U.S. Department of Energy - Energy Efficiency and Renewable Energy

Industrial Technologies Program – BestPractices

CASE STUDY - THE CHALLENGE: IMPROVING VENTILATION SYSTEM PERFORMANCE AT A METAL PLATING FACILITY

Summary

Lockheed Martin Armament Systems was looking for a way to improve the performance of the ventilation system in their Lakeside Avenue industrial plating plant in Burlington, Vermont. By utilizing variable frequency drives (VFDs) and making other modifications to the system, they were able to improve the plant's overall operating efficiency, reduce costs, and improve the work environment and worker health and safety. This Motor Challenge Showcase Demonstration Project has resulted in annual savings of more than $68,000, with a payback of just under one and a half years. Since the project was completed, General Dynamics Armaments assumed ownership of the facility.

Plant Overview

The Lockheed Martin Vermont facility, classified as Small Arms (SIC 3484), primarily manufactures armament systems as well as munitions, fire control systems, and advanced weapon systems sold domestically and to U.S. allies abroad. The Lakeside Avenue plant is headquarters for Lockheed Martin Armament Systems, Lockheed Martin Ordinance Systems, and accommodates the engineering and administrative staffs and a 470,000-square-foot plant dedicated to machining and assembly operations. The plating plant is a small facility attached to the main plant.

Project Background

Concerned with rising overhead rates, Lockheed Martin management targeted energy expenditures as a prime opportunity for cost savings. At the Burlington facility, electrical costs are more than 10 cents per kWh, the highest of any Lockheed Martin plant in the country. The company had considered installing a cogeneration system to supply the plant with electricity and thermal energy, but the payback was calculated to be more than six years. Instead, the company decided to undertake a variety of projects to improve the performance and efficiency of their plant systems. They began by specifying energy-efficient motors and retrofitting their lighting systems with energy-efficient tubes and ballasts. With these projects completed, they targeted the plating operation ventilation system as their next opportunity.

Project Team

To implement this complicated project most efficiently, Lockheed Martin put together a project team. This team involved not only Lockheed Martin personnel, but staff from other organizations including: Burlington Electric (electric metering), GE Motors and Industrial Systems (adjustable speed drives), Johnson Controls (energy management system), the U.S. Department of Energy's (DOE) Motor Challenge (energy savings validation), electrical and mechanical engineering firms and contractors, and motor system equipment manufacturers and distributors.

The Old System

A wide variety of small and large machined metal parts - from small firing pins to 12-foot-long gun barrels - are plated, anodized, finished, and cleaned at the facility. The plant consists of nine plating production lines with 64 tanks handling 19 different plating processes. The existing ventilation system, which has been in use for more than 25 years, was designed for continuous 24-hour operation. Currently, however, the plant is only operating one shift per day. In addition, current production patterns sometimes require a different combination of tanks to be used on any given day.

The constant volume ventilation system provides exhaust for lateral hoods over the plating dip tanks, and prevents toxic fumes from escaping from the tanks into the workers' area. It draws air into the hoods through a series of interconnecting ducts and forces the air outside. To meet EPA Title V Clean Air Act requirements, the exhaust air may pass through a demister and/or filter or scrubber before exiting the system, depending on the chemicals in the airstream. Makeup air is provided by rooftop ventilating units that use direct-fired gas heaters to maintain building temperature. The system has 10 motors ranging in size from 5 to 100 horsepower.

The system had undergone detailed review and numerous modifications and upgrades over the past few years. These included a motor survey, airflow measurements, hood modifications, the addition of side shields to eliminate cross drafts, increasing duct size, and balancing the system to optimize the draw at each hood.

Alternatives Considered

Plant staff considered a number of alternatives to further improve system performance, including the use of floating balls to reduce emissions and therefore the need for ventilation. This proved to be impractical, however, because many of the parts being plated have complex shapes and others are dipped using baskets. The balls became stuck in the parts and the baskets. Covers for the dip tanks were also considered, but they proved difficult to use. Other options included the use of two-speed motors and variable sheaves. The two-speed motors did not offer enough flexibility, and maintenance requirements on the variable sheaves were too high due to the location of the fans. The best solution proved to be the addition of variable frequency drives, which permit variable-speed control of the motors driving the ventilation fans. This allows the ventilation supplied by the fans to be matched to needed levels at any given time automatically.

Project Implementation - The Systems Approach

One of the keys to implementing the project was the determination of relevant industrial ventilation safety standards, which allow for tanks to be ÒreclassifiedÓ when not in use. This means that when a tank is idle, the liquid temperature inside can be decreased and the ventilation supplied to the tank can be substantially reduced. The requirements for each tank were examined individually to the OSHA/ACGIH ventilation requirements, since ventilation needs are largely determined by the type of chemical in the tank.

During the installation of the VFDs, Lockheed Martin also decided to install a new energy management system (EMS) in conjunction with the VFDs. This was done so that the motors could be controlled as a system. The EMS also allows a trending capability and has the capacity to control the entire facility.

The New System

The new variable-output ventilation system includes nine electronic VFDs which reduce ventilation during idle times. VFD line reactors have been installed along with the drives, and the entire system is controlled by the new EMS. Flow has been reduced to 55-65 percent of full speed during idle times. The system also features manual safety overrides and a failure analysis system with an automatic shutoff. Numerous sensors and control points have been added to better monitor and control the system.

Results

The plating tanks are monitored for operating temperature to control the exhaust and air makeup units. During working hours and off-shift hours the EMS detects unused plating lines and reduces the exhaust and makeup air supply.

Benefits of the new system include a 38 percent cost reduction in electric and natural gas utilities, emergency ventilation control, fewer emissions, and improved system control. The project cost approximately $99,400 to implement and has resulted in annual savings of more than $68,000, providing a simple payback of just under 1.5 years. Key to this low payback is the dramatic reduction in VFD costs over the last few years.

Lessons Learned

In addition to the economic and operational benefits of the project, a number of lessons were learned that can be applied to similar projects: (1) the EMS is essential for balancing air flows and pressures for safe operation and as a diagnostic tool for troubleshooting; (2) line reactors may be necessary before and after the drives to reduce noise and improve motor life; and (3) connecting VFDs to rewound motors may cause premature motor failure due to excessive VFD voltage spikes and noise levels. Replacement of motors with high efficiency or inverter-rated motors, or utilizing higher voltage-rated wiring from the VFD to the motor should be considered.

Other Applications

The technology used for this project can be applied to any ventilation or fan system requiring variable output to meet changing demands. Other possible fan applications include climate control systems, laboratory ventilation systems, and draft fans used for boilers and furnaces. VFDs can also be used to improve performance on other systems like blowers, pumps, compressors, grinders, mills, and conveyors. Estimates show that use of VFDs nationwide could result in energy savings of up to 99 billion kWh.
Document Number: ORNL/MC-CS1
Publication Date: August 1996