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AUSAPWS (Australian Association for the Properties of Water and Steam)


IAPWS is an international non-profit association of national organizations concerned with the properties of water and steam, particularly thermophysical properties and other aspects of high temperature steam, water and aqueous mixtures that are relevant to thermal power cycles and other industrial applications. 

The IAPWS objectives are: 

  • To provide internationally accepted formulations for the properties of light and heavy steam, water, seawater, ice and selected aqueous solutions for scientific and industrial applications 

  • To define research needs and promote and coordinate research on steam, water and selected aqueous systems important in thermal power cycles 

  • To develop Technical Guidance Documents (TGD) for the Cycle Chemistry of Fossil and Combined Cycle/HRSG power plants 

  • To provide an international forum for exchange of experiences, ideas and results of research on high temperature aqueous media


IAPWS originated de facto in 1929, when the first of the periodic International Steam Tables Conferences was held in London, UK, driven by the need for international agreement on the properties of steam when performance specifications are set for the steam turbines used in the power industry. The International Association for the Properties of Steam (IAPS) was officially established in 1971 and became the International Association for the Properties of Water and Steam (IAPWS) in 1989. The Association has broadened its scope substantially in the past twenty years, and presently is concerned not only with accurate formulation of steam tables, but also with other physical and chemical properties of light and heavy water, seawater, ice, humidity, steam and selected aqueous systems, and of power plant cycle chemistry. 

Membership of IAPWS 

Countries are members of IAPWS. Membership is held, on behalf of member countries, by National Committees. 

There are two classes of membership: Member and Associate Member. Members pay yearly dues, are entitled to vote on all matters coming before the Executive Committee, and receive all publications and services of IAPWS. Associate members do not pay dues and are not entitled to vote on matters before the Executive Committee but do receive all publications and services of IAPWS.

Full Members have the following obligations: 

  1. To maintain a National Committee 

  2. To secure and make payment of yearly dues to the Association 

  3. To send a National Delegate to meetings to vote on behalf of the National Committee on relevant matters. The National Delegate is a member of the Association's Executive Committee 

  4. To procure the services of qualified personnel to participate in the Association's scientific and technical activities 

  5. To bring to the attention of the Association relevant research in the Member country. 

  6. In the event of a Member defaulting on payment of dues, the Member is required to report to the Executive Committee each year the actions that the Member is taking to rectify the position, and after three years its status will be changed to that of Associate Member. 

Members, acting through their National Committees, are responsible for developing national positions on questions before IAPWS, for evaluating formulations proposed by IAPWS for international acceptance, for participating through national delegates and selected experts in the meeting and activities of IAPWS, and for payment of annual dues. 

The National Committees attract and encourage experts to participate in the activities of IAPWS, bring the results of relevant research on water, steam, aqueous systems and power plant chemistry within the country to the attention of IAPWS, and promote and encourage research on water, steam, seawater, ice, humidity and aqueous systems within the country. 

Benefits of IAPWS Membership:

  1. Information. Membership in IAPWS provides access to information on research in steam, water and power-cycle chemistry throughout the world. Data on technically important properties are continuously re-examined, measurement needs are identified, and new theoretical developments are applied. The members of the Working Groups, in turn, inform their national committees and the scientists and engineers on these new developments, thus minimizing duplication and maximizing effectiveness of their efforts. 

  2. Participation. Membership in IAPWS provides the member country a voice in an influential forum on power plant chemistry, an opportunity to participate in the preparation of data representations and guidelines, and a vote in the acceptance of these. These representations will be used worldwide not only in the design, specification, operation and analysis of steam operated power plants, but also in numerous other scientific, engineering and geological applications where the properties of high temperature aqueous systems are required. 

  3. Recognition. Membership in IAPWS enhances the status and visibility of scientists, engineers and industries in the member countries and worldwide. By engaging in IAPWS-related activities, the capabilities and achievements of these scientists and engineers will receive international recognition. Senior technical experts of the IAPWS working groups that have distinguished themselves by extraordinary service to the organization and internationally can be elected to the status of Honorary Fellow.

Current Members

The current National Country organisations / members of IAPWS are:

National Committees of IAPWS 

In any country desiring to participate in the work of IAPWS, a National Organization or Committee, representative of interests in the properties of water, steam, and aqueous systems, shall be constituted or designated by a governmental, technical, or professional body. Such a National Organization may then apply to the IAPWS Executive Committee for Full Membership. 

Upon acceptance of the application by the Executive Committee, the National Committee becomes responsible for meeting the obligations of membership as delineated above. In addition to these obligations, the National Committee is responsible for the national position on matters to be put before the Executive Committee for vote either at the next meeting or by postal ballot, the vote to be delivered by the National Delegate. Such matters may be of a business or a scientific or technical nature. If of a scientific or technical nature, it is the responsibility of the National Committee to evaluate the quality and appropriateness of the technical material proposed. 

Associate Members are elected on application by the Executive Committee for a period of three years. This period can be renewed once. Associate membership is intended to lead to full membership. It allows a period of time for the establishment of a National Committee, and for the evaluation of the benefits of national membership.

What does IAPWS do? 

IAPWS organizes a yearly Executive and Working Groups meeting in one of the member countries, on a rotating basis. 

IAPWS sponsors and manages the International Conferences on the Properties of Water and Steam (ICPWS) that rotate among the member countries and are held periodically (4-5 years). 

IAPWS establishes, maintains, and oversees Working Groups and Committees that perform the specialized tasks that are part of IAPWS's objectives. 

IAPWS approves and disseminates, as a set of international standards, in the form of Releases and Guidelines, improved representations of the properties of water, steam and aqueous systems that have been developed, or selected, and tested by members of the Working Groups. It produces IAPWS Certified Research Needs (ICRN) documents that call for research on specific topics relevant to the power industry, according to the judgment of members of the Working Groups. IAPWS also produces the cycle chemistry guidelines (TGD) for power plants. Full information is available on the IAPWS website at

How is IAPWS Structured? 

IAPWS is managed by the Executive Committee composed of delegates from each of the member countries. The Working Groups and Committee are managed by the Executive Committee and report to it. 

The Executive Committee is chaired by the President, who serves a two year term. The Presidency is rotated among the member countries. 

The day-to-day affairs of IAPWS are managed by the Executive Secretary, who announces the agendas for the meetings, prepares and circulates the minutes, and directs the flow of the IAPWS Releases, Guidelines, Technical Guidance Documents, and ICRN Documents. 

The four Working Groups and Sub-Committee are staffed by technical experts who are selected with the assistance of the national organizations for their competence in the areas covered by the Working Groups:

  • TheWorking Group on Thermophysical Properties of Water and Steam (TPWS) is concerned with the accurate representation of the thermodynamic, transport, and other properties (such as dielectric constant, refractive index, surface tension, viscosity and thermal conductivity) of ordinary and heavy water and steam for general and scientific use. 

  • TheWorking Group on Physical Chemistry of Aqueous Solutions (PCAS) is concerned with the physical chemistry of aqueous solutions at high temperatures and pressures. It formulates thermodynamic and transport properties in selected systems for which sufficient data are available. 

  • The Working Group on Power Plant Chemistry (PCC) has developed Technical Guidance Documents for the cycle chemistry of power plants. This working group also acts as a forum for the discussion of common problems, defines the areas where information is needed, and stimulates the required research. 

  • The Working Group on Industrial Requirements and Solutions (IRS) maintains and improves the industrial formulation that is used in the design of power plant components and systems; this formulation is usually contractually and sometimes legally required in performance testing and specification of such components and systems. 

  • The Sub-Committee on Sea Water (SCSW) is concerned with the standards for the thermodynamic properties of seawater, ice, and humid air, as an extension of the existing standards for pure water. It works in cooperation with the Scientific Committee on Oceanic Research (SCOR) and the International Association for the Physical Sciences of the Oceans (IAPSO).


  • Biapws – British and Irish Association for the Properties of Water and Steam:

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