Machine guard openings

Machine guard opening/distance-to-point-of-operation measuring tool/stick (these are available from many machine safeguarding suppliers/consultants)... 

Under conditions of normal use, products shall remain physically stable to the degree that they cannot present a hazard to operators or service personnel. The various tilt and tip tests are not applicable for equipment that is intended to be secured to the building before operation, as specified in the installation instructions. When stabilizing means are provided to improve stability, when doors or drawers are opened, they must be automatic. If not automatic, suitable and conspicuous markings shall be provided to caution service personnel. The physical requirements depend on the applicable product standard. Many standards are available for machine guarding and protection. ITE standard EN 60950 gives a good description... 

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. 

There are certain necessary operations, such as setting and adjusting, that may need to be carried out with the guards open. This is permitted provided the machine can be moved, either ... 

How materials are handled from the time they are received and how they are moved and stored, checking the stability of storage racks and the safe storage of flammables/explosives The openings that expose moving parts for pinch points, machine guarding, and other hazards... 

As the video opened I passed the phone around in class for students to glimpse at the information. Unfortunately, the video I randomly selected was about one of my major clients, company name clearly called out in the video, where one of their factories was referred to as a butcher shop because of all the machine guarding injuries that had occurred. I was shocked and embarrassed. 

A semi-guarded machine is an open machine in which part of the ventilating openings in the machine, usually in the top half, are guarded as in the case of a guarded machine but the others are left open. 

A guarded machine is an open machine in which all openings giving direct access to live metal or rotating parts (except smooth rotating surfaces) are limited in size by the structural parts or by screens, baffles, grilles, expanded metal, or other means to prevent accidental contact with hazardous parts. 

A dripproof guarded machine is a dripproof machine whose ventilating openings are guarded in accordance with 1.25.4a. 

A guard of adequate strength must be securely attached to the machine frame. The aim is to enclose the wheel to the greatest possible extent and keep the opening as small as possible. 

Screens, bars, or other mechanical harriers affixed to the frame of a machine, intended to prevent entry by personnel into the hazardous area(s) of a machine, while allowing the point of operation to he viewed. The maximum size of openings is determined by Table 0-10 of Occupational Safety and Health Administration (OSH A) standard 1910.217. It may also he called a fixed barrier guard. 

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. 

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

Point-of-operation devices provide protection when it is not possible to provide an adequate guard. Point-of-operation devices ensure that the machine cannot operate or create a hazard while an operator has fingers or hands in the point-of-operation. For example, it may be necessary to open a guard to insert or remove materials the machine must act on. That allows hands to reach the hazardous area of the machine through such openings. 

A point-of-operation guard will be installed on a machine with a feed table. An operator will feed material into the machine. The material will be 1 1/8 in. thick and require a 1/8 in. clearance in an opening in the guard. How far must the guard be from the danger line ... 

The system boundary could be drawn at various levels — e.g. in the guarding example it could be drawn at the level of the department in which the machine is located, the works, the company, or the country (in the last case there might be inputs across the boundary (frontier) of materials, designs or EEC regulations which would still make it an open system). For a full systems analysis and model it is usually necessary to produce a hierarchy of diagrams showing the total system, main sub-systems and sub-sub-systems etc. 

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