Overview
ISO 4376:2024 - Cycle energy requirement - Test method defines a standardized test procedure to evaluate the cycle energy requirement (CER) of electrically driven compressors. Applicable to both positive displacement and dynamic compressors, the standard quantifies the additional energy consumed when a compressor switches between load and idle states compared with an ideal instantaneous load‑idle cycle. ISO 4376:2024 supports consistent measurement of energy consumed during venting, zero‑flow idle, and loading phases of a compressor package cycle.
Key technical topics and requirements
- Definition of CER: CER is the additional energy used during switching events at the offload discharge pressure and minimum flow rate compared to an ideal load‑idle transition.
- Scope: Applies to compressor packages (prime mover, transmission, auxiliaries) and covers typical industrial air production and higher‑pressure gas compression applications.
- Measurement parameters:
- Pressure accuracy: ±1 % at measured value.
- Temperature accuracy: ±1 K.
- Power measurement accuracy: ±1 % at measured value.
- Logging frequency: at least 10 Hz for pressure and power signals.
- Required hardware and setup:
- Measure package inlet/discharge pressure and temperatures at standard inlet/discharge points.
- Measure upstream and downstream pressures of a non‑return (check) valve; install one downstream if not integral.
- Install an adjustable throttle valve downstream of the compressor package.
- Actual flow measurement shall follow ISO 5167‑1 and ISO 9300 procedures.
- Test procedure overview:
- Ensure thermal steady state before testing.
- Capture the venting phase, steady zero‑flow idle, and reloading phase to determine CER.
- Report measured power, flow, pressures, and calculated CER per the standard’s test report requirements.
- Calibration: All inspection and test equipment that affect results must be calibrated against nationally recognized standards.
Practical applications and users
Who uses ISO 4376:2024:
- Compressor manufacturers for product performance claims and design validation.
- Independent test laboratories and certification bodies conducting energy performance tests.
- Plant engineers, energy managers, and OEMs seeking to optimize compressor control strategies and reduce cycling energy losses.
- Procurement teams evaluating compressor packages based on life‑cycle energy performance.
Benefits:
- Enables objective comparison of compressors’ cycling energy behavior.
- Helps identify opportunities to reduce energy consumption during load/unload events and improve overall compressed‑air system efficiency.
- Supports development of control strategies and specification of low‑CER equipment for energy‑sensitive applications.
Related standards
- ISO 5167‑1 - Measurement of fluid flow by pressure‑differential devices.
- ISO 9300 - Measurement of gas flow by means of critical flow nozzles.
Keywords: ISO 4376:2024, cycle energy requirement, CER test method, compressor energy, positive displacement compressors, dynamic compressors, compressor testing, compressed air systems, energy efficiency, flow measurement, power measurement.
