Energy costs are typically a major component of overall operating and maintenance (O&M) costs in surface finishing plants and have a significant impact on plant profitability. Many plating plants in North America are aging, and equipment is in poor condition and inefficient. Much of the equipment in these plating plants is obsolete and based on old design principles. There are substantial opportunities for cost savings in a modern, renovated or constructed plating plant by planning for energy efficiency in plant design. A well designed plating plant will be optimized to reduce not only energy usage but all manufacturing wastes.
Energy is consumed in surface finishing processes in a variety of ways, including: process solution heating and cooling, part drying, fluid transfer, material handling, rectification, solution agitation and filtration, ventilation and makeup air processing, and water and wastewater treatment. Assessment of these existing processes provides information for estimating the savings/payback opportunity for energy efficiency process improvement.
General approaches to reducing energy usage include:
• Right-Size Equipment: Tanks and other equipment are often oversized, and smaller equipment can often meet process needs at much lower energy load. Oversized fans and blowers can waste enormous energy.
• Orient Process Tanks Vertically: Vertically oriented tanks have a lower open surface area to volume ratio than horizontal tanks and heat loss and ventilation requirements are reduced.
• Manage Process Readiness: Process equipment can be cycled automatically between inactive, standby, and active operating modes, based on the production schedule, so that processes are ready for production only when needed and energy usage is minimized when there is reduced or zero production demand. Operating variables that should be controlled include: process solution temperatures, agitation, filtration, and ventilation.
• Optimize Time, Concentration, and Temperature: Optimize process solution concentration and temperature and cycle time balance for synergistic impacts on heating & cooling, ventilation needs, solution dragout, operating hours, and production throughput.
• Optimize Plating Current Density: Plating efficiency varies as a function of current density and solution operating parameters.
• Manage Process Solution & Rinse Agitation: Process solutions are often over-agitated and rinses only need to be agitated when parts are in the rinse tank. Use more efficient regenerative blowers rather than compressed air for agitation.
• Use Push-Pull Ventilation: Push-Pull ventilation operates at lower ventilation rates and is often more effective when ventilation systems are designed correctly.
• Insulate Process Tanks & Piping: Generally tanks and piping operating with fluids ≥ 140°F or below 70°F should be insulated for energy efficiency.
• Minimize Piping & Ventilation Duct Runs: Optimize piping layouts to reduce the total length of plant piping runs and minimize heating & cooling losses and pump energy. Optimize ventilation duct layouts to reduce fan energy.
• Utilize Automatic Tank Covers: Automatic tank covers and ventilation dampers can be integrated to ramp down ventilation when covers are closed to minimize surface heat loss and ventilation requirements. Covers are normally open only when loading and unloading process tanks.
• Design Part Dryers for Energy Efficiency: Design dryers with air recirculation. Avoid the use of compressed air for part blow-off. Right size fans and blowers.
• Replace Inefficient Equipment: Energy efficient pumps, fans, and motors can be well worth the investment. Incremental gains in the efficiency of rectifiers can be worth the investment. Older boilers, chillers, and compressors are notoriously inefficient.
• Optimize Work Flow: Arrange processes for good overall work flow and material handling efficiency.
• Maintain Equipment: Equipment that is leaking, wearing out, improperly installed, or past due on maintenance can result in significant increased energy consumption and reduced equipment life.
• Keep a Clean House: Good housekeeping is one of the best investments a plant can make. Regular equipment wash-down can mitigate the effects of equipment exposure to corrosive chemicals, maintain peak performance of equipment and extend equipment life.
• Minimize Rework: All energy used in rework is a waste.
Energy efficiency should be assessed process-by-process, and systematically over entire surface finishing process and support system areas, to identify a full range of improvements and cost-savings potential. It is important to quantify existing process energy usage and costs and compare on a life cycle basis to proposed process improvements. Investment in process automation and control systems can provide excellent returns, with increased ability to efficiently manage overall process systems and reduce energy usage.
Surface finishing energy efficiency projects should consider energy usage, losses, and efficiency and the potential for improvement in:
• Piping systems – solution circulation and transfer, steam, condensate, chilled water, hot water, low pressure air, compressed air
• Process tanks – surface, sidewall, and bottom losses
• Process heating and cooling systems
• Boilers, chillers, and compressors
• Process ventilation and makeup air systems
• Process automation and control systems
• Process operating ranges – chemistry and operating temperature
• Hoists and other material handling systems
• Rectifiers and bussing, flight bars, and saddles
• Anodes and cathodes
• Process solution pumping, filtration, agitation, and purification systems
• Part drying and heat treatment systems
• Fans and blowers
• Plant HVAC and lighting systems
Project energy reductions, and other cost savings, depend on existing and planned future surface finishing processes and production requirements; age and condition of existing equipment; process area and facility usage flexibility and constraints; project funding availability; and project phasing logistics. Overall energy improvement project return on investment is often enhanced by other benefits that can simultaneously be gained with effective process improvement practices, well-designed equipment, and automation systems, including: reduced labor, materials, water, wastewater, hazardous and nonhazardous waste generation, and improved production capacity, capability, reliability, flexibility, and efficiency. It is important to take an integrated look at overall savings potential in order to reap the maximum benefits from an energy-efficiency improvement project and to allow the best potential for continuous process improvement and savings.
ITI is a global consulting, engineering, and design-build firm based in Burlington, Vermont. We specialize in manufacturing processes, water and wastewater treatment, recycling, and ventilation applications for the metal and surface finishing industry.