Metals

Plant personnel had experienced ongoing problems with its process grinder performance due to unstable compressed air pressure. This created potential problems in terms of product quality. Grinders do not work properly without the proper pressure. Additionally, plant staff wanted to address these concerns, prior to a proposed 30% increase in production, and suggested raising the header pressure from the current operating pressure of 98 psig to 125 psig. The thought behind this was if the pressure from the header to the grinder process was dropping to 63 psig, then raising the pressure to the process would give the grinders enough pressure to work through higher peak production times.  

The steel mill in this article is a rolling “minimill,” a facility that melts scrap recycled steel and produces rebar for the construction industry. It fits in SIC code 3310. There are many plants like this all over the world, providing an environmentally sound service and product for their local community. They recycle waste steel from local sources and support local infrastructure projects with rebar, using electricity generated locally.

All industrial facilities use some form of compressed air, and in most, the air compressors consume a significant amount of the total energy bill. A facility with a good energy management system is likely to identify their compressed air system as a significant energy user (SEU). If the facility were using an energy management standard, such as ISO 50001, they would be required to assess and track the energy consumption of all their SEU’s. In the case of the metal processing facility, they were measuring the output of more than 250 devices within the plant, including building heaters, RTU’s, dust collectors, and also tracking the consumption of their electricity, natural gas and water. 

Chicago Heights Steel, Chicago Heights, Ill., leveraged an advanced data monitoring system and adopted a demand-based compressor air management approach to save 2.5 million kWh and \$215,037 per year in energy costs. With an incentive of \$188, 714 from local utility ComEd, the project delivered a payback of 2.4 months.

Factory lasers use nitrogen right at the cutting point on the metal because the high temperatures used in the process can often cause oxidation. When oxidation occurs, the metal pieces being cut can be damaged, as can the tooling creating the cut. Structural damage or inaccurate cuts can make parts weak and render them useless. The use of nitrogen at the point of contact from laser to metal removes oxygen from the cutting area and helps cool the die as it cuts, thus preventing oxidation. This prevention improves the quality of the final products, produces less scrap metal and cuts back on the reworking of pieces.

A zinc producer spends an estimated \$516,000 annually on electricity to operate the air compressors in a compressed air system at its north American plant.  The current average electric rate, at this plant, is 5 cents per kWh, and the compressed air system operates 8,760 hours per year. This system assessment recommended a group of projects able to reduce these energy costs by fifty-one percent (51%) to an annualized \$270,000.  The simple payback of the project was 15 months – without taking into account potential incentive dollars from the local utility.

While late summer may not be the time of year many of us think about heat recovery, the potential for energy savings in compressed air systems should be on our minds year-round. For those involved with the compressed air systems within International Wire Group’s facilities, energy savings is on their minds each day. This culture of continuous improvement has everyone on the lookout for savings wherever possible.

A steel distribution and processing company has upgraded and consolidated the compressed air systems in two of their distribution and processing facilities for big energy savings. The previous compressed air systems were running in modes of operation with very low efficiency. A complete replacement of the two systems with new air compressors and dryers has reduced the energy consumption significantly.

The facility uses a large amount of electricity to manufacture laminated glass in the autoclave process. This process is the largest consumer of compressed air in the facility which made compressed air a major target in reducing energy costs for the facility. As the volume of compressed air in the autoclave is significant, the system is constantly pressurized with large 150 HP air compressors to reduce production times and fill times of the autoclave.

The company specializes in fabrication of precision assembled customized parts for OEM’s and system integrators. Since 1997 the company has steadily grown in size and capacity as the demand for its high quality fabrications has increased.  Through the years, many new CNC machines, laser cutters and powder coat painting operations have been added, but with all the expansion the facility has amazingly kept the plant compressed air consumption low. This has been achieved by following excellent “best practice” compressed air efficiency principles and by keeping watch on system waste.