Evolution of Flow Measurement Standards: A Critical Look

Michael Reader-Harris takes a look at the evolution of flow measurement standards

Flow measurement standards in the oil and gas industry are essential in ensuring that revenue and tax are correct; their impact is particularly visible where losses are being determined from differences in meter readings. UK natural gas demand is around £16 billion (€20 billion) annually, and most of this is measured at some stage using the ISO standard for flow measurement using differential-pressure meters, ISO 5167: this standard and its predecessors have been revised over years to avoid both inaccuracy through inadequate specification and excessive cost through over-specification.

Standards give consistency. By the development and adoption of standards, there is wider industrial acceptance of new technologies, and barriers to trade are lowered, transaction costs are reduced and the operation of markets is improved through the smooth flow of goods and services. Standards enable compliance to be demonstrated, provide confidence in product performance, and help to eliminate or reduce disputes between companies and across borders, hence saving costs and time. They help smaller firms by transferring technology from larger ones.

2018 was the 75th Anniversary of the first British flow measurement standard, BS1042:1943: that early one covered differential-pressure meters; ISO differentialpressure- meter standards followed. Standards covering a very wide range of other technologies have also been developed, for example ISO 2714 PD meters, ISO 2715 Turbine meters, ISO 17089 Gas ultrasonic meters, ISO 10790 Coriolis meters and ISO 12242 Liquid ultrasonic meters. Standardisation is not only important for economic reasons; accurate measurement of discharges, of produced water, for instance, is important to ensure a cleaner environment.

The key standards will in practice be revised as required, probably on a similar frequency to that for the differential pressure meter standards, which is roughly every 14 years. Where technology is moving faster, standards revision will be more frequent. For differential-pressure meters there are supporting documents for ISO 5167: ISO 2186 on impulse lines and several Technical Reports (TRs), e.g., ISO/ TR 9464 Guidelines for using ISO 5167, ISO/TR 12767 Differential-pressure meters departing from ISO 5167 and ISO/TR 15377 Differential-pressure meters beyond the scope of ISO 5167.

New application areas for flow measurement require new standards. Wet-gas TRs have already been published: ISO/TR 11583 Using Venturi tubes or orifice plates to measure wet gas and ISO/TR 12748 Measuring wet natural gas. ISO/TR 21354 Multiphase flow measurement will be published this year.

ISO standards are produced by more than 200 technical committees (TCs) and their subcommittees (SCs). The members of these committees are the national standards bodies (NSBs), e.g. BSI. A TC covers a specific technical area, and its SCs are appointed to concentrate on specific areas within the remit of the TC. Under an SC (or under the TC directly) there are Working Groups (WGs), whose members are individual experts nominated by the NSBs.

Documents (standards or TRs) are developed in WGs, with Working Drafts (WDs) being circulated by the WG convenor to the WG members and commented on until the WG is ready to send a draft to ISO. A draft standard from the WG is now sent out as a CD (Committee Draft) to the NSBs. The NSBs’ comments are resolved and a DIS (Draft International Standard) is circulated to the NSBs. If the DIS is approved and no technical changes are introduced in the draft, the project goes straight to publication. However, if technical changes are introduced, an FDIS (Final Draft International Standard) is prepared and voted on; no technical changes can be introduced at this stage. If a TR (rather than a standard) is being prepared then ISO sends it out to the NSBs for a single vote.

From the above, to participate in standards-making it is necessary to be involved in a national standards body; then you can be put on a WG and report back to the NSB; alternatively, you can comment on the CD, DIS and FDIS as part of the NSB.

Two thirds of the ISO standards that include reference to fluid flow measurement are produced by four technical committees: TC 28 Petroleum products and lubricants, TC 30 Measurement of fluid flow in closed conduits, TC 113 Hydrometry, and TC 131 Fluid power systems. Many standards on natural gas properties are produced by TC 193 Natural gas.

TC 30’s remit is to produce standards on flow measurement in pipes for general use. As a result, standards produced by ISO/TC 30 are referred to by many other technical committees, and work undertaken by TC 30 affects a wide range of industries. The author of this article had 15 years as the Chairman of ISO/TC 30, and is now Chairman of ISO/TC 30/SC 2 Differential Pressure Meters. To avoid duplication of ISO standards, the ideal arrangement between ISO/TC 30 and any other ISO TC is that a flow-measurement standard will be produced by TC 30, and standards from other TCs will refer to it, adding instructions for specific applications where required.

This article is written to encourage participation in making standards. Standards are not infallible: they include engineering judgment where data are not available; continuous improvement is always desirable. Standards are of great importance: according to DTI Economics Paper No 12 of 2005 standards contributed to about 13 per cent of the increase in labour productivity over the period 1948-2002 and contribute £2.5 billion annually to the UK economy. It is also worth noting that participation in standards-making is an opportunity not only to share knowledge but also to gain it.

Michael Reader-Harris is Principal Consultant at TUV SUD NEL. TUV SUD NEL is a world-class provider of technical consultancy, research, testing and programme management services. Part of the TÜV SÜD Group, TUV SUD NEL is also a global centre of excellence for flow measurement and fluid flow systems and is the UK’s National Measurement Institute for Flow Measurement.

For further information please visit: www.tuv-sud.co.uk

TUV SUD NEL is a global centre of excellence for flow measurement and fluid flow systems and is the National Measurement Institute responsible for the UK’s National Flow Measurement Standards. As an international technology services organisation and provider of pipeline fluid management services to the global petroleum industry, the company has an impressive track record in the development, design and application of new technologies. TUV SUD NEL is a trading name of TUV SUD Ltd, a company of the TÜV SÜD Group, an international service organisation with more than 24,000 employees and over 1000 locations in around 50 countries.

For further information please visit: www.tuvnel.com