Continuous monitoring of increasing and decreasing vibration levels helps avoid expensive unplanned shutdowns by detecting machinery faults before they become catastrophic events. Early detection is essential for efficient machine maintenance, as well as protecting equipment from further damage during an upset condition. The advancement in vibration switch technology from mechanical to electronic switches has provided a very useful tool for maintenance engineers to allow for better planning and less headaches sustaining equipment performance and longevity.
The classic style of an electronic vibration switch utilizes a built-in, or remotely located, vibration sensor, whose electrical signal is conditioned and monitored. The switch mechanism itself is a circuit board with mechanical relay, typically housed in an electronics enclosure. The circuitry monitors a sensor’s generated vibration signal against a pre-set threshold value and activates the relay when an exceedance is encountered. Such devices are often too bulky for mounting onto a machine, have a limited range, require a separate power source, and require individual wiring to their respective PLC or alarming device.
To overcome some of the complexities and shortcomings of the classic-style electronic vibration switch, a new, smart, two-wire, solid-state vibration switch has been developed. The operating principle for this new switch is shown in figure 1.
Machinery and mechanical systems face potential failure when their ability to function normally is compromised, due to worn components or when their normal operating condition becomes upset in some manner. If a worn component or process upset can be detected, then operator warning or immediate shutdown can safeguard machinery from catastrophic failure. A simple detection technique can be based on vibration -where an increase in measured machinery vibration is utilised to trigger an alarm or shutdown. It is known that machinery vibration increases when problems such as worn bearings, cracked gears, lack or contamination of lubrication, imbalance, looseness, and misalignment become worse. For such applications, the mechanism used to detect a vibration increase and trigger an alarm or shutdown is called a vibration switch. A vibration switch can also be used to alert an operator of a decrease in vibration levels - as may be the case when a motor ceases to function.
