As participants of the Compressed Air Challenge’s Fundamentals of Compressed Air Seminar learn, a compressed air system analysis can highlight the true costs of compressed air and identify opportunities to improve efficiency and productivity.
Compressed air system users should consider using an auditor to analyze their compressed air system. A number of firms specialize in compressed air system analysis. System analysis is also performed by electric utilities, equipment distributors and manufacturers, energy service companies, and engineering firms. “When selecting a service provider it is important that factors in addition to price be considered,” says Niff Ambrosino, Chief Operating Officer for Scales Industrial Technologies, and a CAC Fundamentals and Advanced Instructor, “The qualifications and capabilities of the audit technicians, and reputation in the local industrial community are key and should also be considered.”
An informed consumer should be aware that the quality and comprehensiveness of system analysis can vary. Independent auditors should provide recommendations that are systems-neutral and commercially impartial. Independent auditors should neither specify nor recommend any particular manufacturer’s products.
A comprehensive compressed air system analysis should include an examination of both air supply and usage and the interaction between the supply and demand. Auditors typically measure the output cfm of a compressed air system and the input kW, calculate energy consumption in kilowatt-hours, and determine the annual cost of operating the system. The auditor may also measure total air losses caused by leaks and locate those that are significant.
All components of the compressed air system are inspected individually and problem areas are identified. Losses and poor performance caused by system leaks, inappropriate uses, demand events, poor system design, system misuse, and total system dynamics are calculated, and a written report with a recommended course of action is provided.
“It is critical for compressed air system assessments to investigate the individual system components, the component interactions, and the entire compressed air system as a whole” says Greg Harrell, Ph.D., P.E. of Energy Management Services and a Certified CAC Fundamentals instructor, “Focusing on compressor controls, air dryers, end-use equipment, leaks, and the interactions of all the components are all essential parts of an effective compressed air system management strategy. As an example of the necessity of the system focus consider a leak abatement program. Significant attention could be given to eliminating leaks; however, if the compressor control strategy does not allow the compressors to efficiently reduce energy consumption in response, then this reduction may yield minimal benefit.”
Overview of Levels of Analysis of Compressed Air Systems
The following levels of analysis of compressed air systems have been developed in an effort to provide commonality of terminology, methods, and procedures to be used by service providers as well as the results to be expected by end users. Energy utilities are actively involved in these efforts and some provide incentives to use these analyses to improve the energy efficiency of compressed air systems.
There are two levels of analysis: a basic assessment and a comprehensive audit. Conducting a basic assessment is the first step in analyzing a compressed air system. Depending on individual needs, this can be conducted either by trained plant personnel or by an experienced compressed air system services provider. A basic assessment is not intended to provide the level of detail found in a comprehensive audit, but significant reductions in energy (25 percent or more) and lower maintenance costs can often result from a basic assessment alone. Once initial opportunities have been identified, you can decide whether additional analysis services are required to further define system dynamics and corresponding system improvement opportunities. This decision will depend, in part, on the size and complexity of the system being examined (both supply and demand) and whether critical issues requiring further investigation to identify their causes and potential remedies surfaced during the evaluation.
Basic Compressed Air System Assessment
A basic system assessment of a compressed air system is the first level of analysis. Depending on the complexity of the system, a basic system assessment can be conducted by either trained plant personnel or by an experienced compressed air system efficiency expert. Using readily available data combined with limited measurements, an expert can identify system inefficiencies and make recommendations that will result in reductions in energy costs. Production downtime and maintenance costs also may be reduced. Basic system assessment of the facility could reveal:
- Potentially inappropriate uses of compressed air
- Significant leaks
- Processes, or individual end-uses most sensitive to low pressure
- System instability
- High volume and intermittent uses
- Capacity control problems
- Maintenance and reliability issues
Comprehensive Compressed Air System Audit
A comprehensive system audit is the top level of system analysis, conducted by an experienced compressed air system auditor. It is a detailed analysis of the entire compressed air system and may have been preceded by a basic system assessment. Measurements and data logging generally are part of the comprehensive compressed air system audit procedures.
The customer’s objectives and system problems will be discussed prior to the start of the audit and the proposed procedures also will be explained. The objective is proper management of the complete compressed air system for optimum efficiency and reliability. This includes alignment of the supply side (compressors, their controls, aftercoolers, dryers, filters, primary air receivers) with the demand side (distribution piping system, secondary air receivers, all of the end-uses of compressed air, including leaks), in conjunction with the needs and financial objectives of the business unit.
The auditor should accomplish the following during a comprehensive audit:
- Establish a baseline, against which the results of any proposed changes are measured.
- Draw a block diagram and a review of the compressor room to determine present compressor operations, control strategy, and the storage capacity.
- Record compressor and dryer pressures and temperatures.
- Validate end-use pressure and quality requirements.
- Conduct data logging of readings of power and pressure (and flow, if applicable) throughout the system for a more in-depth analysis of the dynamics of the system and resulting problems. Provide graphs showing data collected over time.
- Construct a demand profile to identify significant end-uses and their impact.
- Construct a pressure profile to identify what determines the system operating pressure and to identify possible changes.
- Review primary and secondary air receiver capacities.
- Establish a controls strategy through real-time analysis.
- Identify customer approach to air leak detection and repair and make recommendations for improvement.
- Review differences in shift operations and impact on air use.
- Identify compressed air end-uses which may be better served by other means and recommend suitable alternatives.
- Compare air quality provided for each end-use with what is really needed and make appropriate recommendation(s).
- Review maintenance procedures and training.
- Review initial verbal proposals with all who attended a pre-audit meeting, to obtain buy-in from all departments involved.
- Provide a comprehensive written report of all findings, recommendations, and results.
