“What you Don’t Have, Can’t Leak.” is the title of a 1978 article by Trevor Kletz (1922 - 2013), a true pioneer of process safety. As one of the very first Technical Safety Advisors in the chemical industry - in the 1960s - he developed the concept of Inherent Safety. By promoting to avoid risks rather than to try to control them, he contributed to a great reduction in accident rates and therefore saved many lives - a true Hero of Chemical Engineering!
But let's start at the beginning: Trevor Kletz was born in 1922 in Britain and attended The King's School, Chester. At age 11, he got a present from an uncle - a chemistry set. This shaped his life and - as a consequence - influenced many others, because he eventually decided to studied Chemistry, graduating in 1944 from the University of Liverpool. So this month's Hero of Chemical Engineering is not an engineer by formal education.
When he started his first job at ICI (Imperial Chemical Industries), though, current issues were more of an engineering nature and so he spend several years solving chemical engineering problems. He later said: “It isn’t as if I ever took a formal degree in chemical engineering, I just became one without even realising it,”
He steadily worked himself up to become a plant manager at different plants at ICI's Billingham facility, when in 1955 he became a safety officer at ICI’s Oil Works, part-time. Back then that only meant eliminating obvious mechanical hazards and issuing protective attire for the workers and Kletz found safety to be a dull topic. But as chemical processes and plant got more and more complex, more accidents occurred and lives were lost. At ICI some engineers realized that safety needed a technical input and that it should be considered while planning chemical processes. This was the beginning of HAZOP (hazard and operability study) of which Kletz later became an important promoter.
To increase the awareness for process safety, the position of technical safety advisor was created at ICI and Trevor Kletz was the first one to hold it. It was a challenging task, to advise plant designers and operators how to avoid not just accidents resulting from the occasional inattentiveness, but also those resulting from flaws in the plant design and operating procedures. As Kletz later said: “it was a challenge I met through persuasion – by showing them the consequences of bad practices and design, sharing the lessons of accidents and near misses.”
The accidents and near misses that he examined in his role as technical safety advisor lead him to developing the concept of Inherent Safety. He summoned it up in the above mentioned article “What you Don’t Have, Can’t Leak.” The article was prompted by an explosion in an very inefficient chemical plant that ran with a large inventory of hazardous chemicals. Kletz's point of view was that with an increased conversion rate, smaller reservoirs of chemical would be necessary and the plant therefore safer. So the idea is to reduce risk by reducing the amount of risky materials rather than improving the technology controlling the hazardous substances.
The four main principles of inherent safety, as explained in Trevor Kletz's book Process Plants: A Handbook for Inherently Safer Design are:
Intensification: Use small amounts of hazardous materials (a smaller inventory) so the consequences of accidents arising from the escape of materials are much reduced.
Substitution: Use a less hazardous material – less flammable or less toxic.
Attenuation: If a hazardous material must be used, use it a) under less hazardous conditions or b) in the least hazardous form.
Limitation of effects: Limit the effects of failures by changing the design or conditions of use rather than by adding protective equipment that may fail or be neglected.
Kletz notes that most plant designers were confident in their ability to control hazards and had not given much thought to minimising inventories. That confidence evaporated in the aftermath of Bhopal – the notorious explosion of a Union Carbide pesticides plant in 1984, which killed 2,000 people. There were safety systems in place - but they failed. Despite the fact that Kletz's ideas had been discussed for almost ten years already, Kletz says he doubts if those concerned at Union Carbide had ever heard of the phrase “what you don’t have can’t leak”, or the concept of inherently safer plants, which springs from it. It took this devastating catastrophe to show that reliance on safety systems is not the safest way.
TrevorKletz was safety advisor to ICI for 14 years, and in that time the company’s fatal accident rate fell from 7 fatalities per 100 million working hours (4 of which were from process risks) in 1968 to 2.5 fatalities per 100 million working hours (with almost none from process risks) at the time of his retirement in 1982. In broader industry, the impact of his work is impossible to chart, and nobody can count how many lives he has saved. Clearly, neither Flixborough nor Bhopal would have been anything near as deadly as they were had the plants in question been designed according to Kletz’ principles – and with his thinking enshrined in today’s safety legislation, there is no question that Kletz is one chemical engineer who changed the world.
In 2000, his autobiography "By Accident...a Life Preventing Them in Industry" was published.
If you liked this article, leave a comment and share it! Also check out our previous articles about Heroes of Chemical Engineering.
12 November 2015