The “Zero-stock”catalogue and its power


Its often said that “Maintenance runs on its stores”, and it is largely true. However, while its not economical to stock everything that Maintenance uses (see “What parts should be in your Maintenance Stores“) those items which are, or may be used in maintenance work and are not kept in stock should be easy to identify and purchase.

From a Maintenance point of view there is great value in integrating the details of many of the non-stocked parts and supplies into the Stores catalogue (or better, the “Materials catalogue”), and assigning them catalogue numbers.

In one large operation a study of the direct purchase requisitions originated over a 3-month period showed that 90% of these purchases were for materials which had either been purchased previously or would likely be purchased in the future. All these items should be included in the integrated stock and non-stock catalogue as “zero-stock” catalogue entries.

As a simple example, consider a specific type of valve that is used in a typical plant. Some sizes, say 2″ and 3″, will be economical to stock and will be held in the Storeroom, with assigned SKU numbers and bins. However, there are also a number of 4″, 6″ and 8″ valves of the same type used in the plant, but their probability of failure, mode of failure and price are such that they are not economical to stock.

Assigning these larger valves a catalogue number (which for stocked items is the same thing as an SKU number) they can be included in the materials catalogue and a Stores search will find them, as it would the 2″ and 3″ valves. There are several advantages to integrating stocked and non-stocked parts in a common catalogue, including:

– it allows all technical and purchasing details of non-stocked parts and supplies to be recorded and filed, just as it is for stock items.

– it encourages the use of plant-standard components.

– it ensures that non-stock items will be purchased from your contract vendors.

– it eliminates the time taken to research and requisition most direct purchases.

– it eliminates purchase requisition errors.

– it moves most of the purchasing process from Planners to Buyers. This can dramatically reduce a Planner’s work load, allowing many more jobs to be planned.

– it encourages the delegation of the purchase of materials.

– it discourages requests to add items to stock, or conversely, allows items to be safely removed from stock, which may result in a significant reduction in inventory.

– it records the price and usage of non-stock materials, which may sometimes demonstrate that a non-stock item would be economical to keep in stock.

– it discourages the development of uncontrolled storage areas.

– it allows a completely rational approach to spare parts management by enabling the full integration of equipment identification and spare parts identification systems (see “Equipment identification and numbering“) . The plant hierarchy from the plant level down to the smallest component can be logically constructed, with some levels occupied by non-stocked assemblies. This greatly simplifies parts and equipment management.

– it should provide the same level of control and authorization of purchases of non-stocked items as is applied to any direct purchase, IF the maintenance computer system has the appropriate functionality (more below).

The zero-stock process is very useful for many common purchases, such as plywood, steel shapes, large pipe, lighting fixtures, etc.

When spare parts lists are being set up for new equipment, all the parts may be included in the catalogue, but only a few of these will be economical to stock and the rest will be recorded as non-stock. Large parts, such as pump volutes, may have a very long life but when the time eventually arises to replace them it is important that their purchasing information be recorded in a secure file that is easy to access. The integrated catalogue is the best place for this information.

For materials with a very short “shelf life” or other special characteristics, there are additional advantages. For example, in one plant the concrete used for equipment base repairs has a complex specification to achieve the necessary fast cure time, corrosion resistance, etc, and it is assigned a materials catalogue number. The purchasing record for this concrete contains all the mix specifications, so that when a job requiring this concrete is planned, the Planner has only to request the required quantity of the catalogue item, through the Stock Issue process. The Planner who provided this example mentioned that prior to this item being added to the catalogue, it would take him considerable time and effort to find the necessary information in the Engineering files.

For items requiring strict controls for security or technical reasons, the zero-stock process works well. Such items include cordless power tools, computer hardware and software, etc. If such items are included in the catalogue, any request can be automatically routed for the appropriate approvals. For example, a request for a notebook computer could be automatically routed for approval to both the department manager and the IT manager. This process ensures that purchases comply with the plant’s standards.

Maintenance system functionality.

To support the zero-stock catalogue process, the maintenance computer system must be able to separate the approval process for stock and non-stock items. Stock items are usually (but not always) issued without approval, while non-stock items should require the same approval as any other direct purchase.

Unfortunately, some maintenance computer systems do not have this functionality and will release purchases for non-stock items without approval. If this is the case with your system, then the potential use and the advantages of the zero-stock process will be severely limited.

Of course, the addition of non-stock materials to the catalogue may greatly increase the number of records. This makes the use of good naming conventions (See “Naming parts“) and other solid data-base practices even more important. And as with any database, the responsibility for the quality of the data must be clearly defined in the appropriate business processes (see “Database principles“).

While the use of “smart” characters in equipment and catalogue numbers is usually not necessary or desirable, there is an exception for non-stocked catalogue items. These catalogue numbers should make it immediately obvious to everyone whether an item is in stock or not, through the use of an appropriate suffix, for example.

It is not necessary to make the addition of non-stock items to the catalogue a “project”, but there should be provision to add items whenever a direct purchase requisition is originated. Ideally, the computer system should prompt the originator to indicate if the purchased item (and similar items) should be added to the catalogue or not, and the business process should then ensure that the description and other fields are correctly entered into the database.

The use of an integrated catalogue strongly supports the Maintenance Storeroom’s purpose, which is to ensure that Maintenance people are provided with the right materials at the right place and the right time. The combination of a well-managed integrated catalogue with a maintenance computer system that has powerful “Google-like” search functionality can greatly increase maintenance effectiveness. If your existing system has complicated and ineffective search features, then a system such as FindIt is well worth considering.



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© Veleda Services Ltd

Don Armstrong, P. Eng, President