Fluids handling: a Solutions! roundtable: this roundtable examines how automation changes the use and maintenance of pumping systems and the prospects for energy savings from more efficient pumping systems.
* Fredrik Eide, Products and Applications Manager, ABS Pumps, Moldnal, Sweden
* Pekka Haapanen, Marketing Manager, Pulp and Paper Industry, Sulzer Pumps Finland Oy, Karhula, Finland
* David Peschell, Global Marketing Manager, Goulds Pumps, Seneca Falls, New York, USA
* Jyrki Uimonen, Managing Director, Ecopump Oy, Kotka, Finland
SOLUTIONS! How is automation changing the use and maintenance of pumps?
EIDE: Automation allows papermakers to use pumps in the best possible way. Operators have a greater opportunity to change the process. For example, they can optimize the power needed from the motor or pump. This can save thousands of euros per pump per year. with the right automation, pumps require less maintenance, experience fewer operating problems, and have less downtime.
Maintenance automation based on predictive maintenance can further optimize pumping systems.
UIMONEN: In vacuum systems, the first application is to build automatic systems to control the vacuum level in the suction position at a set value. This is a very straightforward arrangement and is in use in modern machines. Older machines can also benefit from automation with the proper piping and instrument dimensioning. More advanced systems that control vacuum levels using the dewatering rate as input are becoming more common. These systems require a thorough understanding of system dynamics and reliable components.
PESCHELL: Automation is replacing the old manual monitoring and controlling of pumps. Increasingly, pumps connect to other process equipment for control and monitoring by dm mill distributed control system (DCS). This has led to more sophisticated monitoring for predictive rather than preventive maintenance.
HAAPANEN: Medium consistency stock is typically 10%-18% consistency. This stock requires fluidizing for pumping the fiber network needs disruption so the stock flows like water. The air content in the medium consistency stock can be 10%-40%. This requires removal.
One effective control system measures the stock level in the inlet tank (drop leg). The flow rate through the pump is adjustable depending on the circumstances by a control valve, by changing the speed of the pump, or by applying both methods. The level controller keeps the stock level in the drop leg constant. It does not allow the level to drop or to enter previous equipment such as the washer. This provides stable process operations. A separate or built-in degassing system can adapt itself to the respective volume of air contained in the stock and to the flow rate. Also, remote monitoring systems can be used in critical pumping systems to monitor and gather pump and system-specific data. This data can be used for predictive maintenance, problem solving and system improvement.
SOLUTIONS! As mills cut costs, how can they generate energy savings from pumping systems?
EIDE: Continuously evaluating pumping systems through an energy conservation study and life cycle cost analysis can reduce energy costs by 10-30%. Examples include:
* Optimizing impeller diameter
* Installing variable frequency drives (VFDs)
* Changing pump size
* Using original spare parts
* Integrating the seal in the pump design
UIMONEN: One goal is to pursue process optimization. The intent is to match the optimized process vacuum needs and pump system. For example, our company has worked on an optimization program at Bowater Thunder Bay with a realized power saving of 1.5 MW and water saving of 700,000 m3/yr (175 million gallons). Speed controlled vacuum pumps can also produce significant power savings-up to 30%-60%. We clearly see this as the future of vacuum systems, and it has impact in other pumping systems, too.
HAAPANEN: One approach is to examine shaft sealing closely. Mechanical seals, cord packing, and dynamic seals are the typical shaft sealing solutions for the pulp and paper industry. Conventional cord packing and mechanical seals will wear due to mechanical friction and wear and will eventually form a path for leakage. These seal types require a steady supply of sealing liquid for, lubrication and cooling. This liquid often comes from an outside source. These seals also need regular monitoring and maintenance.
Dynamic seals do not have these disadvantages. With time, they have the lowest total operating costs. Many pumping problems begin with air or gas contained in the liquid. If the liquid for pumping contains approximately 4% free gas or air, a conventional centrifugal pump can usually pump it. The flow rate, head, and efficiency of the pump decrease as the gas or air content increases. Pumping may also cease completely. Gas removal pumps that remove gas or entrained air can maintain optimum pumping and prevent pumping disturbances. They help improve operations and reduce operating costs.
PESCHELL: Electric motors and pumps have reached levels where further efficiency improvements will be difficult to achieve. The U.S. Department el Energy and paper mill managers now recognize that energy saving potential will come from developing a "smart design." Pumping systems that are oversized waste valuable energy in control valve modulation that eclipse any incremental savings from pump or motor efficiency gains.
Key developments involve the design of smart pump systems using VFDs with embedded pump logic, allowing the pump itself' to become the process regulation device. This provides a higher degree of pump protection and reliability. These systems pay for themselves in less than one year and produce savings for the mill maintenance budget.
PROBLEMS AND SOLUTIONS
Sulzer Pumps reports that older pumping systems can be upgraded without replacing entire pumps. For example, Sulzer in stalls Medium Consistency (MCE[tm]) retrofits to existing MC pumps to produce improved process economy and increased production rates. For example, a bleach plant with a pressurized peroxide stage wanted to increase bleaching efficiency by increasing the reactor temperature and the pressure to 3 bar. The bleach plant upgraded its existing 250 kW, 2220 rpm medium consistency pump with a new, third generation MCE pumping systems. The new system required only a new rotating unit. Motor size remained the same, but the pump speed decreased to 1920 rpm. This increased expected pump life. The increased bleaching efficiency produced substantial cost savings.
ABS Pumps said that many pumping problems originate in oversizing, entrained air in the pulp, and plumping of hot liquids. Using a smaller pump or installing a variable frequency drive can solved the oversizing problem. A pump with a deaeration system matched to consistency and the amount of entrained air will solve that problem. Increased temperatures in pumping systems can cause cavitation problems and increased maintenance. One answer is to increase the Net Positive Suction Head (NPSH) available or for pump manufacturers to supply better (lower) NPSH values.
Ecopump redesigned the vacuum system of board machine 4 at Stora Enso Kaukopaa mill in Imatra, Finland. The machine produces approximately 35 metric tons/h of liquid packaging board. In 2000, Ecopump Oy optimized and modernized the vacuum system of the machine and installed new vacuum connection Ecoflow press section dewatering control and Ecodrop droplet separators. According to Ecopump, the results include the following:
* Energy savings of approximately 1000 kW equaling EURO 210,000/year
* 20 kPa higher vacuum level in the couch roll with 1%-2% higher dryness after the wire
* Improved droplet separation and less humidity to the hood.
Goulds Pumps noted that pulp mill bleach plants often modulate medium consistency pulp flow with energy consuming control valves that inefficiency regulate pump flow. Modern pump systems now connect with level measurement devices, consistency transmitters, and pump speed adjustments drives. These provide a more reliable system to compensate for production swings. Goulds Pumps has installed PumpSmart[tm] control system in several mills that combine variable frequency speed control with a dedicated pump protection logic that eliminates custom programming and provides a high degree of upset protection.
IN THIS ARTICLE YOU WILL LEARN:
* How automation has helped make pumping systems mere reliable
* How a properly optimized process can match vacuum needs and a pumping system
* ABS Pumps: www.abspumps.com
* Ecopump: www.ecopump.fi/
* Goulds Pumps: www.gouldspumps.com
* Sulzer Pumps: www.sulzerpumps.com
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|Publication:||Solutions - for People, Processes and Paper|
|Date:||Jan 1, 2003|
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