DrDrreeeaaa
Electrical
- Apr 25, 2008
- 266
Hi All
In your experience has it been neccesary to operate bucket elevators without guards installed?
i.e. for bucket inspection, do you inspect buckets through a window or cage without removing guards or is this impractical i.e. due to not having a clear view through a window due to dust, etc. If this is the case, when you find a damaged bucket, do you remove the guard - replace the bucket, then replace the guard and continue inspection? or do you allow the operators to continue inspection and hence operating the machine with the guard off?
If you do operate the elevator with the guard off, what risk controls do you utilise to reduce the risk to the operators in this case? For example, inching drives, which allow operation of the belt at a slower speed thereby minimising risk to the operators, or operation at a slow speed provided by variable speed drive?
I am trying to determine some industry consensus for how often it is neccesary to operate an elevator with guards removed and the risk controls that people generally use.
If we allow the operators to run the elevator with the guard removed, i.e. at a slow speed, we need to minimise the risk to the operator in the event that the slow speed is exceeded, i.e. due to control system error. If we were using a DOL inching drive there wouldn't be an issue as the inching drive has a fixed speed. However in our case the potential for a VSD speed increase needs to be mitigated to a Category 1 or Category 2 level (per EN954).
In general since a Category 1 system requires well tried components, the use of the VSD to implement the slow speed does not comply. Hence we need to provide a Category 2 or better mitigation in the event we allow the operators to run the elevator with guards removed.
So you can see my problem - I would rather not allow the operators to run the machine with the guard removed, but whether or not this could be done depends on how practicable this would be - could they do bucket inspection and replacement without operating the machine without guards? What other tasks may require to operate the belt at slow speed with guards removed?
Sorry for the long winded post - would appreciate any feedback
Thanks all,
Michael.
In your experience has it been neccesary to operate bucket elevators without guards installed?
i.e. for bucket inspection, do you inspect buckets through a window or cage without removing guards or is this impractical i.e. due to not having a clear view through a window due to dust, etc. If this is the case, when you find a damaged bucket, do you remove the guard - replace the bucket, then replace the guard and continue inspection? or do you allow the operators to continue inspection and hence operating the machine with the guard off?
If you do operate the elevator with the guard off, what risk controls do you utilise to reduce the risk to the operators in this case? For example, inching drives, which allow operation of the belt at a slower speed thereby minimising risk to the operators, or operation at a slow speed provided by variable speed drive?
I am trying to determine some industry consensus for how often it is neccesary to operate an elevator with guards removed and the risk controls that people generally use.
If we allow the operators to run the elevator with the guard removed, i.e. at a slow speed, we need to minimise the risk to the operator in the event that the slow speed is exceeded, i.e. due to control system error. If we were using a DOL inching drive there wouldn't be an issue as the inching drive has a fixed speed. However in our case the potential for a VSD speed increase needs to be mitigated to a Category 1 or Category 2 level (per EN954).
In general since a Category 1 system requires well tried components, the use of the VSD to implement the slow speed does not comply. Hence we need to provide a Category 2 or better mitigation in the event we allow the operators to run the elevator with guards removed.
So you can see my problem - I would rather not allow the operators to run the machine with the guard removed, but whether or not this could be done depends on how practicable this would be - could they do bucket inspection and replacement without operating the machine without guards? What other tasks may require to operate the belt at slow speed with guards removed?
Sorry for the long winded post - would appreciate any feedback
Thanks all,
Michael.