“Retro-Commissioning” (ReCX) of compressed air systems has become a trendy activity with many utility demand-side-management programs emerging in the last 5-10 years. This is intended to be the process of “tuning up” a compressed air system, getting low cost savings from mostly adjustments and repairs. The term was borrowed from the building/HVAC industry, where it means to get a system operating as it was originally “commissioned”.
UniFirst is one of North America’s largest workwear and textile service companies. They outfit nearly two million workers in clean uniforms and protective clothing each workday. Founded in an eight-stall garage in 1936, the Company has grown to 240 customer servicing locations throughout the U.S. and Canada servicing 300,000 business customer locations. The subject of this article is an energy-saving Air Demand Analysis (ADA), conducted by Kaeser Compressors, at UniFirst’s centralized 320,000 square foot hub Distribution Center located in Owensboro, Kentucky.
Technology is available which enables a compressed air flow meter to measure not only the magnitude of the flow, but also the direction. Why is this important? In this article we will describe two case studies where bi-directional compressed air flow measurement plays a key role to come to the right conclusions. In the first case study, we will describe an electronics manufacturing plant, which has a large interconnected ring network with two air compressor rooms located in different buildings. The two air compressor rooms are about five hundred feet apart. In the second case study, the effect of compressed air flow measurement upstream of a local receiver tank is described.
At a Midwest window manufacturing plant, the cooling process for the plastic frame pieces, after leaving the extruder, was critical to process productivity and quality. Too much cooling air (or not enough cooling air) would generate scrap and rejected product. The plants’ 17 extruders and 55 separate blow-offs in these lines had similar cooling stations at the cooling boxes. They consisted of about three hoses at each exit frame angled down to the extruded piece moving past it. The compressed air flow was controlled by a manual control valve set by an operator. The operator used his experience to control the flow delivered and thereby control the product quality.
A Canadian chemical plant installed a large heated blower-purge style compressed air dryer, years ago, to condition the instrument air system against freezing temperatures. The dryer selected was oversized for the connected air compressors and had unused on-board energy savings features. A compressed air assessment revealed the site air compressors and compressed air dryers were running inefficiently and causing in-plant pressure problems. Repairs to a compressed air dryer and the replacement of aging air compressors and dryers has reduced compressed air energy costs by 31 percent.
This northeastern U.S. automotive manufacturing facility spends $269,046 annually on energy to operate their compressed air system. This figure will increase as electric rates are raised from their current average of .019 cents per kWh. The set of projects, in this system assessment, reduce these energy costs by $110,166 or forty percent. Reliability of compressed air quality, however, is the main concern in this plant and the primary focus of this system assessment.
Compressed air optimization measures adopted by PTMSB have reduced the consumption of compressed air by 31 percent resulting in savings of about 3,761,000 kWh per year in energy consumption. The monetary savings are MYR 1,090,627 per year ($255,000 USD). The CO2 reduction is estimated at 2,735 ton per year.
Energy, in all forms, has always been a key Lantech focus. It was, in fact, a key element of the core packaging problem the company’s founders set out to address. They saw an opportunity to capitalize on an inexpensive and under-used resource – stretch film – to displace a high materials cost and energy intensive way of unitizing pallet loads of products – shrink bagging.
Every municipality and utility is facing the reality of rising energy costs. In 2010, the Town of Billerica, MA, which is located 22 miles northwest of Boston with a population of just under 40,000 residents, engaged Process Energy Services and Woodard & Curran to conduct an energy evaluation of the Town’s Wastewater Treatment Facility (WWTF) and pump station systems sponsored by National Grid. The objective of the evaluation was to provide an overview of each facility system to determine how electrical energy and natural gas were being used at the facility and to identify and develop potential costsaving projects.
Air System Pressure Influences Compressor Power - Part 3: The Influence of System Pressure on Compressed Air Demand
Energy conservation measures (ECM) associated with compressed air have received a significant amount of attention over the years, mostly due to a reasonably short financial return compared with other energy consuming equipment. Over time many of the corrective actions put forward to reduce compressed air energy consumption have been simplified with the goal of encouraging action. Although this is done with the best of intentions, sometimes simplifications and generalizations do not necessarily lead to positive results. One of the most common energy conservation measures for compressed air that leverages best practice calculations involves reducing system pressure. It is the objective of this series of articles to highlight some of the more common issues associated with estimating energy conservation resulting from changing system pressure.
This article reviews portions of an audit report of a compressed air system in a food industry factory located in the U.S. Although the audit explored different supply-side options the client should consider to improve dynamic efficiency, we will focus on the demand side of the system for this article.
Compressed air audits are valuable exercises on significant energy users in a plant. Often done on main compressed air systems, these studies are also valuable on secondary systems, like dedicated low pressure circuits that feed production machinery. An audit of such a system turned up some surprising results on a process that was initially thought to be very efficient.
This brewery is a relatively large operation with nine production lines plus a keg line. There are five bottle lines and four can lines. Operations in the plant include palletizing de-palletizing, filling, packaging operations, and brewing. Annual plant electric costs for compressed air production, as operating today, are $693,161 per year. If the electric costs of $43,016 per year associated with operating ancillary equipment such as the blower purge dryers are included, the total electric costs for operating the air system are $736,177 per year. These estimates are based upon a blended electric rate of $0.06 /kWh.
Air System Pressure Influences Compressor Power - Part 2: The Influence of System Pressure on Centrifugal Compressors
It is common to see energy assessment specialists treat centrifugal compressors like positive displacement compressors when attempting to reduce compressed air system energy consumption. Unfortunately, centrifugal compressors are normally much larger, and miscalculations can easily represent hundreds of thousands of dollars in overestimated energy savings. These errors are not malicious; they result from oversimplified best practices perpetuated by individuals with limited centrifugal compressor knowledge. This type of knowledge is not readily available and most energy assessment specialists do not have access to engineering teams responsible for the technical development and design of centrifugal compressors.
This article reviews portions of an audit report commissioned to survey the condition of a compressed air system in a factory located in the U.S. The objective of this study is to determine the current operating conditions and make recommendations for improvement based upon application of industry recognized best practices. Due to article space limitations, this article will focus on portions of the over-all audit report provided to the factory.
Air System Pressure Influences Compressor Power - Part 1: System Pressure’s Influence On Rotary Screw Air Compressors
Energy conservation measures (ECMs) associated with compressed air have received a significant amount of attention over the years, mostly due to a reasonably short financial return compared with other energy-consuming equipment. Over time, many of the recommended corrective actions to reduce compressed air energy consumption were simplified so much that they did not lead to positive results. One of the most common compressed air ECMs is reducing system pressure, and it leverages the best practice calculation —.5 percent power per psi — outlined in the Department of Energy’s Compressed Air Challenge. This article highlights more common issues associated with estimating energy conservation resulting from changing system pressure.
The plant air system consists of eight, single-stage, lubricated, Sullair rotary screw compressors. All units are in good working order. Units 2, 3, 4 and 7 are water-cooled and units 6, 8, 9, 10 and 11 are air-cooled. The main plant air system has two primary compressed air dryers, a Thompson Gordon model TG 2000 refrigerated dryer, and a Sullair model SAR 1350 heatless desiccant dryer. Both units are working according to their design. The TG 2000 uses approximately 11.2 kW and is a non-cycling type unit, and the SAR 1350 uses approximately 200 cfm of purge air to regenerate the wet tower.
When an air system requires large quantities of air (ca. >100 m3/min) and air demand highly fluctuates during the day, it is common belief among end-users that large variable speed screw compressors can deliver significant savings opportunities by precisely matching the compressed airflow to the system’s demand. Where the daily flow demand has a variability of up to 90% of the maximum air demand, the study compares the energy consumption of six alternative solutions in terms of number of installed compressors, compressor sizes and types of compression technologies (i.e., oil free centrifugal and oil free rotary).
This factory, located in the U.S. northeast, spent an estimated $120,000 annually on energy to operate the compressed air system. The group of projects recommended below reduced these energy costs by $73,700 or 61% of current use. These estimates are based upon a blended electric rate of $0.114/kWh.