Lockout/Tagout for Robotic Equipment: A Practical Guide to OSHA 29 CFR 1910.147 for Teams Working on US Sites

On US sites, OSHA's 29 CFR 1910.147 requires lockout or tagout for servicing and maintenance of robotic equipment wherever unexpected energisation, start-up or release of stored energy could injure someone. During normal production it bites only when a worker removes or bypasses a guard, or puts part of the body into the point of operation or a danger zone. Minor tool changes and adjustments that are routine, repetitive and integral to production are exempt, provided alternative measures give effective protection.

Whose rule is this, and when does it concern a UK team?

The Occupational Safety and Health Administration (OSHA) sits within the US Department of Labor, and 29 CFR 1910.147 is part of its general industry standards. It governs employers' procedures in American workplaces. It matters to a UK-based integrator, machine builder or engineering team when you commission cells at a US plant, send service engineers there, work for a US-owned group that applies OSHA practice, or answer a US customer's audit questionnaire.

This article does not describe UK workplace health and safety law, which the Kopik base does not cover; for cells in UK factories, check the official UK guidance. For cells supplied to EU customers, the design-side counterpart is the EU Machinery Regulation 2023/1230, discussed briefly at the end.

Why robot cells are handled under general rules

OSHA's own robotics page is blunt: ‘There are currently no specific OSHA standards for the robotics industry.’ Instead, it lists general industry standards, among them walking-working surfaces, noise, personal protective equipment, machinery and machine guarding (Subpart O), electrical (Subpart S) and the control of hazardous energy, 29 CFR 1910.147. Its Technical Manual chapter on industrial robots says power and other hazardous energy sources should be controlled in accordance with 1910.147 or 29 CFR 1910.333.

The energy picture of a typical cell is mixed. The Technical Manual notes that robot drives are usually electric, that end-effectors often run on pneumatic power at typically 80-90 psi, that hydraulics may serve associated processes, and that hazardous energy can remain in capacitors, springs and pressurised cylinders after shutdown.

Decision path: does this task need lockout?

1. Is the activity servicing or maintenance? The definition covers setting up, adjusting, inspecting, modifying and maintaining, and expressly includes lubrication, cleaning, unjamming, adjustments and tool changes where the employee may be exposed to unexpected start-up or release of energy.
2. Is it outside normal production? If so, the standard applies.
3. If it happens during normal production: does the worker have to remove or bypass a guard or safety device, or place any part of the body in the point of operation or a danger zone during the operating cycle? If either is true, the standard applies (paragraph (a)(2)(ii)).
4. Could the minor servicing exception apply? Only for minor tool changes, adjustments and other minor servicing that are routine, repetitive and integral to production, done with alternative measures that provide effective protection.
5. Is the sector excluded? The standard does not cover, for example, construction and agriculture employment or oil and gas well drilling and servicing.

Worked examples from robot cells

That last case is worth dwelling on. In the incident described by OSHA, cleaning the reflector restored the sensor signal and the robot system resumed its programmed path in automatic mode, striking the worker. The Technical Manual's lessons: no servicing during automatic operation unless safeguarding prevents operation or causes a stop, and lockout/tagout had not been considered for the task.

What the energy control programme must contain

• Documented procedures with specific steps for shutdown, isolation, blocking, securing, device placement, removal and transfer, and verification (c)(4). The exemption from documenting is narrow: all eight listed conditions must hold, including a single, readily identified energy source and no stored or residual energy.
• Proper isolation points. Under the definitions, push buttons, selector switches and other control-circuit devices are not energy isolating devices, so an e-stop or a mode selector does not count.
• Lockout by default. Where a device can be locked, lockout is used unless the employer demonstrates that tagout gives full employee protection (c)(2)(ii).
• Standardised, durable, identifiable hardware supplied by the employer; tag attachments with a minimum unlocking strength of no less than 50 pounds (c)(5).
• At least annual inspection of each procedure by an authorised employee who is not using it, with written certification (c)(6).
• Training and retraining for authorised, affected and other employees, certified with names and dates (c)(7).

Two further requirements are easy to overlook on robot cells. First, after lockout devices are applied, all potentially hazardous stored or residual energy must be relieved, disconnected, restrained or otherwise rendered safe (d)(5), and if energy can re-accumulate, isolation must be verified until the work is finished. On a cell with pneumatic grippers and gravity-loaded axes, that is a step of its own, not a by-product of opening the main disconnect. Second, before devices are removed, the work area must be checked for non-essential items and for people, and affected employees must be told the devices have been removed before the machine is restarted (e).

Points that catch visiting engineers

Visiting integrators and service firms count as outside personnel. Paragraph (f)(2) requires the on-site employer and the outside employer to inform each other of their lockout or tagout procedures, and the host must ensure its own employees respect the visitor's programme. Agree this before the first site visit, not on the day.

• Testing mid-job: devices may be removed temporarily to test or position the robot, but only after clearing tools, removing people and following the release steps; control is reapplied before work continues (f)(1).
• Teams: group lockout gives one authorised employee primary responsibility, and each worker attaches a personal device to the group lockbox (f)(3).
• Shift handover: a specific procedure must keep protection continuous between outgoing and incoming staff (f)(4).
• Power-on work: the Technical Manual says the robot should be in manual mode, with an enabling device and a reduced speed not greater than 10 inches per second (250 mm/second).

For quick checks during a project, the robot and cobot machinery safety base answers questions such as ‘does OSHA's lockout/tagout rule always require a full lockout for a quick, routine tool change on a robotic press?’ and quotes the paragraph it relies on.

If the same cell is also sold into the EU

OSHA regulates the employer's procedures; the EU Machinery Regulation 2023/1230, applicable from 20 January 2027, regulates the machine's design. Its Annex III, section 1.6.3, requires means to isolate machinery from all energy sources, clearly identified and capable of being locked where reconnection could endanger persons, and the ability to dissipate stored energy without risk. Designing isolators that satisfy both makes US and EU deliveries simpler.