Safety alert

Allenwest type A74 GEBs

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Safety Circular

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.

Allenwest Wallacetown
Notification of design change
Notification No. A74/01

This notification contains safety critical information

Unit involved

A74

Reason for notification

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.

Recommendation

1. Examine the date on the TESTED label of the EL5 earth leakage PCB (SP198/4 - PC167) fitted in the A74 control panel and ensure any PCB dated earlier than 1996 has the C4 capacitor replaced.
2. Introduce a programme to ensure that the A74 control panels have the electrolytic capacitors replaced every 5 years.

Implementation date

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 Wallacetown

Notification of design change - Notification No. GEN/01

This notification contains safety critical information

Units involved

• A74 CONTROL PANEL PRIOR TO SERIAL No. 4947-06-91A413
• A77/D CONTROL PANEL PRIOR TO SERIAL No. 0065/0691/A77D2
• B80 CONTROL PANEL PRIOR TO SERIAL No. B80/1226/E/S0791
• B80 NLM MODULE PRIOR TO SERIAL No B80M-527-0791

Reason for the change

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.

Recommendations

1. Replace the power supply PCB SP198/8 on all A74, A77/D & B80 units supplied prior to MAY 1991 with power supply PCB SP 198/8R.
   Priority to be given to the oldest A74 units. Refer to drawings AE6001336 & AE6001736 got identification purposes.
2. Replace the electrolytic capacitors on the current design of power supply PCB SP198/8R every 5 years or at each major overhaul of the unit.

Implementation date

All control panels which are manufactured, repaired or overhauled from NOVEMBER 1995.

Cost

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: