GB2142438A

GB2142438A - Apparatus for use in the testing of a fluid

Info

Publication number: GB2142438A
Application number: GB08317102A
Authority: GB
Inventors: Gerald Anderson
Original assignee: Sarasota Automation Ltd
Current assignee: Sarasota Automation Ltd
Priority date: 1983-06-23
Filing date: 1983-06-23
Publication date: 1985-01-16
Also published as: GB8317102D0

Abstract

A mounting for a measuring instrument (22) whereby the instrument can easily be replaced comprises a conduit (10) through which the fluid flows; a chamber (12) having an aperture (24) which, when open communicates with the conduit (10), the chamber (12) being adapted to contain the instrument (22); a closure member (15) for closing said aperture (24); means (30) for resiliently urging the closure member (25) towards an open position; venting means (41) for venting the chamber (12) to atmosphere so that, when operated, the closure member (25) is held closed, by the pressure of the fluid in the conduit (10); and pressure transmission means (36) for applying to the inside of the chamber a pressure substantially the same as that in the conduit (10) so as to open the closure member (25). With the member (25) closed the instrument (22) can be replaced. The instrument may measure mass flow, density, pH or oxygen content. <IMAGE>

Description

SPECIFICATION Apparatus for use in the testing of a fluid This invention concerns an apparatus for use in the testing of a fluid, e.g. to determine its mass flow.

Devices are known, such as that shown in our British Patent Specification No. 2,058,247B, for introducing a density meter or other instrument into a conduit and for removing it from the conduit while fluid at high pressure is passing through the conduit.

Such devices, however, have involved the use of components such as a screw retractor which occupies a large amount of space, in particular because it requires considerable "head-room" for the screw, and which is cumbersome and time-consuming to operate. Prior devices have also been of complicated construction.

Although, therefore, the present invention is primarily directed to any novel integer or step, or combination of integers or steps, as herein described and/or as shown in the accompanying drawings, nevertheless according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided an apparatus for use in the testing of a fluid comprising a conduit through which the fluid to be tested may flow; a chamber having an aperture which, when open, communicates with the conduit, the chamber being adapted to contain an instrument for testing the fluid; a closure member for closing said aperture, said closure member having oppositely facing first and second surfaces which are respectively open to the pressure of the fluid in the conduit and the pressure within the chamber; urging means for resiliently urging the closure member towards an open position; venting means for venting the chamber to atmosphere so that, in operation, the closure member is held closed, against the action of the said urging means, by the pressure of the fluid in the conduit acting on the said first surface; and pressure transmission means for subjecting the second surface of the closure member to a pressure substantially the same as that in the conduit so as to open the closure member.

Preferably an instrument for testing the fluid is mounted in said chamber. Thus the instrument may be a density meter although it may, alternatively, be a pH probe for determining the pH of the fluid passing through the conduit, an oxygen analyser for determining the oxygen content of the said fluid, or any other instrument which determines a chemical or physical characteristic of the fluid.

The instrument is preferably carried by a removable wall of the chamber to enable the instrument to be removed from the chamber when the chamber is vented.

The venting means and the pressure transmission means are preferably provided with common valve means. Thus the common valve means may control fluid flow between a first duct which communicates with said conduit and a second duct which communicates with the interior of the chamber, the common valve means being settable in a first position in which the first duct is closed and the second duct is vented to atmosphere so that the chamber is similarly vented, and a second position in which the first and second ducts intercommunicate so that the pressure from the conduit is transmitted to the interior of the chamber.

The urging means may comprise spring means such, for example, as a plurality of spring fingers or a coil spring.

The second surface of the closure member is preferably shaped so that, when the closure member is open, the fluid from the conduit is initially speeded up in passing over the second surface and thereby induces a flow of fluid from the conduit through the instrument.

The chamber preferably projects into the conduit.

The conduit preferably has a tee-piece within which a portion of the chamber is mounted, the chamber having a flange which is secured to the tee piece. Thus the said first duct may be provided by a space between the tee-piece and the chamber.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is a diagrammatic sectional view of an apparatus according to the invention for use in the testing of a fluid, Figure 2 is a broken-away sectional view of a modification of part of the apparatus shown in Figure 1, and Figure 3 illustrates diagrammatically a modification of part of the apparatus shown in Figure 1.

Terms such as "upper", "lower", "left" and "right", as used in the description below, are to be understood to refer to directions as seen in the accompanying drawings.

In Figure 1 there is shown an apparatus for use in the testing of a fluid comprising a process line or other conduit 10 through which a fluid to be tested may flow. The fluid may, for example, be a gas which is to be tested so as to determine its mass flow, its pH, its oxygen content, or some other physical or chemical characteristic thereof.

The conduit 10 has a tee-piece 11 within which is mounted a portion of a tubular pocket or chamber 12 which projects into the conduit 10. The chamber 12 has a flange 13 which is integral with or welded to the chamber 12, the flange 13 being bolted to the tee-piece 11 by means of bolts 14.

The upper end of the chamber 12 is closed by a removable wall 15 which is bolted to a flange 16 of the chamber 12 by means of bolts 17. The removable wall 15 is sealed to the flange 16 by means of an O-ring or other seal 20.

The removable wall 15 is welded or otherwise secured to a tubular support member 21. An instrument 22 (e.g. a density meter), which is mounted within the chamber 12, is supported by the tubular support member 21. Mounted at the upper end of the tubular support member 21 is a terminal box 23.

The terminal box 23 houses an electrical device (not shown) which is connected to the instrument 22 by means of wires (not shown) which pass through the centre of the tubular support member 21. The electrical device may be constituted, for example, by an indicator which indicates the mass flow or other characteristic which is being monitored by the instrument 22, or it may be constituted by a control device for controlling the fluid passing through the conduit 10 in such a way that the mass flow, temperature, or chemical constitution of the fluid is maintained substantially constant.

The lower end of the chamber 12 is provided with an aperture 24 which, when open, communicates with the interior of the conduit 10. The chamber 12 is provided with a closure member 25 which is normally in the open position shown in Figure 1 but which may, as described below, be moved into a closed position (not shown) in which the interior of the chamber 12 is sealed from the conduit 10. The closure member 25 has oppositely facing surfaces 26, 27 which are respectively open to the pressure of the fluid in the conduit 10 and the pressure within the chamber 12.

The closure member 25 is urged towards its open position by urging means which may, as shown, be constituted by a plurality of spring fingers 30, the upper end of each of which is secured to the wall of the chamber 12, the lower ends of the spring fingers 30 being arranged to bear and slide on the upper surface 27 of the closure member 25. Alternatively, a coil spring (not shown) could be employed to urge the closure member 25 towards its open positon.

The closure member 25 is retained in position by a circlip 31 which engages the wall of the chamber 12 and prevents the expulsion from the lower end of the chamber 12 of the closure member 25. The closure member 25 has a flange 32 which seals against a shoulder 33 of the chamber 12 when the closure member 25 is in its closed position. When, however, the closure member 25 is in its open positon, fluid from the conduit 10 may pass through a plurality of ports 34, which collectively constitute the aperture 24, and thus into the interior of the chamber 12.

The surface 27 of the closure member 25 is of domed shape so that, when the closure member 25 is open, the fluid from the conduit 10, in flowing from left to right as indicated by arrow 28, is initially speeded up in passing over the surface 27. The speeded up fluid passing over the centre of this domed shape induces a flow of fluid from the conduit 10 to pass through the instrument 22 as indicated by the arrows 35.

A pressure transmission duct 36 is provided by the space between the tee-piece 11 and the chamber 12, and this pressure transmission duct 36 communicates with a valve 37 by way of a pressure transmission duct 38 which passes through the flange 13. A vent duct 41, the flow through which is controlled by the valve 37, communicates with the interior of the chamber 12.

The valve 37 is settable by a handle 42 in a first (or "vent") position in which the pressure transmission ducts 36,38 are closed and the vent duct 41 is vented to atmosphere so that the chamber 12 is similarly vented. The valve 37 is also settable in a second (or "operate") position in which the ducts 36,38, 41 intercommunicate so that the pressure from the conduit 10 may be transmitted to the interior of the chamber 12.

In the construction shown in Figure 1, the valve 37 acts as a common valve which controls both the venting of the chamber 12 through the vent duct 41 and the pressurisation of the chamber 12 through the pressure transmission duct 36. However, it would, if desired, be possible to provide separate valves which respectively control fluid flow to the interior of the chamber 12 to enable the latter to be either vented or pressurised as required.

In operation, when the handle 42 of the valve 37 is in the "operate" position shown in Figure 1, closure member 25 will be in the open position shown in Figure 1 and fluid will be entrained from the conduit 10 and through the instrument 22. The fluid pressure will act on both the surfaces 26, 27, but the closure member 25 will be maintained in the open position by reason of the spring force of the spring fingers 30.

When, however, it is desired to remove the instrument 22 from the chamber 12 in order to service the instrument 22 orto replace it by another instrument, the valve 37 is moved by its handle 42 into its first or "vent" position in which the pressure transmission duct 36 is closed and the vent duct 41 is vented to atmosphere. Consequently, the interior of the chamber 12 will also be vented to atmosphere, with the result that the force of the fluid acting on the surface 26 will be greater than that acting on the surface 27 and the closure member 25 will be closed against the action of the spring fingers 30. The removable wall 15, together with the instrument 22, may then be removed by unbolting the bolts 17.

After the instrument 22 has been services or has been replaced by another instrument, the removable wall 15, together with the instrument 22, is restored to the position shown in Figure 1, the bolts 17 are tightened, and the valve 37 is moved to its second or "operate" position in which the vent duct 41 no longer communicates with atmosphere but communicates instead with the pressure transmission ducts 38, 36. Accordingly, the pressure from the conduit 10 is transmitted to the interior of the chamber 12 so as to act on the surface 27, whereby the spring fingers 30 will move the closure member 25 to its open position.

Provided that the flow through the vent duct 41 is not sonic, then, to a first order,

where Advent and Agap are the areas respectively of the vent duct 41 and of the gap between the closure member 25 and the chamber 12 when the closure member 25 is open, and Advent and APgap are respectively the pressures prevailing across the vent duct 41 and across the said gap If the vent duct 41 has an internal diameter of 1/2" (1.27 cms), then Anent = 0.2 sq. inches (129mum. If the pressure in the conduit 10 is 100 p.s.i.g. (70307 Kglm, then Advent is approximately 100 p.s.i (70307 kg/m. We have found that it is desirable that APgap should be at least 1 p.s.i. (703.07 kgim) in order to overcome both the force of the spring fingers 30 and the weight of the closure member 25 which may be approximately 3 Ibs (1.361 kg). If therefore it is assumed that the closure member 25 is about 2" (5.08 cms) in diameter, then as will be seen from the above equation Agap = 2 square inches (1 290mum'.

Thus, the said gap between the closure member 25 and the chamber 12, when the closure member 25 is open, should be about 0.3" (0.762 cms). It is found in practice that, with these particular dimensions, provided the pressure of the fluid in the conduit 10 is at least 100 p.s.i., (70307 kg/m), the system works satisfactorily. At such a pressure within the conduit 10 of 100 p.s.i (70307 kg/m), opening of the closure member 25 will require a force of more than 300 Ibs (136.1 kg) to open it, and consequently there is substantially no danger of its being opened acciden tally.

The structure shown in Figure 1 has the advantage that, in contrast to the prior art, it is not necessary to provide a large ball valve on top of the tee-piece 11, and no seal housing is required on top of such a ball valve. The structure shown in Figure 1 is also such that it may only be necessary to provide a distance of say 1 foot (0.3048m) between the flange 13 and the terminal box 23 in contrast to the 4 feet (1.2192m) which is normally required for the prior art retractor.

As will be appreciated, the density meter or other instrument 22 is able to operate on a sample from the conduit 10 which is at the same pressure at that of the conduit 10. Moreover, the instrument 22 is directly exposed to the flowing fluid and can re spond rapidly to changes therein. The structure shown in Figure 1 is also easy and quick to operate, in contrast to the need to turn a retractor screw through some 300 turns and to operate a large ball valve. The strucutre is, moreover, fail-safe in that when the valve 37 is in the "vent" position, the chamber 12 continues to be vented even if the closure member does not move, thus giving warning of a faulty condition. Moreover, if there should be loosening of the removable wall 15 by unbolting, this will also result in venting of the chamber 12 with the result that the closure member 25 will shut.

Figures 2 and 3 show constructions which are generally similar to that of Figure 1 and which, for this reason, will not be described in detail, like reference numerals indicating like parts.

In the Figure 2 construction, however, in addition to the circlip 31, which prevents expulsion of the closure member 25 from the lower end of the chamber 12, there is a circlip 43 which, like the circlip 31, is received in a recess in the internal wall of the chamber 12. The circlip 43 acts as an abutment for engagement by a ring (not shown) which is slidably mounted in the chamber 12 and which has spring fingers which engage the surface 27.

As shown in Figure 2, the ports 34 may be constituted by a plurality of angularly spaced apart elongated holes, although these holes could, if desired, be circular. An O-ring 44, which is received in a recess 45 in the closure member 25, is provided to engage a shoulder 46 in the internal wall of the chamber 12 so that the closure member 25, when in its closed position, is sealed to the chamber 12.

As illustrated in Figure 3, the instrument 22 may be replaced by a test probe 49, e.g. a pH probe or an oxygen analyser, which, unlike a density meter, does not have an internal flow passage. In this case, an external flow around the test probe 49 is required and this is provided by mounting the test probe 49 in a tubular device 50 through which a circulation will be induced by reason of the shape of the surface 27 of the closure member 25.

Claims

1. Apparatus for use in the testing of a fluid comprising a conduit through which the fluid to be tested may flow; a chamber having an aperture which, when open, communicates with the conduit, the chamber being adapted to contain an instrument for testing the fluid; a closure member for closing said aperture, said closure member having oppositely facing first and second surfaces which are respectively open to the pressure of the fluid in the conduit and the pressure within the chamber; urging means for resiliently urging the closure member towards an open position; venting means for venting the cham berto atmosphere so that, in operation, the closure member is held closed, against the action of the said urging means, by the pressure of the fluid in the conduit acting on the said first surface; and pressure transmission means for subjecting the second surface of the closure member to a pressure substantially the same as that in the conduit so as to open the closure member.

2. Apparatus as claimed in claim 1 in which an instrumentfortesting the fluid is mounted in said chamber.

3. Apparatus as claimed in claim 2 in which the instrument is a density meter.

4. Apparatus as claimed in claim 2 or 3 in which the instrument is carried by a removable wall of the chamberto enable the instrument to be removed from the chamber when the chamber is vented.

5. Apparatus as claimed in any preceding claim in which the venting means and the pressure transmission means are provided with common valve means.

6. Apparatus as claimed in claim 5 in which the common valve means control fluid flow between a first duct which communicates with said conduit and a second duct which communicates with the interior of the chamber, the common valve means being settable in a first position in which the first duct is closed and the second duct is vented to atmosphere so that the chamber is similarly vented, and a second position in which the first and second ducts intercommunicate so that the pressure from the conduit is transmitted to the interior of the chamber.

7. Apparatus as claimed in any preceding claim in which the urging means comprise spring means.

8. Apparatus as claimed in claim 7 in which the spring means comprise a plurality of spring fingers.

9. Apparatus as claimed in claim 2 or in any other claim when dependent thereon in which the second surface of the closure member is shaped so that, when the closure member is open, the fluid from the conduit is initially speeded up in passing over the second surface and thereby induces a flow of fluid from the conduit through the instrument.

10. Apparatus as claimed in any preceding claim in which the chamber projects into the conduit.

11. Apparatus as claimed in any preceding claim in which the conduit has a tee-piece within which a portion of the chamber is mounted, the chamber having a flange which is secured to the tee-piece.

12. Apparatus as claimed in claim 11 when dependent on claim 6 in which the said first duct is provided by a space between the tee-piece and the chamber.

13. Apparatus for use in the testing of a fluid substantially as herein before described with reference to and as shown in the accompanying drawings.

14. Any novel integer or step, orcombiantion of integers or steps, hereinbefore described andlor shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.