Controlling Hazardous Energy: ...

Servicing and maintenance tasks put workers in places machines were never designed for people to be: inside guards, between rollers, within reach of moving parts and stored pressure. When energy is released unexpectedly during that work, the results can be catastrophic. Lockout/tagout (LOTO) is the disciplined process that prevents it.

The Regulatory Foundation

In U.S. general industry, the governing regulation is OSHA 29 CFR 1910.147, The Control of Hazardous Energy (Lockout/Tagout). It applies to servicing and maintenance of machines and equipment in which unexpected energization, startup or release of stored energy could harm employees. Related requirements include 29 CFR 1910.333 for electrical safety-related work practices, and the consensus standards ANSI/ASSP Z244.1 (control of hazardous energy) and NFPA 70E (electrical safety in the workplace), which many employers use to strengthen their programs.

The standard does not cover normal production operations unless workers must remove or bypass guards or place any part of their body in a danger zone. It also includes a narrowly defined exception for minor tool changes and adjustments that are routine, repetitive and integral to production, provided alternative measures give effective protection.

Forms of Hazardous Energy

Electrical energy is the most familiar, but a competent energy control procedure considers all sources:

• Electrical — supply circuits, as well as stored energy in capacitors.
• Mechanical — rotating or reciprocating parts, flywheels and springs.
• Hydraulic and pneumatic — pressurized fluids and accumulators.
• Chemical — process fluids in lines and vessels.
• Thermal — steam, hot surfaces and cryogenic fluids.
• Gravitational — raised loads, platens and counterweights.

Mechanical and process equipment frequently has several of these at once. A pump may involve an electric motor, pressurized process fluid, elevated temperature and a coupled driver that can rotate from backflow.

The Energy Control Program

OSHA 1910.147 requires employers to establish a program with three core components:

1. Energy control procedures, documented for each machine or equipment, that specify the scope, purpose, authorization, rules and techniques for controlling hazardous energy.
2. Employee training so that workers understand the purpose and function of the program and have the knowledge and skills for safe application, use and removal of controls.
3. Periodic inspections of each energy control procedure, performed at least annually by an authorized employee other than those using the procedure, and certified by the employer.

The regulation distinguishes between authorized employees, who lock out equipment to perform service, and affected employees, who operate or work near the equipment and must understand the purpose of the procedure and not attempt to restart locked-out equipment.

Six Steps of Applying Energy Control

1. Preparation for shutdown. The authorized employee identifies the type and magnitude of energy, the hazards and the means to control it.
2. Machine or equipment shutdown. The equipment is stopped using the normal procedure to avoid creating additional hazards.
3. Isolation. All energy-isolating devices — disconnect switches, circuit breakers, line valves, blocks — are operated to isolate the equipment. Push buttons, selector switches and control circuits are not energy-isolating devices.
4. Application of lockout or tagout devices. Each authorized employee affixes a personal lock or tag to each isolating device.
5. Control of stored energy. Residual energy is relieved, disconnected, restrained or otherwise rendered safe: bleeding lines, blocking elevated parts, discharging capacitors, releasing spring tension. Where reaccumulation is possible, verification continues until the work is complete.
6. Verification of isolation. Before work begins, the authorized employee verifies that isolation and de-energization have been achieved — for example, by attempting a normal start after confirming all personnel are clear, and by testing for absence of voltage with a properly rated meter where electrical hazards exist.

Verification is the step that catches every error made in the five before it. Never skip the try-out.

Lockout Versus Tagout

A lock physically prevents operation of the isolating device; a tag is only a warning. The standard therefore requires lockout where the isolating device is capable of being locked. Tagout alone may be used only where the device cannot be locked, or where the employer can demonstrate that a tagout program provides protection equivalent to lockout, which generally requires additional measures such as removing a circuit element or blocking a control switch. Lockout and tagout devices must be durable, standardized, substantial and identifiable, and they must be used only for energy control.

Complex Situations

Release from Lockout

Restoring equipment is as structured as isolating it. The work area is inspected to ensure nonessential items are removed and components are intact; all employees are safely positioned; affected employees are notified; and each lock or tag is removed by the employee who applied it. The standard provides a limited, documented exception for removal by the employer when the authorized employee is not available, with specific steps to verify that person's whereabouts and inform them before they resume work.

Building a Culture That Supports LOTO

Most energy-control failures involve procedures that existed on paper but were bypassed under schedule pressure or not written for the specific equipment. Machine-specific procedures with photographs of isolation points, periodic field audits, and leaders who stop work when isolation is uncertain are what turn a compliant program into an effective one.

Key Takeaways

• OSHA 29 CFR 1910.147 requires a documented program with procedures, training and annual periodic inspections.
• All forms of hazardous energy, including stored and gravitational energy, must be controlled.
• The six steps run from preparation through verification; verification must never be skipped.
• Lockout is required where devices can be locked; tagout alone requires demonstrated equivalent protection.
• Group lockout, shift changes and contractors require specific procedures.

To strengthen your site's energy control practice, consider IIME's Hazardous Energy Control (Lockout/Tagout) training course.