Over the last two months (“Lockout/Tagout: The devil is in the details,” March 17, 2011; “Lockout/Tagout: When and how?” April 21, 2011), I’ve discussed details of lockout/tagout procedures that often trip people up. It’s not just the threat of an OSHA citation that should motivate you to get LO/TO right, however. Here are two examples of what can happen when LO/TO is ignored or not thought through.
In the first case, workers had just finished repair work inside an 8-ft-diameter pipeline that carried hot oil from its source to a secondary processing station half a mile away. There was one pumping station at the oil source and one at the pipeline midpoint, both operated from a control room a substantial distance away.
During the repairs, workers had properly locked out pipeline valves and pumping stations and returned them to their operating state after the work was done and inspected. They told control-room personnel the work was completed and asked them to start up the system 5 hours earlier than usual so the equipment
could come up to temperature.
Two supervisors decided to check the repairs, a task which required them to walk inside the pipe with flashlights. They did not perform LO/TO on the valves, the pumps, or the controls in the control room, nor did they alert control-room personnel of their last-minute inspection. When the control-room operator started the system as instructed, the two supervisors were in the midst of their inspection and were killed by the hot oil.
The second case also involves hot-oil by-products, specifically road-repair asphalt. The accident happened in a cold-weather state where asphalt is stored in large tanks and flows via gravity into waiting trucks. In order for the asphalt to flow easily, the pipeline is heated by a pressurized hot-water line, which carries
superheated water at more than 250°F.
Supervisors decided to tear down the transfer station and move it to another location. Workers opened the valve at the bottom of the transfer line to drain it of hot asphalt so they could disassemble the asphalt piping and move it to the new spot. However, they made two mistakes.
First, they didn’t stop or drain the hot water that was heating the asphalt pipeline. Second, once the asphalt had drained out, they reclosed the valve at the end of the transfer line.
The workers didn’t know there was a leak in the valve at the other end of the transfer line, the one that controlled whether asphalt stayed in the tanks or flowed into the pipe. Hot asphalt once again filled the transfer line. When two workers disassembled one of the pipe’s joints, hot asphalt sprayed and severely burned them both.
When stored energy is removed from the system, keep the system used to remove the stored energy in place so that the stored energy cannot return and be a danger. If the valve used to drain the hot oil from the line had been left open, the worst that could have happened is that the hot oil would have drained onto the ground. If the hot-water system had been turned off, the asphalt line would have been messy to handle, but the asphalt would not have been a danger.
Lanny Berke is a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a question about safety? You can reach Lanny at firstname.lastname@example.org.