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Matthew Petroleum Notes



'An unfortunate incident that happens unexpectedly
and unintentionally,typically resulting in damage or injury’

That’s a good enough definition to use. You can find lots of others. Some claim that an accident is something that could have been avoided and others that it doesn’t have to have an apparent or deliberate cause. We’ll stick with the one above.



There are about 120 million industrial accidents in the world every year, of which about 0.15% kills one or more people. A lot more get injured and a very lot more get inconvenienced in a big way. Whichever way you look at them, accidents are bad news.

The only good news about accidents is that here at MATTHEWS Integrity Hub: HEAD OFFICE, we think we know what causes them. Not just some of them, but all 120 million of them.

All accidents are caused by?

The answer is multiple causes.

Think of the implications of this for a moment. If someone asks you to find the root cause of, say, a refinery explosion, then by our judgement you cannot provide an answer. It’s nothing to do with the complexity of the accident; the same would apply if you were asked to find the root cause of someone slipping on a banana skin. It’s simply the premise that there is never a single root cause. There isn’t some universal law that says it has to be like that (we’ve checked*) it’s just that’s how things happen to work out. All accidents have multiple causes.

Let’s look at how this works in practice. To do this we need to mix up two sets of accident language a bit.


Banana skin

The multiple causes

‘Je vais a un marketing meeting sur mon scooter ce week-end’ is a perfect example of how one language can adopt parts of another but still be understood and technically correct. We can therefore do the same with accident terminology. From one set of accident words comes two definitions:

  • Immediate factors; these are happenings that occurred immediately before an accident
  • Underpinning factors; these are things which occurred sometime before the accident

Applying a slightly different emphasis provides us with two others

  • Unsafe conditions; conditions that were present before the accident occurred
  • Unsafe acts; acts (or lack of them) performed by people before the accident occurred

Just about all accidents involve a mixture of all of these, in various combination and degrees of severity, but they are generally there. Here’s an example below;

The accident summary

In a critical process in a refinery system, catalyst escaped through an eroded slide valve seat. It mixed with other chemicals and formed an inflammable mixture. This mixture was then mistakenly diverted to an area of the plant containing an electrostatic charge. The result was a big explosion.

Now let’s look at the multiple causes

The slide valve seat was eroded because it had not been inspected at the last shutdown (underpinning factor). This was because of the reduction in inspection budgets agreed at the previous review meeting (underpinning factor again).

The inflammable mixture caused by the undesirable mixing of the chemicals was not indicated on the control system because the alarm was bypassed due to a broken wire (unsafe condition). A note had been left in the maintenance log to fix this but it had not been done (unsafe act) This mixture was then mistakenly diverted (unsafe act) to an area of the plant containing an electrostatic charge (immediate factor) which was still live (unsafe condition) and the result was a big explosion.

There’s an interesting publication on the UK HSE website that explains their methodology on accident causation, and shows the forms etc that they use. 

We urge you to look at the accident case studies and simulations on the US Chemical Safety Board website. They are excellent and well worth a look.

Interested in reading about some real failure/accident cases?..Read our FAILURE BRIEFINGS

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Tel: 07746 771592