Saw Arbor Starts while Clamshell and Arbor Door are Open

Safety Alert Type: 
Coast Forest Region-South Island District-Ladysmith
Date of Incident / Close Call: 
Company Name: 
Western Forest Products
Details of Incident / Close Call: 

While trouble shooting guide locking mechanism the power to the main disconnect was restored to see if the issue was with the

master control power. At this point the clam shell and both arbor doors were open. While this was taking place the machine

operator coming on shift entered the control cab and started up the equipment. The electricians heard the canter and #1 gang

start up but did not believe the #2 gang would start as the proximity switches on the clam shell and arbor doors were open. As

it happens the lower arbor fitted with 17 saws did start and rapidly began to self destruct damaging 6 saws and the main arbor

coupling. Electrician quickly threw the main disconnect before the second arbor cycled. Upon investigation it was found the

logic in the PLC had been modified years earlier to deal with nuisance alarms caused by the prox switches vibrating and cutting

out the arbor motor.


Learnings and Suggestions: 

Interlocks / prox switches / photo eyes are not a substitute for locking out equipment

Ensure adequate pre inspection/communication is in place prior to starting up equipment

For more information on this submitted alert: 

Dan Bowes Saltair Sawmill Manager

File attachments
2010-12-20- Saw Arbor Starts while Clamshell and Arbor Door are Open Coast Forest Region-South Island District-Ladysmith.pdf
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