An acoustic flow meter in the form of a valve key has an acoustic
sensor 12 for measuring the peak sound level which occurs when the
key is used to close a valve in a fluid pipeline. The peak sound
level can be used to accurately calculate the flow through the valve
and provide the flow information on a display unit 11. Parameters
for the upstream supply pressure, pipe diameter and valve characteristics
can be entered to ensure the accuracy of the flow calculations.
The key therefore provides a way of determining fluid flow in a
pipeline to a reasonable level of accuracy without having to install
in-line flow meters.
1. An acoustic flow meter including a shaft which, when in a vertical
position, has a valve-operating head at its lower end for engagement
with a flow control valve and a rotation handle at its upper end
by which the shaft can be manually rotated to progressively close
a flow control valve engaged by the valve-operating head, and an
acoustic sensor for converting sounds produced by the flow of fluid
through the valve into electrical output signal which varies with
2. An acoustic flow meter according to claim 1 in which the valve
operating head includes a resiliently-biassed acoustic coupling
element for engagement with the valve.
3. An acoustic flow meter according to claim 1 which includes a
processing unit which uses said electrical output signal to produce
a calculated value for the flow through the valve.
4. An acoustic flow meter according to claim 3 which includes a
visual display unit for displaying said calculated value.
5. An acoustic flow meter according to claim 3 which includes an
electronic communications port through which the processing unit
can transfer data with external equipment.
6. An acoustic flow meter according to claim 1 which includes a
boot located about the shaft for contact with a surface surrounding
a hole in which the valve is located.
7. An acoustic flow meter according to claim 7 in which the boot
is rotatably mounted relative to the shaft.
8. An acoustic flow meter according to claim 7 which includes a
rotation gauge for providing an indication of the relative rotation
between the boot and the shaft.
9. A method of measuring flow through a fluid supply pipeline provided
with a valve, which includes: providing an acoustic sensor to sense
the level of sound produced by fluid flowing through the pipeline
in the vicinity of the valve; progressively closing the valve to
measure the peak sound level produced during closure of the valve;
and using said measured peak sound level to determine the magnitude
of flow through the pipeline.
10. A method according to claim 9 in which the magnitude of the
flow through the pipeline is calculated by means of a processing
unit taking into account at least one of: the upstream fluid supply
pressure in the pipeline; the characteristics of the valve; and
the diameter of the pipeline.
TECHNICAL FIELD OF THE INVENTION
 This invention relates to an acoustic sluice valve flow
meter in the form of a valve key.
 When monitoring for leaks in a water supply network it is
common to monitor the flow at a convenient point in the network
during off-peak periods, e.g. at night, when water consumption is
likely to be low or non-existent. The amount of leakage in the system
can then be calculated by subtracting the anticipated usage from
the measured flow.
 Orifice meters are commonly used to measure flow in pipes.
These work on the principle of causing water to flow through a restriction
in a pipeline which results in a reduction in pressure. The flow
of water can be accurately calculated from the measured pressure
reduction taking into account the physical characteristics of the
pipe and the restriction.
 Since a flow meter must be physically connected into the
pipeline it is not always possible to measure flow at any desired
position in a supply network. Furthermore, the installation of flow
meters at all points where flow is likely to be measured would be
 A technique commonly used for pinpointing leaks in water
pipelines is to detect the noise generated by the leaking water.
This can be done manually by ear using sounding sticks or ground
microphones. The loudness of the sound is related to the rate of
flow and the proximity of the leak. However, such a technique is
only suitable for locating leaks within a relatively small area
and cannot be used to provide a quantitative measurement of leakage
within a large supply network.
 The present invention seeks to provide a new and inventive
way of providing a reasonably accurate measurement of flow at positions
in a supply network where there is no flow meter installed.
SUMMARY OF THE INVENTION
 The present invention proposes an acoustic flow meter including
a shaft which, when in a vertical position, has a valve-operating
head at its lower end for engagement with a flow control valve and
a rotation handle at its upper end, and an acoustic sensor for converting
sounds produced by the flow of fluid through the valve into electrical
output signal which varies with flow.
 The invention also provides a method of measuring flow through
a fluid supply pipeline provided with a valve, which includes:
 providing an acoustic sensor to sense the level of sound
produced by fluid flowing through the pipeline in the vicinity of
 progressively closing the valve to measure the peak sound
level produced during closure of the valve; and
 using said measured peak sound level to determine the magnitude
of flow through the pipeline.
BRIEF DESCRIPTION OF THE DRAWINGS
 The following description and the accompanying drawings
referred to therein are included by way of non-limiting example
in order to illustrate how the invention may be put into practice.
In the drawings:
 FIG. 1 is a general side view of an acoustic sluice valve
flow meter in accordance with the invention;
 FIG. 2 is a block circuit diagram of the electronic components
of the flow meter;
 FIG. 3 is a graph showing the variation in an acoustic output
signal which is obtained when a valve is closed using the flow meter;
 FIG. 4 is a graph relating the true flow values to the values
calculated using the flow meter with various kinds of valve.
DETAILED DESCRIPTION OF THE DRAWINGS
 Referring to FIG. 1 an acoustic sluice valve flow meter
in the form of a valve operating key 1 includes an elongate metal
shaft 2 which is shown in an upright position in which it is normally
used. At the bottom end of the shaft there is a valve-operating
head 3 which is attached by means of a quick-release coupling 4
so that different heads can easily be fitted for operating different
kinds of water flow-control valve, e.g. sluice valves, stopcocks
and the like. In general, the head 3 may be a hollow shell which
is open at the lower end, shaped to fit over and engage the operating
member of a suitable valve (not shown). At the top end of the shaft
2 there is a transversely-projecting turning bar 5 by which the
key may be manually rotated about the axis of the shaft in order
to operate the valve.
 An acoustic coupling element 6 is mounted generally co-axially
within the shaft 2 to project into the head 3. The coupling element
is resiliently biassed by means of a spring 7 in order to ensure
firm contact pressure with the valve and thereby provide a good
acoustic connection. The element 6 is mechanically coupled through
the shaft 2 via a water-tight acoustic coupling 8 to a remotely-located
electromechanical acoustic sensor indicated at 20. By locating the
sensor at the upper end of the shaft 2 the sensor may be protected
from physical damage or contamination with water or other substances
which may adversely affect its operation. The sensor may be acoustically
insulated to reduce pickup of unwanted external noises.
 Referring to FIG. 2 the sensor 20 operates in the manner
of a microphone to convert sounds into electrical signals. The signals
may represent the amplitude of sounds received through the coupling
element 6 in a simple analogue form or in an encoded form using
pulse width modulation, digital encoding etc. The electrical signals
from the sensor travel to an electronic processing unit 22 mounted
within a water-tight housing 10 (FIG. 1) at the top of the shaft
2. The processing unit 22 is connected with a display unit 11 mounted
on top of the housing to indicate the flow through the valve, e.g.
by means of a digital display, meter, bargraph or the like. In addition,
the processing unit is provided with a communications interface
23 and an external communications port 24 to exchange data with
a remote monitoring point, e.g. by means of an RS232 or similar
serial communication link, or by radio signals, infra red etc. A
keypad 26 or similar input device may be provided on the display
unit 11 to allow information to be manually input into the processing
unit 22 when required.
 In order to reduce the pickup of external noises a flexible
boot 30 is slidably mounted on the shaft 2 as shown in FIG. 1.
The boot is of part-conical shape with an outwardly projecting flange
32 at its lower end having a flexible sealing bead 33 on its undersurface.
The boot can thus be moved along the shaft to rest on the ground
while the head 3 is engaged with the valve. The boot may be coupled
to the shaft via a flexible joint 34 allowing the boot to seat on
uneven ground. A rotation gauge 36 can be used to couple the boot
to the shaft to permit accurate measurement of the angle through
which the shaft has been rotated relative to the boot which is held
stationary by contact with the ground. The gauge allows accurate
setting of the amount by which the valve is opened. The gauge can
provide a manual reading and/or electronic data for use by the processor
 FIG. 3 shows the variation in sound level as detected by
the sensor 20 when the key is used to progressively close a typical
gate valve. The graph clearly shows that the sound level reaches
a distinct peak just before the valve is fully closed. By measuring
the peak sound level as the valve passes through the maximum it
is possible to calculate the flow through the pipeline using the
 where Q is the flow, P is the upstream supply pressure,
S is the peak sound level and a, b and c are constants determined
by the pipe diameter, the physical characteristics of the valve
etc. Since the upstream pressure will usually be known it is therefore
possible for the processing unit to accurately calculate the flow
from the measured peak sound level.
 It has been found that this method of calculating the flow
is surprisingly accurate. FIG. 4 shows the how the actual flow measured
using accurate flow measurement equipment is related to the flow
measured by means of the present invention using a number of different
kinds of valve. In most cases an accuracy to within 10 per cent
is possible, which although not as accurate as calibrated orifice
meters is sufficient for many purposes.
 The level of accuracy can be maximised by manually entering
accurate figures for the upstream supply pressure, the diameter
of the pipeline and the characteristics of the valve. Users can
conveniently be provided with a choice of known valve types from
which to select, which automatically enters the appropriate valve
parameters. Additional data from the rotation gauge 36 can also
be used to ensure that the flow calculation is accurate.
 The key thus provides a convenient and simple method of
measuring flow to a reasonable level of accuracy without the inconvenience
and expense of installing in-line flow meters.
 Although the key is intended for use with water control
valves it could also be used with valves for controlling the flow
of other fluids.
 It will be appreciated that the features disclosed herein
may be present in any feasible combination. Whilst the above description
lays emphasis on those areas which, in combination, are believed
to be new, protection is claimed for any inventive combination of
the features disclosed herein.