GB1579877A

GB1579877A - Method and device for measuring a pressure in a conduit

Info

Publication number: GB1579877A
Application number: GB1436877A
Authority: GB
Original assignee: Ballast Nedam Groep NV
Current assignee: Ballast Nedam NV
Priority date: 1976-04-07
Filing date: 1977-04-05
Publication date: 1980-11-26
Also published as: BE853237A; FR2347667B1; DE2715050A1; DE2715050B2; NL7603673A; NL161221C; NL161221B; JPS52123680A; FR2347667A1; DE2715050C3

Description

(54) METHOD AND DEVICE FOR MEA SURING A PRESSURE IN A CONDUIT (71) We, BALLAST-NEDAM GROEP N.V.

and AMSTERDAMSE BALLAST BAGGER EN GROND (AMSTERDAM BALLAST DREDGING) B.V., both Body Corporates organised and existing under the Laws of the Netherlands, of 2 Laan van Kronenburg, Amstelveen, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement : This invention relates to a method of and apparatus for measuring the pressure of a suspension, for example slush, flowing through a conduit.

Such a method and apparatus is already known in which the pressure of the suspension is transferred through a liquid-filled duct from one end thereof which opens into the conduit to a pressure transducer at its other end, which pressure transducer transmits to a recording and/or indicating apparatus an electrical signal the value of which is related to the fluid pressure transferred to the pressure transducer through the liquid-filled duct. In this known method and apparatus provision is also made for rinsing the end part of the liquid-filled duct which opens into the conduit. When using this known method and apparatus, however, the liquid-filled duct, and particularly the end part thereof which opens into the conduit, may become clogged by the deposition thereon of algae from the rinsing liquid or solid substances from the suspension, which renders the measurements unreliable.

The present invention has for its object to remove this disadvantage of the known method and apparatus.

According to the invention there is provided a method of measuring the pressure of a suspension flowing through a conduit, wherein the fluid pressure in a pressure sensing zone, which opens into the conduit but is otherwise located wholly outside the path of flow of the suspension through the conduit, is measured during successive measuring cycles, each including a rinsing phase in which flushing liquid is discharged through the pressure-sensing zone into the conduit and a pressure-sensing phase, of longer duration than the rinsing phase, in which the fluid pressure is transmitted to the input of a pressure transducer through a liquid-filled duct having a flow area substantially smaller than the flow area of the pressure-sensing zone (if this flow area is uniform at all positions along the path traversed by the flushing liquid during its passage through the pressure-sensing zone in the rinsing phase) or the mean flow area of the pressure-sensing zone (if the flow area of the pressure-sensing zone varies along the path traversed by the flushing liquid during its passage through the pressure-sensing zone in the rinsing phase), causing the pressure transducer to generate an electrical signal which has a value related to the said fluid pressure and is transmitted from the output of the pressure transducer to a recording and/or indicating apparatus.

The invention also includes an apparatus for measuring the pressure of a suspension flowing through a conduit, comprising a pressure-sensing chamber containing a pressure-sensing zone which opens into the conduit while being otherwise wholly outside the path of flow of the suspension through the conduit; rinsing means arranged, when in operation, to clean the pressure-sensing chamber by discharging a flushing liquid through the same in the direction towards the conduit; measuring means including recording and/or indicating apparatus operatively connected to the pressure-sensing zone via a liquid-filled duct, which has a flow area substantially smaller than the flow area of the pressure-sensing zone (if this flow area is uniform at all positions along the path traversed by the flushing liquid during its passage through the pressuresensing zone in the rinsing phase) or the mean flow area of the pressure-sensing zone (if the flow area of the pressure-sensing zone varies along the path traversed by the flush- ing liquid during its passage through the pressure-sensing zone in the rinsing phase), so as to be responsive, when in operation, to record and/or indicate the pressure in the said pressure-sensing zone; and means for controlling the rinsing means and the measuring means so as to cause them to operate in successive measuring cycles each of which includes a rinsing phase and a pressure-sensing phase of longer duration than the rinsing phase.

When carrying out the method according to this invention or using the apparatus according thereto the rinsing phase of each measuring cycle, which is of shorter duration than the pressure-sensing phase, can be performed in such a short time that it is feasible to use distilled water or an algaekilling liquid, instead of normal mains water, for rinsing the pressure-sensing zone.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 are circuit diagrams of a device embodying the invention during a pressure-sensing phase and a rinsing phase respectively, Figure 3 is a fragmentary sectional view on an enlarged scale of a detail III in Figure 1, and Figures 4, 5 and 6 illustrate respectively three variants of the detail III in Figure 3.

With the aid of the device 1 of Figures 1 and 2 the pressure P of a suspension stream, particularly a slush stream, flowing through a conduit 2 in the direction of the arrows 3 can be measured in a reliable manner.

The slush flowing through the conduit 2 contains readily settling sand of different grain sizes as well as mud which is likely to stick in corners.

Apart from the conduit 2, the device 1 comprises a pressure transducer 4 which, during the pressure-sensing phase shown in Figure 1, communicates through a connecting duct 12, a three-way cock 7 and a sensing duct 5 with one end of a passageway 6 formed in a body which is mounted in an opening in the wall 9 of the conduit 2.

The other end of the passageway 6 communicates with a pressure-sensing zone 8 which, in the embodiment shown in Figures 1 to 3 and the variant thereof shown in Figure 4, is constituted by substantially the whole of a chamber 10 which is formed in the above-mentioned body and opens laterally into the interior of the conduit 2. The pressure-sensing zone 8 is thus located wholly outside the path of the suspension stream flowing through the conduit 2. The deposition of solid substances in the chamber 10 is greatly restricted in the embodiment shown in Figures 1 and 3 and in the variant shown in Figure 4 due to the fact that the bottom wall surface part 11 of this chamber 10 slopes downwardly in the direction towards the conduit 2. The pressuresensing chambers 10 shown in Figures 1 to 4 are of conical shape with the end thereof corresponding to the base of the one opening into the conduit 2. The mean flow area of the zone 8 is substantially greater than the flow area of the duct 5. The passageway 6 preferably extends downwardly from its connected with the sensing duct 5 to an opening in the top wall surface of the conical sensing chamber 10 near the apex end thereof, though the last-mentioned opening could alternatively be located in a lateral wall surface part of the sensing chamber 10 as shown in Figure 4. In cases where the sensing chamber 10 is conical, the apex angle a of the cone is preferably of the order of 60".

The pressure transducer 4 has an electrical output 13 which is connected through an amplifier 14 and a switch 15, which is closed during the pressure-sensing phase illustrated in Figure 1, to a memory circuit 16. The memory circuit 16 is of the type in which the information last applied to its input 18 is always available at its output 17, for example, it is a memory circuit of the sample and hold type. The output 17 is connected to a recording apparatus 19 and to an indicator 20 of the pressure P.

The slope of the bottom wall surface part 11 of the sensing chamber 10 in Figures 1 to 4 is too steep to allow the deposition thereon of solid substances, for example, grains of sand. In order to avoid adherence of sticky substances, for example loam and mud, in the sensing chamber 10 near the opening through which it communicates with the passageway 6, the pressure P is sensed in successive measuring cycles each of which includes a rinsing phase and a sensing phase, the sensing phase being of longer duration than the rinsing phase.

During the rinsing phase, which is illustrated in Figure 2, the passageway 6 and the sensing chamber 10 are flushed with flushing liquid 22, for example distilled water or an algae-killing liquid, from a hydrophore 2 which communicates through a metering regulator 24 with the sensing duct 5. The hydrophore 23 is suppled with flushing liquid 22 from a reservoir 26 by means of a pump 27 through a valve 28.

The hydrophore 23 contains a cushion 30 of gas which is compressed above a piston 29 and which, when a valve 15 is open and the three-way cock 7 is adjusted to the position shown in Figure 1, will cause a metered quantity of the flushing liquid 22 to be displaced into the lower part of a housing 32 of the metering regulator 24. The flushing liquid in this lower part of the housing 32 is separated by a piston 33 from a gas cushion 34 in the upper part of the said housing 32. If, after the lower part of the metering regulator 24 has been charged with flushing liquid 22 in the manner just described, the valve 31 and the three-way cock 7 are adjusted to the positions shown in Figure 2, so that the outlet of the hydrophore 23 is shut off from the metering regulator 24, the sensing duct 5 is shut off from the connecting duct 12 and the lower part of the metering regulator 24 is in communication through the sensing duct 5 with the passageway 6, a small metered quantity, e.g. 1 cubic cm, of the flushing liquid 22 will be discharged from the lower part of the metering regulator 24, through the duct 5 and the passageway 6, into the pressuresensing chamber 10, whereby the said duct 5, passageway 6 and pressure-sensing chamber 10 are cleaned.

The device 1 comprises a programme controller 35 which controls the measuring cycles so that each such cycle comprises a short, e.g. 2 second, rinsing phase after a much longer, e.g. 60 second, pressure-sensing phase. For this purpose, the programme controller 35 is connected by a rod 36 to the operating means of the valve 31, the three-way cock 7 and the electric switch 15 so that it can change over the said valve, cock and switch simultaneously from the setting shown in Figure 1 to those shown in Figure 2 and vice versa.

During the rinsing operation, the sensing zone 8 may have a different, for example, higher pressure than the real pressure P of the suspension. Therefore, during the rinsing phase, the switch 15 is opened so that the last information of the preceding pressure-sensing phase is applied by the memory circuit 16 to the recording apparatus 19 and the indicator 20.

In the variant shown in Figure 5, the sensing chamber 10 is formed by a cylindrical bore having a diameter b of, for example, 30 cm. which is large as compared with the bore of the passage 6 and may be connected to a pressure-sensing duct 5 of 1 to 2 mm, preferably 1 5. The steep slope of the bottom 11 of the sensing chamber 10 prevents the deposition thereon of grains of sand or the like.

In the variant of Figure 6, deposition of sand 37 on the bottom of the sensing chamber 101 is, indeed possible, but the sensing zone 8 is located in the upper part of the sensing chamber 10, where sand cannot be deposited.

WHAT WE CLAIM IS: 1. A method of measuring the pressure of a suspension flowing through a conduit, wherein the fluid pressure in a pressuresensing zone, which opens into the conduit but is otherwise located wholly outside the path of flow of the suspension through the conduit, is measured during successive measuring cycles each including a rinsing phase in which flushing liquid is discharged through the pressure-sensing zone into the conduit and a pressure-sensing phase, of longer duration than the rinsing phase, in which the fluid pressure is transmitted to the input of a pressure transducer through a liquid-filled duct having a flow area substantially smaller than the flow area of the pressure-sensing zone (if this flow area is uniform at all positions along the path traversed by the flushing liquid during its passage through the pressure-sensing zone in the rinsing phase) or the mean flow area of the pressure-sensing zone (if the flow area of the pressure-sensing zone varies along the path traversed by the flushing liquid during its passage through the pressuresensing zone in the rinsing phase), causing the pressure transducer to generate an electrical signal which has a value related to the said fluid pressure and is transmitted from the output of the pressure transducer to a recording and/or indicating apparatus.

2. A method as claimed in claim 1, wherein the transmission of fluid pressure from the pressure-sensing zone to the pressure transducer is shut off during the rinsing phase of each measuring cycle.

3. A method as claimed in claim 1 or 2, wherein the output signal generated by the pressure transducer during each pressuresensing phase is stored in a memory device from which it is transmitted and applied to the recording and/or indicating apparatus during the next following rinsing phase.

4. An apparatus for measuring the pressure of a suspension flowing through a conduit, comprising a pressure-sensing chamber containing a pressure-sensing zone which opens into the conduit while being otherwise wholly outside the path of flow of the suspension through the conduit; rinsing means arranged, when in operation, to clean the pressure-sensing chamber by discharging a flushing liquid through the same in the direction towards the conduit; measuring means including recording and/or indicating apparatus operatively connected to the pressure-sensing zone via a liquid-filled duct, which has a flow area substantially smaller than the flow area of the pressuresensing zone (if this flow area is uniform at all positions along the path traversed by the flushing liquid during its passage through the pressure-sensing zone in the rinsing phase) or the mean flow area of the pressure-sensing zone (if the flow area of the pressure-sensing zone varies along the path traversed by the flushing liquid during its passage through the pressure-sensing

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. liquid in this lower part of the housing 32 is separated by a piston 33 from a gas cushion 34 in the upper part of the said housing 32. If, after the lower part of the metering regulator 24 has been charged with flushing liquid 22 in the manner just described, the valve 31 and the three-way cock 7 are adjusted to the positions shown in Figure 2, so that the outlet of the hydrophore 23 is shut off from the metering regulator 24, the sensing duct 5 is shut off from the connecting duct 12 and the lower part of the metering regulator 24 is in communication through the sensing duct 5 with the passageway 6, a small metered quantity, e.g.

1 cubic cm, of the flushing liquid 22 will be discharged from the lower part of the metering regulator 24, through the duct 5 and the passageway 6, into the pressuresensing chamber 10, whereby the said duct 5, passageway 6 and pressure-sensing chamber 10 are cleaned.

zone in the rinsing phase), so as to be responsive, when in operation, to record and/ or indicate the pressure in the said pressuresensing zone; and means for controlling the rinsing means and the measuring means so as to cause them to operate in successive measuring cycles each of which includes a rinsing phase and a pressure-sensing phase of longer duration than the rinsing phase.

5. An apparatus as claimed in claim 4, wherein the recording and/or indicating ap paratus is operated by electrical signals transmitted thereto from the output of a pressure transducer, the input of which is connected to the liquid-filled duct.

6. An apparatus as claimed in claim 4 or 5, wherein the sensing chamber has a bottom surface which slopes downwardly in the direction towards the conduit.

7. An apparatus as claimed in any of claims 4 to 6, wherein the sensing chamber diverges in the direction towards the conduit.

8. An apparatus as claimed in any of claims 4 to 7, wherein the liquid-filled duct extends downwardly towards the sensing chamber.

9. An apparatus as claimed in claim 7 or 8, wherein the sensing chamber is of conical shape.

10. An apparatus as claimed in claim 9, wherein the liquid-filled duct opens into the sensing chamber at a position adjacent the apex end thereof.

11. An apparatus as claimed in any of claims 4 to 10, wherein the sensing chamber is of conical shape and has an apex angle to the order of 60".

12. An apparatus as claimed in any of claims 4 to 11, wherein the rinsing means includes a hydrophore commumcating with the liquid-filled duct through a metering regulator which is arranged during the rinsing phase of each measuring cycle to discharge a metered quantity of flushing liquid through the liquid-filled duct and thence through the pressure-sensing chamber in the direction towards the conduit.

13. An apparatus as claimed in any of claims 4 to 12, wherein a memory device is connected between the pressure transducer and the recording and/or indicating apparatus and is arranged, during the rinsing phase of each measuring cycle, to transmit to the recording and/or indicating apparatus an electrical signal transmitted to it by the pressure transducer during the preceding pressure-sensing phase.

14. A method of measuring the pressure of a suspension flowing through a conduit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

15. An apparatus for measuring the pressure of a suspension flowing through a conduit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.