Processing Magazine

What need be said 'bout pushbuttons?

July 2, 2012

Some years ago, not long after joining my first B2B magazine editorial staff, the guy in the cubicle next to mine was a trained journalist. Most everyone else on that magazine was a chemical engineer by background.

The difference is — for literally almost any subject — the journalist could get on the phone and after a half-dozen calls knock out a 600- or 800 word story that did the job. It might not be the last word or even the latest word on the subject, but it made for an interesting enough story. One day, when the office suite was relatively quiet, I listened and learned while he researched and wrote just such a story on pushbutton technology.  

And there’s no question that if you look at how pushbuttons are used, and why, they can become interesting real quick. For one, pushbuttons play an outsize role in emergency situations. And in those type situations, the challenge is to know what just happened and what has to happen next.

As is well known, a red pushbutton with a yellow background is basically the global standard agreed upon for E-Stops. Banner Engineering, Minneapolis, says it’s made a basic improvement to the emergency-stop pushbutton by making it easier to know when an E-Stop has been activated or an alarm situation persists.

The yellow background, with the Banner E-Stop, when hit, turns to a flashing red indication. It “documents,” if you will, what E-Stop was hit. A steady red background can be used to indicate a STOP condition. With an illuminated base that flashes or sustains “red,” visual feedback is clear cut and extremely useful for operators figuring out where an emergency stop occurred, Banner says.

“In an alarm situation, faced with a panel of pushbuttons, it can be difficult to know what button to push or what buttons have been pushed,” Mike Carlson, Banner safety products marketing manager, says.  “With this system you know what buttons have been pushed, whether it’s still in alarm or if it’s been cleared. “

Carlson says that safety procedures in process plants have been improving for decades based on growing awareness fostered by government regulatory programs, including from OSHA here in the U.S. More robust circuitry, which can’t fail “unsafe,” and ubiquitous, inexpensive PLCs also play a factor. But, Carlson adds, “The idea for the illuminated E-Stop actually came from our customers.”

In future, he says, complex machines will likely be equipped with “safety busses” that bring together all safety-related communications, separate from that used in equipment operation, and will be populated by “safety” PLCs, which also can’t fail unsafe. 

The 30 mm Mount Illuminated Emergency Stop pushbutton has a push-to-stop, twist-to-release or pull-to-release actuator. Its direct (positive) opening operation is compliant with ANSI B11.19, ANSI NFPA79, ISO 13850 and IEC/EN 60204-1 Emergency Stop requirements and meets worldwide safety standards with a red button and yellow background.

And finally, there is one more anecdote about pushbuttons. Once in a briefing to industry journalists by a major French automation vendor, one of its marketing managers said, “we’re bringing our pushbutton technology to China and we’re very excited about it. You understand: many, many fingers…,” as he wriggled his own digits in front of them.