The following information from Allenwest Wallacetown Ltd refers to a potential problem with Allenwest type A74 GEB's . This problem can result in the equipment supplied from the GEB failing to stop when the stop circuit is operated. This indeed occurred recently at a mine.
The problem is caused by ageing of an electrolytic capacitor and can occur on the following equipment . Type A74 ; type A77/D ; type B80 ; type B80 NLM module.
The serial numbers of equipment involved and fuller details are provided in the 'Safety Critical Information sheet' previously supplied to some users by the Manufacturers. It advises that various power supply boards may need to be replaced and that electrolytic capacitors on the power supply boards should be changed every five years or at the time of major overhaul.
It should be noted that if the ' PR ' LED is lit under healthy conditions then there is a probable deterioration of the capacitor. The greater the intensity of illumination the greater the deterioration of the capacitor. Managers and Electrical Engineers will need to ensure that the Manufacturer's recommendations are acted upon.
It should also be noted that there have been instances of equipment involved being overhauled by companies other than the original equipment manufacturer and the related work not having been carried out. This requirement should be made known to companies other than Allenwest when overhaul or repair is required to be carried out by such companies.
S P WingThis notification contains safety critical information
A74
A 'FAILURE TO STOP' of a pump controlled by an A74 GEB, which was supplied during 1988, was the result of ageing of the C4 electrolytic capacitor on the EL5 earth leakage PCB. The control panel (serial No. 3023-06-88A413) had not been overhauled since the date of manufacture resulting in the gradual deterioration of the capacitor.
The above recommendation should be carried out as soon as possible.
Issue No 1 - Date of issue: 10th August 2000
All questions related to the above should be addressed to
ALLENWEST WALLACETOWNThis notification contains safety critical information
A 'FAILURE TO STOP' of an A74 GEB, which was supplied prior to MAY 1991, was caused by premature ageing of electrolytic capacitors on the power supply PCB SP198/8 due to the proximity of the capacitors to the power regulators. The design of this PCB was altered during MAY 1991 as the original power regulator became obsolete. The type of capacitor was also changed due to obsolescence.
All control panels which are manufactured, repaired or overhauled from NOVEMBER 1995.
Refer to Allenwest Wallacetown mining sales department.
Issue No 2 - Date of Issue: 22nd September 1995
All questions relating to the above should be addressed to:
ALLENWEST WALLACETOWN
