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A well-organized and readily accessible storeroom is key to efficient maintenance. Without this support, becoming efficient in maintenance is a challenge, maybe even impossible. There are other factors that play in too, keeping a well-updated bill of material, for example, condition-based store keeping and store deliver and kitting. An up to date BOM is also essential when you optimize your spare parts inventory. Without it, how will you know what parts to keep in stores and how can anyone find parts in the store? How can a planner do an efficient job? Without an up to date BOM all this will be very difficult.
One common question I hear from plants around the globe is whether the stores should report to maintenance or purchasing. I can only share what I have seen work best, and that is when the stores report to maintenance. The maintenance function is responsible for cost-effective inventory levels and well-organized stores. Purchasing acts as responsible for the cost-effective ordering of parts and material making them available when needed. This also includes arranging for items not necessary to be kept in your own store to be available with short lead-time from suppliers.
Poorly managed and organized stores are a large problem in our industry. If items are hard to find, it wastes significant time when planning a job. It can also pose a major problem during an urgent breakdown situation, when both production volume and maintenance time is lost. It is not uncommon that items not easily found are bought again because it is a faster to buy it than to actually find the item.
I’ve done this many times at home. I live very close to a Home Depot, so if I cannot find what I need at home it is easier and faster to make a quick run up the road. It is also good therapy for an engineer to visit a store like Home Depot where you can explore new tools and gadgets. Just watch out if you’re my age, because I’ve heard it’s a pickup place for ladies who might be looking for a partner, and you can get stuck in the isles helping someone out instead of browsing the perfectly organized shelves of screws, hinges and drill bits.
One important interface document between stores and maintenance is the bill of materials. In a BOM all items belonging to each piece of equipment should be documented per equipment identification. The only search you should need to do to find the items you need should be equipment identity number, sometimes called the Functional Location Number (FLOC). This includes also instrumentation loop identification and electric systems identification. In most plants the BOM is poorly updated and not very accurate. It takes a lot of time and resources to update poor BOMs, especially if equipment is old. Therefore the wasted time due to poor BOMs is often something plants do not take action on even if the waste is present every day.
We work with many green field projects and expansion of existing plants and it surprises me that even today the BOM is not delivered by vendors and is not included in contracts, particularly in the early specification of equipment and procurement documents. It’s a document that should be delivered by vendors, and this should be included in all contracts when procuring new equipment. The manufacturers have all the information down to bolt and nuts and should be able to provide complete electronic documentation. Often the supplier provides part of BOMs but they might hide the original manufacturer’s item number and use their own item numbers. This makes it difficult for you as a client to decide whether you need those items or not. You might even already have it in your existing stores.
It is necessary to have an updated BOM in order to optimize inventory levels. Otherwise how would we know stock levels of what you need in stores? We need to be able to search how many of a specific item number we have installed in all equipment. We might find that we have 412 identical seals installed, the consumption is average 62 per year (which is too much) and the lead-time for seals is two weeks. This is information we need in deciding optimal levels to keep in store, re-ordering points and quantity. Knowing that we have 412 seals installed helps our decision whether or not to follow vendor-recommendation for spare parts or make a modification. It also indicates the average life of the mechanical seals and this information can be used as a performance indicator. A short life of common components can trigger improvement initiatives and we can set goals to prolong the lifespan of common high volume components and measuring progress. I have been in plants where the average lifespan of mechanical seals have been anything from one year to over 15 years.
Condition-based store keeping
When optimizing the inventory you should also use the failure distribution and failure-developing period theory on components in your plant as one input.
Thirty years ago, the stern tube, which is where the shaft rotates and connect with the propeller at the stern of a ship, was sometimes made of pockenholz, which is packing material and very hard wood that does not expand when wet.. On one old ship we even pumped in heated sheep fat daily into the stern tube as lubrication and sealing. That was a long time ago, but it worked. In the early 1980s a ship was designed with roller bearings to replace the old design. This had not been tested before so the insurance company increased the premium significantly and requested the shipping company to store a number of bearings at several locations worldwide. Keeping them on board could damage the bearings because of constant vibrations. They also requested an inspection of the bearings after one year.
The SPM (Shock Pulse Method) instrument company offered a solution of installing transducers for continuous monitoring of bearing condition. This resulted in that the insurance premium not increasing and the number of spares kept on hand could be fewer because any failure in bearings could be detected early, allowing for planning and scheduling of replacement with a long lead-time.
Another example is from a plant where they used many steel sprocket-gears for chain conveyors. These sprockets are possible to inspect with simple methods and have a long lifespan. The lead-time to get new sprockets was within a week, and the plant kept many of all types in stores. After introducing and using condition-based maintenance it was decided to keep none in store and only buy when inspection results showed the need to replace any sprocket.
In the best organizations I worked with, the storeroom is closed because almost all items were delivered to staging areas in the plant. This can only work if maintenance jobs are well planned and scheduled, with a two-day lead-time or more.
With items needed for work during shutdowns, it’s especially important that they are kitted and delivered in advance. A work kit is a collection of all items needed for a specific job, a hard copy of the BOM should also be included in the kit for the possibility that additional items are need. Using the hard copy of the BOM and call stores for the item can be faster than going to the store and searching the computer database. Also special tools should be kitted for these jobs.
As a good common performance-indicator goal between maintenance and stores, eighty-five percent, or more, of items should be kitted and staged for day-to-day work and ninety-five for shutdown work.
Store managers are always pressured to reduce inventory value, which is important and can save a lot of money as far as cost of surplus inventory and shelf space. It must be done right, however, as to not saving more than the consequences of being unable to deliver items to important maintenance work. It’s a careful balance.
I recommend that you always measure and trend the service level from stores to maintenance. Track how many times you get the right item at the right time and in the right quantity for a maintenance job. The service level should yield in a constant of 96–97 percent.
If store inventory is reduced and service level is kept at 96-97 percent, you probably reduced store-keeping correctly. If the service level goes below 93-95 percent, trust in the store will deteriorate. And then supervisors and planners typically start stockpiling, checking out two critical items when they only need one. After some time this will mount to “emotional stores” kept by planners and supervisors all over the plant, and there is no way to keep track. The duplicate parts will be hidden in what I call an “emotional store.” This expression is due to the reaction when you want to organize these stores and bring back the parts to the official stores. Planners and supervisors can get very upset, because they don’t trust the store and they are the ones who end up in the hot-seat if they cannot get the items when they need them.
And then we have to opposite of the spectrum—locking in every single part. You can sometimes overdo the control of items in the store. In an old plant in Pennsylvania the store was changed to report to purchasing instead of maintenance. They decided to remove all items from the open storeroom to which everyone had access even bolts and nuts, which were free items and managed by a vendor to fill up periodically.. So then people had to wait at storeroom window to even get bolts and nuts. The idea was that this would save consumption of these items, because people might use too many, including for personal use at home. This ended with people feeling bad and the joke among the maintenance craftspeople became “before this change we got the bolts and nuts when we needed them, now we have to stand in line and wait to steal them.”
A BOM is only one of many documents that should be included in the early phase of procuring new equipment, but its importance and impact on efficient maintenance is too often not understood or even neglected. It is easy for people who work in a maintenance organization to see the results from not having a complete BOM. Inventory in stores will be difficult to optimize leading to excessive capital bound in stores, planners cannot do an efficient job because they cannot easily find parts, shut downs can be delayed. The list goes on and on. Again it is a matter of moving away from the “Budget Silos” and instead bridging the gap between CAPEX and Operations and Maintenance budgets. It comes back to applying a holistic view of cost of buying and owning equipment. Using LCC as a policy and tool can help you achieve that.
Christer Idhammar is the founder of IDCON, Inc., a management consulting firm (idcon.com). This article was excerpted from a recent book authored by Mr. Idhammar entitled Knocking Bolts. More information can be found on this book at https://www.idcon.com/reliability-and-maintenance-books/