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 Portable Skid Tester Calibration Kit

Skid Tester Calibration Kit - NEW -

Portable Skid Tester Type 'A'

Portable Skid Tester Type 'B'

Introductory Note

The calibration procedure which follows is based on BS 812 Part l 114:1989. However it will be replaced shortly by the European Standard EN 1097-8.

This procedure must only be used, together. with the Skid Tester Calibration Rig. This system has been designed to allow laboratories outside the UK to calibrate their Skid Testers without the major expense and inconvenience of sending Skid Testers back to the UK for this purpose.

The Skid Tester is a precision instrument and needs to be calibrated by a competent technician.

Calibration Procedure

  1. Calibration must be carried out in a temperature controlled environment of 20C.
  2. The out of balance moment of the rotating head of the pendulum must be less than 12g.cms. If more, calibration moments and calculations must be adjusted.
  3. Mass of pendulum pointer to be less than 85g, excluding felt pads.
  4. Pointer to balance on a knife edge about the centre of oscillation.
  5. Weigh the complete pendulum arm. 1.5kg 30g.
  6. With the adapter nut in its extreme position and the slider lifting handle down, balance the pendulum horizontally on a knife edge and mark the centre of gravity.
  7. With the arm horizontally balanced on the knife-edge and with the slider lifting handle down, adjust the counterweight until the foot is horizontal.
  8. With the arm mounted oil the Pendulum measure the distance of the centre of gravity mark from the centre of oscillation.
  9. The arm must fall freely from the catch.
  10. Set the pointer to reach tile zero position on the scale by swinging the arm in free air and adjusting the pressure oil the felt pads.
  11. If without pressure from the felt pads the arm fails to reach the zero position on the scale, mechanical problems exist, N.B. bearings, which must be corrected.

  12. Check the alignment of the pendulum foot swinging parallel with the base by measuring the difference at the toe of the foot, of the swing across the front face of the base. 1mm. This measurement can be corrected by setting cotters of the pendulum column.
  13. Check that the foot is square to the base by measuring the difference between the toe & heel of the foot, related to the front face of the base, in the static vertical position. 0.5min. Adjustment can be made by setting the clamp on the adjuster nut.
  14.  

  15. Calibration Weights
  16. The following are used in calibration:

    CW1 -Applied Weight 2244 g.

    CW2 Small Calibration Weight 60 g.

    CW3 - Large Calibration Weight 120g.

    The calibrating weights should be attached to the lifting arm, after removing the cover plate.

  17. With the arm inverted on the calibration rig mounting block and the mean load (CW1 and CW2) applied, raise the slider by turning the screw adjuster anticlockwise until the slider arm just touches the retaining bar. Measure this high point with the micrometer. Turn the screw adjuster clockwise until the slider arm just touches the low stop, measure this low point, set the mean point of these two measurements on the micrometer and turn the screw adjuster anticlockwise until the slider touches the micrometer. This is the mean setting of the slider.
  18. Note:

    The adjusting screw on:

    Type 'B' units requires a screwdriver applied through the access hole in the adapter nut.

    Type 'A' units require removal of the adapter nut assembly to access a thumb screw.

  19. Remove the small calibrating load (CW2) from the mean load, check that the slider arm is still free of the internal rest and measure this setting. Add the large calibrating weight (CW3) to the load and measure the deflection.
  20. Set the alignment of the pointer vertically parallel to the arm.
  21. Adjust the pointer stop until the centre line of the pointer is parallel with the pendulum arni in a vertical position, with the friction tester assembled and levelled.
  22. Adjust the spring tension until the lifting handle is brought to its median position. The complete movement of the slider (parallel to the pendulum arm) when using the lifting handle shall be at least 6.5 mm.
  23. The Complete movement of the slider (deflection) shall be at least 11 mm.
  24. Force of Swinging Arm (In Newtons)
  25. W=Wx9.806

  26. Slider Force (in Newtons)
  27. .037xWx411

  28. Change in Slider Force (In Nmm)

SF=.69/Vertical Displacement (mm)

 

Calibration Certificate

Calibration Laboratory:

Date:

Certificate Number:

Serial Number of Machine:

Manufacturer:

Mass of Swinging Arm (W1)

 

Kg

1.5 0.03

       

Force of Swinging Arm (W)

 

N

14.6 0.03

       

Centre of Gravity from Centre of Oscillation

 

Mm

410 5

       

F Scale Vertical Distance

 

Mm (Nominal)

85 0.5

       

Slider Force (P)

 

N

22.2 0.05

       

Change in Slider Force (SF)

 

N/mm

<0.2

       

Sliding Distance

 

mm

76 0.5

       

Length of Pointer

 

mm

305

       

Mass of Pointer

 

gm

=/<85

       

Distance from Sliding edge to axis of suspension

 

Mm (Nominal)

516

 Diagram 1 Portable Skid Tester Calibration Kit

 Diagram 2Portable Skid Tester Calibration Kit