ANC has only one wood yard crane to supply logs for its paper-making process. Without the crane, logs must be loaded manually with front-end loaders at substantially increased cost to the mill.

ANC’s wood yard crane was first installed at the facility in 1982 with hard-wired relays and GE DC300 drives, now obsolete. The system has become unreliable over the years, leading to lots of maintenance work and downtime.

ANC wanted to upgrade the crane so that technical problems would become more unlikely and make it easier to diagnose – and fix – problems when they occur. And it wanted to upgrade the crane within several short routine outages rather than all at once, to minimise production downtime.

The wood crane was originally built by the Ederer Company and installed in 1982. It has a net capacity of 50 US tons with a load capacity of 40 US tons under the grapple. The crane is rail mounted and is capable of running trolley, hoist and gantry motions simultaneously.

Four GE DC300 SCR drives were originally used for the three motions – hoist, trolley, and left-side and right-side gantry motors. Hoist motors were 200 HP, travel motors 40 HP and trolley motors 25 HP. The DC300 product line has been discontinued and spare parts are no longer available from the OEM. OEM support for the drives has declined over the years requiring the mill to maintain the equipment with its own people. As maintenance requirements for the aging equipment on the crane, more manpower was required to keep it running effectively.

Drive and motor layout was originally designed to provide fault security for the crane. Redundant hoist, gantry and trolley motors were included in the design to provide fault tolerance. Power converters were also arranged to help should a failure occur. Gantry motors were split into two groups (right and left legs), each controlled by a different drive, so that should an individual drive or motor fail, the crane could still move, although at reduced speeds.

The solution

ANC chose a crane control systems with drives made by Avtron Manufacturing and integrated by DAMAS Corp. To achieve Augusta Newsprint’s goal of minimized downtime, the installation was broken into four phases to fit the production schedule of the crane.

1. Installation of the PLC

Over the years so many changes were made to the original hard-wired relay-based control system that it was difficult to troubleshoot and trace wiring diagrams. Old wiring had also caused failures.

To simplify the wiring system and reduce installation and maintenance costs, a programmable logic control system was put in place. A remote I/O network was installed on the gantry legs, in the operators’ cab and on the trolley. This architecture also allowed engineers to work on the crane while it was still in operation. A single day outage was planned to allow tie-in and testing of the PLC communication system.

Augusta Newsprint wanted to use a brand of PLC hardware already in use at the mill. Many of the maintenance people responsible for the crane also were responsible for other electrical systems at the mill, so using the same PLC technology reduces spare parts and training requirements.

2. Trolley Section

Because of the equipment’s age and its analogue controls, the crane trolley routinely caused problems for the crane. The trolley’s analogue control would drift with severe temperature changes, which changed the operation of the trolley. This drift posed operational issues and impacted productivity.

During a single day outage, the old trolley drive was removed and a new panel with the Avtron ADDvantage-32 DC drive and ancillary equipment was installed. Existing field wiring was re-used, when applicable, and the drive was connected to the previously installed PLC system. Fibre-optic communication from the drive to the PLC was also installed.

3. Gantry Drive

The original gantry drive control was designed so that each leg was controlled by its own drive. When a drive failed, the crane could only move by ‘walking’ – skewing on the rails. This would inhibit movement of the crane and cause production problems until the drive repair took place.

ANC wanted a better control system layout that would allow the mill to operate the crane efficiently, without skewing, even if a drive failed. To achieve this goal, the motor-drive combinations were re-wired and contactors were added to allow the Gantry DC drives to control several different combinations of motors.

This control scheme allows the crane to stay in operation longer while drive issues are diagnosed and repaired. A control screen was designed to make motor switchover easy for the operator.

4. Crane diagnostic system

Critical to the selection of a system provider was the diagnostic package that supported the new hardware. After careful evaluation of several vendors’ offerings, ANC selected the CraneView and RemoteView diagnostic packages offered by Avtron/DAMAS.

CraneView uses touch-screen technology to enable most electrical technicians to maintain the system and provide the first line of defence. It was designed to facilitate a MTTR (mean time to repair) of 15 minutes upon problem notification.

OperatorView is a touchscreen unit located in the crane cabin that provides critical data about the crane’s operation and maintenance. Should a problem occur with the system, the operator can monitor the system to give insight into potential problems. This minimises lost production time because the correct maintenance personnel can be called and dispatched immediately. The operator also has some override capability of non-critical parameters that may also help get the crane back into production immediately.

The RemoteView remote diagnostic tool allows maintenance personnel to get a first look at the system so the appropriate corrective action can be taken. In most cases, the problem is located immediately so the correct technician, parts and tools can be taken on the first trip.

Avtron and DAMAS’ installation methods provided Augusta Newsprint with a system implementation that did not impact the production of the crane.

Sectionalised installation approaches allowed the customer to attack problems in key areas and benefit from their installation without the need for the entire project being completed at once.

Avtron’s “Smart Drive” technology allows the drives to provide crane functionality and control, leaving the PLC to do what it does best, logical processing. This allows maintenance personnel to isolate problems quickly to determine whether they are drive or PLC issues. Tying these systems together with a fiber-optic communication link adds robustness to the system and eliminates any problems due to noise seen in copper based systems.