Maintenance of Roller Chains

A roller chain drive must always be designed to be resistant to breakage and wear.

When deflected over sprockets, the oscillating swivelling motion of the pins causes friction and thus unavoidable joint wear – even with correct lubrication.

The standard DIN ISO 10823 provides detailed calculation guidelines for roller chain drives.

Schmierung – Kettenlängung zu Betriebszeit

Lubrication

The chain’s movement around the sprockets causes wear in the joints due to the angular sliding motion of the pins. For this reason, effective lubrication is absolutely essential.

1) no lubrication
2) initial lubrication, no relubrication
3) relubrication, insufficient intervals (periodic dry running)
4) relubrication, incorrect or contaminated lubricant
5) optimal lubrication

Relubrication determines 99% of the service life
3% elongation = chain service life 15,000 hours or longer

Basic principles of chain lubrication

Despite correct lubrication, every chain elongates during operation.
Relubrication is crucial for service life.
The lubricant film between  pin and bushing minimizes wear.

Tip: For new systems, it is recommended to gradually approach the optimal relubrication intervals!

Responsibilities

Participant	Mission
Chain manufacturer	Initial lubrication, recommendation for relubrication
System manufacturer	Specifications for lubricants & intervals, access points, lubrication systems
User	Compliance with specifications, if necessary adjustments in cooperation with manufacturer

Core criteria

Operating temperature (critical)

The decisive factor is the temperature in the chain joint during operation. The suitability of a lubricant is determined by its thermal stability and the maintenance of its lubricating properties at the appropriate viscosity.
Oils, used with an appropriate lubrication method, are suitable for cooling the chain; the oil’s maximum operating temperature must never be exceeded.

Info: Lubricant losses at higher temperatures are inherent in open tribological systems such as the chain joint and do not indicate a deficiency of the lubricant.

Tip: If dripping at higher temperatures is not acceptable, this requirement must be explicitly specified (and taken into account in product and process selection).

Viscosity (lubrication film vs. flowability)

The viscosity must be high enough to provide protection, yet sufficiently fluid to reach the friction points.

Principles

low joint surface pressure,high chain speed → low viscosity
high joint surface pressure,low chain speed → high viscosity
low operating temperature → low viscosity
high operating temperature → higher viscosity

Oil or grease?

Oils: Standard for continuous relubrication
Grease: Preferred in dusty air (e.g., lime, talc, flour)

Wetting of friction points (creepability)

The lubricant must penetrate the lubrication gap on its own.
If necessary, viscosity can be reduced during application using a solvent.

Operating conditions & industry requirements

Moisture/splash water: Lubricants must not be washed away, should be capable of creeping, and still provide corrosion protection even as an emulsion.
Corrosive media: Corrosion protection is particularly important.
Food industry: Lubricants must comply with food safety regulations.
Textile industry: Use non-sticking, drip-free oils.
Material compatibility: Ensure compatibility with elastomers/plastics → compatibility testing required.

WKS lubricants (factory product range)

Application/Industry	WKS‑product	Temperature	Base & properties
Standard, high requirements	WKS‑ C	‑10 to +100 °C	Highly additive-containing grease
Adhesion-resistant	WKS‑W	0 to +80 °C	Wax-containing grease, non-sticky
Corrosion protection	WKS‑D	‑10 to +80 °C	Low-viscosity mineral oil with inhibitors
Food industry	WKS‑H1	‑10 to +140 °C	NSF‑H1‑listed oil
High temperatures / Automotive	WKS‑ Plus	‑10 to +240 °C	Synthetic ester‑oil (spray)
Extreme temperatures	WKS‑ HT	‑10 to +500 °C	Oil with graphite, >300 °C, dry lubrication
Low temperatures	WKS‑ HT	‑55 to +90 °C	Low-viscosity synthetic‑ oil
Spray‑relubrication	WKS‑Special	‑10 to +80 °C	Mineral oil‑spray with additives

Further information on lubrication can be found here.

→ Guideline values for mineral oil viscosity

→ Lubrication methods

→ Initial and relubrication

→ Cleaning

Inspection of Roller Chains

Regular inspection prevents unplanned downtime. Check for:

Twisted pins / loss of press fit
Stiff or elongated inner links
Corrosion (pitting, stress cracks)
Lubrication condition (surface rust)
Breakage & wear from external influences
Misalignment (lateral tooth wear)
Wear elongation (discard limit)
Sprockets – condition of tooth flanks

Wear elongation limits:

Adjustable centre distance	Up to 5 m/s	Max. 3 % elongation
Adjustable centre distance	Above 5 m/s	Max. 1.5 to 2 % elongation
Fixed centre distance	Up to 2 m/s	Max. 1.5 % elongation
Fixed centre distance	Above 2 m/s	Max. 0.8 % elongation
Sprockets > 67 teeth		Max. 200/z in %

Measuring Chain Elongation

Position the chain, including the portion running over the sprockets in the measured section.
Apply light load and tension.
Using a tape measure, measure pin-to-pin distance over approx. 1 m.

Position the chain, including the portion running over the sprockets in the measured section.
Apply light load and tension.
Using a tape measure, measure pin-to-pin distance over approx. 1 m.

Chain Replacement

Replace the chain and sprockets if the discard limit is exceeded.
A chain that has lengthened due to joint wear must shift to a larger effective diameter on the sprocket in order to achieve a stable, form-fitting engagement with the teeth. Only at this diameter, which the chain assumes on its own, do all the sprocket teeth (within the wrap) carry load according to a geometric progression. The continuous shifting of the chain on the sprocket (the roller seating into the base circle followed by sliding along the tooth flank to the effective diameter) is usually indicated by corresponding tooth flank wear; in advanced stages, the characteristic "shark teeth" appear. At this point, there is also an acute risk of the chain jumping over the teeth, since the effective diameter is already close to the tooth tips.