All high-quality chain is manufactured to consistently tight tolerances.
Chain is deemed to be worn beyond its safe service life when the nominal pitch length has been extended by 2% to 3%. At this point the fatigue life of the chain is reduced and the ultimate breaking strength is considerably lower.
A chain that is elongated by 2% is becoming dangerous and the competent person must determine a safe time limit for replacement.
A chain that is elongated by 3% must be renewed immediately. Until the chain is renewed the equipment to which it is fitted must not be used.
It is recommended that wherever possible the chain should be cleaned and measured in situ with the chains placed under load.
The recommended load equates to approximately 1% of the minimum breaking load of the chain.
Without the availability of a set of check weights it is, for the purpose of putting the chain under load, normally sufficient to allow the chains to be tensioned by the weight of the carriage and forks.