How to analyse the plant's compressed air system

The first step in analysing the plant's compressed air system is to determine our compressed air needs, as these are defined by the quality and quantity of air required by the end uses of the facility.

Assessing these needs carefully and understanding the difference between air quality vs. air quantity will ensure that the compressed air system is configured correctly, as well as determining the pressure and demand load requirements, which are also important steps in analysing such a system.

A complete analysis of the compressed air system by a specialised auditor is recommended and should include an examination of both the supply of air usage and the interaction between supply and demand.

When analysing the plant's compressed air system, auditors measure the output in cubic feet per minute of a compressed air system and the kW input to calculate the energy consumption in kilowatt-hours and determine the annual cost of operating the system. 

The auditor may also quantifying and minimising compressed air leakages with the use of specialised equipment, or suggest to the maintenance personnel to take corrective action. All components of the compressed air system should be inspected separately and problem areas identified, as recommended:

• Calculate losses and underperformance caused by system leakage.
• Monitor inappropriate uses.
• Verify demand events.
• Review poor system design and misuse.
• Analyse the overall dynamics of the system.

After this, the next step is to provide a detailed report of the corrective actions to be developed. Focusing on compressor controls, air dryers, end-use equipment, leakage and the interactions of all components are essential parts of an effective compressed air systems management strategy.

This is where the importance of measuring a compressed air system with data logging equipment comes in, as its application allows verification of the operation of the compressor controls, as well as analysing the compressor response when changes in system flow occur to ensure that the system is operating correctly and maintaining its efficiency.

Factors for analysing the plant's compressed air system

1. Air quality. This is determined by the dryness of the air and the level of contaminants required in the end uses. Knowing the actual dryness level required and maximum contaminant level allowed for reliable production is one of the 9 ways to optimise a compressed air system.
2. Air quantity or volume required to analyse the compressed air system of the plant. This can be determined by summing the requirements of your compressed air applications, process operations (taking into account load factors) and the duration of those volumes by those applications.
   The total air requirement is not the sum of the maximum requirements for each tool and process, but the sum of the average air consumption of each.
3. Pressure requirements. The minimum required discharge pressure level to be considered when analysing the plant compressed air system for different pressure ratings, applications, processes and pressure drops of system components.

It is normal that in compressed air end uses there is a pressure drop or it becomes fluctuating, therefore it is also common that insufficient discharge pressure is wrongly diagnosed.

4. Pressure drop. It is a term used to characterise the reduction in air pressure from the compressor discharge to the point of actual end use. The drop occurs as the compressed air travels through the treatment and distribution system and if excessive will not allow the compressed air to reach the point of actual end use. saving energy in compressed air systems and will make it inefficient.
   A pressure profile is a series of compressed air pressure measurements at different points in the system and allows the identification of system components causing excessive pressure drop as a fundamental basis for analysing the plant's compressed air system.
5. Demand side loading requirements, Another key to properly designing, operating and analysing the plant's compressed air system over time, or load profile, is that the variation in air demand over time is an important consideration in system design.

Plants with large variations in air demand need a system that operates efficiently under partial load. In such a case, multiple compressors with sequencing controls can provide more economical operation and use simpler control strategies.

Action plan to analyse the plant's compressed air system and to improve its efficiency.

• Develop a basic block diagram of the current compressed air system.
• Measure the baseline (kW, pressure profile, demand profile and leakage load) in order to establish how to calculate the efficiency of a compressed air system and their costs.
• Work with a compressed air systems specialist to implement a compressor control strategy.
• Re-measuring once the controls are adjusted to obtain more accurate readings of kW, pressures and determine the leakage load, it will also be necessary to recalculate energy consumption and costs.
• Inspect and check for obvious preventive maintenance items or other opportunities to reduce costs and improve performance.
• Identify, repair leaks and correct inappropriate uses by: knowing costs, re-measuring and adjusting controls as outlined in previous steps.
• Begin implementation of continuous improvement programmes to analyse the plant's compressed air system and achieve the expected efficiency.

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