Energy Audit Dictionary: 100+ Key Terms Explained Simply

COMPRESSED AIR KNOWLEDGE

Understanding Your Compressed Air System

A compressed air system is more than just a compressor. It includes air generation, treatment, storage, distribution and end-use equipment. Understanding how these areas work together makes it easier to identify performance issues and energy losses.

Air Generation

Compressors generate the air required for industrial operations. Compressor selection, loading and operating conditions directly influence system efficiency.

Air Treatment

Dryers, filters and separators help maintain the required quality of compressed air while protecting equipment and production processes.

Storage & Distribution

Receivers and piping distribute compressed air throughout the facility. Pressure drops, restrictions and poor piping design can increase energy use.

End-Use & Demand

Production equipment determines how much air is actually required. Understanding demand helps avoid excessive pressure and unnecessary air use.

Audit Perspective: Every part of a compressed air system can affect energy performance. The right measurements help connect technical terms with real operating conditions.

Audit Dictionary

Compressed Air Energy Audit Dictionary

Compressor Types

Term	Definition
Rotary Screw Compressor	Uses two intermeshing helical rotors to continuously compress air; ideal for industrial continuous-duty operation.
Reciprocating Compressor	Uses piston-cylinder mechanism; suitable for intermittent or small-scale applications.
Oil-Injected Compressor	Oil is injected into compression chamber for cooling, sealing, and lubrication.
Oil-Free Compressor	Compresses air without oil contamination; essential for food, pharma, and electronics industries.
Two-Stage Compressor	Compresses air in two stages for improved efficiency at higher pressures.
Variable Speed Drive (VSD)	Adjusts motor speed based on air demand to reduce energy consumption.
Fixed Speed Compressor	Operates at constant motor speed; less flexible under variable load conditions.

Key Compressor Components

Component	Function
Air End	Core compression unit in rotary screw compressor.
Electric Motor	Drives the compressor air end.
Inlet Valve	Controls air intake.
Oil Separator	Removes oil from compressed air before discharge.
Oil Filter	Filters contaminants from lubricating oil.
Air Filter	Prevents dust and debris from entering system.
Aftercooler	Reduces compressed air temperature and moisture.
Cooling Fan	Maintains safe operating temperature.
Thermostatic Valve	Regulates oil temperature.
Check Valve	Prevents reverse airflow.
Minimum Pressure Valve (MPV)	Maintains internal system pressure stability.
Drain Valve	Removes condensate from system.
PLC / HMI	Control and monitoring interface.
Safety Valve	Protects system from overpressure damage.

Performance & Energy Terms (Important for Audit)

Term	Meaning
Free Air Delivery (FAD)	Actual air output under standardized conditions.
Specific Power	kW consumed per m³/min (or CFM) produced; key efficiency indicator.
kW Demand	Electrical power consumed by compressor.
Duty Cycle	Percentage of time compressor operates under load.
Pressure Drop	Loss of pressure due to friction or restriction in piping.
Leakage Rate	Percentage of air lost due to leaks.
Artificial Demand	Extra air usage caused by excessive system pressure.
Energy Intensity	Energy consumed per unit of air delivered.
ROI (Return on Investment)	Financial return from energy-saving improvements.
Payback Period	Time required to recover investment cost.

Compressed Air Audit Terms

Term	Definition
Air Audit	Systematic assessment of compressed air system performance and energy losses.
Data Logging	Recording pressure, flow, and power over time.
Baseline Profile	Standard operating performance benchmark.
Demand Profile	Air consumption pattern over time.
Peak Demand	Highest recorded air usage during audit period.
Load Profile	Compressor loading behavior over defined intervals.

Compressed Air Quality Terms

Term	Definition
ISO 8573-1	International standard defining compressed air purity classes.
Dew Point	Temperature at which moisture condenses.
Pressure Dew Point (PDP)	Dew point measured at operating pressure.
Refrigerated Dryer	Removes moisture using cooling method.
Desiccant Dryer	Removes moisture using adsorption material.
Coalescing Filter	Removes oil aerosols and fine mist.
Activated Carbon Filter	Removes oil vapors and odors.
Water Separator	Separates bulk liquid water from air.

System & Distribution Components

Term	Function
Air Receiver (Tank)	Stores compressed air and stabilizes pressure.
Ring Main	Closed-loop piping system for balanced air delivery.
Distribution Piping	Network delivering air to end-use equipment.
Flow Controller	Regulates downstream air volume.
Pressure Regulator	Maintains consistent outlet pressure.
Drop Leg	Vertical pipe section for moisture drainage.

Safety & Compliance

Term	Meaning
Pressure Relief Valve (PRV)	Releases air when pressure exceeds safe limit.
Emergency Stop (E-Stop)	Immediate shutdown mechanism.
Lockout-Tagout (LOTO)	Safety procedure for maintenance isolation.
ATEX Certification	Certification for equipment in explosive environments.
Overheat Shutdown	Automatic shutdown due to high temperature.

Typical Maintenance Intervals

Service Item	Typical Interval
Air Filter	2,000 – 4,000 hours
Oil Filter	2,000 – 4,000 hours
Oil Separator	4,000 – 8,000 hours
Lubricant (Mineral)	2,000 – 4,000 hours
Lubricant (Synthetic)	4,000 – 8,000+ hours
Leak Survey	Annually or quarterly

FROM TERMS TO ACTION

Why Compressed Air Terms Matter in an Energy Audit

Knowing the terminology is the first step. During an energy audit, these concepts help engineers understand system performance, identify losses and develop practical opportunities for improvement.

Measure Performance

Technical measurements provide a clear picture of compressor performance, pressure, flow and electrical demand.

Identify Energy Losses

Understanding leakage, pressure drop, artificial demand and inefficient operation helps reveal avoidable energy consumption.

Improve System Reliability

Proper knowledge of components, air quality and operating conditions supports more reliable compressed air system operation.

Make Better Decisions

Clear technical information helps turn audit findings into practical actions for improving efficiency and system performance.

From Measurement to Improvement

Measure Collect system data

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Analyze Understand performance

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Identify Find losses & opportunities

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Optimize Implement improvements

Better Understanding Leads to Better Energy Decisions

Use the dictionary as a quick reference when reviewing compressed air system performance, audit measurements and improvement opportunities.