Tackle Block Warning, Use & Maintenance Information.

Tackle Block Information Continued:

Tackle Block Maintenance

Tackle Blocks must be regularly inspected, lubricated, and maintained for peak efficiency and extended usefulness. Their proper use and maintenance is equal in importance to other mechanical equipment. The frequency of inspection and lubrication is dependent upon frequency and periods of use, environmental conditions, and the user's good judgment.

Inspection: As a minimum, the following points should be considered:

1. Wear on pins or axles, rope grooves, side plates, bushing or bearings, and fittings (See Fitting Maintenance). Excessive wear may be a cause to replace parts or remove block from service.
2. Deformation in side plates, pins and axles, fining attachment points, trunnions, etc. Deformation can be caused by abusive service and l or overload and may be a cause to remove block from service.
3. Misalignment or wobble in sheaves.
4. Security of nuts, bolts, and other locking methods, especially after reassembly following a tear down inspection. Original securing method should be used; e.g., staking, set screw, coffer pin, cap screw.
5. Pins retained by snap rings should be checked for missing or loose rings.
6. Sheave pin nuts should be checked for proper positioning. Pins for tapered roller bearings should be tightened to remove all end play during sheave rotation. Pins for bronze bushings and straight roller bearings should have a running clearance of .031 inch per sheave of end play and should be adjusted ac cordingly.
7. Hook or shackle to swivel case clearance is set at .031 to .062 at the factory. Increased clearance can result from component wear. Clearance exceeding .12 to .18 should necessitate disassembly and further inspection.
8. Deformation or corrosion of hook and nut threads.
9. Surface condition and deformation of hook (See Fitting Maintenance and ANSI B30.10.)
10. Welded side plates for weld corrosion or weld cracking.
11. Hook latch for deformation, proper fit and operation.

Lubrication: The frequency of lubrication depends upon frequency and period of product use as well as environmental conditions, which are contingent upon the user's good judgment.
Assuming normal product use, the following schedule is suggested when using lithium-base grease of a medium consistency.

Sheave Bearings

Tapered Roller Bearings - Every 40 hours of con tinuous operation or every 30 days of intermittent operation.

Roller Bearings - Every 24 hours of continuous operation or every 1 4 days of intermittent operation. Bronze Bushings - (Not Self Lubricated) - Every 8 hours of continuous operation or every 1 4 days of intermittent operation.

Hook Bearings

Anti Friction - Every 1 4 days for frequent swiveling; every 45 days for infrequent swiveling.

Bronze Thrust Bushing or No Bearing - Every 16 hours for frequent swiveling; every 21 days for infre quent swiveling.

Tackle Block Maintenance also depends upon proper block selection (see "Loads on Blocks"), proper reeving (see "The Reeving of Tackle Blocks"), consideration of shock loads, side loading, and other adverse conditions.

Sheave Bearing Application Information

BRONZE BUSHING-
Bronze Bushings are used primarily for sheave applications using slow line speed, moderate load, and moderate use. The performance capability of a bearing is related to the bearing pressure and the bearing surface velocity by a relationship known as true PV (Maximum Pressure - Velocity Factor). The material properties of the Bronze Bushings furnished as standard in Crosby catalog sheaves are:

(BP) Maximum Bearing Pressure :4500 PSI

(BV) Maximum Velocity at Bearing :1200 FPM

(PV) Maximum Pressure Velocity Factor: 55000

(It should be noted that due to material property relations, the maximum BP times the maximum BV is NOT equal to the maximum PV.)

Formula for Calculating Bearing Pressure:

Note: Angle Factor Multipliers are found here.

Formula for Calculating Bearing Velocity:

Formula for Calculating Line Speed:

Calculations can be made to find the maximum allowable line speed for a given total sheave load. If the required line speed is greater than the maximum allowable line speed calculated, then increase the shaft size and/or the hub width and recalculate. Continue the process until the maximum allowable line speed is equal to or exceeds the required line speed.

Example

Using a 1 4 in. sheave (Stock # 917191; refer to wire rope sheave section of General Catalog for dimensions) with a 4600 lb. line pull and an 800 angle between lines determine maximum allowable line speed.

Line Speed =

If the application required a line speed equal to 200 FPM, then another calculation would be necessary. Trying another 14 in. sheave (stock #4104828) under the same loading conditions, the results are as follows:

Line Speed =

COMMON (PLAIN) BORE -
Very slow line speed, very infrequent use, low load.
ROLLER BEARING -
Faster line speeds, more frequent use, greater load, Refer to manufacturer's rating.