Lift chains carry the carriage and the load. They wear inside the joints and grow longer long before a plate breaks. This guide shows how to measure elongation, what typical findings mean, how lubrication should look and when a change is due. Every limit comes with its source. The operator and service manual of your truck always takes precedence.
Construction and wear
Mast systems mostly use leaf chain, also called fork lift truck chain. It is built from interlaced plates and hardened pins. Renold describes it as defined in ISO 4347 and notes it cannot run on sprockets because it has no means of engagement. Roller chain with pin, bush and roller to ISO 606 is also used in some lifting applications.
One end of the chain attaches to the carriage. The chain runs up and over a chain wheel. According to Toyota, the other end is bolted to a boss on the inner mast rail. Wear occurs in the joint between pin and plate. It enlarges the pitch, so the chain stretches. The chain maker FB Chain states that at 2 to 3 % elongation, fatigue strength and breaking strength drop considerably.
When to inspect
The sources give different rhythms that complement each other.
- Toyota recommends checking the mast chains at the start of every shift.
- The US rule OSHA 1910.178 requires in paragraph (q)(7) that a truck is examined before it enters service, at least daily, and after each shift in round the clock use. Defects found must be reported and corrected immediately. Under paragraph (p)(1) an unsafe truck stays out of service until it is safe again.
- In Germany, section 37 paragraph 1 of DGUV Vorschrift 68 requires an inspection of industrial trucks by a competent person at intervals of at most one year.
- Still gives a thorough inspection every 6 months as an example, including a measurement of elongation. It also advises checking and greasing every 1,000 operating hours.
According to Renold, a chain in a correctly sized and maintained system lasts about 6,000 hours or 3 years, whichever comes first. Treat this as a rule of thumb, not as a replacement criterion.
Measuring elongation
Measure a clean chain under load. FB Chain names about 1 % of the breaking force, Renold about 5 % of the breaking load. Both allow measuring in place when the carriage or a test weight pre-tensions the chain. Check which load figure belongs to the instructions of your gauge.
Measure the section that runs over the chain wheel, because wear is greatest there. FB Chain advises at least 3 readings in that area. Renold points out that comparing the overall length with the nominal length of a new chain is not sufficient.
A wear gauge shows elongation directly. The FB Chain gauge reads in steps of 0.25 % from 0 to 4 % and shows a red window from 2 %. Without a gauge, calculate it like this. Measured length over X pitches minus nominal length (X times pitch), divided by the nominal length, times 100. Toyota stresses that limits depend on pitch and design and refers to a qualified technician.
Limits according to the sources
| Source | Statement |
|---|---|
| Renold catalogue | Leaf chain at most 3 % elongation, roller chain 2 %. Side plate wear at most 5 % of plate height. |
| FB Chain | From 2 % plan a change. From 3 % replace at once or take the truck out of service. |
| Toyota | Replace above 3 % elongation. |
| Still | Above 2 % arrange a change and note it in the inspection report. Above 3 % replace before further work. For very narrow aisle trucks, 2 % or a fixed deadline applies. |
The values differ. For your truck, the specification of the truck or chain manufacturer applies.
Lubrication
Renold supplies chain pre-lubricated and advises against painting it, because paint blocks the penetration of lubricant. For service, Renold names good quality non detergent mineral oil. According to Renold, heavy oils and greases are too stiff to enter the joints. The oil belongs in the gap between inner and outer plates. For manual lubrication, Renold suggests oiling every 8 operating hours where possible, enough to keep the chain wet. For ambient temperatures from 5 to 40 °C, Renold lists SAE 30.
Still recommends the grease the manufacturer specifies. Clean the chain with steam or solvent without additional detergents, dry it with compressed air and then lubricate. Cold stores need special lubricants. Toyota requires lubricating the chains before every use, because lack of lubrication makes pins turn.
Where the advice conflicts, follow the lubricant chart in your truck manual.
Anchors, sheaves and replacing as a set
Replace chains in pairs. Renold states that fitting only one new chain next to an elongated one makes both fail early. The anchors holding the old chain may also sit at the end of their adjustment range.
Before fitting, check anchors and chain sheaves. According to Renold, broken, damaged or worn parts must be replaced first. Never fit a chain with a used anchor pin, because pins may be bent or carry fatigue cracks that cannot be seen. Connecting links and repairs on the chain are only acceptable with the truck manufacturer's approval. After fitting, all chains must carry load equally.
Still points out that the chain is attached on both sides and can slide violently when one side is released. Secure carriage and mast as the manufacturer prescribes before you release a chain. Work on the mast and hydraulics belongs in the hands of trained personnel.
Finding, cause, action
| Finding | Possible cause | Action |
|---|---|---|
| Pins turn or protrude | Lack of lubrication, high load | Replace the chain set at once, review lubrication (Renold) |
| Cracked plates | Fatigue, stress corrosion | Replace at once, do not repair (Renold) |
| Rust, brown rough joints | Too little lubrication | Open a few joints and inspect, improve lubrication (Renold) |
| Stiff joints | Wear, bent pins, dirt | Clean and lubricate, otherwise replace the set (Renold) |
| Plates worn on the inside | Misalignment | Check and correct alignment (Renold) |
| Plates worn on top | Chain rubs on an obstruction | Remove the obstruction (Renold) |
| Enlarged plate holes | Chain runs misaligned | Replace the set, correct the cause (Renold) |
| Broken anchor | High overload | Replace anchor and chain set, remove the overload (Renold) |
| Worn sheave | Chain misaligned | Replace sheave and chain, correct alignment (Renold) |
| Slapping noise when lifting | Stuck pins | Inspect the chain (Still) |
| One side sags, forks drag | Uneven elongation or tension | Equalise tension, measure chain condition (Still) |
Matching parts from the catalogue
Check fitment before ordering against the data plate and the part number. The parts are listed in the catalogue under mast and chains.
- TCM roller chain designated VFM200, 09001-08041, as an example of a roller chain in the mast.
- TCM leaf chain VFM200, 218G8-45631, and leaf chain VFHM400, 09001-10043, as leaf chains in the catalogue.
- Zinc plated leaf chain for corrosive environments from Crown, 089260-146, for sites where rust attacks the chain.
- Crown chain anchors, 075385-003 and 075385-004, and the chain anchor pin 380030-197, when the finding points to the anchor.
- Chain sheaves for the deflection point, for example 117556-001 from Crown, 1371361 from Hyster, 5042817-96 from Yale and 21608-42031 from TCM, when the sheave shows wear.
FAQ
At what elongation must I replace a lift chain?
It depends on the source. Renold, Toyota and FB Chain name 3 % as the limit for immediate replacement. FB Chain and Still ask for a planned change from 2 %. Your truck manufacturer's specification is the deciding one.
May I replace only one of the two chains?
Renold advises against it. Where a truck has two chains, the pair should be renewed together, otherwise the new and the old chain fail earlier. This includes checking the anchors and sheaves.
Oil or grease for lift chains?
The sources disagree. Renold recommends thin, non detergent mineral oil and advises against grease. Still recommends the grease the manufacturer specifies. Use the lubricant your truck manual names.
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