Electrical Substation Equipment

‘Spring Cleaning’ For Your Fuse Inventory

EP Editorial Staff | April 13, 2017

Improve safety and reap cost savings through smart, streamlined ordering and stocking.

Sometimes it pays to take a fresh look at routine tasks. A major manufacturer of refrigeration and air-conditioning products was contacted by its electrical-equipment distributor regarding the site’s fuse orders. The production operation had hundreds of fuses in its storerooms—numbers that represented a $22,000 burden sitting in inventory.

Over time, those storerooms had accumulated fuses from a variety of manufacturers. For maintenance personnel, the natural impulse is to replace a blown fuse with one of the same brand, type, and rating. While this seems like the safest approach, it leads to unintended duplication in a storeroom. What’s more, workers continue to reorder fuses that may have become obsolete and/or they don’t update to more modern, safer types.

Seeking to determine how much of their current fuse inventory was really needed, managers at the site generated an electronic spreadsheet of such items in their storerooms and asked the electrical distributor to forward it to Chicago-based fuse supplier Littelfuse (littelfuse.com) for analysis. The results were, in simple terms, shocking.

The fuse vendor supplied a consolidated inventory list that reduced the number of SKUs by 37%—from 224 to 164. Several fuses, which may have been on the shelves for 10 to 15 years, were older styles that didn’t provide maximum safety and equipment protection. After managers cleaned out the old and confusing array of fuses and adopted the recommended consolidated fuse inventory, they were able to project a savings of approximately $6,000/year. 

Those savings, however, didn’t include the cost of downtime avoided by switching to indicating fuses that are more quickly identified when outages occur. Nor did the calculation factor in the labor savings from being able to quickly find a needed fuse on the shelf, or the potential costs of inadequate protection from the use of obsolete fuses.

A simple table posted in the storeroom allowed personnel to cross-reference old fuse types and brands with the new types they should use. To top it off, the vendor printed customized bin labels with the plant’s part numbers, reorder numbers, and barcodes for all fuse sizes.

Plants depend on hundreds of fuses, in panels such as this one, to protect workers and equipment.

Plants depend on hundreds of fuses, in panels such as this one, to protect workers and equipment.

Now, it’s your turn

Whether you work with a supplier or do it on an in-house basis, here are the steps for cleaning up your site’s fuse inventory.

1. Inspect for damage. Look for fuses that are not clearly marked and discard them. Issues such as flooding from storms or broken pipes can also damage fuses. If the sand or filler material inside the fuse gets wet, it may not safely quench the arc, and may never completely dry out. When in doubt, throw it out.

2. Identify outdated fuses. Print out your fuse inventory and highlight old fuse types such as Class H (renewable) and even Class K5 fuses.

Unfortunately, some workers still think that renewable fuses can be “repaired” and put back into service, but this is definitely not recommended. They have a low short-circuit interrupting capacity of just 10,000 A. They provide no current limitation, and there is no way to control what a worker will use as a replacement element. These fuses are truly obsolete, and UL prohibits renewables in new applications.

Also called “one-time” fuses, Class K5 fuses were an improvement over renewables. They are tamperproof, and have a higher interrupting rating of 50,000 A, but they provide no current limitation.

Class RK5 fuses are rated to 200,000 A and provide current limitation. They don’t provide the level of current limitation that the newer Class RK1 fuses offer. Current limitation is extremely important. It is used to reduce the danger of arc-flash hazards so that workers can wear less PPE. Current limitation also improves the short-circuit current rating (SCCR) and simplifies selective coordination. 

3. Consolidate. Give your inventory printout to your preferred fuse vendor and ask for a consolidated inventory list. The vendor will know which modern fuses to substitute for older types, know which types fit which fuse holders, and be able to cross-reference with other suppliers. Based on the experience of Littelfuse, typical savings for a large manufacturer range from $18,000 to $30,000.

4. Upgrade to indicating fuses. Indicating fuses are a common-sense way to decrease downtime. When a fuse opens, the maintenance worker can quickly identify which fuse or fuses need to be replaced. In contrast, when indicating fuses are not used, significant downtime can occur and personal safety can be jeopardized.  

When one or more fuses blow and shut down a system or production line, maintenance workers will often ignore OSHA and NFPA 70E safety requirements and go into a live panel to meter each fuse to determine any that have opened. This extremely dangerous approach can create a significant safety hazard for the worker and anyone else nearby. Best-case scenario, the worker de-energizes the system and then pulls the fuses to check for those that have opened. This process, though, can be time consuming and lead to increased downtime. The opened-fuse visual indication of indicator fuses helps eliminate–or at least significantly reduces–these potential issues.

5. Get organized. Some fuse vendors will print bin labels with the facility’s part numbers, reorder numbers, and barcodes. These can be customized to work with your company’s asset-tracking system.

Effective consolidation and organization of a site’s fuse inventory provides many benefits.

Effective consolidation and organization of a site’s fuse inventory provides many benefits.

Bottom line

Any time of year is a good time to “spring clean” your fuse inventory. The benefits are numerous. Sites can decrease downtime by standardizing on indicating fuses that allow open fuses to be identified quickly. Modern fuses simplify selective coordination that can greatly limit the scope and potential magnitude of an outage.

Furthermore, by using current-limiting fuses, operations help protect equipment and workers from faults and dangerous arc flash. In addition to reduced downtimes, better system coordination in the event of a fault, and lower arc-flash hazards due to optimal current-limiting protection, considerable cost benefits can be realized.  MT

Information in this article was supplied by Dave Scheuerman of Littelfuse, Chicago. Learn more at littelfuse.com/MROPlus.

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