Lax tank shop safety can kill
Feb 1, 2002 12:00 PM, By Charles E Wilson
STORIES of disaster and tragedy are far too common in the cargo tank repair business. Catastrophe can occur in the blink of an eye.
Preventing serious accidents can be a challenge for even the most safety-driven tank repair shop. Shop safety takes a total effort that includes rigorous enforcement of policies and worker training that is reinforced continually.
Shop safety was a key area of focus throughout the 2001 Cargo Tank Maintenance Seminar that was held October 29 — 31 in Chicago, Illinois. A parade of speakers reviewed the safety challenges faced by tank repair shop managers and discussed issues that need to be addressed.
Peter Garafano III, Garafano Tank Service, recounted an incident from several years ago that vividly brought home the fact that shop safety must be a priority at all times. A petroleum tank trailer exploded at a competitor's facility killing the shop foreman and badly injuring a worker. A couple of days later, the worker died of burns suffered in the accident.
The building was destroyed. Doors were blown out, windows were shattered, and the roof was gone. Remaining walls were blackened. Two cars in the street were burned up.
“Watching the news helicopters circling above the facility, I thought about how that company was similar to ours,” he said. “They had been in business about 40 years, and the foreman had 20 years of experience.
“It was a wakeup call for us. Looking around our own shop, I could see how an accident like that can happen. I called our workers in for a safety meeting and reviewed our safety procedures. Day-to-day safety is important. You can't cut corners.”
Petroleum tanks in particular present serious risks of fire and explosion. Vapors can gather in many places. Voids between cargo tank bulkheads are the biggest cause of explosions in shops. One reason is that the bottom openings in voids are being capped, allowing product to remain trapped.
“Make sure these drain openings are not plugged,” Garafano said. “The voids also must be steamed out before maintenance work commences on the tank.”
Tankwagons present additional opportunities for trapped product vapors. Meters, pumps, and hose reels are among the areas that are often overlooked when a tankwagon is prepared for repair.
Garafano recommended a two-stage purging process. The tank operator should be encouraged to run several loads of diesel before bringing the tank in for repair work. Next, every section in the tank must be steamed out.
After removing any product meters, workers should apply low-pressure steam (250°F at 50 psi) using a two-inch hose. All domelids and outlets should be open to promote positive draining and prevent heels. Each compartment should be steamed for at least 20 minutes.
“Be sure you don't over steam, because that can dry out gaskets,” Garafano said. “Before work begins on the tank, check the internal atmosphere with an explosion meter and an oxygen meter. Use forced-air ventilation inside the tank even if all of the work is being done on the outside. Always assume that vapors may be present.”
Good supervision also is important, according to Jim Lawson, Tri Tank Corporation. He described a 1978 incident in which a tank repair shop was blown up and one worker was killed.
“Among other factors, we found that the shop was operated by inexperienced workers on nights and weekends,” Lawson said. “No supervisory personnel were on duty at the time of the accident. These two factors were the real cause.”
Shop safety must become a habit, and it must be a top-down initiative. Workers need constant reminders. Most importantly, the shop safety program must be reevaluated from time to time.
Lawson said Tri Tank has turned outside for help in reviewing shop safety. The company has used OSHA (Occupational Safety and Health Administration) onsite consultants to perform voluntary evaluations.
“The program has worked great for us, but there are some strings attached,” he said. “They can find serious problems while inspecting the shop. Violations must be fixed, but they give us adequate time.”
Mike Hougom, Convenience Transportation, recounted a recent incident in which a shop worker started to weld on a petroleum tank after returning from a break. The supervisor stopped him to find out if the tank atmosphere had been metered. Even though the worker had been on break just a few minutes, that was long enough for vapors to collect inside the tank. The meter showed a high lower-explosion-level (LEL) reading.
“We decided we needed more effort in our safety procedures,” Hougom said. “A supervisor — a responsible individual — is now assigned to each tank before repair work begins. The tank is metered before it enters the shop, and it is remetered every four hours. It is remetered after every break. The readings are recorded on a repair permit that hangs on the front of the tank throughout the time it is in the shop.”
The Convenience Transportation shop uses compressed air for degassing tanks. The hoses for the process are grounded. Before the degassing begins, all compartments are opened, and any remaining petroleum products are drained into metal pails with grounding straps.
Explosion-proof blowers ventilate the tank for at least an hour before the tank is metered. Forced air is kept on the tank throughout the time it is in the shop.
Dry bulk trailers generally transport non-hazardous cargoes, but mechanics still need to be cautious when working on them. “These trailers may contain internal pressure,” said Dave Cooper, Stuart Tank Sales. “In addition, they are a confined space just like any other cargo tank.”
Mechanics need to verify that a dry bulk trailer is empty and clean and that it is not under pressure. The blowdown line should be opened to release any pressure. Internal air quality should be metered, and forced-air ventilation should be used.
While inside, mechanics should wear eye and hearing protection and a respirator. Cooper recommended placing 2 × 10 planks inside dry bulkers to provide a safe walkway. Another recommendation is to air-pressure-test dry bulkers outside. Not only is it safer, but also it is easier to hear leaks. The test should never exceed the design pressure.
While the cargo tank itself poses one of the biggest dangers in the repair shop, some of the tank components present hazards of their own. Pressure relief valves and domelids are particular concerns.
“A 6,000-gallon tanker with just 5 psi inside has as much energy as a quarter-pound of TNT,” said John Freiler, Girard Equipment Inc. “A three-inch diameter opening yields 177 pounds at 25 psi. A 20-inch manhole yields 7,854 pounds at the same pressure. That's a lot of force, and it can result in injury and death.”
The springs in pressure-relief vents also pose risks for the unwary tank mechanic. Compressed springs can contain as much energy as a 25-caliber bullet.
Freiler and other speakers also pointed out the dangers associated with working on top of cargo tanks. Fall safety must be a priority. Freiler said the best practice is to remove hardware from the tank top and perform the maintenance at a workbench on the ground.
Dan Burke, Dixon Bayco Ltd, discussed inspection and maintenance procedures for the hoses and couplings that are used in tank repair shops. Regular inspections are the key. Damaged components should be replaced as soon as they are discovered.
Common pipe nipples should no longer be used as hose inserts. Industrial hoses should be coupled with a proper barbed or serrated hose stem. Pipe nipples have no barbs or serrations, and it is friction alone that holds them in place.
It's not possible to fully eliminate risk in a tank repair shop. However, the suggestions made during the shop safety presentations show that managers can develop policies that significantly reduce risk.
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