Rub Block vs. Touchswitch
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 dust hazard environments. Two typical methods of detecting belt misalignment are the rub block and the Touchswitch.
The Rub Block
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.
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 dust hazard environments. Two typical methods of detecting belt misalignment are the rub block and the Touchswitch.
The Rub Block
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.
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| Round Rub Block |
The Touchswitch
The Touchswitch design addresses these 3 issues. First, it detects the lateral force of the belt, and gives you 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 soft brass. Finally, each Touchswitch 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.
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| Touchswitch |
The Touchswitch is an electro-mechanical limit-switch with no moving parts that detects the misalignment of both pulleys and belts in conveyors and bucket elevators. The sensor detects the lateral force of the belt or pulley and activates a voltage free relay contact. This relay contact can be used to send an alarm or shutdown the machine. The sensors are usually installed in pairs on opposite sides of the belt / pulley.
The face of the sensor is made from hardened and annealed stainless steel, not soft brass or aluminium, increasing wear resistance when the belt contacts it. The Touchswitch is not affected by dust or material built up; it will work even when completely covered by material.
The face of the sensor is made from hardened and annealed stainless steel, not soft brass or aluminium, increasing wear resistance when the belt contacts it. The Touchswitch is not affected by dust or material built up; it will work even when completely covered by material.
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| Touchswitch in use |
The Touchswitch sensor is easy to adjust and and can be used with pressures between 2 and 5 kg. It has got a test button which allows to create an error to test the efficiency of the security system.
The Touchswitch is ATEX certified for zones 20, 21 and 22 Ex II 1D T125°C without internal cabling. It also has CSA and IECEx approvals.
The 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.
Simone BiockThe Touchswitch is ATEX certified for zones 20, 21 and 22 Ex II 1D T125°C without internal cabling. It also has CSA and IECEx approvals.
The 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.
Marketing Manager
4B Braime Elevator Components
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