Onsite Oil Analysis Ends - GM's Bus Stop Blues

Frank D'Arcio, General Motors; Ed Bohn, General Motors

Like so many plants, General Motors’s Linden Truck and Bus Assembly plant always depended upon its lube supplier to provide oil analysis.

It was assumed that this free service provided all the information necessary to assure lubricant health and to detect any abnormal contamination and machine wear. With everyone spread thin at the plant, outsourcing oil analysis was a convenient option.

Unfortunately, the flaws in the program boiled to a head when a critical gearbox failed catastrophically and shut down the plant for 27 hours, costing a great deal of money. This prompted the plant’s management and technical team to reevaluate their approach to oil analysis, and ultimately, to completely reinvent it.

Figure 1. GM Linden's Onsite Oil Analysis Lab

A review of the machine’s oil analysis data showed that the sample analyzed two weeks earlier revealed nothing about the impending gearbox failure. If oil analysis can’t detect a failure, why bother? A further investigation revealed that the oil analysis program was simply not complete.

Lubricant supplier-provided oil analysis has historically emphasized monitoring the health of the lubricant, not necessarily the health of the machine with wear debris monitoring and analysis, nor abrasive contaminant levels with particle counting. This seems reasonable because the supplier’s primary objective for oil analysis is to assure customers that the lubricant is chemically and physically fit for service.

While elemental spectroscopy, the cornerstone of supplier-provided oil analysis, does measure wear metals like iron, copper, chromium and lead, it is widely known that the technique is incapable of detecting wear particles that are larger than 5- to 10-micron in size. The reliability team discovered the limitations of its oil analysis program; unfortunately it was after the costly forced outage.

Time for a Change

It became apparent to the plant’s management and technical staff that a change in the oil analysis program must be made. Options were narrowed to the following:

1. Revise the offsite oil analysis program to include tests that detect abnormal machine wear and monitor abrasive contaminants, a common root cause of abnormal wear that leads to failure.

2. Implement an onsite oil analysis program that provides the team with the tools to monitor lubricant health, machine wear rates and damaging contamination levels in critical machines.

Option No. 1 has two primary advantages; revising the offsite program requires no capital investment and no significant additional allocation of labor. Option No. 2 requires an investment of capital and labor, but offers quick-turnaround on testing and the ability to retest immediately if an abnormal reading is discovered.

Perhaps most importantly, onsite oil analysis allows the team to more effectively integrate oil analysis with other condition-monitoring activities. Information can be managed on a common database, and condition-monitoring technicians who specialize in various technologies can work side-by-side to prevent and solve problems.

Figure 2. Properly Labeled Sample Bottles

The plant elected to take a chance and invest in onsite oil analysis. While it broke with convention, the team was passionate and confident that it would work. It did. An interesting discovery was the impact onsite oil analysis had on the plant’s culture and attitudes toward machinery lubrication.

Like most plants, lubricant storage and application was sloppy and uncontrolled. Top-up containers were dirty, open to the atmosphere and untagged; machines were not tagged to identify the required lubricant; and new oils were poorly stored and not filtered prior to use, etc. It was not uncommon to get the wrong oil in the machines, and contamination levels ran very high, which of course increases wear rates and shortens equipment life.

Onsite oil analysis served as the change agent. Once the plant got underway with onsite oil analysis, a new culture of lubrication precision and excellence began to emerge, replacing the old “oil is oil” culture. Education about proper lubrication, oil analysis and contamination control combined with the emphasis on lubrication catalyzed by onsite oil analysis brought about this remarkable renaissance.

The team set up shop in a dedicated internal laboratory space. The laboratory was refitted with shelving, tables and benches, while other measures were taken to minimize extraneous contamination and to get as close to a clean-room environment as possible.

The walls display reference materials about proper sampling, diagnostics and other important information that served as a constant reminder of the need to excel in machinery lubrication and to protect the reliability of the plant’s equipment with high-quality oil analysis.

Targets for contamination were set and oil properties monitored regularly to ensure proactive control, and lubricant health monitoring, including viscometry, revealed wrong oil and degraded oil conditions. The team placed a significant emphasis on monitoring abnormal machine wear.

As an added benefit, onsite oil analysis enabled monitoring of new and stored lubricants, to ensure that they are clean and fit for service. All these efforts contributed to the development of the new “business as usual” that was emerging in the lubrication program.

An important component of the team’s success was integrating condition-monitoring software, which served as the repository for data and the mechanism for trending.

Figure 3a. GM Linden's Oil Analysis Condition-Monitoring Software

Figure 3b. GM Linden's Oil Analysis Condition-Monitoring Software

When a problem is detected with any of the plant’s condition-monitoring technologists, the entire team of technology specialists swarms to it, working together with the full benefit of the information provided by integrated condition-monitoring technologies. With a technology arsenal and a team working in harmony, few problems go undetected to wreak havoc on plant operations.

Proving the Concept

The team didn’t have to wait long for verification that they made the correct decision. An in-house oil analysis report indicated an extreme level of wear on the plant’s critical laser turntable.

Figure 4. Laser Turntable

Investigation with the shop microscope clearly revealed iron spheres in the sample. A work order was generated to drain, flush and replace the oil in the unit. Prior to changing the oil, two additional samples were taken and sent to two different laboratories to conduct basic oil analysis.

One lab indicated that the components and lubricant conditions were acceptable. The other lab reported no corrective action required. At this stage, the maintenance supervisor was understandably upset, wanting to know why a work order was issued for no apparent reason. To confirm the belief that something was wrong, the machine was resampled and analyzed onsite.

Similar results to the earlier report were obtained. On investigation of the machine, it was discovered that one of the inspection plates was missing and weld splatter was getting into the oil. Had the laboratory undertaken ferrographic analysis, this problem might have been found, but to rely on too basic a set of tests that lacks large particle-monitoring capabilities can lead to disaster. This confirms to the team that the decision to bring oil analysis onsite was the correct decision.

By taking ownership onsite at GM’s Linden assembly plant, lubrication quality has improved, machine wear reduced and oil drain intervals extended. The plant’s oil analysis program now enables the team to assure proper lubrication and contamination control, and provides them with a clear understanding of the condition of the machines.

Interestingly, this has all been accomplished while saving money on the lubricants, disposal and sampling. Much of what was done was basic, costing little or nothing to implement, making the success all that much sweeter.

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