Some of the little boxes wired or attached to parts of your process could be signal conditioners. They all have inputs and outputs and commonly perform some functions not being done by the main control system.

As noted so succinctly in Wikipedia, the online encyclopedia, fail-safe or fail-secure describes a device or feature which, in the event of a failure, fails in a way that will cause no harm (or at least a minimum of harm) to other devices or create a dangerous hazard to personnel. What does fail-safe mean for you?

Some little boxes, wired or attached to parts of your process, could be signal conditioners. They all have inputs and outputs and commonly perform some functions not being done by the main control system.

In part 1 of this brief series (April 2008), I looked at the most common application for split-range controllers -- the heating and cooling of the barrel zones of plastics extruders. This month, I will continue the discussion and look at managing heat/cool processes using control valves.

The most common split-range application is the heating and cooling of the barrel zones of plastics extruders. On startup, the heat output of the controller takes the barrel zone up to working temperature. Heat delivery is usually modulated (that is, turned up or down) using the time-proportioning mode, by magnetic or solid-state contactors.

In this brief series, I’ve described three industrial incidents that demonstrate the potential cascading effects that failing to consider the human factor and to ensure equipment reliability can have. What can we learn from incidents such as these?

In Part 1 of this brief series, I described three industrial incidents demonstrating the potential cascading effects that failing to consider the human factor and ensure equipment reliability can have. What can we learn from incidents such as these?

From the three incidents described here, culled from inquiry reports, it is clear that both the human factor and equipment reliability call for close examination in anticipation of the next disaster.

Last month, I started a brief series about the inaccuracies and instabilities caused by misuse of thermocouple extension cable on temperature control systems. I’ll continue by looking at other traps you can fall into when color confusion leads to the wrong thermocouple wiring use.

It has been some six years since I wrote about the inaccuracies and instabilities caused by misuse of thermocouple extension cable on temperature control systems. In 1989, the International Electrotechnical Commission (IEC) published IEC 584-3. Yet even now, some 18 years on, the standard is virtually invisible in North America.