Casing for a fluid flowmeter, and method

Abstract: A fluid flow system, casing and method according to which a chamber is formed in the casing and at least one conduit is coupled to the casing so that fluid passes from the conduit and into the chamber and so that forces acting on the conduit creates stresses on the casing that causes flexure of the casing. At least one groove is formed in the wall of the casing defining the chamber, and is configured and located relative to the chamber to direct the flexure away from the wall of the casing defining the chamber.

Description: This invention relates to a casing and method designed to be used with a meter for metering flow of a fluid. Casings are often provided in a fluid flow line for housing a component, such as a flow meter (see e.g. GB 909 301 A and EP 0 471 865 A1). In these arrangements, the casing is usually placed in the fluid flow path and is provided with a chamber in which the meter is installed. Conduits are also connected to the casing by mounting plates and bolts to pass the fluid through the casing. However, the casing is subjected to stresses caused by various bending moments on the conduits, the plates and the bolts. These stresses distort the physical shape of the chamber which often interfere with the operation of the meter. Although there have been attempts to combat these stresses by adding material to the outside of the casing in an attempt to strengthen it, this adds to the cost, size and weight of the casing and therefore is undesirable. Therefore, what is needed is a casing for housing a component in a fluid flow path that is not affected by the above stresses yet is not relatively high in cost, size and weight. The present invention is defined in the accompanying independent claims. Some preferred features are recited in the dependent claims. An embodiment of the present invention is directed to a fluid flow system, casing and method according to which a chamber is formed in the casing and at least one conduit is coupled to the casing so that fluid passes from the conduit and into the chamber and so that forces acting on the conduit creates stresses on the casing that causes flexure of the casing. At least one groove is formed in the wall of the casing defining the chamber, and is configured and located relative to the chamber to direct the flexure away from the wall of the casing defining the chamber. As a result, the casing is not affected by the above stresses yet is relatively inexpensive and is not bulky or heavy. The invention can be put into practice in various ways some of which will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a isometric view of a casing according to an embodiment of the present invention shown in connection with a fluid flow meter; and Fig. 2 is an enlarged view of the casing of Fig. 1. Referring to Fig.1 of the drawings, the reference numeral 10 refers to a meter for metering the flow of fluid, such as gas, through a fluid flow system. The meter 10 can be of any conventional type such as a positive displacement, rotary type meter, and includes a cover, or housing 12, having an annular flange 12a extending outwardly therefrom that has a plurality of angularly-spaced openings for receiving bolts 14 for reasons to be explained. An accessory unit, in the form of an instrument 16, extends outwardly from the housing 12 and is adapted to provide a visual indication of the amount of fluid that is metered, in a conventional manner. Although not shown in the drawings, it is understood that the meter 10 includes a impeller, or the like that disposed inside the cover 12 that rotates in response to the presence of a pressurised fluid, as will be described. With reference to Figs. 1 and 2, a casing 20 is provided which is approximately rectangular in cross section and which has an internal measurement chamber 22 (Fig. 2) for receiving the meter 10. As shown in Fig. 1, the meter 10 extends through the chamber 22 with the cover 12 and the instrument 16 protruding outwardly from the casing. Although not shown in the drawings, it is understood the above-mentioned impeller of the meter 10 is centered in the chamber and that another cover protrudes out from the opposite end of the casing 20. The casing 20 is provided with an outlet port 24 (Fig. 2) that receives an outlet conduit 26 that, in turn, is connected to the casing by an annular mounting plate 28 that receives the conduit. An inlet port (not shown) is provided on the other side of the casing that receives an inlet conduit 32 that, in turn, is connected to the casing by an annular mounting plate 34 that is connected to the latter side wall by another series of bolts (not shown). The axes of the conduits 26 and 32 thus extend perpendicular to the axis of the chamber 22. The inlet port and the outlet port 24 both extend into the chamber 22 so that the fluid flows from the inlet conduit 32, through the chamber 22, and to the outlet conduit. During the passage of the fluid through the chamber 22, it passes through the above-mentioned impeller of the meter 10 which meters the amount of fluid flow which registers on the instrument 16. With the exception of the specific design of the casing 20 that will be described in detail, all of the above is conventional and therefore will not be described in any further detail. As discussed above, forces acting on the conduits 26 and 32 and the meter 10 establish moment arms that apply stresses to the casing 20 through the plates 28 and 34, the bolts 30, and the bolts associated with the plate 34. These stresses will cause the structure of the casing 20 to flex and thus distort the precise configuration of the chamber 22. This can cause the impeller of the meter 10 to malfunction due to the flexed wall of the casing 20 defining the chamber 22 actually engaging and interfering with the meter's impeller. According to a feature of an embodiment of the present invention, the chamber 22 of the casing 20 is configured in a unique manner to isolate the meter from the above stresses. To this end, the cross-sectional shape of the chamber 22 shown is Fig. 2 is generally in the form of an ellipse 22a having a horizontal axis that is slightly less in length than the vertical axis, as viewed in Fig.2. Two notches 40 and 42 are formed in the wall of the casing defining the chamber 22 and extend for the entire length of the chamber. The notches 40 and 42 are located on the opposite sides, or the relatively long walls, of the chamber as viewed in the drawing. A pair of elongated grooves 40a and 40b are cut into the casing 20 and extend from the opposite ends of the notch 40, and a pair of elongated grooves 42a and 42b are also cut in the casing 20 extend from the opposite ends of the notch 42. The grooves 40a, 40b, 42a and 42b extend for the entire length of the chamber 22 and generally parallel to portions of the inner wall of the casing 20 defining the corresponding portions of the chamber. The notches 40 and 42 and the grooves 40a, 40b, 42a, and 42b are sized to not reduce the load bearing properties of the casing 20. Thus, any stresses occurring on the portions of the casing 20 adjacent the plates 28 and 34 caused by forces acting on the conduits 42 and 32, respectively, as discussed above will cause the latter portions to flex. However, the grooves 40a, 40b, 42a, and 42b are constructed and arranged to direct this flexure away from the wall of the casing 20 defining the chamber 22 and thus isolate, or decouple, the chamber from the structure of the casing that receives the plates 28 and 34. Thus, the physical shape of the chamber 22 is not changed, yet the casing 20 does not require additional material that adds to the cost, size and weight of the casing. It is understood that the number of conduits connected to the casing and the number of notches and grooves formed in the casing can vary. Further, the spatial references referred to above, such as "upper", "lower", "side", etc., are for illustration purposes only and are not intended to limit the specific location or orientation of any of the structure. The shape of the chamber may have an ellipsoidal cross-section in which the groove(s) project generally into the casing defining the chamber in the direction of the major, as opposed to the minor, dimension of the ellipsoidal section. The provision of the grooves can expose at least a proportion of the part of the casing defining the meter (or other working part of the chamber) to the distorting forces, thus balancing the forces to reduce or substantially eliminate distortion.

Claims: A casing (20) defining a chamber (22) being adapted to receive a flowmeter and being adapted to be coupled to at least one conduit so that fluid passes from the conduit and into the chamber (22), whereby forces acting on the conduit create stresses on the casing (20) that cause flexure of the casing, characterized in at least one groove (40a, 40b, 42a, 42b) formed in the wall of the casing (20) defining the chamber (22), the groove (40a,40b,42a,42b) being configured and located relative to the chamber (22) to direct this flexure away from the wall of the casing (20) defining the chamber (22) such that a flowmeter being contained in the chamber (22) is isolated from said stresses. The casing of claim 1 wherein there is at least one notch (40, 42) formed in the wall of the casing (20) defining the chamber (22) wherein the at least one groove extends from the respective ends of the notch. The casing (20) of claim 2 wherein there are two notches (40, 42) formed in the wall of the casing (20) defining the chamber (22) and respectively extending from opposite walls of the chamber (22), and wherein there are two grooves (40a, 40b, 42a, 42b) extending from the respective ends of each notch. The casing (20) of claim 3 wherein the lengths of two opposed walls of the chamber are greater than the lengths of the other two opposed walls of the chamber, and wherein the notches (40, 42) and the grooves (40a, 40b, 42a, 42b) are respectively formed on the former two opposed walls. The casing (20) of any of claims 1 to 4 wherein the forces acting on the conduit create stresses on the portions of the casing (20) where the conduit is coupled to the casing. The casing (20) of claim 5 wherein the grooves (40a, 40b, 42a, 42b) decouple the chamber (22) from the portions of the casing (20). The casing (20) of any of claims 1 to 6 wherein the conduit extends perpendicular to the axis of the chamber (22) and wherein the chamber (22) has an elliptical cross section. A method comprising the steps of forming a chamber (22) being adapted to receive a flowmeter in a casing (20), coupling at least one conduit (32) to the casing (20) so that fluid passes from the conduit (32) and into the chamber (22) and so that forces acting on the conduit (32) create stresses on the casing (20) that cause flexure of the casing, characterized by forming at least one groove (40a, 40b, 42a, 42b) in the wall of the casing (20) defining the chamber (22), and configuring and locating the groove (40a, 40b, 42a, 42b) relative to the chamber to direct the flexure away from the wall of the casing (20) defining the chamber (22) such that a flowmeter being received by the chamber (22) is isolated from said stresses. The method of claim 8 wherein the forces acting on the at least one conduit (32) create stresses on the portions of the casing (20) where the at least one conduit (32) is coupled to the casing (20). The method of claim 8 wherein the at least one groove (40a,40b,42a,42b) decouples the chamber (22) from the portions of the casing (20).

Inventors: LOGA THOMAS H, PARKER JEFFREY S, LOGA, THOMAS H., PARKER, JEFFREY S.
Applicants: DRESSER INC A DELAWARE CORP, DRESSER, INC.(A DELAWARE CORPORATION)
Application year: 1999
Main classification: G01F15
IPC codes: G01F15