Brass Rub Blocks
Belt Misalignment Sensors


Brass rub blocks monitor for belt misalignment problems on bucket elevators and conveyors by detecting heat generated by the friction of the misaligning belt rubbing against the brass.

A temperature sensor within the brass block provides the temperature reading and the system generates an alarm and a shutdown when a trip point is reached.

The sensors are usually installed in pairs on opposite sides of the machine to detect misalignment on either side. Sensors can be connected directly to a PLC input, or for greater safety, to a central independent monitoring system such as 4B’s T500 Elite Hotbus™, Watchdog™ Super Elite or T400N Elite Hotswitch.

Inspection doors are available to assist with periodic maintenance and testing of the brass rub block and system.



  Brass Rub Block Belt Misalignment Sensor  

• Belt Misalignment Monitoring


• Easy Installation


• No Moving Parts (Solid Brass Block)


• Temperature Activated (Friction)


• External Sensor Testing (ADB Tester)



  Product Questions? (309) 698-5611Phone or Email  Email    
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  ADB Temperature Sensor Specifications (NTC Type):   Literature:  
  • Resistance at 77° F - 10,000 Ohms   Product Datasheet Download PDF  
  • Resistance at 140° F - 3,043 Ohms      
  • Resistance at 194° F - 1,264 Ohms   Technical:  
  • Sensing Voltage - 5 to 24 VDC   4 x 2 Inspection Door Manual Download PDF  
  • Current Draw - 1 mA      
  • Maximum Power - 120 mW at 77° F (25° C)   Dimensions:  
  • Body Housing - 304 Stainless Steel   2 x 4 Rub Block (RB2W4LR2)  
  • Fixing Thread - 1/8" NPT      Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
  • Cable - 9 ft. (3 m) - 2 Conductor      
  • Operating Temperature -22° F (-30° C) to 220° F (105° C)   2 x 4 Inspection Door (RBID3X9)  
         Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
  ADB Temperature Sensor Specifications (PT100/RTD Type):      
  • Resistance at 77° F - 109.73 Ohms   2" Round Rub Block (RB2D)  
  • Resistance at 140° F - 123.24 Ohms      Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
  • Resistance at 194° F - 134.70 Ohms      
  • Temperature Coefficient - 3850 PPM/K (385)   • 2" Round Mounting Plate (RBP1)  
  • Sensing Voltage - 5 to 24 VDC      Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
  • Current Draw - 1 mA      
  • Maximum Power - 1 mW      
  • Body Housing - 304 Stainless Steel      
  • Fixing Thread - 1/8" NPT      
  • Cable - 9 ft. (3 m) - 4 Conductor      
  • Operating Temperature -22° F (-30° C) to 220° F (105° C)      
  ADB Temperature Sensor Approvals:      
  • CSA Class II Div 1 Groups E, F & G (USA & Canada)      
  • ATEX Versions Available      
  CSA - USA & Canada ATEX - Europe  CE - Europe       
  Part Numbers and Accessories:      
  • RB2W4LR2 ~ 4 x 2 Brass Block      
  • RBID3X9 ~ 4 x 2 Rub Block Inspection Door      
  • KIT-RUB-7 ~ 4 x 2 Brass Block & Inspection Door (Set)      
  • RBH1 ~ 2 in. Round Brass Block      
  • RBP1 ~ 2 in. Round Mounting Plate      
  • RB2D ~ 2 in. Brass Block & Mounting Plate (Set)      
  • ADB20V3C/D3 ~ ADB Temperature Sensor - NTC Type      
  • ADB29V3C/D2 ~ ADB Temperature Sensor - PT100/RTD Type      
  • ADBW ~ ADB Sensor Probe Wrench      
  • ADBT4 ~ ADB Sensor Tester      
  • WDC4V46C ~ Watchdog Super Elite (Monitoring Control Unit)      
  • T5004V46C ~ T500 Elite Hotbus (Monitoring Control Unit)      
  • T400N4NV46C ~ T400 Elite Hotswitch (Monitoring Control Unit)      
  Literature:   Dimensions:  
  Product Datasheet Download PDF   2 x 4 Rub Block (RB2W4LR2)  
         Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
  4 x 2 Inspection Door Manual Download PDF   2 x 4 Inspection Door (RBID3X9)  
         Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
  Note: Product manuals for older part numbers can be      
  found under the Technical Support area.   2" Round Rub Block (RB2D)  
         Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
      • 2" Round Mounting Plate (RBP1)  
         Download AutoCAD .dwg (AutoCAD)      Download PDF .pdf  
Rub Block Inspection Door RBID3X9

Inspection Door (RBID3X9)

The rub block inspection door simplifies the installation process of 4 x 2 rectangular brass rub blocks. During routine maintenance inspections, the hinged design allows for easy access to inspect both the belt and the rub block for wear.

Mounting Plate RBP1

Mounting Plate (RBP1)

Designed for installing 2" round brass rub blocks. The plate mounts directly to the casing of the machine.

ADB Bearing Temperature Sensors

ADB Temperature Sensors

The sensor probes are adjustable for more accurate temperature readings. Available sensor types: NTC or PT100/RTD.

More Info

ADB Temperature Sensor Tester

ADB Sensor Tester

The ADB Sensor Tester has been designed to test 4B adjustable depth bearing (ADB) temperature sensors in the field.  During planned maintenance or periodic testing, this diagnostic tool to verify the alarm and shutdown sequences of the control unit are functioning as expected.

More Info

Watchdog Super Elite Hazard Monitor

Watchdog™ Super Elite Hazard Monitor

The Watchdog™ Super Elite processes signals from sensors for belt misalignment, belt speed & slip, continuous bearing temperature, pulley misalignment and plug conditions for bucket elevators or belt conveyors.

More Info

T500 Elite Hotbus Hazard Monitor

T500 Elite Hotbus™ Hazard Monitor

The T500 Elite Hotbus is a serial communications system designed to monitor up to 256 sensors on multiple bucket elevators and conveyors for belt speed, belt alignment, bearing temperature, level and plugged conditions.

More Info

T400N Elite Hotswitch Temperature Monitor

T400N Elite Hotswitch

The T400N Elite Hotswitch is a microprocessor controlled temperature monitor, which works in conjunction with NTC type temperature sensors.  The unit can provide an alarm and automatic shutdown, on up to 2 machines, when a hot temperature condition is detected.

More Info

  What is the difference between the Touchswitch sensor and a rub block?  
  The Touchswitch is a pressure sensitive contact switch.  When the belt misaligns and contacts (touches) the  
  sensor with enough force, an alarm is triggered.  
  Rub blocks are designed to detect the heat generated by friction when the belt rubs against the brass block.  
  Touchswitches provide an immediate alarm, while brass rub blocks can take longer to activate due to the time it takes  
  for enough heat to build up to trigger an alarm.  
Rectangular Rub Block
Rub Block Inspection Door
Round Rub Block