Overview
ISO 3977-2:2023 - Gas turbines - Procurement - Part 2: Standard reference conditions and ratings defines the standardized reference conditions, fuel heating-value basis, and rating conventions used when specifying, testing and commercially comparing gas turbines. The standard ensures consistent definitions for ISO nominal ratings and the way in which in‑situ or site ratings are reported, enabling objective procurement, acceptance testing and performance guarantees.
Key topics and requirements
- Standard reference conditions for air intake
- Total pressure: 101.325 kPa
- Total temperature: 15 °C
- Relative humidity: 60 %
- Exhaust condition
- Static pressure at exhaust flange: 101.325 kPa
- Cooling water (if used)
- Water inlet temperature: 15 °C
- Heater/cooler of working fluid
- Ambient reference: 15 °C and 101.325 kPa
- Power and performance characteristics
- Output power is proportional to absolute ambient pressure and strongly dependent on inlet air temperature; ISO nominal values exclude inlet/outlet pressure losses while site ratings include them.
- Manufacturer must declare ISO nominal powers (electrical at generator terminals or shaft power) for defined modes.
- Two ISO nominal operating modes specified:
- ISO peak load: average ~2 000 h/year and ~500 starts/year
- ISO base load: average ~8 760 h/year and ~25 starts/year
- Manufacturer must specify the required type, frequency and level of control/maintenance for each mode.
- Fuel heating value (LHV) basis for performance)
- Liquid fuel (typical): 42 000 kJ/kg
- Gaseous (100 % methane): 50 000 kJ/kg
- Hydrogen (100 % H2): 119 907.4 kJ/kg
- Site-specific fuels may be agreed with the manufacturer
- Testing fuel
- If test fuel differs from the agreed service fuel, a mutually agreed test fuel must be used.
- Other notes
- Water or steam injection may be used to increase power and reduce NOx; effect should be considered in ratings.
- In-situ ratings must account for plant conditions, auxiliaries and operational mode (per ISO 2314 references).
Applications
- Procurement specifications and contractual performance guarantees
- Factory acceptance and site acceptance testing comparisons
- Power plant performance modelling and site-correction calculations
- Selection and sizing of gas turbines for industrial, utility and offshore installations
- Standardizing documentation between OEMs, owners and testing laboratories
Who uses this standard
- Gas turbine OEMs and vendors
- Plant owners, utilities and IPP procurement teams
- Performance engineers and commissioning teams
- Testing laboratories and certification bodies
- Consultants and contract authors drafting guarantees and SLAs
Related standards
- ISO 2314:2009 - Gas turbines - Acceptance tests (referenced for test definitions, corrections and measurement methods)
Keywords: ISO 3977-2:2023, gas turbines, standard reference conditions, ISO ratings, gas turbine procurement, power rating, LHV, site rating.
