The Concise Industrial Flow Measurement Handbook

A Definitive Practical Guide

Michael A. Crabtree

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9781000754407
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

The Concise Industrial Flow Measurement Handbook: A Definitive Practical Guide covers the complete range of modern flow measuring technologies and represents 40 years of experiential knowledge within a wide variety of industries, and from more than 5000 technicians and engineers who have attended the author's workshops.

This book covers all the current technologies in flow measurement, including high accuracy Coriolis, ultrasonic custody transfer, and high accuracy magnetic flowmeters. The book also discusses flow proving and limitations of different proving methods. This volume contains over 300 explanatory drawings and graphs and is presented in a form suitable for both the beginner, with no prior knowledge of the subject, as well as the more advanced specialist.

This book is aimed at professionals in the field, including chemical engineers, process engineers, instrumentation and control engineers, and mechanical engineers.

1

Background and History

1.1 Introduction

Over the past 60 years, the importance of flow measurement has grown, not only because of its widespread use for accounting purposes, such as the custody transfer of fluid from the supplier to consumer, but also because of its application in manufacturing processes. Throughout this period, performance requirements have become more stringent – with unrelenting pressure for improved reliability, accuracy,* linearity, repeatability, and rangeability.

These pressures have been caused by major changes in manufacturing processes and because of several dramatic circumstantial changes such as the increase in the cost of fuel and raw materials, the need to minimise pollution, and the increasing pressures being brought to bear in order to adhere to the requirements for health and safety.

Industries involved in flow measurement and control include:

•Food and beverage

•Medical

•Mining and metallurgical

•Oil and gas transport

•Petrochemical

•Pneumatic and hydraulic transport of solids

•Power generation

•Pulp and paper

•Distribution

Fluid properties can vary enormously from industry to industry. The fluid may be toxic, flammable, abrasive, radio-active, explosive, or corrosive; it may be single-phase (clean gas, water, or oil) or multi-phase (e.g. slurries, wet steam, well-head petroleum, or dust-laden gases).

The pipe carrying the fluid may vary from less than 1 mm to many metres in diameter. Fluid temperatures may vary from close to absolute zero to several hundred degrees Celsius and the pressure may vary from high vacuum to many thousands of bar.

Because of these variations in fluid properties and flow applications, a wide range of flow metering techniques have been developed with each suited to a particular area. However, of the numerous flow metering techniques that have been proposed in the past, only a few have found widespread application and no one single flowmeter can be used for all applications.

1.2 Why Measure Flow?

There is of course no single answer. Flow measurement is normally concerned with the question of ‘how much’ – how much is produced or how much is used. For small quantities this can normally be achieved by volumetric measurement (e.g. pulling a pint of beer). But as the amount grows larger this becomes impractical and, for example, it becomes necessary to measure the volumetric flow (e.g. dispensing fuel from a garage petrol pump).

However, most petrol pump calibration is carried out using a test measuring can, which is a purely volumetric measurement. On this basis, during hot weather, it would be prudent to purchase petrol early in the morning when the temperature is low so that you would end up with more mass per litre. Alternatively, a more practical and consistent approach would be to make use of a mass flow metering system.

A further use of a flow measuring system is to control a process. In closed-loop regulatory control, there are several instances where the prime consideration is repeatability rather than accuracy. This is particularly true in a cascaded system where the prime objective is not to control the inner loop to an absolute value but rather to increment up or down according to the demands of the master. Another instance of where absolute accuracy is relatively unimportant is in controlling the level of a surge tank. Here, the requirement is to allow the level to vary between an upper and lower value and absorb the upstream surges – thus preventing them from being passed downstream.

Accuracy is of prime importance in automatic blending control, batching and, of course, custody transfer and fiscal metering. In fluid measurement, custody transfer metering involves the sale, or change of ownership, of a liquid or gas from one party to another. On the other hand, fiscal measurement involves the levering of taxes – again relating to the production or sale of a liquid or gas.

1.3 Background

The book, Principles and Practice of Flow Meter Engineering by L.K. Spink, first published in 1930, is generally recognised as the first, and for many years the only, definitive collected ‘body of knowledge’ appertaining to industrial flow measurement. Undergoing nine revisions, the last addition was printed in 1978 – 21 years after Spink’s death.

In the flyleaf of this last addition the publishers lay claim to the book covering ‘… the latest developments in flow measurement’. A weighty tome, by anyone’s standards, the book comes in at 575 pages. However, in essence Principles and Practice of Flow Meter Engineering is a eulogy ‘… devoted primarily to the characteristics of flow rate measurement based on a differential pressure generated by the flow of liquid through a restriction (such as an orifice) inserted in a line’.

Only a single page is devoted to the magnetic flow meter. A single page is likewise devoted to the turbine meter. And barely a single paragraph is used to allude to ultrasonic, thermal, and vortex-shedding meters – already key players in the field of flow measurement. And barely a single page is dedicated to the electrical pressure transmitter (already in common use in 1978) – contrasting noticeably with long descriptions covering a variety of mechanical–pneumatic-type transmitters.

Readers, lured into purchase of the ninth edition of his book by the flyleaf promise of ‘new data on the target meter’, might be disappointed to discover less than two pages devoted to the subject. A similar enticement extends to the promise of new data on the Lo-Loss tube, which is similarly dismissed in approximately a page and a half.

Of course, it could be said of Spink’s work that he spent most of his life in the oil and gas industries and was instrumental in the early work of the American Gas Association. In the oil and gas industry, in particular, conservatism is rife. A case in point is that in the United States, most graduate facility engineers are taught in, and make use of, the metric SI system (abbreviated from the French Le Système International d’Unités). And yet, because of their mentoring programme, they will have a reverted back to fps (the Imperial ‘foot–pound–second’ system used extensively in the United States) within a few years.

Generally regarded as the heir apparent to Spink, R.W. Miller’s Flow Measurement Engineering Handbook weighs in at more than 1,000 pages. Although still referenced as a standard for orifice plate sizing, the second edition, published in 1989 still devoted less than 15 pages in total to the combined technologies of magnetic, ultrasonic, and Coriolis metering.

Too many process engineers, having had extensive experience with measuring instruments and systems that have stood the test of time, see no reason to change. Consequently, they will cling to the familiar, despite numerous shortcomings when compared with the benefits offered by newer systems. And so, more than 50 years after Spink’s death, the orifice plate still reigns supreme – not because of its technological superiority but because of the industry’s unwillingness to accept and implement new ideas and new technologies.

1.4 History of Flow Measurement

Early flow measurement was centred round the question of disputation: ‘how much has he got’ versus ‘how much have I got’. As early as 5000 BC flow measurement was used to control the distribution of water through the ancient aqueducts of the early Sumerian civilisations from the Tigris and Euphrates rivers. Such systems were very crude, based on volume per time: for example diverting flow in one direction from dawn to noon, and diverting it in another direction from noon to dusk. And although not fully comprehending the principles, the Romans devised a method of charging for water supplied to baths and residences, based on the cross-sectional areas of pipes.

The first major milestone in the field of flow technology occurred in 1738 when the Swiss physicist Daniel Bernoulli published his Hydrodynamica (Bernoulli 1738) in which he outlined the principles of the conservation of energy for flow. In his book, he produced an equation showing that a...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• Preface
• Author
• Units Conversion
• Chapter 1: Background and History
• Chapter 2: Fluid Mechanics
• Chapter 3: Measurement Considerations
• Chapter 4: Flow Profile and Conditioning
• Chapter 5: Positive Displacement Meters
• Chapter 6: Head Loss Meters
• Chapter 7: Inferential Volumetric Meters
• Chapter 8: Oscillatory Flow Meters
• Chapter 9: Electromagnetic Flowmeters
• Chapter 10: Ultrasonic Flowmeters
• Chapter 11: Coriolis Mass Flowmeters
• Chapter 12: Thermal Mass Flowmeters
• Chapter 13: Open Channel Flow Measurement
• Chapter 14: Multiphase Flow Metering
• Chapter 15: Meter Proving
• Chapter 16: Common Installation Practices
• Chapter 17: Flow Meter Selection
• References and Bibliography
• Index