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Brake Application Pressure Tester

Portable device for verifying application pressure during brake testing

Developed by: Applied Vehicle Data, Inc., supplier of brake testing equipment

  • Verifies that brake application pressure during slack adjuster testing is 90 PSI or greater
  • Catches out-of-service trucks that pass at low brake application pressures
  • Sets up quickly and is portable
  • Verifies compliance with CFR and CVSA requirements

AVD Brake Application Pressure Tester

Summary of Features:

  • Verifies application pressure is 90 PSI or greater during slack adjuster testing
  • Light illuminates when brake application pressure is 90 PSI or greater
  • Portable design attaches to glad hands with light that lies on ground under vehicle
  • When performing slack adjuster measurement testing under vehicle, light can be seen from all brake chambersCatching Out-of-Service Vehicles:
  • Vehicles tested at improperly low brake application
    pressure may appear to be “in service,” but when tested at the proper
    brake application pressure, these vehicles are out of service

    Importance of Testing at Proper Application Pressure

    Catching Out-of-Service Vehicles:

  • Vehicles tested at improperly low brake application
    pressure may have slack adjuster displacements that are less than 2
    inches, but when tested at proper brake application pressure, these
    vehicles may have displacements that exceed 2 inches
  • Vehicles tested at low brake application pressure may appear to
    be “in service,” but when tested at the proper brake application
    pressure, these vehicles are out-of-serviceSpring Brakes and Slack Adjustment:
  • Vehicles equipped with spring brakes with slack adjusters are approximately 98 percent of all off- and on-road trucks
  • Slack adjustment maintains clearance between the brake shoes and the brake drum
  • Slack adjuster clearance is critical because it is the primary factor in determining the ultimate braking capacity of the brake
  • Slack adjusters operate in a very narrow band of adjustment.
    For class 8 tractor trailers, normal adjustment of the slack adjuster is
    in the 1.5 to 1.75 inch range with the readjustment point at 2 inchesExample of Out-of-Service Vehicle:
  • Tractor-trailer was tested twice using a slack adjuster
    data acquisition system that captures the exact displacement of slack
    adjusters and brake application pressure
  • During first test, brake application pressure was 30 PSI and all slack adjuster displacements were 2 inches or less
  • During second brake test, application pressure was increased to 96 PSI
  • At 96 PSI all slack adjusters moved greater than 2 inches
  • Vehicle is out-of-service

    The Items Included:
     
  • Self-contained pressure sensor that connects to glad hands
  • Indicator light that is placed on ground under vehicle
  • Connectors for power from vehicle
  • Calibration papers for pressure sensor
  • Custom-built fully padded cases for storage and transportHow to Set up the Brake Application Pressure Tester:
  • Connect pressure sensor to glad hands
  • Connect trailer cord to pressure sensor
  • Place indicator light under truck
  • While driver applies brakes, watch for indicator light to illuminate
  • Illuminated light indicates brake application pressure is 90 PSI or greater

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