Flowmeters

Frontmatter

1. Basic Principles of Fluid Flow

Abstract

This book is about measuring the flow of fluids, and especially of fluids contained in pipes and ducts. To understand this subject it is useful to know something about the way fluids behave, and especially about the properties mentioned below.

Alan T. J. Hayward

2. Basic Principles of Flow Measurement

Abstract

The term ‘flow measurement’ can refer to any of six different types of measurement. These are briefly described below.

Alan T. J. Hayward

3. Differential Pressure Meters

Abstract

For many years, differential pressure meters were the only devices available for measuring volumetric flowrate in a pipe with reasonable accuracy at a reasonable cost. Nowadays there are many alternatives, but even so, the differential pressure meter family still holds the largest slice of the market.

Alan T. J. Hayward

4. Other Flowrate Meters Utilising Pressure Difference

Abstract

There are many other flowrate meters which, although not qualifying as differ­ential pressure meters, make use of pressure differences generated in flowing fluids. The most important types of these are described in this chapter.

Alan T. J. Hayward

5. Rotating Mechanical Meters

Abstract

This chapter is concerned with rotating mechanical flowmeters of the ‘full-bore’ type, for measuring either the total volume or the volumetric flowrate of a fluid flowing in a pipe. Rotating mechanical devices used for measuring velocity at a point are dealt with in Chapter 7, and those used for mass flow measurement in Chapter 8.

Alan T. J. Hayward

6. Other Volumetric Flowmeters

Abstract

The electromagnetic flowmeter utilises the same basic principle as the electrical generator: when a conductor moves across a magnetic field a voltage is induced in the conductor, and the magnitude of the voltage is directly proportional to the speed of the moving conductor. If the conductor is a section of conductive liquid flowing in a non-conductive pipe through a magnetic field, and electrodes are mounted in the pipe wall at the positions shown in Figure 6.1, the voltage induced across the electrodes should be proportional to flowrate.

Alan T. J. Hayward

7. Fluid Velocity Measuring Instruments and Insertion Meters

Abstract

Thus far this book has been concerned with meters for measuring total flow and flowrate in pipes. We come now to instruments of a related but essentially different type, namely instruments for measuring the velocity at a point of a flowing fluid.

Alan T. J. Hayward

8. Special Problems in Flow Metering

Abstract

There are two alternative ways to tackle the problem of measuring mass flowrate. One is to design a meter whose response is a function of mass flowrate only, so that a knowledge of the physical properties of the fluid is not necessary. Such meters are known as ‘true mass flowmeters’.

Alan T. J. Hayward

9. Choosing the Right Flowmeter for the Job

Abstract

In principle there is no room for argument about what ‘the right flowmeter for the job’ means. The right flowmeter is the one that will do the job adequately at the lowest possible total cost, including initial cost, running costs, and the indirect costs arising from inaccurate measurements and from loss of plant utilisation when the flowmeter is out of action.

Alan T. J. Hayward

10. Pitfalls, and How to Avoid Them

Abstract

One thing must be made plain at the outset: the way a flowmeter is installed matters a lot.

Alan T. J. Hayward

11. How to Calibrate Flowmeters and Velocity Meters

Abstract

Where anything more than a moderate standard of accuracy is required, flowmeters need calibration. Sometimes, as in the case of large turbine meters used for the fiscal metering of petroleum, the meters may have to be calibrated every day against a built-in calibration device. At the other extreme, some meters may only need to be taken out of the line for calibration once every couple of years or so, in which case the user will probably prefer to send them to an independent laboratory rather than to maintain his own calibration facilities.

Alan T. J. Hayward

12. Instrumentation used with Flowmeters

Abstract

This is an enormous subject which really needs a book-or, rather, a series of books-to itself, and this chapter must therefore have a very limited aim. This is firstly to deal with a few matters of special importance to flowmeter users, such as the design of piezometer rings and thermometer pockets, secondly to give some idea of the great variety of equipment now available, and thirdly to offer a few practical tips on the use of some of the devices most commonly found in flow metering situations.

Alan T. J. Hayward

13. Where to go for Help and Information

Abstract

The purpose of this chapter is to bring together a collection of miscellaneous information likely to benefit the flowmeter user faced with the need for calibrations, for advice or for information. Sources of published information on specific areas have already been given in the ‘Where to learn more’ sections at the end of the earlier chapters; this chapter fills in the gaps by listing the information sources of a more general character.

Alan T. J. Hayward

Backmatter