How to properly lubricate and inspect your lift chains.
There are three basic types of lift chain; leaf chain, roller chain and roller less chain. While all these types of chain effectively transmit lifting forces from the hydraulic cylinders to the forks, leaf chain is by far the most prominent in modern lift truck.
An important consideration in field maintenance of leaf chain is lubrication. Hard working heavily loaded chains cannot provide acceptable wear life without periodic lubrication. Like all bearing surfaces, the precision-manufactured, hardened-steel, joint-wearing surfaces require a film of oil between mating parts to prevent accelerated wear.
Maintaining a lubricant film on all chain surfaces will:
a. Minimize joint wear.
b. Improve corrosion resistance.
c. Reduce the possibility of pin turning.
d. Minimize tight joints.
e. Promote smooth, quiet chain action.
f. Lower chain tension by reducing internal friction in the chain system.
Use Chain and Cable Lubricant for lubrication of chains. The lubricant will penetrate into the chain joint to prevent wear. Applying lubricant to external surfaces will prevent rust, but the lubricant must flow into the bearing surfaces for maximum chain life.
The frequency of lubrication will change with the operating conditions and the environment. The best lubrication time is during each P.M. (50-250 hours or four weeks maximum actual truck operating time). Trucks that are parked outdoors or in very severe service may need lubrication more often to keep a layer of oil on all chain surfaces.
In dirty operating conditions, lubricated chains will gather dirt. Even under these conditions, chain life will be increased by periodic lubrication. Joints get a “paste” of oil and dirt, but joint wear will still be much less than if the chain is permitted to operate dry with metal-to-metal contact between pins and plates (pin and bushing in roller chain).
PROCEDURE TO CHECK FOR CHAIN WEAR
Elongation can be measured using a Lift Chain Wear Gauge. Select a section of chain that regularly moves over the sheaves, since this area accumulates the most wear. Identify the chain pitch and the appropriate points on the chain wear gauge (either ‘A’ or ‘8’). Position the corresponding point of the gauge on the center of the first pin. Please look at the descriptions listed below for further instructions on checking wear.
LIFT CHAIN INSPECTION
Every 50 to 250 hours or after each 30 days of operation (more frequently in hostile environments), lift chains should be inspected and lubricated. Inspection should focus on the following:
2. Edge Wear
3. Chain Side Wear
4. Turning or Protruding Pins
5. Cracked Plates due to:
a. Fatigue cracking
b. Stress corrosion cracking
c. Corrosion fatigue
6. Tight Joints
7. Ultimate Strength Failure
8. Chain Anchors and Sheaves or Sprockets
9. Missing Parts
A chain’s normal life expectancy is expressed as a maximum percent of elongation. This is generally 3% of pitch. As leaf chain flexes back and forth over the sheave or roller chain runs over the sprocket, the bearing joints (pins, inside link plates on leaf chain, and bushings on roller chain) gradually wear. As with all bearing surfaces, the precision hardened steel joints require a constant film of oil between mating parts to prevent rapid wear and also to resist corrosion.