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Project Descriptions: |
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PAPER MACHINE WINDER CONTROLS
PROBLEM
Inconsistent roll diameters and sheet lengths produced, and excessive spool waste.
SOLUTION
I used an Allen-Bradley SLC503 (originally) to provide automatic stop of the winder to provide close tolerance diameters and sheet lengths of wound rolls. The winder operator had previously watched a gage and manually initiated the stop sequence. The SLC503 control system utilized a pulse tachometer to determine the amount of paper on wound rolls and automatically calculated the proper point to begin (initiate stop) slowing the machine down in order to stop at the proper roll size. This required compensating for machine running speed by means of equations I derived and programmed into the SLC503 processor. The program automatically checked the system and made adjustments as required to keep the rolls within the desired tolerances.
I expanded this system by upgrading to an Allen-Bradley PLC5 and included far more advanced features. A laser was added to measure wound roll diameters. I derived and programmed mathematical equations into the PLC5 to calculate on-the-fly the amount of paper on the jumbo reels feeding the winder and to calculate the number of rolls that could be wound to a selected nominal diameter, and to calculate and use the specific roll diameter set point at which the winder would stop. The system had the capability of automatically (at backtender option) initiating paper web turn up to an empty reel spool each time a jumbo reel formed to the proper size.
This was far more than a programming project. It was an engineering project which spanned four years with periodic revisions. It required analysis of the winder operation to determine what needed to be in the program to achieve the desired results. It was a successful machine optimization project. I did the analysis, determined what needed to be done, did the programming, engineered the installation, and provided technical support for installation and operation. I could have provided installation services but this owner chose to do the installation. The system provided the owner the capability to make consistent roll sizes and meet customer requirements with minimum capital cost and minimum spool waste of finished paper that had to be recycled. The reduction in spool waste saved the paper mill approximately $1 million per year according to there estimates. This was all accomplished without causing any machine down time.
This link describes the system features in detail
PROBLEM
Inability to produce market hardwood pulp and excessive machine down time.
SOLUTION
I and a friend were engaged to provide the solution, resulting in the owner moving from no market hardwood production to a dependable 1100 tons per day. The friend had the pulp machine experience. I did the controls. The control portion of this upgrade in productivity consisted of several Allen-Bradley PLC applications. These applications were in the areas of process control and motor speed control.
Motor speed control was done using a PLC 5 PID instruction to provide current reference signals to the current regulators driving the pulp machine DC motors. This bypassed the old speed regulators which were causing excess downtime. The plant was able thus to achieve dependable volume production without spending hundreds of thousands of dollars for the purchase and installation of new drives. This was innovative cutting edge use of PLC technology. No one in the plant had seen it done before. Even the Allen-Bradley representative said it was new ground. Apparently/perhaps the company had already ordered new drives. But the PLC 5 program was working so well that when the drives arrived they sat on the floor for around six months, uninstalled. The drives did have some features that were not in the PLC program.
Process control applications included linking the pulp flow rate to the machine speed to control basis weight. The PLC was programmed to provide the control signal to the stock flow control valve resulting in stock flow proportional to machine speed. A speed ramp was programmed so that the operator could key in a new machine speed without difficulties they had been experiencing. Previously the operator had to manually change both the machine speed and the pulp flow rate, attempting to do it in a synchronized fashion. If he failed the system would fail causing lost production. Now all he has to do is key in the new speed. The system responds automatically.
Another PLC application was the control of a new tailcutting machine to facilitate threading stock through the pulp machine sections. This included control of motor speed and a solenoid valve, also numerical control of the cutter position.
Also a PLC program was developed to control a steam desuperheater to optimize sheet drying and contribute to system economy. The program provided for digital input of the desired steam temperature and automatic positioning of a water flow control valve.
The required man/machine interface for these applications was provided by utilizing Allen-Bradley "Panelview" station.
PAPER MACHINE REEL TURN-UP CONTROLS
PROBLEM
Inconsistent reel sizes leaving excessive waste on spool after winding.
SOLUTION
PCI proposed a control system that automatically coordinates reel sizes with winder requirements for making paper rolls to meet customer specifications and leave a preset amount of paper on the reel spool. PCI was engaged to design the system. The system was completed and is currently performing as projected. The customer’s spool waste has improved from 1.75% to 1.1% which means in a strong improvement in company profit. The system performance is good enough that spool waste can be reduced even more, all the way down to using virtually all the good paper produced on each reel.
PCI’s design utilized the customer’s existing PLC (Allen-Bradley PLC 5/60 ) for the control system. The control of two winders and the reel sizing system were added to the existing program. This design performs precise automatic analysis of paper roll density in order to predict how much paper is needed to make a roll of any set diameter. The system stores critical data from analysis of each class of paper for future reel sizing. It incorporates an operator’s terminal that allows the operator to set the reel sizes to whatever is needed by the winders to produce precise roll sizes. The system initiates reel turn-up at the proper time to produce the desired reel size. The system remembers data related to each reel. Upon command it transfers the data to the winder operator’s terminal. The data is used by the winder operator to setup the winder to produce the required roll sizes leaving minimum waste on the reel spool.
PCI worked with the paper company’s personnel to customize the operator’s terminals to function according to their requirements. Ease of operation was a premium factor.
The system design and installation was accomplished with no paper machine down time.