Critical spares: Is your electrical storeroom ready to serve?
According to Terry Wireman, “The inventory and purchasing staff have the largest impact on maintenance productivity, more than any other support group”. The basis of this assessment comes down to wait time. While it is a bold statement, Terry makes a great point. The accessibility, ordering, and other delays associated with spare parts adds up. These delays certainly apply to items in the storeroom, where the greatest total cost and risk are with critical spares.
What are critical spares?
A critical spare is a part that significantly threatens ongoing operations when it fails due to the difficulty of replacement. The threat could be financial, resulting from downtime and lost production. It could also be non-monetary, such as personal safety. Difficulty of replacement could stem from a combination of factors such as lead time, access, support availability and other factors.
Critical spares are typically associated with equipment or processes that are critical to continued operations. The equipment can typically be segmented into subsets which can help isolate potential issues. For example, an assessment of a critical motor examines the entire circuit required to operate, including the motor control and circuit protection.
When was the last time you assessed your critical spares parts list?
Things change over time. Components such as variable frequency drives become obsolete. Accessories such as programming interfaces become more difficult to source. Production increases, stressing the limits of equipment and components. There are also expansions and replacements. All of which combine to create uncertainty in your critical spares parts list.
There are two basic questions to answer:
What needs to be added to the critical spares list?
What needs to be removed from the list?
While the first seems straightforward, the second is often overlooked. Obsolete, or end of life, components should be targeted for replacement, in the plant and in the storeroom. Moreover, we often find critical spare inventory for equipment that no longer exist, or that no longer meet critical spare criteria.
Conducting an assessment of critical spares.
A criticality assessment begins with a team that shares a stake in the response to critical failures. This discussion establishes the foundation of a critical spare program. The team typically includes representation from the storeroom, maintenance, operations and engineering.
A few high level questions to begin with include:
What are the most critical equipment and processes?
What is the consequence of failure (usually expressed as cost)?
What are the resulting criteria of a critical component?
Establishing the criteria of a critical component can be difficult. Wally Wilson and others have produced very helpful guides on this. Experienced personnel can be a tremendous help here, especially so because they can quickly move through known areas of risks. Their understanding of the repair requirements and outage planning can help define the required availability of any given component (onsite, next day, 1 week).
This is also where experienced vendors can be a huge help. You will need to know the typical lead time on these items. Combined with your own repair history, you can begin defining criticality levels and ranking spares.
Planning your response
Planning the repair evolution, step by step, can be enlightening. Going from a list of defined parts to the actual repair work order can reveal additional items and uncover hurdles. Are there special safety considerations to be prepared for? As you work through the repair evolution you may even challenge the components on your list. There are times we find that while an onsite repair is possible, it is not practical during an emergency outage. In those cases, it may be better to stock an entire component versus the repair parts.
During this phase it is important to assess what capabilities you will need to respond. Can you support them? Are you working with a qualified vendor who can? What future action could be taken to reduce your risks?
Documenting your plan
With your vetted and updated critical spare list complete, you may also chose to document the process behind it. From the first meeting to the response planning there is a considerable amount of material that could be very useful in the future. Furthermore, it will be much easier to “refresh” a few years down the road.
Consider recording the list of critical equipment, consequence of failure, and criteria for critical components. You may also be able to incorporate your response planning into your work procedures. This could include important vendors, contacts, and links to other necessary documentation.
Getting started on a critical spares plan
Depending on how long it has been since your last criticality assessment, this project could range from a simple 'update' to an extensive review.
With so much demand on your time it may be tough to find the energy to get started, so here are a few tips:
Don’t try to tackle it all at once. Start with a subset of your spares, perhaps the most visible or new.
Use your qualified vendors to assist you with the analysis.
Combine your criticality assessment with migration planning (obsolete and end of life components).
