Anyone in the trade, or who has had occasion to touch maintenance work, knows well that spare parts control which is not effective will delay a breakdown whose cause and whose remedy are both known — because there is no part on hand to use at once. Whatever the reason, this is a problem that comes from the control of spares.
Why this matters
Maintenance management does not have as its goal merely that the machine should not break down. Its highest goal is a better result for the organisation as a whole — built by a maintenance system that gives weight to developing the skill, knowledge and capability the maintenance department needs, to managing maintenance strategically, and to everyone in the organisation taking part in it.
The purpose of spare parts control
To further the efficiency and reliability of the machines and equipment, through effective purchasing, contracting and storage
To give breakdown maintenance and preventive maintenance the confidence that whenever a part is wanted for a repair or for maintenance, it can be found at once or in the least possible time
To reduce the spare parts inventory to the smallest it can be — cutting tied-up capital, cutting the cost of storage, and cutting the space storage takes
Classifying maintenance material
Classifying maintenance material and equipment is the first step in managing and controlling spares — so that priority can be assigned, and so that a suitable approach to purchasing and storage can be found.
Parts for routine replacement, at a firmly fixed interval
Parts for emergency or sudden need — breakdown spare parts
Parts that must be held in stock at all times — reservation spare parts
Parts that can be used again, whether on the same machine or another, normally kept by the maintenance department
The tools and equipment used in maintenance
Ordering method
Ordering divides into three broad kinds: ordering the particular item at the time it is wanted (individual order), ordering in regular batches (permanent stock method), and ordering under a special contract with the supplier (special contract method).
Individual order — buying only the item, the quantity and the time wanted, taking no interest in the discount or the cost of placing each order. Its advantage is in the quantity of spares that must be stored; its risk is late delivery from the supplier.
Permanent stock method — a quantity of spares is held at all times, and an order placed each time the moment comes, so as to save on ordering cost, obtain a good discount and, importantly, make raising the order easy. But often what is bought goes unused, and by the time it is wanted it has deteriorated. And sometimes what is used was not bought, while what was bought is not used. So permanent stock must be run by a method that suits it.
Special contract method — a special contract is drawn up with the supplier to give the convenience wanted in the terms of ordering, delivery and storage. All of it ties back to the one measure of effective purchasing: a part available in time, at the moment it is wanted, while the inventory stays low.
Fixed-quantity order
a fixed order quantity · order-point method · double-bin method · package method · batch issue method
Fixed-period order
a fixed time at which to order
Fixed-number
a fixed rate of use, ordering exactly the quantity that rate calls for
Partial delivery
buying in quantity but having the supplier deliver in instalments, to cut the cost and the management of storage
Deposit system
the supplier places the material or spares inside the buyer’s plant, in the warehouse, and charges only for what is used. This avoids tying up money in paying for everything at once, while still having parts available in time.