The ISO 5167 Story


ISO 5167: a measurement standard that delivers

The money involved in differential-pressure flow measurement is enormous.  Most flows can be measured using an orifice plate or a Venturi tube.  An orifice plate has the special and valuable property that it does not require calibration in a flowing fluid, but the flow can be calculated from ISO 5167.  So the actual equations in ISO 5167 are of immense importance: the measured flow is directly proportional to both the discharge coefficient and the expansibility factor, for which the equations were both derived at NEL.  In the last few years both equations have been shown to deliver what they promise: the data for the discharge coefficient equation are given in Figure 1.  Fulfilment of the promise depends both on the equations and on the design of the orifice meter being in accordance with ISO 5167 (and ISO 5167 being correct).

Discharge Coefficient Data

Figure 1: Percentage mean deviation in discharge coefficient from the Reader-Harris/Gallagher (1998) Equation (in ISO 5167) from more than 50 orifice plates not used to fit the Equation (almost all the data were published in 2001 or later)

A deep understanding

A systematic record and an analysis of the experimental data on which ISO 5167 is based have been undertaken and published by Michael Reader-Harris of NEL as ‘Orifice Plates and Venturi tubes’ (Springer, 2015).  The analysis is based on an understanding of the physics of the flow gained from experiment and computational fluid dynamics over a career at NEL particularly devoted to this topic.

Impact and relevance

‘Orifice Plates and Venturi tubes’ enables the reader to estimate the effect of a deviation from ISO 5167.  Moreover, the book will be particularly useful for members of standards working groups and committees when it comes to revise ISO 5167: it shows where the data can be found to justify each clause and how the data have been analysed.  At present the author chairs BSI CPI 30/2 (differential pressure meters) and ISO/TC 30 (flow measurement), but he has now ensured that in due course his successors can build on what has been achieved.

In the UK most natural gas is measured at least once using an orifice plate: each year perhaps £25 billion of natural gas is so metered with an uncertainty of about £250 million.  NEL and others have done work over decades to ensure that ISO 5167 is correct, that is fully justified, neither inadequately restrictive, causing error, nor too restrictive, causing unnecessary expense.

ISO 5167 is not restricted to measurements of natural gas; it is referred to in standards of many ISO Technical Committees: in a survey a few years ago there were references in the standards of the following 13 Technical Committees (in addition to Measurement of fluid flow in closed conduits and Natural Gas): Refrigeration and air-conditioning, Compressors and pneumatic tools, machine and equipment, Road vehicles, Fire safety, Industrial fans, Welding and allied processes, Acoustics, Cleanrooms and associated controlled environments, Equipment for fire protection and fire fighting, Gas turbines, Hydrometry, Pumps, and Valves (TCs with references in many standards are given first).  Such wide use demonstrates the value of years of effort.

Flow Measurement and Fluid Mechanics Research Centre

A research and development centre, which will play a pivotal role in the understanding of complex flows, benefiting the energy, manufacturing and process industries, is opening next April at Coventry University.

The Flow Measurement and Fluid Mechanics Research Centre brings together unique expertise and facilities from Coventry University and NEL, as well as partner Universities. The centre will embrace new approaches to flow instrumentation and modelling as well as developing better understanding of the fundamentals of flow of gases and liquids used in a wide range of sectors, including oil and gas, aerospace, food, process industries, water, nuclear, and automotive.

The research centre will have a huge impact on optimisation of processes involving flows of complex mixtures.

Professor Andrew Hunt, the interim Executive Director of the centre, said:

The centre willbe the first of its kind to embrace a new approach to flow measurement across a wide range of application areas.  To achieve this we have drawn together a strong multidisciplinary team including experts in mathematics, engineering, control theory, fluid dynamics,pervasive computing, manufacturing and instrumentation. Conventional flow measurement methods rely on limiting the effect of the complexity of flows, whereas we plan to simultaneously measure and model that complexity through a network of self-monitoring sensors, located within the pipeline or instrument. This gives more accurate data and is the cornerstone of better decision making, allowing end users to take efficient action to optimise their processes.”

By 2020 Coventry University, with its partners, will build the foundations for a first-class thirty student-strong doctoral training centre, establishing the research centre as a thought-leading authority in flow measurement and fluid mechanics by 2025.

The uniquely equipped research centre will prioritise the development and testing of new concepts – from design and prototyping of new instrumentation,development of new models, through to practical testing in real-world trials – with a key focus on developing research impact in three significant areas:

  • Novel Measurement Techniques for Complex Flows
  • Flow Measurement Uncertainty and Diagnostics
  • Regimes in Multi-Component Flows

We are already working with a range of clients and developing a number of projects. The developments achieved by the centre will position Coventry University as the key academic leader in regards to the monitoring, analysis, and understanding of fluid mechanics and complex flow measurement.

Brian Millington, Managing Director of NEL, said:

“We are delighted to be working with Coventry University in the development of this centre. I believe that this will help establish the UK as the world lead in flow measurement, particularly in the field of high-pressure multiphase measurement. Through this we, and other partners, can realise our shared vision to develop a doctoral training centre in flow measurement and fluid mechanics within the foreseeable future. This will help maintain the UK’s growing position in complex flow measurement.”

For further information about the centre please contact us at the FMI or James Stride at Coventry University.

Offshore Europe

FMI hosted a networking reception at Offshore Europe in September 2015.

We were delighted to welcome over 40 people from the flow measurement community to the stand.  As well as allowing some very familiar faces to chat, there were several new contacts made and a couple of new initiatives emerged too.

The flyers used to describe and promote the FMI are available to download.

Offshore Europe Achievements Offshore Europe Flyer Background and Objectives

Industry Consultation

The Flow Measurement Institute was formed following extensive industry consultation, the outputs of which are available to view in the download below.

Following facilitated and chaired discussion sessions, attendees were asked for their feedback on a range of topics.  The responses from representatives of over 60 organisations were used to shape and develop the FMI.

Subsequent consultations, including over 300 people at the 2014 North Sea Flow Measurement Workshop, have shown that the initial results are truly representative of industry.

The FMI exists for the benefit of its members.  Please get in touch to comment on, or add to, the original consultation findings.




Offshore Europe Expo

We’ll be at Offshore Europe in Aberdeen from 8 – 11 September so why not come and say hello?  We’d love to hear the highs and lows of life in flow measurement and you can make new contacts at the same time.  We’ve got a long list of achievements from our first year of operation which we’d love to share.

Our stand is shared with NEL and will be manned throughout the show – 2E38.

There is a networking reception on the stand at 3pm on Thursday 10th.  This is a super opportunity to hear more about the 4 groups which are delivering the vision and to make sure your organisation’s interests are being represented.

Please let us know if you’d like to come to the reception so we can order enough refreshments.  Call on +44 (0) 1355 220222 or use the contact form on this site.