Flying by the seat of your pants?
There was a time in the history of aviation when “flying by the seat of your pants” had real meaning given the relative lack of gages in an early airplane’s cockpit. Yet, in many ways we still operate our plants this way. We instrument what we consider to be critical measurements based on historical operation, but we don’t necessarily perform a detailed analysis of the process to determine if there are other things that might be just as important to the operation in terms of throughput or quality or, possibly even more importantly, to uptime and equipment longevity. Even those organizations that don’t have a “run it till it breaks” mentality don’t necessarily make the best use of the instrumentation they have, while more thoughtful companies install things that could be beneficial in improving uptime and operation of the facility.
While there’s something to be said for the ability of the human body to detect small changes in things, like vibration or the sound of a piece of equipment, there’s no substitute for good measurement to detect it before it becomes bad enough for a human to detect. Heuristic capabilities built into some instruments have extended this human capability for sensing problems so they can be detected well before an operator can. One manufacturer, for example, has built a plugged sensing line detection capability into their transmitters that uses the noise signature of the process. When it decreases by a threshold amount, it generates an alarm. Sensing these changes in process noise can also be used to detect other problems like pump impeller wear, which can also create pressure fluctuations that then cause a valve to cycle excessively leading to an early failure. Digital valve positioners can analyze the motions of the valve that would go unnoticed by an operator to alert maintenance to the need for service before the valve fails. This use of heuristics can be applied to any number of other situations to prevent failures before they happen.
So why aren’t more plants taking advantage of these kinds of diagnostic capabilities? The problem is that organizations are in many ways constrained either externally or internally from deploying these technologies. One key constraint is financial. Some of what’s required to perform the analysis falls into the realm of capital expenditures, which in most cases requires a payback. If the system does its job so you keep from having the outage and down time that would have cost you the money you justified buying it on, then without the down time you can’t show that you actually saved any money, making the successful system a failure. Talk about a “Catch-22.” Another constraint is cultural. One engineer for a major U.S. corporation has said that his company won’t buy some of these technologies because to use them effectively would require rewriting their maintenance procedures, which they won’t do. A competitor of theirs has stated that having the plugged line sensing technology would have prevented an explosion that occurred at one of their refineries. That means the first company is unwilling to install something that would prevent an explosion because they would have to change a procedure that is meant to prevent explosions. Really? What Catch-22s have you run into that have prevented you from implementing something that logically should have been implemented?
This post was written by Bruce Brandt. Bruce is a technology leader at MAVERICK Technologies, a leading system integrator providing industrial automation, operational support, and control systems engineering services in the manufacturing and process industries. MAVERICK delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, and business process optimization. The company provides a full range of automation and controls services – ranging from PID controller tuning and HMI programming to serving as a main automation contractor. Additionally MAVERICK offers industrial and technical staffing services, placing on-site automation, instrumentation and controls engineers.