Power transmission belt safeguards

Under 1926.307(a)(1) small, low‑speed belts are exempt. The standard specifically exempts the following when operating at 250 feet per minute or less:

• Flat belts 1 inch (2.54 cm) or less in width (1926.307(a)(1)(i).)
• Flat belts 2 inches (5.08 cm) or less in width that are free from metal lacings or fasteners (1926.307(a)(1)(ii).)
• Round belts 1/2 inch (1.27 cm) or less in diameter (1926.307(a)(1)(iii).)
• Single‑strand V‑belts with width 13/32 inch or less (1926.307(a)(1)(iv).)

If a belt does not meet one of these specific size/speed conditions, the general guarding requirements of 1926.307 apply.

You may use a nip‑point belt and pulley guard for vertical and inclined belts when they meet the size and speed limits in the standard. Specifically, vertical and inclined belts not more than 2½ inches (6.35 cm) wide, running at less than 1,000 feet per minute, and free from metal lacings or fastenings may be guarded with a nip‑point belt and pulley guard (1926.307(a)(2)).

• If the belt is wider, runs faster than 1,000 fpm, or has metal lacings/fasteners, you must use the full guarding required by the section.

Yes — for textile operations you may limit guards to the sides and face of nip‑point belt and pulley guards because lint accumulation creates a fire hazard. The guard must extend at least 6 inches (15.24 cm) beyond the pulley rim on the in‑running and off‑running sides and at least 2 inches (5.08 cm) away from the rim and face of the pulley in all other directions (1926.307(a)(3)).

• This allowance is only for the textile industry and is intended to reduce lint buildup that can create fire risks.

Flywheels 7 feet or less above a floor or platform must be guarded using one of the methods the standard lists. Acceptable methods include:

• An enclosure of sheet, perforated or expanded metal, or woven wire (1926.307(b)(1)(i)).
• Guard rails placed not less than 15 inches nor more than 20 inches from the rim (and a toeboard if the flywheel extends into a pit or is within 12 inches of the floor) (1926.307(b)(1)(ii)).
• If the wheel rim protrudes through a working floor, enclosure or surrounding guardrail and toeboard are required (1926.307(b)(1)(iii)).
• For small smooth‑rim flywheels (≤5 ft) where other methods won’t work, a disk attached to cover spokes may be used if keys or dangerous projections are cut off or covered (1926.307(b)(1)(iv)).

Choose the method that provides the required protection and allows for inspection and safe maintenance.

Flywheel guards located above working areas must be strong enough to support the flywheel if a shaft or wheel mounting fails. The standard requires guards have sufficient strength to hold the weight of the flywheel in the event of a shaft or wheel mounting failure (1926.307(b)(1)(vi)).

• This means design the guard and its mountings so they will not collapse onto workers if the flywheel comes loose.

Cranks and connecting rods that are exposed to contact must be guarded either by the requirements of paragraphs (m) and (n) or by a guardrail described in paragraph (o)(5). See 1926.307(b)(2).

• If you use the (m)/(n) approach, follow those specific guard design and mounting rules in 1926.307(m) and 1926.307(n).
• Alternatively, a guardrail per 1926.307(o)(5) may be used to prevent contact.

The standard requires continuous shafting be secured against excessive endwise movement, and inclined/vertical shafts (including inclined idler shafts) be held against endwise thrust. See 1926.307(c)(1)(i) and 1926.307(c)(1)(ii).

• In practice, provide adequate bearings, thrust collars, end stops, or other mechanical means so shafts cannot move endwise under load.

Exposed horizontal shafting 7 feet or less from the floor or working platform must be protected by a stationary casing that completely encloses the shafting or by a trough that encloses the sides and top or sides and bottom as location requires (1926.307(c)(2)(i)).

• Exceptions include runways used only for oiling or running adjustments. When using troughs under bench machines, ensure the sides extend close to the underside of the table or floor as required (1926.307(c)(2)(ii)).

Projecting shaft ends must present a smooth edge and shall not project more than one‑half the diameter of the shaft unless guarded by nonrotating caps or safety sleeves; unused keyways must be filled or covered (1926.307(c)(4)(i) and 1926.307(c)(4)(ii)).

• In short: minimize exposed projecting parts and eliminate sharp edges or open keyways to prevent contact injuries.

You may omit the usual guarding for belts, pulleys, and shafting in a basement, tower, or room used exclusively for power transmission equipment only if all of the conditions listed in the standard are met. Those conditions include:

• The space is locked against unauthorized entrance (1926.307(c)(5)(i)).
• Vertical clearance in passageways is at least 5 ft. 6 in. (1.672 m) (1926.307(c)(5)(ii)).
• Illumination meets ANSI A11.1‑1965 (R‑1970) requirements (1926.307(c)(5)(iii)).
• The oiler’s route is protected to prevent accidents (1926.307(c)(5)(v)).

If any condition is not met, the normal guarding requirements of 1926.307 apply.

Pulleys with any part 7 feet or less from the floor or working platform must be guarded in accordance with the guarding standards specified in paragraphs (m) and (o) of 1926.307 (1926.307(d)(1)).

• That means use the guard designs, heights, and mesh/fill requirements described in 1926.307(m) and 1926.307(o).

If the distance to the nearest fixed pulley, clutch, or hanger does not exceed the width of the belt used, the standard requires a guide be provided to prevent the belt from leaving the pulley on that side (1926.307(d)(2)(i)).

• In practice, install flanges, guide rails, or collars that keep the belt aligned where side clearance is limited.

Pulleys with cracks or pieces broken out of rims must not be used. The standard clearly prohibits using broken pulleys (1926.307(d)(3)).

• Remove and replace damaged pulleys before returning equipment to service to avoid failure and flying debris hazards.

When both runs of a horizontal belt are 7 feet or less from floor level, the guard must extend to at least 15 inches (38.1 cm) above the belt or to a standard height; however, if both runs are 42 inches (106.68 cm) or less from the floor, the belt must be fully enclosed (1926.307(e)(1)(i)).

• In powerplants or power‑development rooms a guardrail may be used instead of this guard (1926.307(e)(1)(ii)).

Horizontal overhead belts above 7 feet must be guarded for their entire length if any of these conditions apply:

• The belt is located over passageways or work places and travels 1,800 feet or more per minute (1926.307(e)(2)(ii)(a)).

• The center‑to‑center distance between pulleys is 10 feet (3.04 m) or more (1926.307(e)(2)(ii)(b)).

• The belt is 8 inches (20.32 cm) or more in width (1926.307(e)(2)(ii)(c)).

• If none of these conditions apply, partial guarding may be acceptable, but evaluate hazards and guard accordingly.

If passage between upper and lower runs would be possible, the standard requires either:

• Completely bar the passage with a guardrail or other barrier according to paragraphs (m) and (o); or

• Provide a platform over the lower run guarded on both sides with filled‑in mesh or a solid barrier, and guard the upper run to prevent contact by workers or objects they carry (1926.307(e)(2)(iii)(a) and (b)).

• In powerplants only the lower run need be guarded.

Vertical and inclined belts must be enclosed by a guard that meets the standards in paragraphs (m) and (o), and guards for inclined belts must be arranged so there is at least 7 feet (2.128 m) clearance between the belt and floor at any point outside the guard (1926.307(e)(3)(i) and (ii)).

• Ensure guards are designed and placed to keep belts out of reach and to maintain the required clearance for safe passage.

Cone‑pulley drives must have a belt shifter constructed to adequately guard the nip point of the belt and pulley; if the shifter frame does not do so, a vertical nip‑point guard must be placed in front of the cone extending at least to the top of the largest step of the cone (1926.307(e)(5)(i)).

• If the belt is endless or laced with rawhide and you don’t use a shifter, a nip‑point guard shaped to the cone contour may be used (1926.307(e)(5)(ii)).
• If the cone is less than 3 feet (0.912 m) from the floor, the cone pulley and belt must be guarded to a height of 3 feet regardless of belt type (1926.307(e)(5)(iii)).

Suspended counterbalanced tighteners and all their parts must be of substantial construction, securely fastened, and have securely capped bearings; the employer must provide means to prevent the tightener from falling if the belt breaks (1926.307(e)(6)(i) and (ii)).

• If location alone doesn’t guard the counterweight, it must be encased to prevent accidents (1926.307(e)(6)(ii)).

Gears must be guarded by one of the following methods: complete enclosure; a standard guard at least 7 feet high extending 6 inches above the mesh point; or a band guard covering the face with flanges extending inward beyond the root of the teeth (1926.307(f)(1)(i)–(iii)).

• If any part of a gear train guarded by a band guard is less than 6 feet from the floor, use a disk guard or a complete enclosure up to 6 feet high.
• Hand‑operated gears used only for adjustment that stop when hand power is removed are not covered by (f)(1), though guarding is recommended (1926.307(f)(2)).
• All sprocket wheels and chains must be enclosed unless they are more than 7 feet above the floor or platform (1926.307(f)(3)).

Under 1926.307(f)(4) you must provide openings with hinged or sliding self-closing covers whenever frequent oiling must be done while the machinery is in service.

• These openings let you oil moving parts without removing guards. See Openings for oiling in 1926.307(f)(4).
• If points are not readily accessible and you must add lubricant while machinery is running, install oil feed tubes so workers do not have to reach into moving parts (same paragraph).

Under 1926.307(g) the driving point of any exposed friction drive must be guarded, and arm/spoke friction drives and web friction drives with holes must be completely enclosed.

• The rule also requires guards on any projecting belts on friction drives that are exposed to contact. See Guarding friction drives in 1926.307(g).
• In practice, that means you must fully enclose exposed pinch points, spokes, or perforated webs, or fit fixed guards to prevent worker contact.

Under 1926.307(h)(1) all projecting keys, setscrews, and other projections on revolving parts must be removed, made flush, or guarded by a metal cover.

• Exceptions: this does not apply to keys or setscrews inside gear or sprocket casings or other enclosures, nor to keys, setscrews, or oilcups in hubs of pulleys less than 20 inches in diameter when they are within the plane of the rim of the pulley. See Keys, setscrews, and other projections 1926.307(h)(1).
• OSHA also recommends avoiding projecting setscrews or oilcups in any revolving pulley or part of machinery (see 1926.307(h)(2)).

Under 1926.307(i)(1) collars must be cylindrical and any screws or bolts in collars must not project beyond the largest periphery; under 1926.307(i)(2) shaft couplings must be built so bolts, nuts, setscrews, or revolving surfaces present no hazard.

• Bolts, nuts, and setscrews may be used only if they are covered by safety sleeves, used parallel to the shaft and countersunk, or do not extend beyond the coupling flange. See Collars and couplings 1926.307(i)(1) and 1926.307(i)(2).
• In short: make collars smooth and avoid exposed hardware on couplings that could snag or contact workers.

Under 1926.307(j) all drip cups and pans used in bearings and oiling must be securely fastened.

• This prevents accidental spills, falling parts, or oil getting on moving machine elements where it could cause slip or fire hazards. See Bearings and facilities for oiling 1926.307(j).

Under 1926.307(k)(1) clutches, cutoff couplings, or clutch pulleys that have projecting parts and are located 7 feet (2.128 m) or less above the floor or work platform must be enclosed by a stationary guard.

• The guard must be constructed in accordance with the section's guarding requirements to prevent employee contact. See Guarding of clutches, cutoff couplings, and clutch pulleys 1926.307(k)(1).
• If the device is higher than 7 feet, different protections may apply but evaluate worker access and exposures carefully.

Yes. Under 1926.307(k)(2) in engine rooms a guardrail (preferably with a toeboard) may be used instead of the stationary guard required by 1926.307(k)(1), provided the room is occupied only by engine room attendants.

• That is allowed because engine room attendants are typically trained and restricted to the area. See Engine rooms exception in 1926.307(k)(2).

Under 1926.307(l)(1)(i) all tight-and-loose pulley systems installed on or after August 31, 1971, must have a permanent belt shifter with mechanical means to prevent a belt from creeping from the loose to the tight pulley.

• OSHA recommends upgrading older installations to match this requirement. See Belt shifters 1926.307(l)(1)(i).

Under 1926.307(l)(1)(ii) belt shifter and clutch handles must be rounded, positioned as far from accidental contact as possible yet within easy reach, and if not directly over a machine or bench the handles must be cut off at 6 ft. 6 in.

• This reduces the chance of accidental engagement while keeping the control accessible. See Belt shifter handles 1926.307(l)(1)(ii).

Under 1926.307(l)(2) OSHA does not recommend using belt poles as substitutes for mechanical belt shifters.

• Belt poles are less reliable and increase worker exposure to moving parts compared to mechanical shifters. See Belt shippers and shipper poles 1926.307(l)(2).

Under 1926.307(l)(3) belt perches (brackets, rollers, etc.) must be used to keep idle belts away from shafts where loose pulleys or idlers are not practicable.

• They prevent idle belts from contacting rotating shafts or other moving parts, reducing entanglement hazards. See Belt perches 1926.307(l)(3).

Under 1926.307(l)(4) belts that must be shifted by hand and belts within 7 feet (2.128 m) of the floor or working platform that are not guarded shall not be fastened with metal or with any fastening that by construction or wear will create an accident hazard.

• Use nonmetallic or other safe fasteners on hand-shifted or low-unprotected belts to reduce cut, pinch, or snag risks. See Belt fasteners 1926.307(l)(4).

Under 1926.307(m)(1)(i) standard guards may be made of expanded metal, perforated or solid sheet metal, wire mesh on an angle-iron frame, or iron pipe securely fastened; under 1926.307(m)(1)(ii) all metal should be free from burrs and sharp edges.

• Choose sturdy materials that resist contact with moving parts and finish them so edges are smooth to protect workers from cuts. See Standard guards materials 1926.307(m)(1)(i) and 1926.307(m)(1)(ii).

Under 1926.307(m)(2)(i) expanded metal, sheet or perforated metal, and wire mesh must be securely fastened to their frames.

• Proper fastening prevents guard displacement or loss of protective function during operation. See Methods of manufacture 1926.307(m)(2)(i).

Under 1926.307(o)(1)(i)(a) all guards must be rigidly braced every 3 feet (0.912 m) or fraction of their height to some fixed part of the machinery or building structure.

• If the guard is exposed to contact with moving equipment, additional strength beyond this bracing may be necessary to resist impact. See Guard bracing 1926.307(o)(1)(i)(a).

Under 1926.307(o)(2)(i) wood guards may be used in woodworking and chemical industries, where fumes or manufacturing conditions would rapidly deteriorate metal guards, in construction work, and outdoors where extreme temperatures make metal undesirable; in all other industries wood guards are not permitted.

• Use wood guards only in the listed situations; otherwise provide metal guards. See Wood guards 1926.307(o)(2)(i).

Under 1926.307(o)(3)(i) guards for horizontal overhead belts must run the entire belt length and either follow the pulley to the ceiling or be carried to the nearest wall to enclose the belt effectively.

• Per 1926.307(o)(3)(iii), the interior surface of overhead guards must be smooth and free from projections; the guard must be at least one-quarter wider than the belt (but need not exceed a 6-inch clearance on each side). See Guards for horizontal overhead belts 1926.307(o)(3)(i) and 1926.307(o)(3)(iii).

Under 1926.307(o)(5)(i)–(iii) guardrails must be 42 inches (106.68 cm) high with a midrail, posts no more than 8 feet apart and of specified strength, and toeboards must be at least 4 inches (10.16 cm) high made of wood, metal, or metal grill not exceeding 1 inch mesh.

• Posts must be permanent, smooth, and free from protrusions; if pipe, at least 1 1/4 inch inside diameter; if wood, at least 2×4 inches. See Guardrails and toeboards 1926.307(o)(5)(i)–(iii).

Under 1926.307(p)(1) all power-transmission equipment must be inspected at intervals not exceeding 60 days and be kept in good working condition at all times.

• Regular inspections help catch misalignment, wear, or loose guards before they become hazards. See Care of equipment 1926.307(p)(1).

Under 1926.307(p)(2)(i) shafting must be kept in alignment and free from rust and excess oil or grease, and under 1926.307(p)(2)(ii) you must consider the hazard of static sparks from shafting where explosives, explosive dusts, flammable vapors, or flammable liquids exist.

• Keep shafts clean and aligned and evaluate static-spark risks in flammable atmospheres. See Shafting 1926.307(p)(2)(i)–(ii).

Under 1926.307(p)(3) bearings must be kept in alignment and properly adjusted, and under 1926.307(p)(4) hangers must be inspected to ensure all supporting bolts and screws are tight and hanger-box supports are properly adjusted.

• Routine checks reduce bearing failures and hanger drops that could damage guards or cause belt derailment. See Bearings and hangers 1926.307(p)(3)–(4).

Under 1926.307(p)(5)(i) pulleys must be kept in proper alignment to prevent belts from running off, and under 1926.307(p)(6)(ii) belts, lacings, and fasteners must be inspected and kept in good repair.

• Misaligned pulleys or worn fasteners increase the risk of belt failure or workers needing to reach into guarded areas. See Pulleys and care of belts 1926.307(p)(5)(i) and 1926.307(p)(6)(ii).

Under 1926.307(p)(7) workers doing lubrication must wear tight-fitting clothing.

• Tight-fitting clothing reduces the chance of garments being caught in moving parts while oiling machinery. See Lubrication clothing 1926.307(p)(7).
• For broader PPE selection and hazard assessment considerations, see OSHA's PPE hazard assessment guidance in the letter of interpretation at https://www.osha.gov/laws-regs/standardinterpretations/2024-03-28 which explains employer responsibilities to assess hazards and select PPE where required.

Under 1926.307(h)(1) projecting setscrews and oilcups in the hubs of pulleys less than 20 inches (50.8 cm) in diameter are allowed when they are within the plane of the rim of the pulley (they are excepted from the removal/flush/guard requirement).

• Even though this is an exception, OSHA still recommends avoiding projecting setscrews or oilcups in any revolving pulley or machinery part per 1926.307(h)(2). See Keys, setscrews, and other projections 1926.307(h)(1) and 1926.307(h)(2).

Under 1926.307(o)(3)(iii) you must provide suitable reinforcement for ceiling rafters or overhead floor beams where necessary so they can safely sustain the weight and stress imposed by overhead guards.

• The interior surface of the guard must be smooth and free of projections, and side clearances and width requirements must be met. See Overhead belt guard construction 1926.307(o)(3)(iii).

Under 1926.307(o)(3)(iii) overhead belt guards shall be at least one-quarter inch wider than the belt on each side, except that this clearance need not exceed 6 inches (15.24 cm) on each side.

• This ensures enough room to avoid rubbing while preventing excessive open space that could allow contact with moving parts. See Overhead belt guard clearance 1926.307(o)(3)(iii).

Under 1926.307(o)(4) guards for horizontal overhead rope and chain drives must conform to the rules for overhead-belt guards in 1926.307(o)(3).

• That means they should run the full length, follow the pulley to the ceiling or nearest wall, be smoothly finished inside, and have appropriate side clearances and reinforcement where needed. See Guards for horizontal overhead rope and chain drives 1926.307(o)(4) and overhead belt rules 1926.307(o)(3).

Under 1926.307(m) and 1926.307(o) if a guard is exposed to contact with moving equipment it may require additional strength, and guards must be rigidly braced (every 3 feet or fraction of their height) to the machinery or building structure.

• In short: strengthen frames, increase fastenings, or use heavier materials if guards might receive impact or sustained contact. See Standard guards 1926.307(m) and Approved materials and bracing 1926.307(o)(1)(i)(a).