Regulations (Preambles to Final Rules) - Table of Contents Regulations (Preambles to Final Rules) - Table of Contents
• Record Type: Control of Hazardous Energy Sources (Lockout/Tagout)
• Section: 2
• Title: Section 2 - II. Hazards


II. Hazards

Whenever machines or equipment are utilized in industry, there are hazards not only to the employees who work with the machines or equipment but also to other employees who work or otherwise are in the immediate area. Moreover, when it is necessary to perform maintenance or servicing on machines or equipment, such activities generate additional unique hazards due to the continued presence of the energy used by the machine or equipment to perform its production function. This energy can emanate directly from a power source or can be stored in the equipment itself.

OSHA believes that failure to control energy adequately accounts for nearly 10 percent of the serious accidents in many industries. The following accidents, taken from the NIOSH report entitled "Guidelines for Controlling Hazardous Energy During Maintenance and Servicing" (Ex.4), are typical of these hazards and demonstrate the applicability of the pertinent provisions in the final standard.

1. An employee was cleaning the unguarded side of an operating granite saw. The employee was caught in the moving parts of the saw and pulled into a nip point between the saw blade and the idler wheel, resulting in fatal injuries. (Failure to shutdown or turn off the equipment to perform maintenance -- 1910.147(d)(2) .)

2. An employee was removing paper from a waste hogger. The hogger had been shut down, but the conveyor feeding the hogger had not been. The employee climbed onto the machine, fell onto the conveyor, was pulled into the hogger opening, and was fatally crushed. There was no energy control procedure at this operation. (Failure to document and implement an effective energy control procedure -- 1910.147(c)(4).)

3. Two employees were repairing a press brake. The power had been shut off for 10 minutes. They positioned a metal bar in a notch on the outer flywheel casing so that the flywheel could be turned manually. The flywheel had not completely stopped. The men lost control of the bar, which flew across the workplace and struck and killed another employee who was observing the operation from a ladder. (Failure to control stored energy -- 1910.147(d)(6 ).)

4. An employee was partially inside an asphalt mixing machine, changing its paddles. Another employee, while dusting in the control room, accidentally hit a toggle switch which caused the door of the mixer to close, striking the first employee on the head and killing him. Electrical switches to activate the machine were not deenergized and air pressure to move the doors was not shut off. (Failure to isolate equipment from energy sources -- 1910.147(d)(3).)

5. An employee was setting up a vacuum forming machine for a run of violin cases. He leaned over the press and accidentally activated the starting switch. His head was crushed between an air cylinder and the frame hogger opening, and was fatally crushed. There was no energy control procedure at this operation. (Failure to document and implement an effective energy control procedure -- 1910.147(c)(4).)

6. A trainee employee was cleaning a flour batch mixer. The employee was reaching into the machine when another worker activated the wrong switch, thereby turning the machine on. The employee cleaning the flour batch mixer suffered fatal crushing injuries to his neck. There was an unwritten company procedure for locking out during all maintenance. The procedure was not followed. (Failure to document and implement an effective energy control procedure -- 1910.147(c)(4); failure to train employees adequately in lockout/tagout procedures -- 1910.147(c)(7).)

7. An employee was cleaning scrap from beneath a large shear when a fellow employee hit the control button activating the blade. The blade came down and decapitated the employee cleaning scrap. (Failure to isolate, lockout/tagout or otherwise disable all potential hazardous energy sources before attempting any repair, maintenance or servicing -- 1910.147(c)(2).)

Servicing and maintenance activities are necessary adjuncts to the industrial process. They are needed to maintain the ability of all machines, equipment or processes to perform their intended functions. Additionally, erection, installation, construction, set-up, changeover, and dismantling usually must be performed with the equipment deenergized. These types of operations can present the employee with the same types of hazards of unexpected activation, reenergization, or release of stored energy, therefore, they are addressed by this standard. Similarly, lubricating, cleaning, unjamming, and making minor adjustments and simple tool changes are activities which often take place during normal production operations, but which may expose employees to the unexpected activation of the equipment or to the unexpected release of the energy stored in the equipment. All of the above activities are considered to be "servicing and/or maintenance" for the purposes of this standard.

With regard to servicing and/or maintenance which takes place during "normal production operations," it is important to note that this standard is intended to work together with the existing machine guarding provisions of Subpart O of part 1910, primarily 1910.212 (general machine guarding) and 1910.219 (guarding of power transmission apparatus). When a machine is being used for production, 1910.212 requires that the point of operation be guarded. For example, when an employee is using a table saw to cut wooden parts, the employee would be protected by guards around the blade of the saw. If the employee needs to reach into the point of operation in order to adjust the work piece as part of the production process, 1910.212 requires that the guarding protection be maintained. As long as guarding is not removed or bypassed, the lockout/tagout standard is not intended to apply to these types of situations. By contrast, using the same table saw, it may be necessary for the employee to remove a piece of wood which has become jammed against the blade of the saw. In doing so, the employee might need to bypass or remove the guard on the saw and reach into the point of operation. Although this action takes place "during" normal production operations, it is not actually production, but is servicing of the equipment to perform its production function. When such servicing may expose the employee to the unexpected activation of the machinery or equipment, or to the release of stored energy, this Final Rule will apply. If the servicing is performed in a way which prevents such exposure, such as by the use of special tools and/or alternative procedures which keep the employee's body out of the areas of potential contact with machine components or which otherwise maintain effective guarding, this standard will not apply. Thus, lockout or tagout is not required by this standard if the employer can demonstrate that the alternative means enables the servicing employee to clean or unjam or otherwise service the machine without being exposed to unexpected energization or activation of the equipment or release of stored energy.

The above mentioned servicing and/or maintenance activities are currently being accomplished in general industry with varying degrees of safeguarding or protection for employees. This safeguarding or protection ranges from allowing the employee to conduct the servicing or maintenance activity which the machine or equipment is energized and operating (virtually no protection), to requiring that the machine or equipment simply be turned off or shut down, to providing for deenergization and lockout or tagout of the machine or equipment. OSHA believes that the least desirable situation is to allow employees to perform maintenance, repair, or service activities while the machine or equipment is energized and capable of performing its normal production function. The Agency recognizes that there are certain servicing operations which, by their very nature, must take place without deenergization, such as operational testing of machines or equipment. Locking out or tagging out cannot be performed during these operations, since both lockout and tagout require that equipment to be deenergized. Additionally, this standard does not apply when certain tasks are conducted during normal production operations such as repetitive minor adjustments or simple tool changes when these activities do not increase the risk of injury to employees. Conversely, operations such as cleaning and unjamming machines or equipment are covered by this standard when the employee is exposed to greater or different hazards than those encountered during normal production operations; it should be emphasized that this rule applies to cleaning and unjamming when an unexpected activation or release of energy could occur.

The vast majority of servicing or maintenance activities can safely be done only when the machine or equipment is not operating and is deenergized; therefore, these activities are covered by the standard.

Some servicing operations do not expose employees to hazards which would necessitate that a machine, equipment or process be deenergized and locked out or tagged out. Practices such as reaching around guards during the cleaning of rollers of printing presses or the feed points or screw conveyors while the equipment is operating, violate the safeguarding requirements set forth in 1910.212, and therefore, such activities are violations of that rule.

Performance of maintenance or servicing activities on a machine or equipment that is in operation has the potential of exposing employees not only to contact with moving machinery components at the point of operation, but also to contact with other moving components, such as power transmission apparatus, and also increases the risk of injury due to the position the employee must assume and the need to remove, bypass or disable guards and other safety devices. In many cases, these activities expose the employee to the hazard of being pulled into the operating equipment when parts of the employee's body, clothing or the material or tools used for cleaning or servicing become entrapped or entangled in the machine or equipment mechanism. The use of extension tools or devices to permit the operator to stay outside these danger areas, while of some benefit in reducing direct employee exposure to the hazards of entanglement or entrapment, can in itself, result in injuries to employees. This can occur, for example, when an employee is struck by the tools or devices that inadvertently come in contact with moving machine components, and are pulled from the employee's grasp.

However, shutting down a machine or equipment usually is not the total solution to the problem. Once the machine or equipment has been stopped, there remains the potential for employee injury from the unanticipated movement of a component of the machine or equipment, or from movement of the material being handled. This unanticipated movement can be caused either by the release of residual energy within the machine or equipment or as the result of the conversion of potential energy to kinetic energy (motion). For example, residual energy can be manifested by the presence of springs under tension or compression, or by the presence of pressure (either above or below atmospheric) in systems containing gases or liquids.

Potential energy is considered to be a function of the height of an object above some datum plane. This datum plane is usually considered to be where that object would come to rest if the restraint holding the object were released, such as where the upper die in a punch press is positioned above the lower die. If the restraining device holding the upper die in place was to be removed, the potential energy of the upper die would be converted into kinetic energy (downward motion), resulting in the upper die being propelled downward, coming to rest on the lower die. This motion can cause a crushing, cutting, lacerating, amputating or fracture injury to an employee's arm, hand or some other part of the body which occupies the space between dies.

OSHA believes that the most effective method to prevent employee injury caused by the unanticipated movement of a component of a machine or equipment, or of the material being handled, is either to dissipate or minimize any residual or potential energy in the system, or to utilize a restraining device to prevent movement. This can be accomplished by moving machine or equipment components to a point at which springs are at or near a neutral state, by moving components so that liquids or gases reach or approximate atmospheric pressure, and by blocking material or components or moving them to a point of minimum potential energy (moving components to a stable, resting position).

Further, even though the machine or equipment has been shut off, and even if residual energy has been dissipated, an accident can still occur if there is an inadvertent activation of that machine or equipment. Inadvertent activation can occur due to an error on the part of the employee who is conducting the maintenance or servicing activity, or by any other person. For example, the servicing employee can unintentionally cause the machine or equipment to start by shorting across electrical switches or by accidentally moving controllers (either electrical controls or valves) into the "on" or "operational" position.

An accident can also occur when another person who is not necessarily involved with the maintenance or servicing operation causes the activation of the machine or equipment being serviced. This can occur when a person uses the wrong controller and starts a machine or equipment that the employee did not intend to start. It can also occur when a person finds a machine or equipment not operating and starts it, without knowing someone else is performing maintenance or service on it. This latter type of accident is more apt to occur when the machine or equipment is large and /or complex, and the employee who is conducting the servicing activity is at a part of the system which is some distance from or not visible from the controls. The generally accepted best means to minimize the potential for inadvertent activation is to ensure that all power to the machine or equipment is isolated, locked or blocked and dissipated at points of control using a method that cannot readily be removed, bypassed, overridden or otherwise defeated. In the case of an electrically run machine, piece of equipment or process, this can be done by going back toward the original source of the power and shutting off a main switch or by disconnecting the electrical lines. OSHA believes that this action must be followed by the placement of some safeguard to prevent the reenergization of the circuit during the maintenance or servicing. To ensure that another employee will not attempt to restart the machine or equipment or to reenergize the circuit, there must be some assurance that all other employees know that the circuit is deenergized and must remain so. This can be accomplished by the utilization of a standardized procedure for deenergizing the system; by training employees to familiarize them with the restrictions of the procedure which apply to them; and by enforcing a prohibition on another employee removing or bypassing another's safeguard. Those employees whose job require them to operate or use a machine or equipment that must have maintenance or servicing performed on it, must be aware that the machine or equipment is going to be stopped or shut down, and locked out or tagged out, and that they should not attempt to restart or reenergize it. Additional training is also needed for those employees who must utilize the procedure.

Even if all other protective measures are taken, accidents can still occur following the completion of the maintenance, repair or servicing activity, if the machine or equipment is reenergized and started before all guards and other safety devices have been replaced or reinstalled. Additionally, all tools and other foreign objects must be removed from the location and a check completed to ensure that no employees are in a place where the re-energization and starting of the machine or equipment will endanger them.


Regulations (Preambles to Final Rules) - Table of Contents Regulations (Preambles to Final Rules) - Table of Contents