'Dieselgate': Fiddling the system...

Volkswagen (VW) have been caught fiddling tests. Well they're not unique. A couple of examples from my own experience highlight where something similar has been attempted.


The current VW 'dieselgate' scandal, where technology has been used to defeat tests, reminds me of two similar - although much less sophisticated examples - from my past.

The first is from my very early days and involved heat treatment furnaces (the same ones as in “The Blue Flame Syndrome”) forging cranks for Rolls Royce. The specification called for a very high level of temperature uniformity across the furnace (1000C) which we saw as very difficult to consistently achieve and really couldn't understand how the existing plant managed it.

When we looked at a furnace in operation we could see a visible difference in temperature across the hearth without using our instruments (the colour was distinctly brighter in places). When we tested, we found that the temperature was more like plus or minus 100C across the hearth.

When we checked the combustion analysis the chemistry graduate that I was couldn't understand the data. Used to systems that were relatively homogeneous I couldn't understand why I was seeing Carbon Monoxide in the 5% range and Oxygen levels in the 15% range – that shouldn't be possible.

More experienced heads pointed out that the furnace had something like 20 burners along each side, each with its own controls (and as the gas trimming was on the on/off valve, it changed every time the furnace was lit) and each was adjusted differently - some would have large quantities of excess air, some would be gas rich and some adjusted “properly”. So these products were mixing through the furnace and giving the strange analysis.

We were privileged to watch a “test” of the temperature distribution and the way the certification was achieved became apparent. They loaded a pallet full of cranks into which thermocouples had been placed and then adjusted the burners until the temperature compliance was displayed. So for that moment the standard was recorded. Trouble is, a few minutes later the temperature distribution was massively different!

We were able to obtain a consistent 10-degree differential across the furnace (at a saving of, I think, 38% of the gas used) which actually meant the product was MUCH better but technically we didn't make the required conditions.

That was only a commercial breach and obviously the delivered product was actually fit for purpose (or there would have been a lot of recalls), the second had potential safety implications.

Those of you who know about gas burners know that they are required to purge out the combustion chamber before ignition is attempted by blowing air through the burner. That air flow (and that for combustion) is proved by means of a pressure switch. An improvement in the regulations was to ensure that the switch was working by testing that it was in the “no air” position before the purge was started (a sensible measure to protect against failures that might cause a problem).

Now this caused some problems when the fan wasn't started by the control box because the switch might already be made when the box tried to check the air pressure was zero. There are three solutions...

1) (the best) - make the box the fan starter possibly by use of a relay (not practical if the air flow is part of a large process).
2) Use valves to vent the switch at the appropriate time (effective but expensive).
3) Use relays to give the box the signals it requires.

Now the last makes the system work but - like VW - it completely defeats the object of the exercise and makes the system potentially unsafe. (Yes, I did prevent it being done on any installation I had anything to do with).

Now, in neither of these instances was there any real intent to defraud. The people concerned were honestly trying to deliver the requirements. However (certainly in the last case), lack of understanding lead to completely the wrong outcome. I suspect that VW's case may be very different...

Andy Clarke

Topics: edie
Tags: | certification | Data | gas | technology
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