SECTION 20. MECHANICAL SAFETY

20.1 MACHINE GUARDING

GENERAL

Guarding is an effective approach toward eliminating personal injury, secondary only to elimination of hazardous exposure by machine design and process revision. Machines or equipment, especially unique or specialized types including telescopes and domes, require a combination of physical barriers, special safety control devices, and effective procedures to assure protection of personnel. If the hazard cannot be eliminated, it will be covered. If it cannot be covered, other controls will be installed which completely protect operation and maintenance personnel. Guards or other controls will be installed before the equipment is put into service. All mechanical equipment will be inspected prior to initial use to ensure guarding is effective.

Machine tools will be locked when not in use; keys are only available to certified personnel. Prior to being certified and receiving a key, personnel will receive additional training and must prove proficiency and safe work practices when operating these machines. A list of certified personnel will be maintained by the Site Safety Officer and posted in the machine shop.

MECHANISMS REQUIRING GUARDS

Mechanisms with exposed moving parts/surfaces or are hot, cold, sharp, or chemically contaminated require guarding. Points of operation that involve cutting, punching, bending, sawing, or shearing require guarding. This includes production, service, maintenance, materials handling, and building equipment. The following are examples of machine mechanisms that require guarding:

- rotating mechanisms including flywheels, grinding wheels, wire brush wheels, drive shafts, couplings, and fans;
- cryogenic and chemical process equipment;
- machinery that could generate hazardous flying objects (metal chips, sparks, chemical spray, etc.).

FIXED GUARDS

Fixed guards are preferable because they prevent entry into the area of the hazard and remains in position throughout the machine cycle.

Points of power transmission and hot, cold, or chemically contaminated surfaces must be guarded by fixed enclosures. Enclosures should be designed with consideration for routine maintenance. For example, lubrication fittings should be extended through the guard, or openings provided in the guard, to permit the machine to be safely serviced.

INTERLOCKED GUARDS

Where fixed guards cannot be used, moveable guards may be used if equipped with interlocks designed to prevent machine operation when guards are not in place. Interlocks may be mechanical, electrical, pneumatic, or a combination of these types. Interlocks must be “fail safe,” permitting machine operation only when interlocks are operating properly. They should be designed to require a tool to bypass the interlock when the guard is not in place. The guard must remain fixed while the parts creating the hazard are in motion. When the guard is opened, the interlock must immediately stop all motion until the guard is replaced and the normal starting procedures are repeated.

REMOVING AND OVER-RIDING GUARDS

All operations that require employees to enter the point of operation after removing or overriding a guard, including inspection, maintenance, repair, or other operations, must be carried out only by experienced, qualified individuals.

Written procedures will be established which state the steps necessary to perform these operations safely. Lockout-tagout procedures will be used.

Power Interruptions

Every operator-controlled machine will require manual reset to start after a power interruption.

20.2 SAFE WORK PRACTICES

GENERAL

Safe work practices must be based upon full knowledge of machine operations, potential hazards, and proven methods of avoiding the hazards. Employees who operate, service, or maintain mechanical equipment must thoroughly understand its operation and the safety precautions to be taken. A separate policy will be written to cover the operating policy for the machine shop. See Appendix/Safety Memo 6.

Qualified Personnel - no employee will operate a machine before being instructed in its operation and the safety precautions to be taken.

Guards - all guards will be inspected by the operator before starting the machine. Guards must be in place and functioning properly when the machine is in use.

Unattended Machinery - machines must be shut off and all cutting tools must have stopped moving before a machine is left unattended.

Work Area - machine operators will be responsible for maintaining safe conditions at their workstations. Floors must be kept free of slip/trip hazards. Parts, tools, and accessories will be safely located.

Clothing and Proper Attire - jewelry, loose fitting clothing, and shirtsleeves that extend beyond the elbow should not be worn around machinery having exposed moving parts. In these areas, neckties and neck chains or cords should not be worn. Long hair must be kept from moving machine parts by a protective cap or net. Refer to Section 12, "Personal Protective Equipment.”

Eye and Face Protection - safety glasses, face-shield, or goggles are required in all areas where the use of power machinery presents an eye hazard that cannot be eliminated. Grinding operations require face-shields even if safety glasses are worn. In operations, which normally require only safety glasses, goggles and safety glasses with side shields will be provided for employees who request additional protection. Refer to Section 12, "Personal Protective Equipment.”

Compressed Air for Cleaning - where compressed air must be used to clear chips from keyways, holes in the work, etc., the air gun must be equipped with a pressure reducing device decreases the pressure to less than 30psi at the nozzle when dead-ended, and the operator must wear goggles or safety glasses and side shields. A brush or vacuum cleaner is the preferred tool for this job.

Before unique machines or equipment are placed in service, the Site Operations Manager and Site Safety Officer will jointly conduct a hazard evaluation study to establish guarding requirements and safe work practices. This will also apply to new models of existing machines/equipment.

If the nature of the work, at times, requires the point of operation be unguarded, it is particularly important safe work practices are strictly followed. These will include the following:

- portable or fixed shields will be required for operations that throw sparks, chips, cutting oils, coolants, etc.;
- the workplace must be properly secured to prevent movement during machining;
- band saw, power hacksaw, and rotary cutoff blades will be completely enclosed except where covered by the work piece at the point of operation.

20.3 GRINDING MACHINES

GENERAL

Grinding machines will be positioned such that if a wheel disintegrates, or the wheel throws a work piece, debris is directed away from co-workers or aisles. Machines must be set to allow a minimum of 22 inches clearance between the full travel of table or other movable part and any other object. Grinders must be attended while running.

SAFE OPERATION

Grinding wheels must be visually inspected for cracks before using; a cracked wheel may disintegrate at normal operating speed. As an added precaution, wheels will be tapped gently (while suspended) with a light instrument, such as the handle of a screwdriver; a sound wheel will emit a clear metallic ring.

The flanges on each side of the wheel must be the same diameter and in good balance to prevent vibration. Blotters will be used between wheel and flanges whenever possible to ensure uniform distribution of flange pressure.

Abrasive wheels and disks must be operated at speeds not exceeding those recommended by the wheel manufacturer.

Caution must be exercised when dressing wheels to ensure dust is trapped and excessive pressure is not applied to the wheel. The correct wheel should be selected for each job. Wheels must not be modified by over-dressing.

An insecurely clamped work piece and an unenergized magnetic chuck can be a cause of injury. Care must be exercised to ensure the work piece is securely clamped and the chuck is turned on (energized) before the wheel contacts the work piece.

On pedestal and bench grinders the work rest must be maintained at no more than 1/8 inch from the wheel and positioned at or above the other wheel. Wheel guards are required on grinders. They serve two functions: to protect operators in case of wheel breakage and to trap grinding dust. The wheel guard tongue must be maintained at a maximum of 1/4 inch from the wheel. Pedestal and bench grinders must be firmly secured to the floor or bench.

WHEEL STORAGE

When grinding wheels are removed from their shipping containers, special precautions are required to prevent wheel damage. Small wheels will be protected by storing them vertically, on pegs or in bins, sloped so the wheels will not slide off or roll out. Straight wheels, cup wheels, and disk wheels, 6 inches or more in diameter, should be stacked flat with a cushion, such as corrugated paper, between layers.