a Determining Spare Parts Requirements 
Using Repair Scenarios
a By Michael V. Brown - New Standard Institute Inc. 
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The task of reorganizing an existing a storeroom, or starting new one, can be daunting.  Often, there are many parts held in storage (or just lying around) that donít belong to any equipment in the facility.  This happens slowly, over time.  Equipment in the facility may be retired and no longer at the site, but the parts for that equipment may still be on the storeroom shelves.  In other cases, someone may have ordered and/or received the wrong a part but didnít return it.

You could take on the task of cataloging all the parts you currently hold.  Then, after four or five years, you can review the usage and reevaluate the need to hold some of the parts.  Obviously, this approach wastes part of your set-up time, wastes space, and requires extra work later.

The ideal way to ensure that the parts in your inventory are the parts you need is to connect all the parts you store to equipment in the facility.  One way of doing this is to add related equipment data to the stores item description.  This is less than optimal because an identical item may be used on different equipment of various manufacturer and model, such as on a pump Model ABC and on a compressor Model XYZ.  A better solution already exists in almost all computerized maintenance management systems (CMMS).

An often ignored function in a modern CMMS is the ability to tie an inventory item record to an asset or location record through the use of a third record called spare parts list or bill-of-material (BOM). An example of this relationship is shown in the following graphic. An often ignored function in a modern CMMS is the ability to tie an inventory item record to an asset or location record through the use of a third record called spare parts list or bill-of-material (BOM).  

For an example of this relationship CLICK HERE to display graphic. 

The bearing in the stock item record is generic and can be used in many types of equipment.  In this example, it is used in a pump.  Both the pump and bearing are related to the spare parts list by Equipment Location Number and Item Number respectively.

Maintenance workers love the spare parts list or BOM approach to viewing inventory data.  In the past, companies had difficulty getting these workers to use a CMMS, let alone perform an ad-hoc search for a part in an inventory management module.  The availability of a good spare parts list seems to conquer both the fears associated with computers and the urge to rummage through the storeroom to find a part.  The worker only has to key in the equipment they are working on and a list of parts is displayed.  Usually, clicking on the item number with a mouse brings up the location of the item and current inventory status.  Some systems allow the worker to build an order of all the parts they need.  This order can be pulled by the storekeeper for the worker to pick up later, or may even be delivered to the equipment site.

An additional benefit is derived when equipment in the facility is retired or removed from service.  The parts associated with that equipment are quickly identified so they can be removed from the storeroom as well.  This frees up space for other items.

This all sounds great, so what stops most people from building spare parts lists?  The time it takes to do it.  Some computerized maintenance management systems claim they build the spare parts list "on the fly".  Parts charged out against an equipment number are assumed to be a spare part for that equipment.  Unfortunately, parts are often charged to the wrong work order or to the wrong equipment number.  The result is an erroneous parts list.

The best results are derived from building the spare parts lists from scratch.  Prioritizing the effort can really help.  It's not a good idea to build a spare parts list for every piece of equipment in a facility.  For example, stocking all the spare parts required to rebuild an air compressor is worthless if facility workers donít have the skills to do the work, or if an outside service organization will be hired to perform the rebuild.  However, parts required for preventive maintenance or simple repair, such as lube oil, a filter, a spare motor, or a spare coupling, should be stored.

Facility personnel only need to list the equipment there and identify the level of maintenance to be performed.  

For a table that can be used to facilitate this step CLICK HERE


Repair Scenarios and Criterion to Hold Spare Parts

The table above describes potential repair scenarios for four assemblies or pieces of equipment: a Pump, a Conveyor, a Gearbox, and an HVAC Unit.  Two potential categories of repair are shown; repair Upon Failure or PM/PDM (preventive/predictive maintenance).  A person knowledgeable in plant maintenance has identified the repair scenarios for each piece of equipment by placing an X in the appropriate field.  A guideline for the Items to be Stored is quickly determined from the checked items.  The most common spare part solutions are:

With the repair scenario and spare parts solutions derived for each piece of equipment in a facility, the task of building spare parts lists becomes more focused.  First identify the lubrication, couplings, motors, and normal wear parts for all equipment to be maintained by facility workers.  Next, build lists of the parts that will be used to rebuild equipment.  Manufacturersí operations and maintenance manuals are the best resource for this, but persons who normally perform the rebuild should also have some input.

  • A complete spare is required. A full complement of spare parts is required for rebuilds. Lube and normal wear parts are also required.

  • Full complement of spare parts as well as lube and normal wear parts are required.

  • A complete spare is required. Lube and normal wear parts are also required. No rebuild parts are necessary.

  • No parts should be stored - require the contractor to provide all parts for repair and maintenance.

Donít think you have to store every part identified as a spare.  Some parts can be listed in the spare parts and inventory management records, but only ordered as needed.  Automated inventory/purchasing software functions available in even the simplest CMMS make this a snap.

The next step is to identify the parts you already store which are on the new spare parts lists, purchase the parts you donít have, and cull out all the parts that arenít on the lists.  One industrial plant actually terminated plans to expand their storeroom when they found out that about 25% of the items on the shelves were for equipment they no longer owned.  They always knew they were storing obsolete items, but developing spare parts lists brought the magnitude of the problem into perspective. 

Conclusion

If youíre not using the spare parts list or BOM function in your CMMS, get started.  Youíll probably need some help, and it will take a little time, but the result will be a productivity boost to both the storekeeper and the people who use the storeroom.

This article was written by a consultant from New Standard Institute, Inc. 
For other articles on Maintenance-related subjects, view our website at http://www.newstandardinstitute.com or contact us via email at nsi@newstandardinstitute.com or call (203) 783-1582 to discuss the subject with one of our consultants. 

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