A gas-fired paint drying oven at a manufacturing plant shut down unexpectedly, and a crew was assigned to relight it. The crew was under pressure to troubleshoot and re-light the oven as soon as possible to minimize the unscheduled downtime. After a few attempts to light the pilot, gas had built up in the oven. One final attempt to light the pilot sparked an explosion in the oven that caused the death of a crew member.
The fatal incident, resulting in devastating loss for the decedent's family, friends and employer, was blamed partly on maintenance. Some critical parts of the oven were out of adjustment. Valves were out of alignment, not calibrated or nonfunctional. Important safety-related settings were incorrect. Further, similar equipment in the plant had been the center of some previous troubles that, if seen as warning signs, could have led to a detailed review of safety systems and devices. Tragically, the oven could likely have been much safer simply if a well-designed maintenance program had been in place.
Regular Inspections
"Things fall apart," wrote William Butler Yeats, in his poem "The Second Coming." He wasn't referring to plant maintenance, of course, but he might as well have been. Equipment failures are inevitable unless influenced by the quality, frequency and extent of maintenance activities. In the preceding case, the complicated oven's safety devices and controls required regular scrutiny by highly qualified people. Incidents with other, similar equipment that pointed to problems should have been the beginning of prompt technical examinations and remedial work.
A typical preventive maintenance program can be based on regular inspections to find deficiencies, make minor adjustments and lubricate moving parts. Because maintenance has costs as well as benefits, companies have to carefully weigh their needs against available resources to determine how much to allocate to maintenance.
Downsizing when money is tight, or shutting off funding for periodic training or equipment maintenance, might not necessarily save money in the long term. One reason is that prevention generally suffers first by being postponed or eliminated when budgets and staffing levels shrink. Breakdowns must be repaired, so the unplanned emergency work is not considered to be as expendable.
Without some type of planned maintenance, facilities can rely only upon observable warning signs or breakdowns as triggers for unplanned action. Problems arise when there are delays in responding to signs of impending failure. Quick, reliable communication between operators and maintenance is critical.
Operator Involvement
Operators need to know the importance of early communication when they detect warning signs of a need for maintenance. They need to know that their reports are taken seriously. If not, they will quickly lose interest in reporting. In some locations, employee reports are only a high priority when there is a possibility of lost production or a grievance. Also, employees cannot report without a knowledge of typical warning signs, so training and experience should teach operators how to monitor the condition of their equipment.
In one case, a forklift driver was off-loading pallets of masonry block from a flatbed trailer. He parked the forklift on an incline with the load elevated, set the handbrake and stepped off the forklift. When he walked between the lift and the trailer with his back to the lift, the forklift rolled forward and pinned him against the trailer. The brake on the forklift was worn out. The operator had been using the brake as instructed, but it did not work. Operator training should have included clear instructions on inspecting the brakes and other safety-related features, and where to report deficiencies.
In cases where operators may not be capable of detecting deficiencies, preventive maintenance should be implemented to the extent necessary to provide safe, productive and reliable equipment. Carbon monoxide (CO) hazards can exist without any visible indications. A sudden cold snap can change a tolerable and unnoticed carbon monoxide source into a potentially fatal concern. This change takes place when employees close down loading dock doors, windows and other sources of cold drafts and fresh air.
Carbon monoxide poisoning cases are common around the seasonal transition from a comfortable autumn to a cold winter. One early December, a number of employees working in a large building complained of headaches. Eight or nine propane-powered fork trucks were in use at any given time, and natural gas heaters were in use. Tests showed some carbon monoxide had accumulated in the building. Doors were opened, and employees were sent home a little early. By noon the next day, the employees were again complaining of headaches. Carbon monoxide levels were tested and the building evacuated. Nearly 50 employees went to the hospital for examination; some were poisoned badly enough to be admitted for overnight observation.
Rather than look at this situation and conclude that the problem was caused by a slow or half-hearted response to the headache complaints, let's examine the real cause. Some of the forklifts and gas heaters were found to be in need of fine-tuning, and the gas heaters had various exhaust problems that had developed over a long period of time.
These emissions had gone unnoticed while the doors had been left open during the workshift. Although not to the level where masses of people complained, lower CO levels would still degrade the air quality and might affect people with respiratory problems. Cold weather meant closed doors and greater use of the gas heaters. The near-elimination of natural ventilation concentrated the CO.
Unfortunately for this company, a CO panic was the only way that CO prevention work would ever have been ordered. As long as the trucks and heaters were operating, maintenance people left them alone. Luckily, no deaths occurred, but the large number of people affected resulted in substantial media coverage that painted a
negative picture of the company's safety program and prompted an OSHA investigation. This is only one of many examples that prove use of gas-powered equipment necessitates CO checks and fine-tuning as part of a preventive maintenance program.
Training Needed
Regular training is such a valuable part of good maintenance that it should be a part of annual maintenance budgets. The drive to make equipment more efficient has resulted in continuous technical advancement, and it only makes sense to help maintenance staffers concurrently improve their working knowledge.
Particularly when safety may be affected by mechanical failures, great care should be taken to utilize the technical knowledge developed by the machine's designers, builders and installers. Ignoring this knowledge base might be disastrous.
In a particularly unfortunate case, a well-meaning maintenance operation was carried out on an aerial transportation device that elevated and carried personnel. This machine was used outdoors, exposed to rain and snow. Inspection revealed that crucial support bolts were rusting, potentially weakening them, and a decision was made to replace the bolts.
The individual who purchased the bolts was concerned that the replacements should be strong enough for the job and spared no expense to get the best bolts available. High-strength alloy bolts were selected and installed. Because the original bolts were common, mild steel bolts, it was assumed that the much stronger and much more expensive alloy steel bolts would be better than the originals.
As it turned out, there was a good reason for the manufacturer's use of mild steel bolts. High-alloy steels can be prone to a condition known as "stress corrosion cracking" when subjected to tension and exposure to rainwater. Mild steel is far less subject to such cracking. The unsuspecting owners of the machine had no idea that the well-intended substitution would lead to failure until the day that the machine was loaded with a group of people and several of the bolts broke. The machine dropped, and multiple fatalities resulted, all because a maintenance job was carried out without sufficient technical information.
Without knowing more details, it is only speculation to say what might have prevented the accident. The manufacturer's shop manuals might have specified a certain grade of bolt. Following the maker's specifications would mean that bolts equivalent to the originals would have been specified, if the manual covered requirements for these small parts in detail. This would depend on the technical quality of the manual.
Deviating from specifications, at least in safety-critical areas, would likely increase the responsibility for any resulting problems with the altered equipment. For certain equipment, such as cranes and forklifts, ANSI standards and other rules expressly restrict the modification of equipment without the manufacturer's formal approval.
Perhaps if the usual practice had been to replace "in kind" (i.e., use identical replacement parts), the bolts would have been the proper grade and not have failed. Having the manufacturer supply all critical replacement parts might have helped in this situation. Moreover, using an original equipment part might have helped reduce the responsibility of the end user for any potential failures.
There are many approaches to maintenance, so there is no single recommendation that can be made for a wide audience. Technical knowledge, preventive measures and appropriate monitoring of equipment should be implemented, where appropriate, to meet the intertwined needs of safety, productivity and reliability. The important role of maintenance in supporting a safe working environment should not be ignored.
William H. Kincaid, P.E., CSP, is a senior loss control consultant with Lockton Cos., St. Louis. His last article for Occupational Hazards was "Fire Prevention: Top 10 Priorities for Safety Managers" in the June 2001 issue.