JPH034848B2 - - Google Patents

Description

Claim 1: A composite liquid flow meter comprising: a. a casing that is open along one side and has an inlet connected to a supply conduit at one end and an outlet connected to a discharge conduit at the opposite end; b. the opening in the casing. c) a main flow passage through the casing, which is supported by the cover and is responsive to increasing flow rates with precise accuracy characteristics in a first flow range greater than a predetermined flow rate; a main flow path including: (b) a main valve for controlling flow through the turbine instrument; (d) an auxiliary flow path extending from the inlet to the outlet; and the first
(b) a low flow rate measuring instrument having accurate accuracy characteristics in a second flow rate range that is lower than the flow rate range and partially overlaps with the first flow rate range; (b) supported by the cover and having a pressure difference on both sides thereof; an auxiliary valve that controls the flow through the low flow rate measuring meter by smoothly closing when the value exceeds a predetermined value; a transverse wall located between the inlet and the outlet and having a hole; f the transverse wall movable along the direction of flow so that the main valve controls flow through the hole; g. spring means for biasing the main valve into a closed position in which the main valve closes a hole in the transverse wall; h) a downstream end of the turbine instrument on the upstream side of the transverse wall; means for sealing around said hole; i a hole forming part of said auxiliary channel;
a cover transverse wall in the cover abutting the transverse wall in the casing.

2 a a cylindrical valve seat extending through said hole and having a flange abutting upstream of said transverse wall and a threaded end downstream of said wall; b at said end of said valve seat; a threaded ring; c a circumferentially spaced array of rods projecting downstream from said ring and having downstream-facing shoulders; d a spring retainer abutting the shoulders of said rods; means for retaining a spring retainer against said shoulder; f said main valve being disposed within said array of rods facing a downstream end of said valve seat; and g said spring means retaining said main valve against said shoulder; 2. A composite liquid flow meter according to claim 1, wherein compression is applied between the retainer and the main valve to urge the main valve against the valve seat.

3. A composite liquid flow meter according to claim 1 or 2, characterized in that the accuracy characteristics are within 3% of 100 percent accuracy over the entire flow range of the meter volume.

TECHNICAL FIELD This invention relates to the measurement of liquid flow in closed conduits where the flow is subject to a wide range of variations.

BACKGROUND A composite liquid flow meter has parallel flow paths, one of which includes a turbine meter that is accurate over a wide range of relatively high flow rates, but inaccurate below a known minimum flow rate. The other flow path contains an instrument that is accurate at low flow rates but has a narrow range with a lower maximum flow rate that is greater than the minimum flow rate of the turbine instrument.
It is essential that the flow path through the turbine instrumentation be closed by a valve in low flow ranges where the instrumentation is inaccurate. It is necessary to make the valve act quickly in response to the flow rate so that it opens quickly when the flow rate exceeds a minimum accurate flow rate of the turbine instrument and closes quickly when the flow rate falls below that minimum flow rate. previously thought.

Many fast-acting valve mechanisms have been proposed in the past. For example, US patent no.
36770084 and Pelt U.S. Patent No.
See issue 4100800. Conventional fast-acting valve mechanisms are complex. Masson et al. use a combined cam and toggle mechanism. Pelt uses a complex mechanism that includes two cams and an angled plane. Conventional composite instruments that include fast-acting valve mechanisms have reduced accuracy during flow transition ranges where the valve is opening or closing.
This lack of accuracy has been recognized in the standard for such meters published by the American Water Works Association and designated as Standard C-702-78. The standard allows the composite meter to have a minimum accuracy as low as 90% in the transition range where the valve is opening or closing, but the total flow rate transition range with an accuracy of less than 97% is limited ( For example, 20 gallons per minute for a 3-inch meter).

BRIEF SUMMARY OF THE INVENTION This composite liquid flow meter has a main flow path that includes a wide range turbine meter that is accurate over a range of flows greater than a predetermined minimum flow. The meter also includes parallel auxiliary flow paths through known gauges such as positive displacement gauges that are accurate over a lower range of flow rates. The upper end of that lower range overlaps the lower end of the turbine instrument flow rate accurate range.

The compound instrument includes a casing that is open along a portion of one side and has an inlet at one end and an outlet at the opposite end. The casing has a transverse wall between the inlet and the outlet, and the hole in the wall is part of the main flow path.

A main valve, disclosed as a simple poppet valve, controls flow through the hole. The valve is mounted on a stem that extends through a valve guide that also serves as a retainer for a spring that biases the valve into the closed position. When there is no flow through the valve, the total pressure difference between the upstream and downstream sides of the compound instrument acts on the valve in the direction of valve opening. A valve assembly including a valve, stem, guide, and spring is mounted downstream of the transverse wall within the casing.

A cover for the open side of the casing supports turbine instruments within the casing upstream of the transverse wall. Turbine instruments must have very precise characteristics, ie, high and constant accuracy at flow rates slightly above the minimum flow rate that starts the turbine rotation. A low range instrument is supported by a cover containing the parallel flow paths.

The auxiliary flow path must contain a fixed orifice of carefully selected size that determines the pressure drop across the composite instrument when the main valve is closed, and therefore the pressure drop across the composite instrument when the main valve begins to open. Determine the flow rate.

The auxiliary flow path may also include a secondary flow responsive valve that is biased open and closed in response to a predetermined pressure differential across the meter. This flow responsive valve has the smallest opening so that there is always some flow through the positive displacement meter.

This composite instrument provides improved accuracy during the transition between the closed main valve position, where only the low range instrument is functioning, and the open main valve position, where both instruments are functioning. The main valve assembly smoothly opens to turn on the turbine instrument when the flow is large enough, and smoothly closes to turn off the turbine instrument when the flow is below the minimum correct flow for that instrument.

This smooth action begins to open the main valve at a predetermined pressure difference equal to the sum of the pressure differences across the orifice, across the secondary valve, and across the low range meter. As the flow rate increases, the pressure difference across the main valve increases, opening it further, and this pressure difference plus the head due to the flow velocity causes the secondary flow responsive valve to close, causing that valve to close. Reduce the speed of the small flow meter to the value determined by the minimum opening. As the flow rate decreases, the secondary valve opens before the main valve closes so that when the main valve closes the low flow meter is operating at about 50% of its maximum capacity, and then all flow down to zero decreases. Measured only via flow meter.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a composite instrument embodying the present invention. FIG. 2 is a schematic illustration of an alternative register arrangement for the outputs of the two instruments in FIG.
FIG. 3 is an elevational view of a composite instrument embodying the present invention. 4 is a plan view of the instrument of FIG. 3; FIG. Fifth
The figure is a greatly enlarged sectional view taken along line 5--5 in FIG. FIG. 5a is a fragmentary cross-sectional view taken along line 5a-5a in FIG. FIG. 6 is a graph illustrating typical accuracy characteristics of a conventional compound meter. FIG. 7 is a graph showing the flow characteristics of a conventional low flow meter when used in a compound meter. 8th
The figure is a graph similar to FIG. 6 showing the accuracy characteristics of a composite instrument constructed in accordance with the present invention. FIG. 9 is a graph similar to FIG. 7 showing the flow characteristics of a low flow device when used in the composite meter of the present invention. FIG. 10 is a sectional view showing a turbine instrument suitable for use in the composite instrument of the present invention. FIG. 11 is a graph illustrating the accuracy characteristics of the turbine instrument of FIG. 10.

DETAILED DESCRIPTION FIG. 1 This figure schematically depicts a combined flow meter constructed in accordance with the present invention. The composite instrument includes a conduit 1 carrying liquid flowing either through a main channel containing a wide range turbine instrument 2 and a valve mechanism 3 or via a parallel auxiliary channel 10 containing a low flow range instrument 8. Turbine instrument 2 operates indicator 5 and low range instrument 8 operates indicator 9
operate. The total flow through the composite meter is obtained by taking readings from indicators 5 and 9 and adding them.

Valve mechanism 3 includes a poppet valve 4 mounted on a mandrel 4a and biased to a closed position by a spring 6. The mandrel 4a is slidably mounted in a hole in the wall 7 which has another hole 7a to allow passage of liquid.

In the auxiliary channel 10 there is preferably provided a valve 15, shown as a leaf spring fixed at one end on a wall 17 with a hole 17a, preferably upstream from the meter 8. Valve 15 is self-energized to the open position and is movable to the closed position by the pressure differential across the valve.
The valve 15 is provided with a hole 15a, which is connected to the valve 1.
It serves to allow a minimum flow through the meter 8 even when the meter 5 is closed.

Downstream from the meter 8 is a fixed orifice 16, the diameter of which is selected such that the pressure drop across it balances the spring rate of the spring 6 to determine the flow rate when the valve 4 opens. ing.

The pressure drop between the inlet and the outlet of the composite meter is divided in the main flow path between the pressure drop across the main meter 2 and the pressure drop across the main valve 4. In the auxiliary flow path, the pressure drop between the inlet and the outlet is the sum of the pressure drops across valve 15, across meter 8, and across orifice 16.

The primary function of valve 15 is to reduce the flow through low flow meter 8 after turbine meter 2 has reached a certain portion of its accuracy characteristic (FIG. 11). At such times, it is desirable to reduce the speed of the meter 8 in order to reduce wear by preventing the meter 8 from operating continuously at high speeds.
On the other hand, it is also desirable to keep it operating at low speeds, since turbine instruments in some installations can operate at high speeds for long periods of time. If the low flow meter is allowed to shut down during those periods, it is conceivable that it will become fixed in position and will not be able to start up again when the flow through the turbine meter is reduced.

For equipment where the above functions are not required,
Valve 15 may be omitted.

When there is no flow through conduit 1, valve 4 is subject to a pressure difference between the inlet and outlet of the composite meter and is held closed by spring 6. As the flow increases, the pressure difference increases. At a given flow rate established by the force of spring 6 and the characteristics of orifice 16 and low flow meter 8, the pressure difference becomes large enough to initiate the opening movement of valve 4.

FIG. 2 This figure schematically shows another device for determining the sum of the flow through the turbine instrument 2 and the flow through the positive displacement instrument 8. Turbine instrument 2 operates transmitter 11 and positive displacement instrument 8 operates transmitter 12. Transmitters 11 and 12 drive adder 13, which drives register 14. Register 14 displays the sum of both meter readings. A recorder may be used instead of a register.

FIGS. 3-5 These figures illustrate in detail one preferred embodiment of the invention. The compound instrument includes a casing 20, shown at 20a in FIG. 5, which is open at the top and closed by a cover 21 held in place by bolts 22. A gasket 18 seals the connection between the casing 20 and the cover 21. The casing 20 has an inlet 20b at the right end and an outlet 20c at the left end when viewed in the figure. The cross wall 23 is the entrance 20
It extends across the casing 20 intermediate between b and outlet 20c and has a central hole 23a.

A wall 2 is provided on the transverse wall 23 and extends through the hole 23a.
A valve assembly 24 is mounted which includes a valve seat 25 having a flange 25a that engages the upstream surface of the valve. A sealing ring 26 is provided between the flange 25a and the wall 23.
is provided. The valve seat 25 projects through the wall 23. A ring 27 is placed on the protruding end of the valve seat 25.
are screwed together. Ring 27 includes a plurality of circumferentially spaced studs 30 projecting downwardly from wall 23.
is carried. The guide and retainer 31 is the stud 3
It has a flange 31a drilled to engage a shoulder on the 0. Flange 31a is held in place on stud 30 by nuts 32. The guide and retainer 31 cooperates with the valve seat 25 of the valve 3
It has a deep dish-shaped shape with an incurved central cone 31b that acts as a guide for the valve stem 33 supporting the valve stem 33. A coil spring 35 is held in a compressed state between the valve 34 and the guide/retainer 31.

Cover 21 supports turbine instrumentation 36 located upstream of wall 23 within casing 20 . Instrument 36 is a conventional turbine instrument 74 shown in FIG.
It must have a sensitivity to low flow rates similar to that of , and its accuracy characteristics at low flow rates are shown in FIG. The meter 36 is a rotating permanent bar magnet 3 that drives a display 40 (FIG. 3) of known construction.
8 at its upper end. The downstream end of the meter 36 is sealed to the flange 25a by a molded sealing ring 39.

Cover 21 also carries a low flow meter 41, which may be a known positive displacement meter of the downward disc type.
Gauge 41 drives another permanent magnet 42, which drives a display 43 (FIG. 3).
The low flow meter 41 is positioned snugly within the cover 21 and is held in a closed chamber at its lower end by a plate 44 held in place by screws 45.

A stud 46 projects downward from the cover 21. A rod 47 is fixed to the top of the turbine instrument 36 and is attached to the stud 46 by a bolt 48.

A parallel auxiliary flow path from inlet 20b through positive displacement instrument 41 is followed through a narrow space (illustrated arrow 50) at the upstream end of turbine instrument 36 and then through a valve 52 mounted on the underside of cover 21. . Valve 52 is best shown in Figure 5a;
It is shown as a simple leaf spring valve that is self-biased to the open position shown in the figure. The leaf spring valve 52 has an opening 52a aligned with an opening 51a in the transverse wall 51 of the cover 21. As the pressure drop across the valve 52 increases, the valve smoothly closes, and the opening 52a then becomes an operational limit that limits the maximum flow through the meter 41. A transverse wall 51 extends across the cover 21 and connects the transverse wall 2 within the casing 20.
I agree with 3. The auxiliary flow path extends through the opening 51a into the chamber housing the positive displacement instrument 41. The auxiliary flow path leads from the meter to the outlet 2 via the outlet passage 21b and a restriction 53 of selected dimensions.
It extends to 0c.

When assembling the composite instrument, the valve assembly 24
is mounted on the transverse wall 23 of the casing 20. Instruments 36 and 41 are mounted on cover 21. The assembly consisting of the cover and two instruments is then placed in place on the casing 20. Gauge 36 passes through opening 20a in the top of casing 20 with appropriate clearance on all sides. The cover assembly is then tightened in place with bolts 22 to complete the composite instrument.

FIGS. 6-7 These figures illustrate the accuracy of typical conventional combined flow meters. The term "percent accuracy" as used in the art refers to a low reading if the number is less than 100% and a high reading if the reading is greater than 100%.

In FIG. 6, solid line 61 indicates the acceptable low reading accuracy limit for composite meters as established by American Water Works Association Standard C-702-78. Straight line 64 represents a satisfactory high reading accuracy limit as established by the same standard. Line 61 has an area where the satisfactory low reading accuracy drops to 90% between about 6 gallons per minute and 33 gallons per minute, whereas in other areas it is low except at the very low end of that range. 97
% can be maintained. This is the transition region where the instrument changes from a positive displacement instrument to a condition where both instruments are functioning together. The dashed curve 62 shows the accuracy characteristic of a typical conventional compound flow meter under conditions of increasing flow, and the solid curve 63 shows the accuracy characteristic of the same meter under conditions of decreasing flow.

Dashed curve 65 shows the variation of head loss across a conventional composite meter as the flow increases. Solid curve 66 shows the head loss for the meter at reduced flow. In FIG. 7, the change in flow through the positive displacement meter under conditions of increasing flow is shown by dotted line 67. Solid line 68 shows the corresponding flow rate through the positive displacement meter under conditions of decreasing flow.

FIGS. 8 to 11 FIGS. 8 and 9 correspond to FIGS. 6 and 7, respectively, and illustrate the characteristics of the composite meter of the present invention. In FIG. 8, lines 61 and 64 are the same as similarly numbered lines in FIG. 6 and indicate acceptable accuracy limits for the compound instrument. Curve 71 illustrates the accuracy of an instrument constructed in accordance with the present invention. The curve is the same for increasing and decreasing flows. Curve 72 shows the variation in head loss across a composite instrument constructed in accordance with the present invention. Curve 7 in Figure 9
3 shows the change over the entire range of flow through the low flow meter 8 or 41, which may be a positive displacement meter of the downward disc type, to the complete composite meter. The disc meter measures most of the flow up to about 15 gallons per minute, after which valve 4 or 34 begins to open and the flow through the disc meter begins to flow through valve 52 or valve 1 in FIG.
It decreases by closing the valve 15 in the figure.

FIG. 10 shows a turbine instrument 74 of the type known in the art, which is particularly suited for use in complex instruments constructed in accordance with the present invention. 1st
Turbine instrument 74 in FIG. 0 includes an impeller 75 fixed on a shaft 76 mounted in bearings 77 and 78. Two thrust fillers 81 are provided at both ends of the shaft 76.
and 82. The end play of the shaft can be adjusted by a nut 83 pivoting on a stud 84 carrying a thrust filler 81. The shaft 76 is a large gear forming part of a gear train 87 (not shown in detail) which drives a vertical shaft 88 carrying a magnet 91 at its upper end which cooperates with another magnet 92 on the opposite side of the fixed wall 93. It carries a pinion gear 85 in cooperation with 86. Magnets 91 and 92 may be arranged as a magnetic coupling in accordance with Southall US Pat. No. 3,442,126. Once the turbine meter 74 exceeds its minimum flow rate, it accelerates rapidly, as shown by the steep slope on the low flow portion of curve 93 in FIG. This rapid acceleration characteristic is achieved by supporting rotor 75 on a live shaft that pivots in spaced bearings 77 and 78 with adjustable end play to limit end loads. Shaft 8 of turbine 75 and magnet 91
The reduction gear train between 8 and 8 gives impeller 75 a substantial mechanical advantage over magnet 30 and thus contributes to a high rate of acceleration. Furthermore, all thrust by the magnet is carried on the bearing carrying the shaft 88 and is not transmitted back to the impeller 75. Magnet 91, shaft 88 and gear train 77 operate in a clean liquid supplied through a capillary seal to further reduce friction. Therefore, impeller 75 starts easily and quickly accelerates to a speed at which its accuracy is approximately 100%, as shown by curve 93 in FIG.

The disc meter flow curve 73 in FIG. 9 gradually increases from zero flow until it reaches a maximum value as shown at 73a, and then the flow decreases rapidly as shown at 73b. This rapid decrease is caused by the closing of valve 52 in FIG. 5 or valve 15 in FIG. 1. After the valve is closed, the disk meter remains operating at a lower flow rate for all higher flow rates through the compound meter. This low flow rate through the disc meter is to prevent the disc meter from becoming fouled by mineral precipitation from the liquid being measured, which may occur if the disc meter is to remain stationary for long periods of time. belongs to. In FIG. 8, the initial portion 71a of the accuracy curve 71 is due to the low flow meter, but at approximately point 71b, the curve for the turbine meter becomes substantially larger than that via the disc meter, and the curve 71 becomes portion 71c.
It can be seen that almost all of the results are due to turbine instruments.

In order to ensure the maintained high accuracy characteristics of FIG. 8 in a composite instrument, it is essential that the turbine instrument employed has rapid acceleration characteristics in response to increasing flow. It is also important to use a simple main valve mechanism that opens gradually, as shown at 3 in FIG. 1 or 34 in FIG.

Both the auxiliary valve 15 of FIG. 1 and the auxiliary valve 52 of FIG.
Both the illustrated limiting orifice 16 and the limiting orifice 53 of FIG. 5 are located downstream from the low flow meter. It is possible to locate the auxiliary valve upstream or downstream from the low flow meter. However, locating the orifice immediately upstream from the meter tends to increase turbulence in the flow through the meter and can disrupt its accuracy. Valves 15 and 52 are shown upstream of their respective instruments for convenience.

Although the low flow meter has been described above as a downward disc type positive displacement meter, other suitable types of low flow meter may be used in the composite meter of the present invention.

The specific scales and flow rates described above and shown in FIGS. 6, 7, 8, 9 and 11 are determined by the size of the meter and are a limitation of the present invention. It shouldn't be considered.

In accordance with the present invention, the auxiliary flow path is provided with an auxiliary valve for controlling the flow through the low flow meter and is provided with spring means for biasing the main valve into a closed position. By providing a spring means to bias the main valve to the closed position, the operation of the main valve is smooth and no pressure shock or surge occurs due to the operation of the main valve. This has the effect that this auxiliary valve restricts the flow through the auxiliary passage when the main valve is open, resulting in a higher total flow rate through the main passage.