed to fit various switches, valves and effectors. For example, most modern circuit-breakers have a provision to have a small padlock attached to prevent their activation. For other devices such as ball or gate valves, plastic pieces which either fit against the pipe and prevent movement, or clam-shell style objects, which completely surround the valve and prevent its manipulation are used.

A common feature of these devices is their bright color, usually red to increase visibility and allow workers to readily see if a device is isolated. Also, the devices are usually of such a design and construction to prevent it being removed with any moderate force. (That is to say that an isolation device does not have to stand up to a chainsaw, but if an operator forcibly removes it, it will be immediately visible that it has been tampered with).

To protect one or more circuit breakers in an electrical panel a lockout tagout device called the Panel Lockout can be used. It keeps the panel door locked and prevents the panel cover from being removed. The circuit breakers remain in the off position while electrical work is done.