A FLOW SWITCH IS JUST A FLOW SWITCH, OR IS IT?

For many years, industry relied on paddle switches for protection against low flow conditions. Being both inaccurate and unreliable the lowly paddle switch has slowly gone the way of the dodo. weber Sensors pioneered thermal flow switches in Germany in 1968. Like any good idea, it did not take long for other companies to copy the idea by producing cheaper versions or what are often referred to as “knock offs”. Fast forward to today and people still ask us why our 4120 flow switches are more expensive? To begin with, let’s start by taking a close look at the tip of our stainless thermal well: This is one of the reasons for our legendary reliability, but also why our accuracy is so vastly superior. Now compare our thermal well to that of our competitors: SO, WHAT ABOUT ACCURACY? On applications where the fluid is at a steady temperature, most of our competitors are hard pressed HANG ON IT GETS WORSE Now imagine a process where the fluid temperature is changing. As bad as our competitor’s accuracy is for a constant temperature process, it gets much worse if the temperature substantially changes. The chart below reveals what happens if there is, for example, a 20° C (68° F.) change in temperature of the process. When the flow is at .8 m/s (~2.5 ft./sec) the cheaper sensors begin to experience tremendous decline in accuracy. This decline continues until finally at around .2 m/s (~.5 ft./sec.) the error reaches 100%. In other words, the sensor thinks the flow is twice as high as it in fact is. THE TAKEAWAY Admittedly, there are some applications where accuracy may not seem to be that important, however, reliability usually is. Since flow switches often serve an important function of either protecting a process or piece of equipment that has a substantial value, why risk the consequences by skimping a little bit of money on the flow switch? The reality of the world we live in is one that demands constant productivity improvements with shrinking budgets. Yet given all the constraints, lets agree that quality is and always will be the best value.

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