Locks, tags and lockout devices

A lockout is only as good as the hardware that holds it. A lock that can be pried off with a screwdriver, a breaker lockout that slips off the handle, a valve cover that does not fit, or a tag that fades in the rain can all leave a worker exposed while believing they are protected. This lesson describes the main types of lockout hardware, the requirements they must meet, and the limits of tags.

Requirements for lockout hardware

CSA Z460 and Canadian regulations expect lockout devices to be suitable for the conditions, to hold the isolating device in the safe position, and to identify the person who applied them. Personal locks must be individually keyed, with the key kept by the person who applied the lock, and several provinces add specific rules: British Columbia, for example, prohibits combination locks and requires each personal lock to be marked or tagged to identify the worker.

In practice, good hardware is:

• dedicated: used only for lockout, never for tool boxes, lockers or gates;
• individually keyed, with one key per lock held by the person who applied it;
• identified, with the worker's name, photo or number on the lock or an attached tag;
• standardized, so that everyone recognizes a lockout lock at a glance, often by a distinctive colour;
• suitable for the environment: non-conductive bodies for electrical work, corrosion-resistant materials for wet or chemical areas, high-temperature rating near hot equipment;
• matched to the isolating device, so it holds the device firmly in the off or closed position.

Personal locks and keys

The personal lock is the core of the system. Most programs issue each authorized person a set of locks, all keyed alike for that person but different from everyone else's, so one key opens all of that person's locks and no one else's. Some programs use a different colour for each department or trade, or a special colour for supervisors' or contractors' locks. Duplicate or master keys are a weak point. If they exist at all, they must be strictly controlled, logged and used only under the formal lock removal procedure in lesson 9.

Locks should have the person's name and photo or another clear identifier. A lock that says only 'Danger' does not tell anyone whom to find if the lock is still on at the end of a shift.

Devices for electrical isolation

Electrical disconnect switches designed for lockout have a hasp or a hole in the handle that accepts a padlock when the switch is in the off position. Circuit breakers need an add-on device: clamp-on breaker lockouts that grip the toggle, pin-in or pin-out devices that fit into holes in the breaker, or panel-mounted devices for large moulded case breakers. Plug lockouts are boxes or covers that enclose the plug of cord-and-plug equipment so it cannot be reconnected. Fuses that are removed should be kept by the authorized person, and the fuse holder may need a lockout device. Lockout devices on electrical equipment are often made of non-conductive materials.

Lockout must be applied at the energy-isolating device, not at a control. Locking a start button cover or a control panel door does not isolate the energy.

Devices for valves and fluid systems

Valves are locked with devices that fit over or around the handle. Gate valve covers enclose the handwheel so it cannot be turned. Ball valve lockouts clamp around the lever so it cannot move from the closed position. Butterfly valve lockouts and universal valve lockouts with adjustable arms fit other designs. Cable lockouts, which thread a steel cable through several handles and lock its ends, are useful where several valves or awkward handles must be secured together.

For hazardous chemicals, steam and high-pressure lines, closing a single valve may not be enough, because valves leak. Stronger isolation methods include double block and bleed (two closed valves with an open vent between them), physically disconnecting and capping the line, or inserting a blank or blind flange. Pneumatic lines can be isolated with lockable quick-disconnect devices that prevent the hose from being reconnected.

Blocks, pins and restraints

Gravity and mechanical energy are often controlled with physical restraints rather than locks on isolating devices. Examples are die blocks placed between the platens of a press, safety props under a raised dump body, pins inserted through holes in a lift mast, and chains or straps that hold a part in place. These must be rated for the load, positioned according to the procedure, and themselves locked or tagged where possible so no one removes them while people are exposed.

Hasps and group lock boxes

When several people work on the same equipment, each must be able to apply their own lock. A hasp is a hinged steel loop with several holes. It is placed on the isolating device, and each worker puts their lock through a hole. The isolating device cannot be operated until every lock is removed and the hasp is opened. Hasps typically hold four to six locks, and hasps can be linked for more.

For larger jobs, a group lock box is more practical. The isolating devices are locked with a set of locks whose keys are placed in the box; each worker then puts their personal lock on the box. Lesson 8 explains group lockout in detail.

Tags: what they do and what they cannot do

A tag is a warning device. It identifies who applied the lockout and why, and it warns others not to operate the equipment. Tags are attached to locks in almost every program, because a lock alone may not say who applied it or why. A good tag:

• carries a clear warning such as 'Danger: Do not operate';
• shows the name of the person, the date, the reason and a contact number;
• is durable enough for the environment, including moisture, chemicals and sunlight;
• is attached securely so it cannot come off by accident.

CSA Z460 and Canadian regulations treat tags as supplementary to locks. Tag-only systems are not an acceptable substitute for lockout under most provincial regulations, except where an alternative method has been justified by a risk assessment and gives equivalent protection.

Whatever the rules, everyone must understand the limitations of tags:

• a tag is a warning, not a physical barrier, and does not stop anyone from operating the device;
• tags must be legible and understandable by everyone, including workers who read a different language or have limited literacy;
• tags can be torn off, fall off or become illegible;
• tags can give a false sense of security;
• a tag must never be removed or ignored by anyone other than the person who applied it, or bypassed in any way.

Inspecting and caring for hardware

Lockout hardware wears out. Locks corrode, shackles bend, breaker lockouts lose their grip, valve covers crack and cable lockouts fray. Authorized persons should inspect their devices before use and remove damaged items from service. Hardware should be stored at lockout stations near the equipment so it is available when needed; a common reason for skipping lockout is that the right device was not at hand. A well-stocked lockout station with labelled devices for the machines in that area makes the correct choice the easy choice.

Lockout for equipment that cannot accept a lock

Older equipment may have isolating devices that were never designed for a lock: a disconnect without a hasp, a valve with a removable handle, a breaker without lockout holes. The right long-term fix is to modify or replace the isolating device so it can be locked. In the meantime, programs use adaptable devices such as universal breaker lockouts, cable lockouts or valve covers, or remove a handle or circuit element and secure it, combined with additional measures. Any interim method must be written into the machine procedure so that every authorized person applies it the same way.