By Aaron Hand
When folks debate about how to set up an operator interface, the conversation usually heads toward making things as easy and as intuitive as possible. But what if your goal in life is to make things harder for the operator?
System designers at Savannah River Remediation (SRR) decided that things were too easy for their operators. It was too easy to set operations in motion with single clicks of a mouse. "I want to slow the operators down; I want to force them to think twice," said Jim Coleman, principal engineer at the Savannah River site in Aiken, S.C. Coleman described SRR's unique challenge and solution this week at the Emerson Global Users Exchange in Nashville. "In our industry, errors are absolutely unacceptable."
The industry is remediation of radioactive waste. The U.S. Department of Energy facility doesn't make bombs, but it makes the juice that goes into the bombs, Coleman explains. The waste from those nuclear weapons has been put on-site in 51 holding tanks carrying some 37 million gallons of "highly radioactive nasties," he said. "Our goal is to clean the "ooky' out of these tanks and put it in storage for the next million years."
That "ooky" removal process is a highly automated one in which buckets of radioactive soup are scooped from tanks, mixed with a special sand and then cooked in a melter at 1,200 °C and turned into glass. "It's the Cadillac of disposition methods for our nation as far as dealing with radioactive waste."
However, Coleman tells a story of one operator walking into the control room talking to another and sitting down on the desk. "He put his hiney on the keyboard," Coleman says, and hit a combination of keys that turned off the ventilation fans controlling radiation in the facility. "That was a big problem. We want this guy to slow down, think twice."
So what the engineers did was to incorporate extra steps into the interface, forcing operators to perform at least two clicks with a mouse move in between to take an action. The designers used an out-of-the-box Emerson faceplate and added Accept and Cancel buttons. They had to be sure to avoid pop-up messages so that the operational graphic would never be covered, therefore, they added a separate faceplate at the bottom of the screen instead.
They made some other changes while they were at it, including using messaging to give operators more visibility into activities outside their primary view, getting supervisor approval for critical actions and prodding operators with reminders. All of the modifications, Coleman points out, can be done with out-of-the-box Emerson tools. "We don't want to write special code," he explained. "Also, this way all this stuff will upgrade, and we don't have to do anything special for that to happen."