The missing link
Spare Parts Maintenance
By Phillip Slater, contributing writer
Oh no, not again! This the perennial cry of the maintenance and reliability professional. We all know this situation: A part or component, recently repaired, has now failed again. Not only is this annoying and frustrating, it also means costly and unnecessary downtime.
In this situation we are usually quick to blame the technician, technique or design. But none of these may be at fault; the cause of the breakdown could be a poorly maintained spare part.
This might be a hard idea to swallow, but many self-induced and premature failures are more likely the result of poor material-handling and storage methods for spare parts than any other cause. For many maintenance and reliability practitioners, understanding the impact of materials management is the missing link in achieving reliability.
Storage of spare parts and reliability
Is it any wonder that many early life failures can and do result from poor preservation of the spare parts? The accompanying photo shows a cupboard in a workshop where the bearings are being stored in anything but an acceptable manner.
Did the people that set this up really expect to get the full life from this arrangement? Ask yourself now if you have one of these cupboards in your spare-parts storage system.
The key issues for equipment maintenance are the dynamic effects of being in operation and exposure to the environment. This includes the effects of wear, heat and vibration. For the spare parts that we have in storage, the issues are similar.
We still need to deal with the effect of exposure to the environment, but we also need to deal with the effect of not being in operation, that is, the effect of being stationary.
Exposure to the environment
The key things to consider when dealing with exposure to the environment are where and how the parts are stored. For example, sometimes we are very careful to protect the operating equipment with environmental controls such as air-conditioning or dust-proofing but then keep the spares in a storeroom without either of these.
Even items kept in suitable storage or undercover are exposed to the environment and exhibit failure modes from exposure, such as:
l Oxidation of rubber components in seals, belts, and other parts
l Build up of dust (especially important in electrical, rotating and reciprocating equipment)
l Lubrication failure (through contamination, migration and evaporation)
l Vibration from the operating facility — slight vibration over a period of time can degrade many spare parts, from bearings to electronic components
Effect of being stationary
It is easy to assume that because a part is not in operation and is environmentally protected, it will be OK. But for items that are stationary, the enemy of reliability is gravity, and gravity is always with us! The two main influences of gravity are:
l Flat spots that result from a constant weight on one section in seals, shafts and bearings.
l Lubricants ‘flowing’ to the lower areas, leaving upper areas without lubrication.
Passive and active controls
Exposure can be controlled, but gravity must be managed (that is, the effects of gravity). Therefore environmental control is likely to be passive (in that we provide infrastructure which provides control) whereas managing the effect of gravity will need to be active (we need to perform tasks regularly in order to ensure the integrity of the part).
To demonstrate this visually, Figure 1 shows the relationship between parts in operation and parts in storage, and Figure 2 shows, for parts in storage, the crossover between active and passive issues.
In Figure 1, we see that whether a part is in storage or in operation, we must still manage the effects of rust, dust, lack of lubrication and other environmental impacts. This diagram alone indicates that for reliable plant operation we must maintain our parts because they are subject to many of the same issues as the items in operation.
In Figure 2, we see that those same core issues of rust, dust and lubrication require active involvement if we are to ensure that a part will operate as required when needed. This is in addition to actions that we take in order to counter the effects of gravity and other environmental protection.
Transform storeroom function
By viewing spare-parts management in this way, we can see that the real function of the storeroom is not just to store and control access to parts. It also serves to maintain them in a condition so that they are fit for use when required. This means ensuring an appropriate care and maintenance routine as well as providing environmental protection. Neatness and organization of spare parts only helps ensure storeroom efficiency — it does not guarantee spare-part integrity.
Some basic storeroom practices that impact reliability include:
l Proper storage — safe from the environmental effects of dust, water, vibration and light
l Preservation of parts — appropriate lubrication and management of the effects of gravity
l Rigorous rotation of parts, that is, using the oldest parts first
l Proper labeling of parts to ensure selection of the correct part
l Proper access and equipment for lifting devices in order to avoid mechanical damage to parts when storing or retrieving them
Establishing a spares maintenance program is really similar to establishing the rest of your maintenance/reliability program. Whereas maintenance/reliability programs typically address kinetic effects — or reliability issues that arise through the physical operation of the asset — a spares maintenance program will address static effects — issues that arise through non-operation of the asset. Both programs, of course need to address environmental effects.
Therefore, establishing a spare-parts maintenance program only really requires a change in mindset for your failure mode and effects analysis (FMEA).
You now need to consider how the item will fail through not operating rather than how it will fail through operating. The rest of the program development is the same as with any other maintenance/reliability program: You need to identify the what, why, when, how, who and where of your spares maintenance program. This is an opportunity to expand your maintenance process and procedures to the personnel in the storeroom.
A world-class spares maintenance program is likely to not require any more personnel than you currently have. It is an opportunity to transform the perception of your storeroom personnel from a simple receiving, issuing, and counting role to a role integral to the reliability of the facility. A written, detailed program could add the structure and professionalism to transform your storeroom and your storeroom personnel.
The missing link
Maintenance and reliability professionals, charged with the responsibility of ensuring the preservation of the equipment in their care, often overlook one of the single greatest causes of equipment failure and subsequent downtime: poor spare-parts management. For many, this is the missing link in their reliability program.
Poor spare-parts management results from systemic issues with the way that reliability data is collected, inappropriate techniques for storage, a misalignment of responsibilities, poor training, and a lack of formal policy and procedures in this area.
Empirically we know all this to be true and so, equally, we know from experience that correction of these issues can have a significant impact on the outcomes from any maintenance and reliability program.
Phillip Slater is an international materials and spare-parts management specialist. He is a qualified engineer, an experienced operations and maintenance manager, a seasoned management consultant, and the author of four operations management books. For access to more information on spare parts management visit his Web site, www.PhillipSlater.com, or contact him at pslater@InitiateAction.com.