Last week we had layers of ice and daytime temperatures that averaged 16°F. This week all of the ice melted as the daytime temperature held steady in the upper 40s. The only evidence of winter was the shovel standing idle alongside the front door of most every home in my neighborhood. My guess is that in a couple of weeks those shovels will be needed to clear another blanket of snow and ice. Of course, it’ll be spring by then.
Variation like that seems to be increasingly common here in the Northeast. While the weather’s unpredictability can make it hard for me to pack when traveling for business, any inconvenience I experience is simply that – inconvenience. Unless I’m going to Arizona’s desert, Alaska’s North Slope, or some other extreme location, I usually pack a little of everything. As the weather shifts, I can just as easily change into a short-sleeve shirt when it’s hot as I can throw on a heavy jacket when it’s cold. Big swings in temperature, rainy or dry conditions, whatever – I can easily adapt with little to no added wear and tear. The same isn’t true for a production facility’s installed assets.
Seasonal variability is known to affect the performance of production systems and assets that are exposed to external conditions as well as those operated in HVAC-controlled areas. Indeed, the impact of weather is well-documented. If the weather conditions near your facility are increasingly erratic, then here are a few things to consider:
Humidity
Humidity feels sticky. As the air’s moisture level increases, it changes how some production assets perform. In fact, there’s a term for the additional "sticky" friction that affects how valves and dampers function – it’s called stiction.
Changing humidity levels and temperature can cause buildup, (e.g. ice, scaling, and rust) on valves and dampers, affecting the way they respond to movement commands. A valve affected by stiction, as an example, can’t move freely in response to process changes until additional force is applied. It’s typical for added force to result in a valve position that is either too wide or too narrow. A cyclical pattern of behavior and a jagged trend often follow because the process is constantly correcting for the valve’s position and accelerating its time to failure.
Look for the early signs of valve stiction, particularly on a facility’s production-critical processes, and schedule valves to be repacked during normally scheduled maintenance.
Temperature
Most assets have limits to the range of temperatures under which they operate safely and efficiently. For certain, temperature is a key attribute that most every reliability technology takes into consideration. It’s also an essential consideration in the control of many processes.
Think of a facility’s heat-transfer equipment (e.g., cooling towers and heat exchangers). If the outside temperature changes significantly from one day to the next, then the behavior of those systems also can be expected to change. Note that a facility’s PIDs are tuned to respond to dynamics that occur within a production environment and ultimately to maintain control. When the ambient temperature changes dramatically, it can undermine the ability of those PIDs to do their job effectively.
Keep an eye on the ability of PID controllers to track their set points and retune them as necessary to avoid excessive process variability and unnecessary wear and tear on the associated production assets.
It’s always helpful to consider how environmental factors influence the performance of a facility’s production assets. In short: If you need to rethink what you’re wearing because of a change in the weather, then it’s not unreasonable to think that assets and processes are in need of little extra attention, too.