Metals

When a company is considering making an investment of more than a million dollars in system upgrades, it is crucial for them to review all options to get the best return. By exploring energy efficiency impacts throughout the entire compressed air system, vendors can propose projects resulting in both a larger sale for them and increased financial benefits for their customers, while still meeting capital expenditure guidelines. This “best of both worlds” scenario was evident when a foundry in the Midwest was evaluating options for replacing its steam system used to drive the plant’s forging hammers.

EnSave, an energy auditing company based in Richmond, Vermont, recently performed compressed air audits at two facilities of a leading U.S. steel manufacturer. Both plants are mills that melt, cast, and roll steel to produce a variety of products, including: rebar, merchant bar, steel flats, rounds, fence posts, channel bar, steel channels, steel angles, structural angles and structural channels. These products are used in a diverse group of markets, including: construction, energy, transportation and agriculture. Compressed air is provided at 100 psig in both plants for a variety of applications — from optical sensor cooling to pneumatic cylinders for stacking finished products.

A major Midwestern aluminum plant was experiencing dwindling compressed air capacity, primarily due to air leaks. If those capacity issues went unresolved, the facility would have needed rental compressors to keep up with demand. Instead, they turned to flow metering to identify and fix the leaks. In this article, they share their solutions with others who may be having similar difficulties.

Compressed air use in the metal fabrication industry is widespread. It is used to cool, clean, convey and coat a multitude of products and improve processes across the world. In fact, it is difficult to name processes in metal fabrication where compressed air cannot be found. A few processes where compressed air is used include: annealing and pickling, slitting, rolling, welding, stamping, punching, tube making, painting, finishing, turning, drilling, milling and sawing. Many of these processes and applications continue to use inefficient devices to deliver the compressed air, and — worse yet — many companies fail to recognize the simple implementation and significant payoff of improving compressed air efficiency.

Nissan North America operates on a massive scale. The company’s powertrain assembly plant in Decherd, Tennessee, alone encompasses 1.1 million square feet, and manufactures engines for 14 different vehicles. The facility also handles crankshaft forgings, cylinder block castings, and other machining applications. Over the course of one year, the powertrain plant churns out approximately 1.4 million engines, an equal number of crankshaft forgings, and 456,000 cylinder block castings.

Quite a number of worst-case compressed air scenarios have been encountered over the years but none may compare to the conditions that existed in a metal foundry somewhere in North America. For reasons you are about to discover, we will not reveal the name of this factory or its location, in order to protect the innocent from embarrassment.

This metal fabrication and machining facility produces high-quality precision-built products. Over the years, the plant has grown and there have been several expansions to the current location. The company currently spends \$227,043 annually on energy to operate the compressed air system. This figure will increase as electric rates are raised from their current average of 9.8 cents per kWh.

As you walk past the “sandblasting cabinet” back in the corner of the plant running alone and without the need for monitoring, does the thought of operational costs enter your mind? When it does, are you happy knowing the cabinet is automatic and does not need a full-time operator? Then, did you say to yourself, I wonder how much that abrasive media costs? How long does it last? Is this a more cost competitive alternative? Is there something that might last longer?

TIGG Corporation, a manufacturer of activated carbon adsorption vessels, custom air receivers and other steel tanks and pressure vessels, substantially reduced its energy costs after implementing equipment, labor consolidation and procedural changes resulting from a compressed air energy audit. The audit was performed at TIGG's 155,000 square feet manufacturing facility in Heber Springs, Arkansas to determine the efficiency of the existing compressed air system and to set a baseline for TIGG's participation in Entergy Arkansas’ Large C&I Custom Incentive Program.

Air gauging relies on a law of physics that states flow and pressure are directly proportionate to clearance and react inversely to each other. As clearance increases, air flow also increases and air pressure decreases portionately. As clearance decreases, air flow also decreases and air pressure increases.