MRO Magazine

In The Danger Zone

Crushed hands and arms, severed fingers, blindness. We could go on -- the list of possible machinery-related injuries is as long as it is horrifying.When you consider the number of such injuries that ...


Health & Safety

November 1, 2003
By Simon Fridlyand, P.Eng

Crushed hands and arms, severed fingers, blindness. We could go on — the list of possible machinery-related injuries is as long as it is horrifying.

When you consider the number of such injuries that occur in the workplace each year, you might wonder if there is a way of working safely around moving equipment or machinery.

It only takes a split second to make a mistake or lose concentration when working around unprotected equipment or machinery. We cannot expect operators to watch every move they make in order to avoid injury while using unguarded machinery or equipment, especially when they have to concentrate on production.

The only way to work safely around moving equipment or machinery is to have it properly guarded. A good rule to remember is: Any machine part, function or process that may cause injury must be safeguarded.

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Dangerous moving parts in any machine or piece of equipment can be divided into three basic areas:

The point of operation: This is the point where work is performed on the material, such as cutting, shaping, boring or forming of stock.

Power transmission apparatus: This includes all components of the mechanical system that transmit energy to the part of the machine performing the work. These components include flywheels, pulleys, belts, connecting rods, couplings, cams, spindles, chains, cranks and gears.

Delivery apparatus: All parts of the machine which move while delivering raw materials to the point of operation or taking finished goods from the point of operation are included in this area. These can include reciprocating, rotating and transverse moving parts, as well as feed mechanisms and auxiliary parts of the machine.

A wide variety of mechanical motions and actions may present hazards to the worker. These can include the movement of rotating members, reciprocating arms, moving belts, meshing gears, cutting teeth, and any parts that impact or shear.

These different types of hazardous mechanical motions and actions are basic in varying combinations to nearly all machines, and recognizing them is the first step toward protecting workers from the danger they present.

Basic types of hazardous mechanical motions and actions include:

Motions

Rotating (including in-running nip points): Rotating motion can be dangerous; even smooth, slowly rotating shafts can grip clothing, and through mere skin contact force an arm or hand into a dangerous position. Injuries due to contact with rotating parts can be severe.

Reciprocating: Parts can rotate in opposite directions while their axes are parallel to each other. These parts may be in contact (producing a nip point) or in close proximity. In the latter case, the stock fed between the rolls produces the nip points. This danger is common on machines with intermeshing gears, and in rolling mills and calendars.

Transversing: Transverse motion (movement in a straight, continuous line) creates a hazard because a worker may be struck or caught in a pinch or shear point by the moving part.

Actions

Cutting: Cutting action may involve rotating, reciprocating or transverse motion. The danger of cutting action exists at the point of operation where finger, arm and body injuries can occur and where flying chips or scrap material can strike the head, particularly in the area of the eyes or face. Such hazards are present at the point of operation in cutting wood, metal or other materials.

Punching: Punching action results when power is applied to a slide (ram) for the purpose of blanking, drawing, or stamping metal or other materials. The danger of this type of action occurs at the point of operation where stock is inserted, held and withdrawn by hand. Typical machines used for punching operations include power presses and iron workers.

Shearing: Shearing action involves applying power to a slide or knife in order to trim or shear metal or other materials. A hazard occurs at the point of operation where stock is actually inserted, held and withdrawn. Examples of machines used for shearing operations are mechanically, hydraulically or pneumatically powered shears.

Bending: Bending action results when power is applied to a slide in order to draw or stamp metal or other materials. A hazard occurs at the point of operation where stock is inserted, held and withdrawn. Equipment that uses bending action includes power presses, press brakes and tubing benders.

When the areas of power transmission apparatus and delivery apparatus do not require any operator’s involvement under normal operating condition, these areas need to be properly guarded with fixed guarding. The Canadian Standards Association (CSA) Standard Z-432 describes proper fixed guarding arrangements for equipment and machinery.

When the area of the point of operation requires operator involvement, such as loading or unloading the machine or equipment, this area must be protected by an electronic or electrical device which signals the machine to stop when a body part is in the danger zone or is sensed by a proximity device.

A light curtain, interlock gate or floor mat are examples of electrical/electronic devices that can signal a machine to stop. Pullback or restraint devices would be examples of proximity devices. They basically restrain the reach into the danger zone.

Properly guarded machinery or equipment must be completely guarded by fixed guarding around the power transmission and delivery apparatus areas. The area of the point of operation must be guarded by an electrical/electronic device that has a proper degree of redundancy built into it. In other words, should a component of the safety device fail; the safety device would still be able to stop the machine.

It’s important to note that Ontario’s Occupational Health and Safety Act stipulates that the responsibility for providing a safe work environment lies with owners, company officers and employers.

Safety File columnist Simon Fridlyand, P.Eng., is president of S.A.F.E. Engineering of Toronto, a company specializing in industrial health and safety issues and compliance. He can be reached at 416-447-9757 or at simon@safeeingineering.com.