Guard removal, bypassing, maintenance and lockout

Most machines that injure people were guarded at some point. The guard had been removed for maintenance and not replaced, an interlock had been taped down to save time, a light curtain had been moved out of the way, or a worker reached in to clear a jam while the machine was still energized. This lesson looks at why safeguards are defeated, how to prevent it, and how guarding connects with the control of hazardous energy during maintenance and servicing.

How common is defeating safeguards?

Defeating safeguards, sometimes called bypassing, manipulation or tampering, is widespread. A frequently cited study by the German Institute for Occupational Safety and Health (IFA) estimated that roughly a third of protective devices on machines in Germany were manipulated, permanently or temporarily, and that manipulation contributed to a substantial share of machine accidents. Inspection blitzes in Canada and enforcement data in the United States tell the same story: missing, removed and defeated guards are among the most common findings.

Why people defeat safeguards

People rarely defeat safeguards out of carelessness alone. They usually do it because the safeguard makes the job harder, slower or impossible, and because the organization rewards output. Common reasons include:

• The guard blocks the view of the work, so the operator cannot see what they are doing.
• Jams are frequent, and opening an interlocked door means a long restart sequence.
• The interlock trips during setup or adjustment tasks that the designers did not consider.
• The guard makes loading or unloading awkward or slow.
• The light curtain causes nuisance trips from swinging workpieces, chips or reflections.
• There is production pressure, piece-rate pay or a supervisor who tolerates shortcuts.
• The safeguard is poorly maintained and fails often, so people learn to work around it.

Understanding these reasons points to the solution. If a safeguard is being defeated, the safeguard or the task design is often the problem. Asking operators why they bypass a guard, without blame, often reveals a design fix that makes the safe way the easy way.

Preventing defeat by design

Standards now require machine designers to anticipate manipulation. ISO 14119 asks designers to assess the motivation to defeat interlocking devices and to take measures against it: tamper-resistant mounting with one-way screws, hidden or coded actuators, monitoring that detects a device permanently held in the actuated state, and designing operating modes so that every reasonable task can be done without defeating the safeguard. Users can also choose coded RFID interlocks, trapped-key systems and safety controllers that detect abnormal patterns.

Good design gives workers a legitimate way to do every task. Setup modes with reduced speed and enabling devices allow observation and adjustment. Viewing windows let operators see the work. Jam-clearing tools let people reach in from outside the hazard zone. Fast, simple restart sequences remove the time penalty for opening a guard. When the safe way is also the easy way, bypassing becomes rare.

Management and culture

Design is not enough on its own. Supervisors must not tolerate defeated safeguards, and they must be seen to stop production when a guard is missing. Inspections should look specifically for bypasses: tape, cable ties, spare actuators, jumpers in panels, magnets on reed switches, and moved or blanked light curtains. When a bypass is found, investigate why it happened, fix the cause and only then consider discipline. If workers fear punishment, they will hide bypasses rather than report the problems that cause them.

OSHA holds the employer responsible for ensuring guards are in place. The employer cannot rely on telling workers not to remove guards; it must supervise and enforce. An employer that knew guards were being removed and did nothing can face willful citations.

Maintenance, servicing and lockout

Maintenance and servicing tasks such as repairs, adjustments, lubrication, cleaning, changeovers and jam clearing often require people to remove guards or enter hazard zones. At those times the guard no longer protects them, so the hazardous energy itself must be controlled. HSE-210 covers lockout in depth. The key points for machine guarding are:

• Before removing a guard or entering a hazard zone for maintenance, stop the machine and isolate all energy sources with energy-isolating devices: electrical disconnects, valves, blocks.
• Apply personal locks and tags so the machine cannot be restarted while anyone is exposed.
• Release or restrain stored energy: bleed air and hydraulics, block raised parts, let flywheels stop, discharge capacitors.
• Verify zero energy by trying to start the machine and testing for voltage before beginning work.
• Replace all guards and check that interlocks work before removing locks and restarting.

OSHA 1910.147 requires lockout or tagout for servicing and maintenance. A minor servicing exception, in 1910.147(a)(2)(ii), allows minor tool changes, adjustments and other servicing that are routine, repetitive and integral to production to be done without full lockout, but only if the work is performed using alternative measures that provide effective protection. ANSI/ASSP Z244.1 explains how to assess and design such alternative methods. The exception does not allow reaching into a running machine with no protection.

Returning machines to service

Many injuries happen when a machine is returned to service after maintenance with a guard missing or an interlock not reconnected. A return-to-service check should confirm that all guards are back in place and fastened, all interlocks and devices work, safety distances have not changed, tools and materials are removed, everyone is clear, and the operator is told the machine is ready. For safety-related control changes, a competent person should revalidate the safety functions, as Lesson 7 described.

Cleaning and sanitation

Cleaning, especially in food plants, is a special case. Cleaning crews often work at night, under time pressure, with water, chemicals and hoses. Some cleaning appears to require the machine to move, for example to expose all parts of a belt. These tasks need specific engineering solutions: cleaning modes at limited speed with enabling devices, clean-in-place systems, belt lifters, and procedures developed with the cleaning crew. Many serious amputations in food processing happen during sanitation, often to young workers or workers employed through staffing agencies or contract cleaning firms, so host employers must make sure contractors are trained and that lockout applies to them too.

Making the safe method visible

Some plants post a simple card at each machine showing the approved way to clear a jam, change a blade or clean the machine, with photographs. The card names the energy sources, the isolation points and the steps. When a safe method is easy to see and quick to follow, workers are far less likely to invent their own. Cards are reviewed whenever the machine or the task changes, and workers are asked whether the method still works in practice.

Supervisors can also ask a simple question at the end of every jam or breakdown: how was it fixed, and was the machine locked out? Asking routinely, without blame, makes lockout a normal part of the job rather than an exception.