Posted By keith molyneux
has anyone got a copy of domino theory which I could use.

Thanks.
Stuart Yates

Posted By Brian Smith
I've got a few pages from my NEBOSH Part 1- includes Heinrich's Single Cause Domino Theory + diagrams.

Let me know if you want a copy and I'll post them on.

Regards
Brian Smith

Posted By Merv Newman
Or is your name Stuart Yates ?

Posted By Merv Newman
Domino theories say that high level errors can cause accidents unless lower levels can compensate.

As in - "I dont care how much it'll cost you. I aint going in there" Here, the fourth domino "human behaviour" compensates for first second and third level failures.

Posted By Merv Newman
Alan,

I completely agree with you, but the first question was about the domino theory. Perhaps you could summarise jim's swiss cheese proposition in a dozen or so words for the edification of all of our corespondants, especially he who posed the question ?

Merv Newman

Posted By keith molyneux
Could you send them to my colleague who is completing his N.V.Q EITHER electronically via e mail address Stuart.Yates@knaufinsulation.com or
Knauf Insulation
Stafford Rd
St Helens
Merseyside
wa10 3ns

Thanks

Posted By john o'meara
The earlier descriptions of Reason's Swiss cheese model are helpful. A picture certainly does make it easier. Not hard to loocate.

I wonder if there's a couple of things the model does not include that ought to be included.

First, I think there are times when the "beam" or "arrow" when it penetrates a slice, locks that slice into a fixed position. So, once it's past that layer of defence it stays past it. It can then wait till it gets the chance to penetrate the next layer, and then lock that layer into place.

Reason's model suggests the holes in the layers appear and disappear and when a series of holes all appear simultaneously and aligned, the "beam" penetrates completely and causes harm.

I'm thinking that there can be an interaction between the holes and the "beam", that the beam penetrates one hole at a time and holds the hole in place.

Second, if the beam is a strong energy force, then there are times when it actively seeks the holes. So, if a hole appears, you are guaranteed that the force will find it, given time. So it isn't like a beam or arrow that travels in a straight line. It goes looking for the holes.

J.

Posted By john o'meara
Hi Alan,

> is it not also the case that as and when
>(and if) we discover holes in the layers >they are then repaired?

Yes, but "if" is the key word, isn't it?

>So whilst agreeing that some holes may be >locked by the beam, not all of them will be >locked permanently.

Sure, not all of them will be "locked in" and I'm not sure I'm expressing that in the best way. I need to come up with an example. The analogy might be wrong.

Imagine a large tank of nasty chemical. A seal on a valve or a piping joint loosens. The chemical finds this hole in the defence (containment) and leaks out.

It's now past the defence. You can tighten up the seal or joint, but the danger's out.

Maybe the actual leakage went unnoticed. Say the liquid pooled in a sump in a manhole in the floor. It might sit there happily waiting the next defence hole to appear. That might be someone entering the manhole without doing the prescribed atmosphere tests.

So, what I'm suggesting is that the holes don't need to be aligned at the same time. The hazard might be an patient opportunist and get through the holes one by one, rather than all at once.

Makes me think that if failed or failing equipment is spotted, then perhaps there are instances where a broad examination ought be mandatory to see if any hazard has "escaped".

If a zookeeper found the tiger cage door open one morning, would she close it and not do a stocktake of tigers?

J.

Posted By john o'meara
Here's a terrific real-life case of the dominoe theory in action.

This was a fire on a ship arising from an electrical short. That doesn't sound unusual, but the fire was not an "electrical fire" and occurred well away from the electrical fault.

First there were two latent failures -

1. an undersized clamp had been installed on a mains cable coming from a diesel driven generator

2. the circuit breaker on this particular circuit had been set too high

Those factors remained in place for some time. Then the following occurred:-

. over time the undersized clamp compressed and deformed the plastic insulation of the inner cores of the cable, breaking down their insulation properties
. the insulation failed
. current leaked from phase to phase and from phase to earth
. the overcurrent did not trip the circuit breaker as it was set too high
. the generator reacted to the overcurrent by locking, ie, the fastly spinning rotor seized
. the locked rotor imposed a severe breaking effect on the drive shaft from the diesel engine
. one of the engine's connecting rods broke
. the rod smashed a hole in the engine's sump
. hot oil exited the sump
. the oil self ignited
. the fire was under the plastic fuel filter
. the fuel filter melted
. flow of diesel added to the fire
. the heat from the fire penetrated an adjacent steel bulkhead
. on the other side of the bulkhead was a storeroom
. cardboard boxes of fuel filters ignited

So, from an undersized cable clamp to a fire in a storeroom. Falling dominoes.

Also illustrates Reason's idea of latent failures, ie, the badly set circuit breaker.

J.