Compressor capacity definition (standard delivery basis) In industrial air systems, compressor capacity is typically specified as the actual volume flow delivered by the machine but referenced back to normal temperature and pressure (standard conditions). Which statement correctly defines this capacity?

Introduction / Context:
Air is compressible, so the same mass flow can occupy very different volumes depending on temperature and pressure. To compare compressors fairly, the capacity is stated at a standard reference, often called Free Air Delivery (FAD) at normal temperature and pressure.

Given Data / Assumptions:

• Reference conditions are fixed (e.g., 1.013 bar and 15°C or as per standard).
• Capacity is used for sizing tools, piping, and receivers.
• Delivery basis, not suction stroke displacement alone.

Concept / Approach:
Capacity equals the volumetric flow that the compressor delivers, converted back to a standard reference state using the ideal gas relation. This allows apples-to-apples comparison across sites and climates and decouples performance from ambient variations.

Step-by-Step Solution:
Measure actual mass flow delivered.Convert mass flow to volume at NTP: V_NTP = m * R * T_NTP / p_NTP.Report capacity as this standardized volume per unit time.

Verification / Alternative check:
Vendor datasheets use SCFM or m^3/h at standard conditions. Site readings are corrected back using temperature and pressure data.

Why Other Options Are Wrong:

• Raw delivered or sucked volume (options b and c) depend on instantaneous conditions and are not comparable.
• “None of the above” and mass-only definitions omit the standardized volumetric basis used in practice.

Common Pitfalls:
Confusing displacement (geometric) with capacity (delivered); ignoring correction to reference conditions leads to sizing errors.

Final Answer:
actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions