Belt misalignment is a common problem in belt conveyors and bucket elevators. When the belt is severely misaligned it can cause damage to the machine casing while generating dangerous heat in potentially explosive atmospheres like that found in grain handling.
Two typical methods of detecting belt misalignment are the rub block and the Touchswitch.
The rub block consists of soft brass with an embedded temperature sensor. The sensor alarms when the brass heats to the trip temperature. Three main drawbacks exist for this sensor. First, by the time the brass heats, the belt has already been misaligning for a period of time. Second, the belt could periodically rub against the brass and move away, wearing through the rub block without ever giving an alarm, leaving you unprotected. Finally, there is no simple way to test the rub block without introducing heat into a potentially hazardous environment.
The Touchswitch design addresses these three issues. First, it detects the lateral force of the belt, and gives an immediate voltage-free
relay contact change when the
belt contacts it. Second, the face of the sensor is made of
hardened stainless steel, which is much more resistant to wear than
softbrass. Finally,eachTouchswitch has a test knob and status LED, so you can
tighten the test knob to simulate a belt misalignment and watch the LED go out followed by machine alarm/shutdown. When you loosen the test knob it simulates the belt
moving off of the Touchswitch and the LED turns back on. The Touchswitch sensors are usually installed in pairs on opposite sides of the belt/pulley. As the Touchswitch is not
affected by dust or material built up; it will work even when completely covered by material.
It is easy to adjust and can be used with pressures between 2kg and 5kg.
The Touchswitch is ATEX certified for zones 20, 21 and 22 Ex II 1D T125°C without internal cabling and also has CSA and IECEx approvals.
The Touchswitch sensor can be connected direct to a PLC or for increased security to an independent monitoring system such as the B400 ELITE, WATCHDOG ELITE or T500 Hotbus, all ATEX approved zone 21 and 22.