Merrydown Funware - Humorous Stories

All the stories in this section really happened (well maybe there is a little of adjustment for comic effect!).

I was commissioning a DCS at a paper mill. One of the most difficult plant items to control was a very small open tank (about 0.5m diameter and 2 meters high--a thick bit of pipe really) into which the processed paper pulp was dropped. From the small tank it was pump to a large storage tank using special pumps.

The control strategy was this: If the level in the small tank is falling water must be added to the tank so that the pumps never run dry (dropping level indicates a slight hold up in the pulp supply). If the level was rising this indicates that the pulp is too thick for the pumps to pump and so water is added. This maybe a strange strategy to you but it works!

One of the problems with this kind of process is how to measure pulp level. In this case a capacitance probe was used. This worked very well except for one day when an instrument engineer was standing next to the tank and decided to radio the control room.

Instrument Engineer:" Bob to control room--is this tank level control working? Arrrrrrgh."

It took us in the control room a couple of seconds to realise what had happened then we all burst out laughing and one wag radioed back "Bob you do know not to use your radio near a capacitance level probe don't you."

When the instrument engineer had used his radio he caused the capacitance probe to see a high level in the tank. A piece of logic then sprung into action and shut everything upstream down and to shutoff the pumps. However conveyors etc take a short while to stop thus allowing several large dollops of pulp to drop into the small tank. Rapidly this became full and the only place it could go was on the instrument engineer!