It is recommended that bending plate installations are checked every six months.
Each check should include:
- pavement integrity (depressions, potholes, cracks)
- frame installation (look for loosened parts, pavement break-outs)
- weigh pad suspension (banging during passage of trucks indicates loose rail or bad support)
- drain outlet (clean if necessary)
- cabinet and cabling condition (clean if necessary)
- if necessary the lane needs to be closed for closer inspection and repairs, e.g. filling of cracks, tightening of nuts.
Figure: Bending plate maintenance
Source: TMR 2008a
In addition to the six-monthly checks above, the annual check should include:
- condition of weigh pads (zero point, noise on signal, insulation resistance)
- condition of loops (frequency, switching characteristics, symmetry between the two loop signals, if necessary check continuity, insulation resistance and inductance)
- modem, power supplies and surge arrestors
- one-hour traffic survey (comparison of traffic with recorded data) with the aid of a video camera
- documentation on relevant forms (WIM maintenance visits, volume and classification record comparison).
Once the full function of the WIM system is confirmed, an annual calibration check with two trucks is conducted.
Although there are means to see fluctuations in the weight sensitivity during the year it is important to check on variations caused by changing pavement levels resulting in different dynamic weights for various axle configurations.
The PAT WIM has a feature in the calibration where the different sensitivity (correction) factors can be applied in three speed ranges
Electronic Load Weighing Co. of Australia 2008, ‘Eastlink, Victoria weigh-in-motion system installations: PAT WIM system basic maintenance reference manual’, Electronic Load Weighing Co. of Australia, NSW, Australia