True Story No1


A Sticky Problem !

At a large Defence Contractors in the 60s, in keeping with most others, all manufactured equipments were called assemblies and those assemblies contained more assemblies and these contained sub-assemblies and so on. The subject of this story is a printed circuit board. It was probably used in a complex electronic assembly for unscrambling digital data.

When a printed circuit board is designed, one of the collection of documents, in which all the individual components are identified, is an "Items List" which carries a table noting (for each component) a brief description, the manufacturing reference number and a quantity. This particular circuit board had to be "conformally coated" to protect it from damage, say from being in a ship near to corrosive seawater.

The designer duly looked up the code for the conformal coating material and entered it on the items list. Some time after being checked and "computerised" in an all-knowing system, carrying all the codes and sources of supply for everything, a quantity of the circuit board was eventually included in an order from a Government Agency.

The Purchasing Department, as a matter of routine, entered the details of the contract, and purchase orders for the complete breakdown of the thousands of components required to build the equipments were duly generated by the manufacturing computer system.

Over a period of time lots of postmen, parcelforce vans, supplier's delivery vans and lorries arrived at the factory gate. The biggest lorry delivered the conformal coating. Why? It turned out that the code used by the draughtsman was for a gallon drum of the stuff when all that was needed was a dip of a paintbrush and a quick wipe. As there were 1000 printed circuit boards ordered, the computer had calculated that 1000 gallon drums were needed!

This affair was hushed up and nobody found out about the mistake. That is until many years later when the drums on the bottom of the heap rusted through and conformal coating leaked across the garage floor (the garage was where the drums had been hidden away and was located under the factory). A message went round the factory "does anyone want any stuff for painting their garden shed/fence". "If you do, take a carrier bag with you and meet in the garage after 6 o'clock".

It turned out that in the past when Items Lists were broken down manually everyone knew about conformal coating and all we ever needed was a pint or two. How was the computer supposed to know this?


Return to Story Page