GB2135457A

GB2135457A - Improvements in or relating to apparatus for flow measurement

Info

Publication number: GB2135457A
Application number: GB08303811A
Authority: GB
Inventors: Alwyn Michael Dobson; William David Nichol Pritchard
Original assignee: British Steel Corp
Current assignee: British Steel Corp
Priority date: 1983-02-11
Filing date: 1983-02-11
Publication date: 1984-08-30
Also published as: GB8303811D0

Abstract

The invention provides apparatus for the ultrasonic measurement of flow of fluid in a conduit (1) including at least two sets of ultrasonic transducers (9) facing each other across the conduit, the transducers in each set being spaced apart along the conduit of a baseplate (3), in which the members of the sets of transducers on one side of the conduit are mounted within at least one tube (4) mounted upon and connecting with (6) the interior of the conduit, each such tube incorporating an isolating valve (7) between the conduit and the or each transducer, the arrangement being such that the or each transducer is removable from its associated tube in location upon the conduit after actuation of the isolating valve. A welded self-aligning frame for the apparatus is provided. <IMAGE>

Description

SPECIFICATION Improvements in or relating to apparatus for flow measurement This invention relates to apparatus for flow measurement, and more particularly to ultrasonic apparatus for flow measurement of a fluid within a conduit, especially but not exclusively gases at or near atmospheric pressure.

It has previously been proposed to use ultrasonic devices for measuring flow of a fluid through a conduit in which for example two sets of ultrasonic transmitters and related receivers are spaced apart along the conduit, and correlation between the signals impinging upon receivers from their respective transmitters is used to calculate the speed of flow through the conduit.

It is an object of the present invention to provide improved apparatus for this purpose.

According to the invention there is provided apparatus for the ultrasonic measurement of flow of fluid in a conduit including at least two sets of ultrasonic transducers facing each other across the conduit, the transducers in each set being spaced apart along the conduit, in which the members of the sets of transducers on one side of the conduit are mounted within at least one tube mounted upon and connecting with the interior of the conduit, each such tube incorporating an isolating valve between the conduit and the or each transducer, the arrangement being such that the or each transducer is removable from its associated tube in location upon the conduit after actuation of the isolating valve.

Each tube may be mounted directly on the conduit by welding for example, or alternatively may be mounted upon a baseplate itself arranged to be secured to the conduit.

It is to be appreciated that the ultrasonic transducers will be located in their associated tubes so as to be directed for transmission and reception of ultrasonic pulses directly down the associated tube and into and across the conduit.

In one embodiment of the invention we have found that it can be advantageous in reducing adverse sound reflections from across the conduit if the sets of transducers are angled with respect to the axis of the conduit so that in practice transmission and reception transducers face each other at an angle inclined with respect to the axis of the conduit thereacross.

The transducers may be mounted at the furthermost ends of their associated tubes from the wall of the conduit to improve their removability.

In order that the invention may be more readily understood two embodiments thereof will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side elevation of a first embodiment of the invention of two transducer members and associated apparatus according to the invention: Figure 2 is a side elevation of a second embodiment of the invention; and Figure 3 is a side elevation for the support structure of the embodiment of Figure 2.

In Figure 1 one side only of a gas flow conduit 1 is illustrated on which is mounted an assembly 2 of two transducers. It will be appreciated that on the other side of the conduit which is not illustrated an identical assembly of transducers will be arranged facing in line with the transducer assembly illustrated.

The transducer assembly comprises a baseplate 3 secured to the conduit. Tubes 4 are welded (as shown at 5) to the baseplate 3, openings 6 in the conduit wall communicating with the interior space of the tubes.

The tubes lead from the conduit to isolating valves 7 and then onto transducers 8 secured and sealed to the ends thereof.

The isolating valves will be of any convenient full bore design and each serves to enable the transducer at the end of its respective tube to be isolated from the conduit so that the transducer may be easily removed for maintenance purposes.

It will be observed that the tubes 4 and the transducers 8 mounted at the ends thereof are at an inclined angle with respect to the axis of the conduit and it will be appreciated that the corresponding tubes and transducers of the complimentary transducer assembly (not shown) mounted on the other side of the conduit will be similarly inclined so as to be directed towards the assembly illustrated. By this means we have found that adverse sound reflections during operation are reduced.

The use of a baseplate 3 with the assembly 2 as illustrated greatly enhances the ability to align the assembly correctly with respect to the conduit 1 and in addition ensures minimum disruption of fluid flow through the conduit during installation.

An alternative arrangement would be to provide the appropriate transducer assemblies mounted upon a short section of the conduit which for installation purposes could be inserted into and replace part of the existing air flow conduit by means of annular flanges for example.

It will be appreciated that by means of the invention transducers of large diameter can be incorporated. Typically the face 9 can be 25 to 50 mm in diameter. By using such large diameter transducers sufficient transducer power can be assured for pulse signal transmission and reception.

The operating electrical and electronic circuitry of the assembly illustrated can be of known nature. However, we have found it particularly advantageous to provide a transducer frequency in the range of 15 to 500 KHZ. With a frequency in this range we find that we avoid excessive attenuation created by high frequencies whilst also avoiding the problem of a wide beam angle with lower frequencies.

As will be seen two transducers are diposed side by side along the line of the transducer. Each of these are arranged to transmit and/or receive pulses in association with the identical assembly located on the other side of the duct. Flow measurements can be attained by known electronic circuitry using for example correlation techniques. It is to be noted that two sets of transducers will be arranged to operate at slightly different frequency such as 470 KHZ and 486 KHZ.

The arrangement as illustrated can be used with respect to conduits from 10 cm to 3 meters in diameter. The angle of inclination with respect to the duct can be 900, 800 or 45 0. An inclination of 800 is preferred but if the sound signal is sufficiently intense, a sharper angle (and hence longer signal path) can be used.

In one embodiment of the invention the duct was 450 mm in diameter, the transducers were spaced apart 50 mm along the length of the duct at an angle of 450 to the axis of the duct and flow measurements between 6 and 38 meters per second were successfully carried out using a known correlation electronic circuit.

The embodiment illustrated in Figure 2 is similar to that of Figure 1. However it is to be noted that in this embodiment two transducers 10 (each of about 32 mm diameter) are located within a single conduit tube 11 welded via a baseplate 12 to the conduit 1 at an angle of approximately 800 thereto. The conduit tube 11 is provided with electrical connections 1 3 for the transducers. A sliding gate valve 14 is provided to enable the tube 11 to be isolated from the conduit 1 for access to the transducers 1 0.

Figure 3 illustrates a welded self-aligning frame 1 5 for carrying the apparatus of Figure 2 on both sides of the conduit 1. The frame arrangement enables installation of the apparatus with the minimum of on site work and welding, including by suitable means the installation whilst the duct is filled with gas and operational.

Claims

1. Apparatus for the ultrasonic measurement of flow of fluid in a conduit including at least two sets of ultrasonic transducers facing each other across the conduit, the transducers in each set being spaced apart along the conduit, in which the members of the sets of transducers on one side of the conduit are mounted within at least one tube mounted upon and connecting with the interior of the conduit, each such tube incorporating an isolating valve between the conduit and the or each transducer, the arrangement being such that the or each transducer is removable from its associated tube in location upon the conduit after actuation of the isolating valve.

2. Apparatus as claimed in Claim 1 wherein the tubes are mounted directly on the conduit.

3. Apparatus as claimed in Claim 1 wherein the tubes are mounted upon a baseplate which is arranged to be secured to the conduit.

4. Apparatus as claimed in any one of the preceding claims wherein the sets of transducers are angled with respect to the axis of the conduit so that the sets face each other across the conduit at an angle inclined to the axis of the conduit.

5. Apparatus as claimed in any one of the preceding claims wherein the tubes are cylindrical and each transducer is mounted within its associated tube such as to be aligned with the axis thereof.

6. Apparatus as claimed in Claim 5 as dependent upon Claim 4 wherein the tubes are inclined to the axis of the conduit.

7. Apparatus as claimed in any one of the preceding claims wherein the transducers are mounted within the tubes at the ends thereof remote from the conduit.

8. Apparatus as claimed in any one of the preceding claims wherein the valve is a full bore sliding gate valve.

9. Apparatus for the ultrasonic measurement of flow of fluid in a conduit substantially as shown in and as hereinbefore described with reference to Figure 1 or Figure 2 and 3 of the accompanying drawings.