ASME B29.28-2015 pdf – High-Strength Chains for Power Transmission and Tension Linkages
ASME B29.28-2015 pdf – High-Strength Chains for Power Transmission and Tension Linkages.
A-3.1 Type A — Manual or Drip Lubrication
(a) For manual lubrication, oil is applied copiously with a brush or spout can at least once every 8 hr of operation. Volume and frequency should be sufficient to prevent overheating of the chain or discoloration in the chain joints.
(b) For drip lubrication, oil drops are directed between the link plate edges from a drip lubricator. Volume and frequency should be sufficient to prevent discoloration of lubricant in the chain joints. Precaution must be taken against misdirection of the drops by w indage.
A-3.2 Type B — Bath or Disc Lubrication
(a) For bath lubrication, the lower strand of chain runs through a sump of oil in the drive housing. The oil level should reach the pitch line of the chain at its lowest point while operating.
(b) For disc lubrication, the chain operates above the oil level, The disc picks up oil from the sump and deposits it onto the chain, usually by means of a trough. The diameter of the disc should be such as to produce rim speeds between 600 ft/mm (182.9 rn/mm) and 8,000 ft/mm (2.44 km/mm).
A-3.3 Type C — Oil Stream Lubrication
The lubricant is usually supplied by a circulating pump capable of supplying each chain drive with a continuous stream of oil. The oil should be directed at the slack strand, and applied inside the chain loop and evenly across the chain width.
Consult chain manufacturers when it appears desirable to use a type of lubrication other than that recommended.
Sprockets should have tooth form, thickness, profile, and diameters conforming to ASME B29J. Sprockets with fewer than 25 teeth should have an odd number of teeth to equalize wear on all of the teeth. Sprockets with 25 teeth or less should have hardened teeth. Normally, large sprockets should not exceed 120 teeth.
A-5 CENTER DISTANCE
In general, a center distance of 30 chain pitches to 50 chain pitches is most desirable. The distance between the sprocket centers should provide at least a 120-deg chain wrap on the smaller sprocket.
Drives may be installed with either adjustable or fixed center distances. Adjustable centers simplify the control of chain slack.
For drives on fixed centers, an idler or shoe may be used to provide slack adjustment. These devices may also he used to control backlash, or to ensure a 120-deg minimum chain wrap on the smaller sprocket. Idler sprockets should have at least three teeth engaging the chain. There should be at least three free pitches of chain between engagement points on adjacent sprockets.
NOTE: Sufficient housing clearance must always be provided for the slack chain to obtain full chain life.
Accurate alignment of shafts and sprocket tooth faces provides uniform distribution of the load across the entire chain width and contributes substantially to optimum drive life. Shafting, hearings, and foundations should be suitable to maintain the initial alignment. Periodic maintenance should include an inspection of alignment to ensure optimum chain life.
Adequate guarding should be provided to contain the chain in the event that a broken chain is thrown off a drive while operating at speed.
If the chain is used in a hoist or other lifting device (not for human passengers), a brake or other restraining device should be provided to stop and hold the load in the event of a broken chain.
A-8 HORSEPOWER RATINGS TABLES
To use the horsepower ratings in Tables A-i through A-9 properly, the following factors must be taken into consideration:
(a) Service Factors. See Table A-b.