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Reducing Risk in the Chemical Process Industries

Posted on April 21st, 2016 by in Chemical Manufacturing Excellence


No one should die at work.  Yet people do.  Even the safest job in the United States, librarian, has a work-related fatality rate of 0.3 fatalities per year per 100,000 librarians.  Other jobs are more dangerous and employers are all required to provide employees a workplace free from recognized hazards.

In addition to the usual hazards found in all jobs—transportation related fatalities, workplace violence, and slips, trips, and falls—the chemical process industries have three special hazards to worry about:  fires, explosions, and toxic releases.  These are recognized and we are obliged to protect our workers from them.  What that means, though, is worth discussing.

NPR’s “Morning Edition” recently ran a story about oilfield workers dying while atop well-side oil storage tanks, taking samples and checking volume.  The story made a very convincing case that when truck drivers climbed up on the catwalk and opened the thief hatch to dip their sample bottles down into the tank and then to manually lower a level stick into the tank to check the volume, they were often overcome with vapors that had collected in the headspace of the tank.  Energywire, a source for the NPR piece, showed that the vapors not only caused chemical asphyxiation because of their toxicity, but were also capable of displacing enough air in the vicinity of the hatch to cause simple asphyxiation as a result of low oxygen concentration.

The story reported that in the past six years, nine workers had died atop well-side oil storage tanks.  If it wasn’t before, clearly this is a recognized hazard now.  The story suggested a few different approaches to addressing the hazard.

One approach was automated level monitoring, the cost of which the story reported as $2,000 per tank.  However, there are objections from the Bureau of Land Management, which is concerned that automated instrumentation is not as accurate as having a driver measure volume by eye, especially because this measurement is done for the financial purposes of custody transfer.

Another suggested approach was outfitting each driver with air-supplying respirators that also purify toxic vapors.

An approach favored by the companies that operate these tanks is to have drivers open the thief hatch and then allow the vapors to disperse before pulling the samples and measuring the level.

What is the best approach?

This is the point at which a risk assessment, which includes a cost-benefit analysis, is important.  In the absence of a risk assessment, any decision will be based on emotion and opinion.  The NPR piece, which simmered with barely contained outrage, erupted in full-blown condemnation of corporate greed when the public weighed in with comments.  Emotion and opinion are cheap; actually addressing hazards requires thoughtful consideration.

Consider the benefit

The benefit is reducing the fatality rate of this task from 1.5 fatalities per year for all drivers.  This rate is about 20 times lower than the fatality rate associated with driving to and from the wells.  How much lower is low enough?  While it would be nice to insist on a fatality rate of zero, that can only be achieved when a risk reduction measure is perfect, and nothing is perfect.  A measure that lowers the risk by a factor of 10 would give a fatality rate for working at the thief hatch that is 200 times lower than driving; a measure that lowers the risk by a factor of 100 would give a fatality rate for working at the thief hatch that is 2,000 times lower than driving.

Generally, administrative controls reduce risk by a factor of about 10.  No matter how well designed the administrative control is, it still relies on being properly executed by a person, and people aren’t perfect.  Administrative controls can include things like wearing special PPE like a respirator, or carrying out special procedures, such as allowing vapors to clear after opening a hatch.

Instrumented controls also reduce risk, also by a factor of about 10, but only if they address the hazard.  An instrumented control would have to address the entire hazard—automating the level measurement in a way that satisfies everyone concerned with custody transfer, but also collecting representative samples from unstirred tanks.  Controls engineers are very clever, however, and they might be able to come up with something.

So there are three options, each with same benefit—a risk reduction factor of 10.  So which to choose?

The automated solution

It would indeed take very clever controls engineers to come up with a design that does everything that needs to be done for the $2,000 installation cost reported by NPR.  Taking maintenance and training costs into account, it would have an annualized cost of about $1,000 per year.  This is the point in the analysis where someone feels compelled to ask the maddening question:  “Well, isn’t a life worth a $1,000 per year?”  Of course it is, especially if it is someone else’s $1,000 being spent.  But the question isn’t about $1,000 per year.

If we knew in advance which tanks would be associated with a fatality and could avoid that fatality by spending $1,000 per year on that tank, the decision would be a no-brainer.  Even the most callous, selfish executive in the country would spend $1,000 per year to avoid a certain fatality, if only to avoid the paperwork involved.  But since we don’t know which tanks may be involved in a fatality, we would have to install one on each tank. The NPR piece stated that there are 83,000 oil wells on public lands.  At an average of two tanks per well (some have just one, some have as many as four), that works out to over $150 million per year to automate the tanks.  This would reduce the fatality rate while taking samples and checking levels in oil storage tanks on public lands from 1.5 fatalities per year to 0.15 fatalities per year.  In other words, over $100 million per avoided fatality.  That assumes that the oil storage tank fatalities only take place on public lands. With more than 600,000 oil wells throughout the industry, the cost jumps to nearly $1 billion per fatality avoided.

What about respirators?

Respirators would help, but are not panaceas.  Air supplying respirators are useful in an oxygen deficient atmosphere, but do not remove the toxic substances in the air. Toxic concentrations of some vapor components of crude oil can be in the parts-per-million range. These concentrations don’t result in simple asphyxiation; they’re a problem because they’re poisonous. They need to be purified.  Purifying respirators, however, do not create oxygen where there is none.  Moreover, a purifying respirator must be specifically selected for the impurity of concern.  A respirator that removes acid vapor won’t remove hydrocarbon vapor.

Breathing through a respirator also imposes a burden on the body.  Additionally, people’s faces aren’t all the same shape, so not all respirators fit all people.  As a result, OSHA forbids the use of respirators without routine fit testing, medical testing, inspections, and lots of paperwork.  This means that purchasing a respirator is just a small part of the cost of a respirator program.

All drivers would need to be equipped with an appropriate respirator, one that supplies air and protects against toxic exposure.  Taking into account the annual fit testing, the annual medical examinations, and the other expenses associated with a respirator program, the cost would be about $6,000 per year per driver.  With 150,000 drivers, the annual cost is $900 million per year, or almost $700 million per fatality avoided.

Better procedures?

There is more to better procedures than telling drivers “be careful and stand downwind.”   This is especially true if there is to be any credit taken for risk reduction.  Procedures have to be written, and drivers need training on the procedures and on the hazards against which those procedures protect.  The effectiveness of the training needs to confirmed with written tests and observation.  Refresher training must be conducted and the effectiveness of the procedure needs to be checked periodically.  If all these things are done, we can take credit for an order of magnitude risk reduction.

This credit won’t come without cost.  The procedures need to be developed.  The training needs to be conducted.  Drivers will need to take time to execute the procedure at each storage tank and they’ll be paid for that time.  An estimated cost for all involved companies to develop training and keep their drivers trained is around $30 million per year.  An estimated cost of the extra time drivers will have to spend at wells carrying out the procedure of waiting for the vapors to clear is around $50 million per year.  The total annual cost comes to about $60 million per fatality avoided.

The gorilla in the room

How low must risk be to be low enough?  How much should be spent to avoid a fatality?  No organization, no industry, no society operates with unlimited resources.  The amount to spend to avoid a fatality is something about which reasonable people may disagree, but I don’t know anyone that would peg the figure at $1 billion, even if it isn’t their money that’s being spent.

The world can definitely be a safer place, and I work toward that goal every day. But there are more effective ways to spend a billion dollars to save lives.  Spending a $100 million to avoid a fatality probably doesn’t make sense either.  Many people would still balk at $10 million.  Somewhere, though, there is an amount that would make sense, at least to many people.  Until we talk about it and agree to it, we’re left to make those decisions on our own, knowing that we may be second-guessed by a jury or regulator.

What to do?

For all of us, the first thing to do is to recognize and acknowledge the hazards our processes expose us to and get on with efforts to address them.  The second thing to do is to address them by considering measures that actually reduce the risk, ignoring dread and outrage, and evaluate those options.  Finally, follow through with the risk reduction measures that make the most sense.  We’re scientist and engineers.  We can do this.


All opinions shared in this post are the author’s own.

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