Uptime: Don’t Overlook Spare-Parts Reliability

Maintenance management covers a variety of functions, including the managing of spare parts. We know that the quality of those parts has a direct impact on the reliability and maintainability of equipment, machinery, and facilities. There’s more to it, though, than simply managing a storeroom.

How spare parts are specified, purchased, shipped, stored, dispersed, and installed reflects critical elements in physical-asset performance and operating cost. Unfortunately, the parts are often overlooked in ways that compromise equipment reliability.

Real-world impact

Even the most reliable equipment can fail if the right spare parts—fit for service and mission ready—aren’t installed properly. While a maintenance staff’s skill and knowledge is an important reliability factor, the inherent reliability of spare parts at the time of installation is even more so.

Consider these examples of how spare parts can contribute to machine failures, excessive downtime, higher costs, and financial losses.

Transportation damage. Several catastrophic failures of the fan in a plant’s heat-treatment carburizing furnace led to enormous production and financial losses, not to mention a disruptive domino effect on production schedules. Removing and replacing the fan is difficult and time consuming, given its location in the bottom of the furnace.

A failure analysis determined that cracks in the fan cooling jacket led to bearing failures. These events continued even after months of discussing fan construction with the OEM, changing welding methods, and carefully installing new fans.

Eventually a root-cause analysis session was held with operators, maintainers, supervisors, area managers, plant engineers, and the fan company’s owner. All potential failure causes were quickly ruled out based on prior actions. The facilitator then asked the group to take a hard look at the fan currently installed in the furnace and a new spare in the storeroom.

As participants checked out the new spare firmly strapped to a wooden pallet with its shaft in a horizontal orientation, the fan manufacturer asked a question that ultimately unraveled the mystery of repeated failures: “Is that how we ship these fans to you?”

At this point, a mechanic interjected that when a fan is installed, its shaft is vertical. “That could cause bearing problems,” he said. Others weren’t so sure.

The OEM began speculating: “These fans are shipped more than 800 miles to your plant by truck,” he said. “Imagine the bumping and jarring with the weight of the fan and shaft supported by the bearings on the cooling jacket. The cracks in the failed units seem to start around the upper side of the shaft-bearing mounts. Shipping them flat, in the same orientation as they are installed in the furnace, may prevent the cracking.” Was he on to something?

Once the manner of shipping was changed, i.e., with the fans strapped to pallets in the same orientation as they were to be installed, the failures ceased. The maintenance group also found that the fan bearings lasted longer.

In-plant moving methods. “It’s a big electric motor. How did you expect me to move it?” The speaker was a forklift operator who found it easier to pick up large motors by the shafts located at each end of the units. After all, they fit nicely between the forks, with minimal adjustment, and would roll to the back of the forks when they were tilted back slightly. Great move for the forklift driver.

As for the motors, their shafts were becoming hammered, especially at the keyway. Maintenance techs thought the units sometimes seemed to be out of balance. Taking note of the forklift operator’s preferred methods, they finally realized the cause of the problems: improper handling of electric motors from the receiving dock to the storeroom and from the storeroom to the job site.

Behind-the-scenes. One of the most frequent and penalizing mechanical failures on a brewery’s packaging lines was attributed to conveyor-belt drive- and tail-roller bearings. Improper installation and lubrication and incorrect bearing types were ruled out early on. The bearings themselves then became suspect.

Packaging-line parts were kept in a storeroom near the lines. Operated by the purchasing department, it was staffed 24 hours a day as an inventory-control measure. Nobody else was allowed inside—that is until the purchasing manager granted access to a consultant.

During a failure investigation, stored conveyor bearings, many in open boxes, were found covered in rust. “Not a problem,” replied the storeroom attendant when asked about the situation. He explained that with “a little steel wool, lubricating spray, and lots of buffing” those bearings would look just like new. The problem with the brewery’s packaging-lines was solved on the spot: High humidity in the storeroom and unprotected bearings were identified as major factors in the failures.

Extreme environments. Handling and storage of spare parts is especially challenging for offshore oil- and gas-production platforms. If bouncing around on the boat trip from an on-shore warehouse to an offshore platform doesn’t contribute to early failures, improper maintenance of the stored items will. Humidity and salt air are also tough on parts.

Offshore platforms are compact, often-congested configurations of piping, pumps, motors, and compressors. Vibration in these operations—ever-present and frequently ignored—can lead to spare-parts failures. For example, when motor and pump bearings are stored near rotating equipment, vibrations created on the platform can damage them. Moreover, regular maintenance of stored spares such as rotating shafts is mandatory.

The counterfeit scourge. The spare-parts supply chain has gone global. The upside is online ordering and competitive pricing. The downside is explosive growth of the counterfeit marketplace.

Knock-off trademarks, look-alike labeling and branding, and sub-standard-quality spare parts have invaded our storerooms. These reliability time bombs include bearings, seals, nuts and bolts, pipe and hydraulic fittings, electrical/electronic components, wiring, and cables.

Monitoring your spare-parts supply chain, buying from trusted sources, and rigorously inspecting parts before placing them in a storeroom should form the basis of your organization’s spare-parts management practices.

Sometimes, the inexpensive. One spare-parts-management technique I learned from working with top NASCAR race teams over the years is to carefully inspect parts before they’re put on the shelf—especially those that can affect racecar performance. And for good reason.

In the 1990s, a race team suffered a catastrophic engine failure caused by an unlikely culprit: a three-cent nylon zip tie. When the zip tie failed, the oil line it was restraining dropped onto the alternator fan belt. It was only a matter of minutes before the engine failed due to oil streaming from the cut line.

Inexpensive spare parts are often overlooked. These tend to be commodity items where low cost shapes purchasing decisions. With many commodities, though, you get what you pay for. Be sure to consider the function of such items and the impact of their failure when making purchasing decisions.

Manage your supply chain

Paying attention to the spare-parts journey from the OEM, through distributors, into your storerooms, and on to equipment makes sound business sense. The bottom line is that proactive storeroom-management practices, coupled with supply-chain management, can eliminate most causes of spare-parts failures.

For more information on the management of storerooms and spare parts, see Put Efficiency in MRO Storerooms and Bob Williamson’s ISO 55000 column.