Press 4: Log Loading System (automation improvements)
With little room to manouvre the logs into position when loading them onto
the loading chains, issues were being created with the logs being placed on
the chains on one side and the guide rails on the other. This would cause
problems when the loading chains tried to traverse the logs.
Curved mirrors have now been mounted directly above each guide rail. This
will give the fork lift truck drivers a better view when loading the logs onto the
loading chains.
The guide rails used to try to keep the logs on the loading chains were
adjudged to be too close together, leading to the loading issues we currently
see.
To improve this, the distance between the guide rails has been widened, to
allow more room to manouvre the logs onto the loading chains, and hopefully
preventing skewing of the logs when running the pre-load cycle.
The location of the control desk for manually loading is situated in a location
where it’s almost impossible to see what’s happening.
In the past, we had situations where the log hasn’t loaded correctly onto the
pusher chain and this has resulted in damage to the shock absorber assembly
when the manual command to push the log was executed.
This resulted in major damage and downtime to production in repair work.
The only means of monitoring what’s happening in the manual loading
sequence is through a small viewing window situated too far away from the
manual control station.
Furthermore, the condition of the remote control station is in a pretty poor
state, and doesn’t provide the necessary information needed to ensure a
correct ‘manual’ load sequence has been completed successfully, and more
importantly, completed safely, and without the possibility of injury to others.
As mentioned in the previous slide, the existing manual control station –
although giving the operator a means of loading the logs onto the log loading
system, there is little information presented on the ‘on-board’ PV500 operator
panel.
The final deciding factor in deciding to go ahead with this improvement
project is the time taken for the operator to set the station up, in order to
carry out the manual functions necessary to perform a manual load.
Prior to the implementation of these project changes, a screen was available
on the main operator press panels (both left and right hand side operator
panels), but had no means of carrying out manual functions.
Instead, it only provided information relating to pusher arm position and
sensor status. This screen has now been completely re-engineered to give
better information, as well as full manual loading functionality that effectively
mimics the existing remote loading station.
The new screen offers the following
functionality: The option to turn on or off control of the
on-screen command buttons.
Full control of all manual movements to
allow safe loading of the new log in the
event of an automatic loading failure.
The option to switch between the pusher
arm measuring device – encoder or laser.
Feedback for pusher arm position and
more importantly the actual log
measurement taken during a manual load
operation – the latter being a crucial
addition in the prevention of slithers.
Last week (21st February, 2020), at around 9.00pm, we experienced a slither after a billet cut. When I first joined
HYDRO, the issue of slithers was a pretty regular occurrence and due to an incorrect Konstant in the software for
the physical position of the measure PEC for snapshotting the position of the pusher value, that’s then used to
calculate the effective length of the newly loaded log. This problem has since been resolved and has been
correct for the past three years. Periodical checks to ensure this Konstant remains correct are carried out on a
regular basis, as if the value is incorrect then we will have major issues with slithers.
The system however still had a serious flaw – and this was to do with when loading in a log in manual mode.
 In manual load mode, the old software would NOT calculate the effective length of the new log, but rely on
operator input to manually key in the length of the new log.
 IF THIS VALUE IS INCORRECT – AS SEEMS TO HAVE BEEN THE CASE LAST WEEK, THEN THE SOFTWARE CAN’T
CALCULATE WHERE THE END OF ONE LOG FINISHES AND THE START. OF THE FOLLOWING LOG BEGINS. THIS
RESULTS IN A PERFECT CASE SCENARIO WHERE SLITHERS CAN AND WILL BE FORMED.
 It’s easy to blame sensors - as is usually the chosen diagnosis as to why we get slithers, but it’s also seldom the
actual cause of why we get the slither.
Previously, and prior to the new software modifications, if the new log was loaded
manually, then it was up to the operator to input the actual log length of the newly
loaded log.
For some reason, the value entered would ALWAYS be 7400mm – without an actual
measure being taken of the true log length!
As log lengths from the cast-house can vary from 7350 – 7490, this immediately creates
chaos within the software.
The software can accurately calculate the overall log train length, but relies on correct
information to monitor where the joins are within the log train.
Entering an incorrect log length when loading in manual will give an error in position, of where the actual
physical position is between two logs, and that calculated by the software.
In this example above, if we have a true log length of 7420, but a value of 7400 is entered, then the software
thinks the point at which the two logs touch is 20mm out from the actual join positions.
As the manually entered log length approaches the ‘active log’ – the expiring log being cut, at the front of the log
train, the software calculates, based on the value entered by the operator, whether or not it is allowed to make
one last cut. As it thinks that the join line between expiring and next log is further back, it will execute an illegal
cut!!
…………AND THIS IS HOW WE END UP WITH A SLITHER!!!!
7407
On a manual log load, the software will capture the position of the
pusher arm value and from this, calculate the effective length of the
newly loaded log. This will be automatically entered into the system
in position L4 of the heater screen. This in effect removes the need
for manual intervention and shouldn’t require any operator input
when performing a manual log load.
PLEASE NOTE: The function for operator over-ride is still in place. This is in the event there is a failure in the PEC
sensor that triggers the log measurement reading. In this case, a measure of the newly loaded log should be
taken, before the manual value is keyed in.