Machine guard interlock

A. Material handling and storage B. Machine guarding, interlocks and controls C. Health and hygiene D. Fire protection E. Other standards 15 ... 

In addition to the machine guarding, the control system should be interlocked with an electronically monitored failsafe system. The control software should have an awareness of the position and action of all moving parts and measurement devices. Therefore, if an unplanned incident or out-of-protocol action does occur, the system will take action or stop action to minimize the likelihood of additional safety hazards. In some cases, as with system calibration or super user access, graded access levels can be custom-built into the design for specialized and infrequent operations. 

An enclosure attached to the frame of a machine and interlocked so that the machine cycle cannot be started normally unless the guard, including its hinged or movable sections, are in position. In some situations, movement of the guards will interrupt the machine cycle. See also Machine Guarding. 

A form of guard that has a movable part connected with the machinery so that the parts of the machine causing a hazard cannot be set in motion until the guard is in place. Before the guard can be opened sufficiently to allow access to the work area, the power is turned off and the motion is braked to prevent potential injuries to workers. It may also be called Interlocked Barrier Guard. See also Barrier Guard Interlock Machine Guarding. 

Machine guards are examples of safety devices. They prevent operators from getting into a hazardous area of a machine. Fences, interlocks, shielding, and enclosures are all forms of safety devices. 

While properly designed and maintained interlocks generally provide effective machine guarding, 1910.212 does not require the use of interlocks. 

Isolation of the hazard with interlocks, machine guards, blast shields, welding curtains, or other means and... 

Interlock A device that interacts with another device or mechanism to govern succeeding operations. For example, an interlocked machine guard will prevent the machine from operating unless the guard is in its proper place. An interlock on an elevator door will prevent the car from moving unless the door is properly... 

INDUSTRIAL SAFETY PROVISIONS. In the design of the APE and associated operational shield, conventional machine design practices are used to protect operators from hazards associated with moving parts. Proper techniques for guarding of hazardous machine areas are used, including the use of interlocks In the control system to prevent movements until certain conditions are satisfied, or to stop movements In emergency situations... 

Interlocked Guards—Shut down the machine when the guard is not securely in place or is disengaged. 

A switch used on guard doors that is used to detect if the door is opened while the machine is running, and uses a coded actuator to prevent intentional defeat. Safety interlock switches use positive opening contacts, which ensure that the closed switching contact is forced open when the guard is opened, without reliance upon spring action. 

A type of machine interlock system that has a mechanical device that requires a specific time period for a guard to be released after the power has be shut off... 

A form of distance guard whereby access to the area of hazard of the machine is prevented since materials are passed into the machine via a metal enclosure or tunnel. It is commonly used on metal cutting machines and usually incorporates an interlock, so if the tunnel guard is raised the machine stops operating. 

A typical molding cycle will not start until a number of interlock conditions are satisfied. While the interlock conditions vary with the machine, the machine will not enter semiautomatic or automatic mode in the absence of these interlock conditions. Generally, the gate (operator guard door) must be closed and the gate safety (interlock) switches tripped. In hydraulic machines, the front gate has three switches (electrical, mechanical, and hydraulic) whereas the rear gate usually has one or more electrical limit switches. The electrical interlocks are usually electrical limit switches. When tripped, the hydrauHc interlock pre-... 

The U.S. Patent and Trademark Office issued the first patent for an interlock in 1868. The interlock was a mechanical arrangement. The agency issued the first electrical interlock on a power transmission guard in 1923. In 1899, the agency issued a patent for a press guard that prevented the machine from acting if the guard was not fiiUy closed. 

Figure 13-8. An example of an interlock. (From OSHA 3067) Opening the hinged guard activates the microswitch to interrupt power to the machine.

Example 34-4 A company wants to reduce the hazards of injury in a machine. There are two options that may help installing a guard or using an interlock device. The goal is to compare each approach and express the solution as a return on investment. Table 34-12 compares the two alternatives. 

Interlocks—Design machine to not be capable of running in continuous RUN mode with interlocked guards out of position or... 

In summary, fixed guards have many attractive features. Their disadvantage, compared for example with interlocking guards, is that access is barred equally when the machine is safe as when it is in a dangerous condition. 

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