Question:

There is a disagreement in my plant about graphic displays for use by the control room operators. Some people (including my management) want to use "3-D" graphics that go to the extreme in almost photographic representation of the process -- valves symbols that actually look like the valves, round tanks and pipes, display that mimics the actual layout of the process, etc.

Others, particularly the managers of the operators, want old style graphics-thin lines to represent pipes, ISA type symbols for valves (with color of actuator representing command from control, color of valve body representing feedback from limit switches), simple rectangles for tanks with bar graph and numeric indication for the level inside the rectangle, etc. They say that each page would be able to show a larger part of the process with the operators having to change pages less often.

What should I do? Is there a real advantage to 3-D realistic graphics?

Answer:

First, make sure your resume is up to date. Your management will not like my answer.

I once was asked for some guidelines for when to use 3-D pipes and vessels. My response was to use 3-D if all or most of the following conditions were met. Otherwise use simple thin lines.

1. The operator would not normally know whether a pipe was round or square.
2. The operator needs to know whether a pipe is round or square
3. A pipe changes from round to square.
4. If (3) is true, there is a way of detecting the pipe shape and that information is available as an input to the control system.

I was thanked, but my comments were not used.

Those are the reasons to use 3-D graphics. There are some good reasons not to use them:

They add to the clutter of the screen and, as your operations manager suggests, less information can be placed on one screen requiring the operator to change screens more often. When low resolution CRT based displays first replaced panel boards, operators sometimes referred to CRT displays with a low amount of content as “keyhole control”.

Graphics are usually a symbolic representation of the process and, like a flow sheet, try to illustrate the process flow--major fluid flows enter from the left and exit to the right, when possible. Lines are drawn to make it easier to follow. If you look and the actual process you will often see pipes run through a spaghetti like pattern, as anyone who has walked down a line through a plant will know.

If the graphic looks too photographic and less symbolic it can offer confusion to an operator who normally sees the process on graphics but has to, at times, actually enter the process area and find something. If it is shown the diagram symbolically he knows that it is a schematic and does not represent what the process actually looks like.