PMT: On the Cutting Edge of Energy Innovation March 2013

EL PASO, TEXAS— A growing concern for today’s manufacturers across the industry spectrum, energy consumption continues to be a prime target for improving sustainability practices.

The focus of much of this concern is on the plastics industry, due to its considerable energy usage and often untapped potential for energy savings. With annual energy consumption in the 1,070 trillion Btu range, plastics manufacturing contributes to 6% of overall U.S. industrial energy use, according to the U.S. Department of Energy. However, the American manufacturing sector is pushing more toward sustainability. Total energy consumption saw a 17 percent decrease from 2002 to 2010, according to new 2010 Manufacturing Energy Consumption Survey data released earlier this year by the U.S. Energy Information Administration.

In response to the need for action, El Paso-based Plastic Molding Technology Inc. has implemented environmental best practices as part of the company’s continuous improvement efforts.

For example, PMT was the first business in the Paso del Norte region to voluntarily participate in the “Lean & Green” program, working with the Texas Manufacturing Assistance Centers (TMAC), the EPA’s El Paso Border Office, New Mexico State University and the New Mexico Manufacturing Extension Partnership (MEP). “Lean & Green” is part of the “E3: Economy-Energy-Environment- Supporting Manufacturing Leadership Through Sustainability” initiative, which uses a Lean and Clean approach to identify and eliminate waste—defined as non-value added activities—through continuous improvement while lessening environmental impact.

PMT now uses this approach throughout the factory, whether processing parts composed of recyclable plastics, blending plastic regrind into new material or assigning reusable containers to customer orders. PMT has also implemented more cost-effective ways of using energy by improving operational techniques and adding state-of-the-art equipment.

The E3 program impacted PMT’s environmental footprint, leading to a 187,725 kWh reduction in energy usage, along with a overall reduction of 56 tons of solid waste and 126 tons of CO2. The plants made strides in saving energy, but one culprit of substantial energy consumption still remained.

Three years earlier, PMT participated in an Energy Efficiency Opportunity Assessment with the El Paso Electric Company’s Commercial Solutions Program. Several energy conservation measures were recommended, but most notable was the 425,220 kWh estimated annual energy savings that would come with installing on/off controls on PMT’s 40 granulators.

The granulators, commonly known as plastic grinders or regrind machines, are prevalent energy consumers in the plastics industry. The machines grind the excess plastic from the molding process into a reusable pellet form. At PMT, the grinders were on continuously, though the need for use was intermittent—as little as 5 percent or less of total production time.

This gap between machine usage and corresponding energy consumption led PMT’s maintenance engineer John Getlein and Clark Energy Group’s senior energy engineer Kevin Carpenter to create a solution.

The issue concerning the effectiveness of grinder controls extends across the industry. Commercially available grinder controls exist, but are not conducive to fast-turnaround or just-in-time production goals. Common controls on the market consist of a proximity sensor, which starts the motor when plastic parts are present for grinding, and a vibration detector, which turns off the motor after a specified amount of time lapses without material being ground. These controls are commonly prone to user error. A problem persists when production staff loads a large amount of scrap before the motor reaches peak speed, jamming the blade. The controls are also often overridden or disabled to avoid maintenance and productivity issues.

Getlein and Carpenter conducted an innovative pilot project at PMT, studying a representative sample of 6 out of the total 40 grinders on the factory floor. After a two-week sample period, the logged data indicated the motors drew substantial power—between 25 to 50 percent of full-load power—when idling. Grinding was taking place a mere 2 to 3 percent of the entire logging period.

Out of their research and consideration of current market-available controls, a novel control system was designed, constructed and implemented on the representative sample of grinders. The control system was user-interactive, turned on via a start button. A green light illuminated when the motor reaches a safe speed for loading; a red light illuminated when the machine is off, upon motor start-up or when the motor is overloaded. After two minutes of idle-amperage detection, the motor would shut off automatically.

After retrofitting the controls, the same 6 grinders were using 6,660 less kWh in a two-week period. The total energy savings during this trial period was an impressive 96 percent.

The energy saving results led Getlein and Carpenter to install the control system on all 40 grinders at PMT. The research from the successful pilot project concluded the control system substantially reduced grinder idling time without compromising functionality. The system saved over 95 percent of grinder energy use, with no machine jams or maintenance time.

The annual energy savings results further proved the control system impacted the plant’s energy consumption: extrapolated energy savings were 891,395 kWh, more than double the original 425,220 kWh savings estimated by the Commercial Solutions Program. PMT also achieved an annual energy cost savings of $58,183. Each novel control system was built and installed for less than $1,000, resulting in a payback of less than nine months.

In addition to saving energy, the user-friendly controls gained favor among plant operators. The mechanism that alerts operators of the machine’s readiness to accept product is projected to reduce equipment maintenance costs.

 The development of these controls places PMT on the cutting-edge of energy savings during a time when the environmental impact of the plastics industry is being scrutinized. The effects of innovative projects like the grinder control contribute to a more energy-efficient and economical future for the plastics processing industry.