Norske Canada’s Crofton, BC paper mill produces 1,400 tonnes per day of newsprint, directory and other specialty printing papers. Fir and hemlock wood chips are washed, screened and refined (ground) by one of (3) primary and secondary refining Thermal Mechanical Pulping (TMP) lines. The pulp from the TMP and other sources is then cleaned, conditioned, blended and run through one of (3) paper machines. The finished rolls of paper are slit, barcoded, wrapped and labelled for shipment to the customer.

Installed Schneider Electric equipment includes Telemecanique Modicon Quantum PLCs, Square D lighting panels and Federal Pioneer power distribution centres.

TMP plant saves $2 million by keeping existing I/O while upgrading to Quantum PLC
A single supervisory Schneider Electric Telemecanique Modicon Quantum PLC controls the entire TMP plant process - chip washing, screening, primary and secondary refining, cleaning and storage. The PLC controls 2,500 physical I/O points and 4,000 internal I/O points for communications to other devices. Machinery is powered by motors with a combined horsepower of over 80,000 HP, including (6) motors each larger than 10,000 HP.

The TMP plant’s existing Schneider Electric Telemecanique Modicon 200 series I/O and 800 series I/O were recently upgraded to a Quantum PLC - without changing the existing I/O. “The fact that we could upgrade to a Quantum PLC without having to change our existing Modicon 200 and 800 series I/O minimized equipment upgrade, downtime and documentation costs – a savings of $2 million”, observes Stephen Hinde, Electrical/Instrument Maintenance Manager, Norske Canada Crofton Division. Mr. Hinde plans to expand the TMP operations to include a third stage refiner.

High-speed vibration monitoring system produces high quality pulp while minimizing equipment damage
The wood chips are ground to a fine pulp by 3 primary and secondary refiners, each of which consists of a large fixed metal disc located between (2) 6-foot diameter (1.83 m) metal discs. A shaft attaches all 3 discs to the motor. To ensure the chips are ground as finely as possible, the 3 discs are located only 1/10 of an inch (2.5 mm) apart. Should the plates touch, however, the grooves could lock, potentially costing half a million dollars of equipment damage and downtime, as well as the hazard of flying metal. A high level of vibration also creates the potential for serious equipment damage. “This is why we rely on a high speed, reliable vibration monitoring system to control the refiners, which considerably minimizes potential equipment damage”, explains Mr. Hinde. The Bentley-Nevada vibration monitoring equipment communicates to the Quantum PLC. This safety supervisory system ensures the gaps between the discs are maintained at an optimal width, thereby maximizing pulp quality while minimizing safety hazards, equipment damage and downtime. “I specified a Schneider Electric Modicon Quantum PLC not only because of its high speed and reliability, but also because of its increased internal addressing space”, says Mr. Hinde. This allows more complex communication via the Modbus Plus bridge mux to the distributed control system and operator console programming logic to be configured to facilitate troubleshooting and improve internal program diagnostics.

Stock preparation process requires hot standby PLC
Once refined, the stock (pulp) from the TMP plant and other sources is conditioned and blended. This process - the single link between the stock source (TMP) and the paper machines - has no surge capacity. If the machines go down, the entire plant shuts down, costing $30,000 per hour. “Because of this situation, we must avoid downtime in our stock preparation PLCs. They must be reliable and allow us to perform on-line programming changes”, explains Mr. Hinde. “That’s why we installed a Schneider Electric Telemecanique Modicon Quantum hot standby PLC to control the stock preparation process.”

High speed paper machines run at 1,200 meters per minute
The blended and conditioned stock is processed through (3) high speed paper machines (with a combined motor horsepower of 20,000 HP) running at 1200 meters per minute. Each machine is controlled by a Schneider Electric Modicon Quantum PLC. “We installed a Quantum PLC because of its ability to communicate via Modbus Plus to 3rd party devices”, states Mr. Hinde. “The Quantum’s capabilities also allow us to shut down a single machine for maintenance while keeping the other 2 running – essential to minimizing downtime.”

Finishing line automatically handles over 200 combinations of customized packaging specifications
When it exits the paper machines, the paper is slit into rolls. Each roll is barcoded, wrapped and labelled for shipment to the customer. A single Modicon Quantum PLC controls the finishing line. The inventory tracking/barcoding system communicates the packaging specifications for each customer shipment via Modbus to the PLC, which ensures the paper machines cut each roll to the required weight, length and diameter. The finished rolls are then packaged for shipment according to precise customer specifications – including the type of spool to insert in the core (that will fit on their specific printer) and the type of protective outer paper wrapping to use. For consistency of label positioning, a robot applies the barcoded shipping labels to the packaged rolls. A final machine adjusts the position of each roll to ensure that the shipping label, when palletized, can be easily read by the warehouse forklift operators. “Our packaging operations are very complex – we handle over 200 sets of different packaging specifications required by customers”, says Mr. Hinde. “So we installed a Modicon Quantum PLC to facilitate execution of the higher level functions necessary to communicate to the I/O devices.”

Standardizing on Telemecanique Modicon PLCs minimizes training costs
Mr. Hinde has standardized on Quantum PLCs, not only because these highly reliable PLCs minimize downtime, but also because training and documentation costs are minimized. “Training is so important for us at Norske Canada Crofton Division that we’ve set up a dedicated Modicon equipment training program at the British Columbia Institute of Technology (BCIT).”

For more information, contact Paul Galbraith, Senior Technical Representative, Schneider Electric, at (604) 273-3711 x 3506 or paul.galbraith@ca.schneider-electric.com.