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Breakthrough Technology For Speed Control Ponderay Newsprint Usk, Washington Field Testing the MagnaDrive Adjustable Speed Drive on Northwest Industrial Applications Report on Pulp and Paper Field Test Site Ponderay Newsprint was searching for a way to improve the operational efficiency of its Usk, Washington manufacturing facility. After seeing a demonstration of the MagnaDrive Adjustable Speed Drive (ASD), the company agreed to become a test site in the Northwest Energy Efficiency Alliance test program. Application Overview The application selected for the test is a 250 HP, 1800 RPM motor running a centrifugal pump. The main issue to be addressed was significant wasted energy in the pumping of TMP whitewater to the pulping process and de-inking system. Typical operation of this process had the pump running at full speed (1780 RPM) through an elastomeric coupling on a constant 24-hour basis. A bypass valve around the pump was opened to maintain a constant 50 PSI of TMP water pressure on the line when valves downstream were throttling. The de-inking part of this system draws water from the pump for about 12 minutes an hour. During this time, the bypass was closed and flow was redirected to the de-inking process. For the remaining 48 minutes, the bypass stayed open and energy was wasted when TMP water to the de-inking system was not being used. To maintain constant pressure on the line, the bypass valve had to be opened to redirect the excess water back to the pump. The pump never had a reduction in flow and the motor never had a reduction in load. Energy demand remained at a constant 173 kW throughout these batch cycles. A VFD was not considered due to the higher costs associated with a 2300-volt motor system. Interestingly, the bypass valve was temporarily out of service during pre-audit prior to the MagnaDrive ASD installation. Because of this, the pressure was allowed to fluctuate during the de-inking cycles. Though not as restrictive a control as the bypass, this process also consumed excess energy. Additionally, when the de-inking system was not taking in water, significant vibration (up to .297 inches/second) caused by increased line pressure created excessive cavitation. “We are excited about the potential for this equipment and have budgeted for future applications throughout the plant.” Don Guenther, Energy Manager Ponderay Newsprint Test Site Ponderay Newsprint in Usk, Washington is a manufacturer of high-quality newsprint products. The company is owned by Bowater, Inc.– one of the world’s largest producers of newsprint and market pulp, and nationally recognized for its outstanding management practices, environmental policies and global competitiveness. Problem The pump was always running at full capacity during normal operations, resulting in cavitation and excessive vibration leading to maintenance problems. Energy was being wasted when water was redirected through a bypass valve to maintain constant pressure in the line. Solution The MagnaDrive ASD was installed on the 250 HP motor and TMP pump running at 1780 RPM. The ASD was chosen for this 2300-volt system because of its low equipment installation and infrastructure costs when compared to a Variable Frequency Drive. Benefits The MagnaDrive ASD eliminated the energy wasting bypass valve with estimated savings of 633,333 kWh/year in energy consumption worth nearly $19,000. Also, cavitation was eliminated and vibration was dramatically reduced, lowering long-term maintenance costs. Ponderay Newsprint has included MagnaDrive ASDs in its future operating budgets. Breakthrough Technology For Speed Control 12 min/hr 48 min/hr Amperage 46 Amps 46 Amps Flow 3200 GPM 1610 GPM* Pressure 50 PSI 50 PSI Motor Energy 173 kW 173 kW *1590 GPM redirected through the bypass valve This configuration did not reduce energy demand on the motor. The kW demand stayed at 173 kW and the pump flow rate was always 3200 GPM. Operating Process with Bypass Valve Figure 1 shows average flow, pressure and energy consumed by the motor during two complete batch cycles1. This is how the system operated using a bypass valve around the pump in order to maintain a constant line pressure of 50 PSI. During a 12-minute de-inking cycle, the line pressure would start to drop and the bypass would close to maintain constant pressure. At the end of this cycle when the system only needs 1610 GPM of TMP water, the bypass would open redirecting approximately 1590 GPM of water from the discharge back to the pump. 12 min/hr 48 min/hr Amperage 51 Amps 39 Amps Flow 3200 GPM 1610 GPM* Pressure 70 PSI 127 PSI Motor Energy 173 kW 145 kW Operating Process without Bypass Valve Figure 2 shows average flow, pressure and energy consumed by the motor during two complete batch cycles*. This is how the system operated with the bypass valve out of service. Pressure on the system was not controlled and was allowed to change with the changes in flow rate. The trend shows that for 12 minutes an hour when the de-inking system draws water, the pressure drops and kW demanded increase. During the 48 minutes of the cycle that the de-inking valve is closed, pressure increases and kW demanded decrease. *Graph data displays average actual data taken during onsite energy audits. 12 min/hr 48 min/hr Amperage 46 Amps 23 Amps Flow 3200 GPM 1610 GPM* Pressure 50 PSI 50 PSI Motor Energy 173 kW 65 kW Operating Process with the MagnaDrive ASD Figure 3 shows average flow, pressure and energy consumed during two complete batch cycles*. This is how the system operates with the MagnaDrive ASD installed. During the 12 minute de-inking cycle, the ASD is adjusted to maintain a constant line pressure of 50 PSI. The resulting energy draw during this phase is about the same as the system using the bypass valve. Energy is saved during the 48 minutes when the flow demand is less and the pump can be slowed down. *Graph data displays average actual data taken during onsite energy audits. 12 min/hr 48 min/hr Motor Energy With bypass valve 173 kW 173 kW With MagnaDrive ASD 173 kW 65 kWI Savings 0 108 kW Impressive Savings Ponderay considered a Variable Frequency Drive for this application but ruled it out because of the high installation expense and additional infrastructure requirements. Using an 18.5 size MagnaDrive ASD enables them to control the pumping process through variable speed and, at the same time, eliminate the energy-consuming bypass valve. The ASD is connected to the pressure control loop. By varying the air gap within the ASD, the pump’s speed is changed to maintain a constant 50 PSI. The pump runs at maximum speed during the 12-minute de-inking cycle. Figure 4 shows energy savings achieved with the MagnaDrive ASD versus the bypass valve. The pump is slowed down during the 48 minutes when flow demand is reduced. Energy demand drops to 65 kW – a savings of 108 kW representing 62% of the motor’s energy consumption. This reduces energy costs by approximately $18,800 per year, and potentially reduces costly demand charges. [BACK] FAQ | Contact Us | Home Copyright © 2008 MagnaDrive Corporation, All Rights Reserved.