The fatal accident had become company lore repeated at countless safety orientations. An experienced engineer inspecting some work on top of a silo lost his balance when a screw conveyor unexpectedly started up. He fell into the silo — pieces of him have been showing up ever since.
My personal experience with a lockout/tagout (LOTO) mistake involved an electrician and a young chemist. The electrician had been trying to clear a jammed screw conveyor. He thought it was de-energized. He found out it wasn’t after being partially fed through it. He staggered into the lab. The young chemist called 911, helped the man as best she could, then went into the bathroom and threw up.
LOTO is serious business. So, let’s consider some basic rules so you don’t have a similar war story to relate someday. OSHA in developing its standard (29 CFR 1910.147) addressed most forms of energy: mechanical, i.e., dynamic or potential, and electrical. But the chemical industry also must confront reactive agents’ risks, e.g., fires and explosions. (Nuclear facilities face similar issues such as exposure to radiation.) Chemical plants normally pay attention to LOTO for maintenance activities but often overlook it during routine process operations. When was the last time you took a sample with a single isolation valve?
The LOTO process basically involves: 1) defining the task; 2) determining skills necessary to competently complete it; 3) gauging staffing requirements and defining the team; 4) estimating risk; 5) spelling out safeguards and procedures for blocking energy; 6) evaluating risk with safeguards in place; 7) conducting a gap analysis of training; 8) updating the training and safeguards as necessary; 9) running a drill exercise (optional); 10) updating safeguards, procedures and training; 11) using the procedures; and 12) doing a post-mortem on procedures to improve them for the next time.
One of the most common problems with any process is poor definition. This probably explains why procedures, when they do exist, sometimes are circumvented. One fatality occurred when a worker was electrocuted when he attempted to break a 2,300-V circuit without testing it. So, define a simple common-sense procedure that people will follow — which brings me to my next point.
Obviously, this worker wasn’t the best person to do this task. Where was the plant electrician? Every LOTO procedure should include a table with the skills necessary and number of people needed, along with an estimate of job duration and list of safety gear required.
Always consider risk. As defined by OSHA regulations, risk falls into three rankings: public, personnel and equipment. Public risk gets highest priority because people driving home from work shouldn’t have to deal with the dangers of a toxic cloud appearing in the road in front of them. Besides, they don’t have training to deal with the hazard.
Risk is the product of probability and potential consequence. If either is zero you don’t need a LOTO procedure. This is unlikely. Most evaluations wisely focus on the consequence and ignore the probability, which is difficult to estimate. If failure of LOTO procedures will destroy the plant do you really want to take the risk?
Now, we come to the difficult task of defining safeguards. The best method is to completely remove the danger by, say, installing a blind flange or pulling motor cables — as this provides a physical barrier or gap between the danger and people. The worst is tagging equipment. Once you’ve defined safeguards, evaluate them. Consider how you’ll communicate up and down the chain of command and between shifts. Because you’ll probably use a lock-box, think about how you’ll manage access to it, especially during a turnaround with all its competing work. Useful tools include flow diagrams and fault tree diagrams.
After answering these and other questions, you may want to update your safeguards, procedure and — especially — training. For complicated or dangerous LOTO regimens, you may need a drill to identify shortcomings.
As with all procedures, test them for practicality. One reason why LOTO requirements exist is because workers tend to take shortcuts to make their jobs easier.
For instance, clearing a set of teeth on a machine like a saw may involve jigging motors off and on. Dealing with machine guards takes time, so eventually someone may remove them and afterwards a person may get hurt when trying to clear the teeth when the motor starts. If your equipment can’t be operated safely during any phase of the process from startup through maintenance, look at alternatives. Remember what Trevor Kletz once said, “If you think safety is expensive try an accident. Accidents cost a lot of money, not only in damage to plant and claims to injuries but also in the loss of the company’s reputation.”
I strongly recommend a review at the conclusion of the LOTO job. Investigate and document any near-miss events that occurred.
Dirk Willard is a Chemical Processing contributing editor. You can e-mail him at firstname.lastname@example.org.