Mechanical Power
Transmission Hazards
Tech Guide
The power transmission apparatus is all components of the mechanical system which transmit energy to
the part of the machine performing the work. This includes flywheels, pulleys, belts, connecting rods,
couplings, cams, spindles, chains, cranks and gears. All guarding including materials and dimensions
must be in compliance with the requirements set out in the power transmission standard (29 CFR
1910.219).
Prime Mover Guards:
 Flywheels located so that any part is seven feet or less above the floor or platform must be
guarded.

Guard cranks and connecting rods exposed to contact.

Guard tail rods or extension piston rods.
Shafting:
 Secure each continuous line of shafting against excessive end movement.

Secure inclined and vertical shafts against endwise thrust.

Guard all exposed parts of horizontal shafting seven feet or less from the floor or working
platform, except runways used exclusively for oiling, or running adjustments.

Enclose shafting under bench machinery by a stationary casing or by a trough at sides
and top or sides and bottom, as location requires.

Guard vertical and inclined shafting seven feet or less from the floor or working platform,
except maintenance runways.

Ensure that projecting shaft ends have a smooth edge and do not project more than onehalf the diameter of the shaft unless guarded by non-rotating caps or safety sleeves.

Fill up or cover unused keyways.
Pulleys:
 Guard pulleys that have any parts seven feet or less from the floor or working platform.

A guide must be provided to prevent the belt from leaving the pulley on the side where
insufficient clearance exists unless the distance to the nearest fixed pulley, clutch or hanger
exceeds the width of the belt used.

Do not use pulleys with cracks or pieces broken out of rims.

Pulleys intended to operate at rim speed in excess of manufacturers normal
recommendations must be specially designed and carefully balanced for the speed at which they
are to operate.
Belt, Rope and Chain Drives:
 Where both runs of horizontal belts are seven feet or less from the floor level, the guard has to
extend to at least fifteen inches above the belt or to a standard height.

Fully enclose the belt if both runs of a horizontal belt are forty-two inches or less from the
floor.

Overhead horizontal belts that have lower parts seven feet or less from the floor or
platform must be guarded.

Guard vertical and inclined belts.

Guard the nip point of the belt and pulley of cone-pulley belts.

If the cone is less than three feet from the floor or working platform, the cone pulley and
belt must be guarded to a height of three feet.
Gears, Sprockets and Chains:
 Guard all gears.

Enclose all sprocket wheels and chains unless they are more than seven feet above the
floor or platform. Provide protection against falling where the drive extends over other machinery
or working areas.

Provide openings with hinged or sliding self-closing covers when frequent oiling must be
done.
Friction Drives:
 Guard the driving point and all projecting belts on friction drives if they are exposed to contact.

Fully enclose all arm or spoke friction drives and all web friction drives that have holes in
the web.
Projecting keys, setscrews and other projections:
 Projecting keys, setscrews and other projections in revolving parts must be removed, made flush
or guarded by a metal cover.
Collars and Couplings:
 All revolving collars must be cylindrical and screws or bolts used in collars must not project
beyond the largest periphery of the collar.

Shaft couplings are not to have any hazards present from bolts, nuts, setscrews or
revolving surfaces.

Bolts, nuts and setscrews are permitted on shaft couplings if they are covered with safety
sleeves or if they are parallel with the shafting and are countersunk or else do not extend beyond
the flange of the coupling.
Clutches, Cutoff Couplings and Clutch Pulleys:
 Guard clutches, cutoff couplings or clutch pulleys that have projecting parts if the clutches are
located seven feet or less above the floor or working platform.
Care of Equipment:
 Inspect all power-transmission equipment at intervals not exceeding 60 days.

Keep shafting aligned and free from rust and excess oil or grease.

Keep bearings aligned and properly adjusted.

Inspect hangers to make certain that all supporting bolts and screws are tight and that
supports of hanger boxes are adjusted properly.

Keep pulleys in proper alignment to prevent belts from running off.

Inspect belts, lacings and fasteners and such equipment.

When oiling equipment, tight fitting clothing should be worn and machinery should not be
oiled when in motion wherever possible.
Resources:
http://www.osha.gov/SLTC/etools/machineguarding/index.html (Machine Guarding E-Tool)
http://www.oshainfo.gatech.edu/techguides.html (Georgia Tech OSHA Safety and Health Consultation
Program’s Tech Guides)
http://www.osha.gov/pls/oshaweb/owastand.display_standard_group?p_toc_level=1&p_part_number=19
10&v_description=General+Industry+-+%28Standards+-+29+CFR%29 (OSHA’s General Industry
Standards)
http://www.cdc.gov/niosh/docs/2004-101/chklists/r1n52p~1.htm (NIOSH Mechanical Power-Transmission
Apparatus Self Inspection Checklist)