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ASME B133.1M-1983 — Gas Turbine Terminology
📖 ASME B133.1M-1983 (ANSI B133.1M-1983) is the American National Standard for Gas Turbine Terminology, prepared by the ASME B133 Standards Committee (Procurement Standards for Gas Turbines). It is a revision of the 1978 edition of B133.1 and received final ANSI approval on September 23, 1983. The Standard provides a comprehensive, alphabetical list of technical terms pertinent to the B133 series of gas turbine standards. Its purpose is to let procurement specifications and bid responses for gas turbines be prepared and evaluated in a shared “language” — with buyers and sellers interpreting every term identically.
💡 The value of a terminology standard lies not in specifying how a component is built, but in removing ambiguity: if “rated output,” “heat rate,” or “availability” are understood differently by buyer and seller, later acceptance testing becomes a dispute. B133.1M is the shared language for the B133 procurement series.
1. Scope and Role of the Standard 📌
Within the broader B133 series, the gas turbine procurement standards aim to provide guidance and criteria that facilitate the preparation of — and response to — gas turbine procurement specifications. The series applies to open-cycle, closed-cycle, and semi-closed-cycle gas turbines for industrial, marine, and electric power applications, including the auxiliaries needed for proper operation. Excluded are gas turbines applied to earthmoving machines, agricultural and industrial tractors, automobiles, trucks, buses, and aeropropulsion units. For gas turbines using unconventional or special heat sources (such as chemical processes, nuclear reactors, furnaces, or supercharged boilers), the Standard may be used as a basis for procurement, though appropriate modifications may be necessary.
As the first part of the B133 series, B133.1M provides alphabetically organized definitions (Section 1, “Definitions”) covering fuels and combustion products (aromatics, ash, blast furnace gas, etc.), components (axial compressor, fluid film bearing, rolling contact bearing, etc.), and cycle and operating terms (bleed gas turbine, availability, etc.). The glossary reflects customary U.S. engineering usage so that procurement documents can cite it directly.
⚠️ The Standard does not cover aeropropulsion units or gas turbines installed in vehicles and agricultural machinery. Before citing this terminology in a specification, confirm the unit falls within industrial, marine, or electric power applications; otherwise the reference may mislead.
2. Core Terminology by Category 📚
Typical glossary entries grouped by subject (definitions summarized in general engineering terms; always follow the Standard text):
- Fuels and combustion products: aromatics — compounds derived from benzene rings of carbon atoms, as distinct from aliphatic or alicyclic compounds; ash — the solid residue left when a combustible material has been thoroughly burned; blast furnace gas — a low-BTU gas generated by blowing air through hot coke, dolomite, and iron ore, composed mostly of nitrogen, carbon monoxide, and hydrogen.
- Components: axial compressor — a compressor in which rotor discharge and diffusion processes occur in passages of approximately constant mean radius; fluid film bearing — a bearing in which the bearing and journal are separated by a lubricant whose separating pressure is hydrostatic or hydrodynamic (e.g., sleeve/journal or tilting-pad bearings); rolling contact bearing — ball or roller bearing, also called an anti-friction bearing.
- Cycles and operation: bleed gas turbine — a gas turbine with extraction of compressed air between compressor stages or at compressor discharge, and/or extraction of hot gas at the turbine inlet or between turbine stages, for external use; availability — the percentage of total elapsed time that the gas turbine power plant was ready for operation or performing its intended functions.
| Category | Representative Terms | Definition Highlights | Engineering Significance |
|---|---|---|---|
| Fuels and combustion | Aromatics / Ash / Blast furnace gas | Benzene-ring compounds; residual solids after combustion; low-BTU industrial gas | Fuel adaptability, ash deposition, heating-value corrections |
| Compressor | Axial compressor | Compression and diffusion in near-constant-mean-radius passages | High flow and efficiency; mainstream for power generation |
| Bearings | Fluid film / Rolling contact | Oil film separation; ball/roller supports | Vibration, life, and lube-oil system design |
| Cycle | Bleed gas turbine | Interstage/discharge air bleed or hot-gas bleed | Combined cycles, process air, inlet humidification |
| Operating index | Availability | Time ready or performing intended functions vs. total time | Core index for procurement and reliability acceptance |
💡 The glossary is not a performance-parameter handbook, but it fixes the “naming rules” of performance parameters: the B133.1M definition of availability, for instance, directly determines how contract acceptance is calculated. Specify in the contract that definitions per B133.1M apply.
3. Performance and Operating Terminology 🔥
Drawing on general gas turbine engineering knowledge, the performance and operating terms most relevant to B133-series procurement documents include:
- Rated Output: the guaranteed power that the unit can deliver continuously at rated speed under stated inlet conditions (typically ISO conditions: 15°C, 101.325 kPa, 60% relative humidity) and stated fuel.
- Heat Rate: the fuel lower heating value consumed per unit of electrical (or shaft) output — expressed in kJ/kWh (or Btu/kWh) — and the central economic index of a gas turbine; the lower the heat rate, the higher the cycle efficiency.
- Pressure Ratio: the ratio of compressor discharge total pressure to inlet total pressure; modern industrial machines typically achieve 12:1 to 25:1.
- Turbine Inlet Temperature (TIT)/Firing Temperature: the gas temperature entering the first turbine stage, which governs specific work and efficiency as well as the materials and cooling design of hot-gas-path components.
- Simple / Regenerative / Combined Cycle: the Brayton cycle without exhaust-heat recovery, a cycle that preheats inlet air with exhaust gas, and a cycle where the gas turbine exhaust drives a heat-recovery steam generator and steam turbine, respectively.
| Cycle Type | Typical Efficiency Range (industrial, approx.) | Main Applications | Key Related Terms |
|---|---|---|---|
| Open simple cycle | 30%–42% | Peaking generation, mechanical drive, emergency power | Rated output, heat rate, pressure ratio |
| Regenerative cycle | 35%–45% | Distributed energy, industrial captive plants | Regenerator, exhaust temperature |
| Combined cycle | 50%–62% | Large base-load / peaking plants | HRSG, bleed gas turbine |
| Cogeneration | 70%–90% overall efficiency | Chemicals, pulp and paper, district heating | Bleed, exhaust recovery, availability |
⚠️ “Rated output” must be qualified by inlet conditions and fuel heating-value basis; otherwise machines are not comparable. Procurement documents should cite ISO standard conditions or site conditions and state that heating value is lower heating value (LHV).
4. Engineering Practice Essentials 🛠️
- 🔍 Specification drafting: cite B133.1M in the “Definitions and Terminology” section to avoid conflicting interpretations of the same parameter; define any new terms not covered by the Standard.
- 🔧 Acceptance basis: write “availability,” “rated output,” and “heat rate” into contract annexes per the Standard definitions as the calculation basis for performance and reliability acceptance.
- 📊 Fuel flexibility: low-BTU fuels such as blast furnace gas require high-flow combustion systems and fuel treatment; the glossary’s “ash” definition affects blade erosion/wear and washing intervals.
- 📋 Auxiliaries: the Standard covers auxiliary-equipment terms; include lube-oil, starting, control, and protection systems in the specification scope.
✅ Good practice: in the “Terms and Definitions” section of gas turbine tender documents, cite B133.1M and attach a “term — definition — project convention” cross-reference table, separating the Standard definitions from project-specific agreements at the source and reducing commercial and technical disputes.
5. Frequently Asked Questions ❓
❓ Q: What is the difference between open cycle and closed cycle?
A: In an open cycle the working fluid (air/combustion gas) is drawn from the atmosphere and exhausted back to it; in a closed cycle the working fluid (typically an inert gas) circulates in a closed loop inside the machine, with heat transferred in through a heat exchanger from an external source (e.g., nuclear reactor, high-temperature furnace). A semi-closed cycle lies between the two.
A: In an open cycle the working fluid (air/combustion gas) is drawn from the atmosphere and exhausted back to it; in a closed cycle the working fluid (typically an inert gas) circulates in a closed loop inside the machine, with heat transferred in through a heat exchanger from an external source (e.g., nuclear reactor, high-temperature furnace). A semi-closed cycle lies between the two.
❓ Q: How do heat rate and cycle efficiency relate?
A: For a generator set, heat rate HR (kJ/kWh) and electrical efficiency η satisfy η = 3600/HR on an LHV basis. A lower heat rate means higher efficiency — two expressions of the same economics, and procurement documents often guarantee both.
A: For a generator set, heat rate HR (kJ/kWh) and electrical efficiency η satisfy η = 3600/HR on an LHV basis. A lower heat rate means higher efficiency — two expressions of the same economics, and procurement documents often guarantee both.
❓ Q: Why does the B133.1M definition of “availability” matter?
A: Availability is “the percentage of total elapsed time that the plant was ready for operation or performing its intended functions” — the basis for reliability acceptance. If the contract uses a different basis (such as excluding planned maintenance), results differ markedly, so the basis must be fixed first.
A: Availability is “the percentage of total elapsed time that the plant was ready for operation or performing its intended functions” — the basis for reliability acceptance. If the contract uses a different basis (such as excluding planned maintenance), results differ markedly, so the basis must be fixed first.
🔍 Q: What are the boundaries of the B133 series scope?
A: It applies to gas turbines for industrial, marine, and electric power applications, in open, closed, or semi-closed cycles, including necessary auxiliaries; it excludes earthmoving machines, tractors, automobiles, trucks, buses, and aeropropulsion units. Units with special heat sources may use it as a modified basis.
A: It applies to gas turbines for industrial, marine, and electric power applications, in open, closed, or semi-closed cycles, including necessary auxiliaries; it excludes earthmoving machines, tractors, automobiles, trucks, buses, and aeropropulsion units. Units with special heat sources may use it as a modified basis.
