April 2008

Applying feedforward

If the distillation column described in the February Certification Review CAP question (page 78) was controlled according to what was called the correct answer, C, the following would take place:

An increase in feed rate would, through feedforward action, increase reflux flow. With steam flow unchanged, however, this would result in a decrease in the flow of distillate product. The result would be an imbalance because more light material would be entering the column than is being removed as distillate. Top temperature would then fall until TC 1-2 reduced reflux flow to a value lower than it was before the increase in feed rate. The feedforward action was therefore in the wrong direction.

To apply feedforward to this column requires a different structure for the individual loops.

Greg Shinskey, ISA Fellow

Illustrating teamwork

In response to February's Talk to Me: Several years ago, following a merger between two competitors (my company had a manufacturing organization but competitor did not they outsource everything), there was a major cultural clash. I was part of a team of "change agents" to attempt to ingrain "teamwork" into the mind-set of the non-manufacturing folks. I had an artist friend of mine draw the series of three sketches (see below) to illustrate my point. It was a very, very slow process. I for one did not survive.

Jack R. Jones


Bill Stanford (http://www.wildbillartshow.com/)