Situated in an industrial park that was once a World War II supply depot, Lifetime Products Inc. (Clearfield, UT) is a major producer of plastic products such as residential basketball equipment, folding tables and chairs, and outdoor storage sheds. Their products are made with high density polyethylene pellets that are delivered by rail cars that travel through the industrial park daily. From the exterior, Lifetime’s two-story building seems ordinary, yet inside is one of the most sophisticated, energy-efficient plastics processing plants in the country.
For most plastics plants, maintaining the continuous process of cooling machinery and tooling takes an enormous amount of power and refrigeration. Lifetime was operating four separate water systems that were purchased over the years through AEC, Inc. (Wood Dale, IL), a longtime equipment partner to Lifetime and a leading provider and integrator of plastics auxiliary equipment.
Lifetime consolidates chiller system to conserve electricity
As the Lifetime facility reached maximum capacity, the company began looking for ways to run the plant more efficiently to conserve electricity. Michael Mueller, AEC corporate account manager, advised Lifetime to consolidate its four chiller systems and four cooling tower systems into one highly-efficient cooling system for the 120,000 square foot plant. The combined systems provide over 890 tons of refrigeration and 1500 tons of cooling tower water.
Lifetime would also receive a financial benefit from the state of Utah. As one of the largest users of power in the state, it was to Lifetime’s advantage to streamline their power systems and conserve energy. In turn, this would alleviate the Utah Power Company from adding additional infrastructure to support the power usage and could therefore pass along savings to Lifetime.
The two companies agreed on installing a new cooling system, a modular pump tank system and a motor control center incorporating a programmable logic controller (PLC) for data collection from sensors and output devices. Adams also wanted to incorporate existing energy conservation programs in the plant, such as standardizing on Baldor high-efficiency motors and upgrading chiller technology to rotary compressor design.
Improved communication with process control sensors
"To monitor process control, I recommended the ‘ifm efector upgrade’ for system feedback," said Mueller. ifm efector inc. (Exton, PA) manufactures a complete line of electronic fluid control sensors and switches with communication capability. Lifetime was already familiar with ifm efector and their line of level sensors that had been used on their conveying systems for years. By applying ifm fluid sensors, Lifetime would receive consistent programmable setup, alphanumeric displays, small housings, and analog and switching outputs.
Monitoring differential pressure for preventative maintenance
 AEC’s heat exchangers transfer the coldness of the Winter-Kooler tower water to the process loop without mixing the two flows. Differential pressure across the heat exchangers is monitored. AEC installed ifm efector’s PNI differential pressure monitoring system for monitoring cleanliness of the heat exchangers on the tower side (shown in photo). A pressure sensor and a pressure transmitter are installed on either side of the heat exchanger and are connected with a 5-meter patchcord. The system continuously monitors the heat exchangers and sends a signal to the PLC when pressure drop increases indicating the accumulation of scale or dirt. Lifetime uses this sensor system as a preventative maintenance tool and can clean heat exchangers before an equipment failure occurs.
Temperature feedback on chiller and tower systems
 For fluid temperature feedback on the chiller and tower systems, ifm efector’s temperature monitors and remote sensing probes are used. The monitor is installed on the outside of the tank and its remote platinum Pt100 resistive temperature detector (RTD) probe is installed directly in the tank. The large numeric display indicates process temperature.
For level control on the tanks, ifm efector’s compact pressure sensors are used. The sensor is installed at the bottom of the tank to provide liquid level (shown in photo). The weight of the liquid creates pressure on the sensor’s diaphragm. As the level changes, the pressure output changes. Lifetime sets the large, 3-digit display to read in inches of water.
Modular pump tanks improve efficiency
AEC designed pump tank assemblies for the cooling towers and central chilling systems. An existing tank was used for the Winter Kooling system. Several 30-, 40- and 75-hp centrifugal pumps that circulate the process cooling water are placed four pumps per deck. "Rather than installing one or two enormous pumps, we provided multiple, modular pumps," said Mueller. "Our customers can maintain the equipment much easier and troubleshoot more efficiently," he added. The pumps are used in an alternating schedule to minimize wear and extend their life. Variable frequency drives ramp capacity up and down depending on Lifetime’s current loads. PID control loops cycle pumps on and off-line as required.  The pump tank assemblies feature stainless steel reservoirs, Baldor high-efficiency motors with variable frequency drives, and full sized valving and the multiple ifm efector sensors. Each pump is equipped with automatic standby. ifm efector’s PK pressure switches (shown in photo) are used for "pressure on" detection. If the sensor reads "no pressure" from the pump, the PLC will turn on a standby pump. The PK switch’s strain gauge sensor element is rated for over 50 million switching cycles. Setpoint and resetpoint values are established using the switch’s two rotating dials that can be set without system pressure and supply voltage. LEDs provide status indication.
Higher efficiency results in dramatic savings
By giving the chilling system a rest for several months out of the year, Lifetime prolongs the life of the chillers while still maintaining the same, consistent process temperature. Lifetime has been using the new cooling system since March 2005. The energy-efficient system has saved the company tens of thousands of dollars and provided a comprehensive feedback control system for the plant.
"Integrating continuous feedback from sensors is a growing trend in the plastics industry," says Mueller. "Fortunately, there is a transition going on as equipment prices come down and customers learn what these sensors can do."
AEC takes a fresh approach in designing these systems for their customers. Mueller states, "We listen to what our customers want and help them decide what will work best for their process. We recommend modular systems to our customers so that they can add equipment, controls and sophistication as their company grows."
More information - PNI Differential pressure sensors
More information - PK pressure sensor
More information - Temperature sensors
More information - Pressure sensors for level control
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