FR2626987A1 - Method and device for measuring a volume of liquid at a random flow rate, with a meter whose measurements are insufficiently precise at a low flow rate - Google Patents

Abstract

The device includes, interposed between a pipe and a volume meter 5, a buffer reservoir 1, fitted with a discharge valve 2 operated by a rod 10. A middle float 35 is shackled to the rod 10 by a fork 12, its high and low positions determining the opening or the closing of the valve 2. The rod 10 is locked open by a jaw 33 of a lower float arm 30, which engages under a tongue 11, when this float is submerged. The float 35 is immobilised in the low position by a hook 43 of an upper float arm 40, when this float is not wetted. When the valve 2 is closed, the condensates fill the buffer reservoir until the upper float 40 is made to float, which frees the middle float 35 which opens the valve 2. The lower float 30 locks the valve 2 open, until the level in the buffer reservoir 1 falls until the float 30 is made to descend, which unlocks the rod 10. Thus a minimum flow rate is ensured in the meter 5 and metering is kept within an accurate range.

Description

"Method and device for measuring a volume of liquid
in random flow, with a measurement counter
insufficiently precise at low flow "
The invention relates to a method for measuring the volume of liquid flowing at a random rate in a pipe, using a meter whose measurements are not reliable at rates lower than a given minimum rate.

 The invention also relates to a device for measuring the volume of liquid at random flow rate according to the method mentioned above.

 By random flow, is meant a flow which is capable of taking any value over time, under the effect of external causes. In practice, the flow can vary from zero to a maximum.

 The invention was born for the metering of the energy supplied to heating substations of buildings connected to an urban steam distribution network.

 As most of the energy supplied corresponds to the condensation of steam, the energy metering is done by means of the condensate volume metering.

 The fluctuations in demand for power, daily and seasonal, are very significant, whether it is the heating of the buildings served or the production of domestic hot water; the usual meters of the turbine-propeller type, electromagnetic, ultrasonic, have varying precision between a practically zero flow and a maximum flow.

 The most mediocre details correspond to extreme flows, and in particular to low flows; indeed there is always a maximum flow, in relation to the maximum power of the installation, and lton sizes the meters according to this maximum flow.

 It will be noted that the strict volumetric meters, with standard volume chambers alternately filled and emptied, do not lend themselves to very high flow rates because of their bulk, in particular. Dynamic meters can then be used, for example flow meters associated with an integrator. Unfortunately these meters are inaccurate at low flow rates. In addition, they give in particular erroneous indications when the liquid vein which crosses them does not completely fill the section of the pipeline.

 In any case, it is possible to determine, for a particular type of meter, the maximum flow rate that it can measure satisfactorily, which constitutes the caliber of this meter, and the minimum flow rate below which the measurements are considered. as insufficiently precise.

Caliber and minimum flow are technical data of the particular type of meter1 defining a range of reliability.

 The subject of the invention is a method which ensures that the measurements of a flow liquid volume meter will be carried out within the reliability range.

 To this end, the invention provides a method for measuring the volume of liquid flowing at a random flow rate, in a pipe, using a counter whose measurements are not precise enough at flow rates lower than a minimum flow rate. given, characterized in that there is on the pipeline, upstream of the counter1 a buffer tank1 and the passage of liquid in the pipe between the buffer tank and the counter is cut off when the level of liquid in the buffer tank is insufficient to induce a flow in the meter greater than the minimum flow given.

 It is known that the liquid flow rate in a passage section is a direct function of the hydrostatic pressure between upstream and downstream of the passage section considered.

Thus, when the flow of liquid upstream of the buffer tank will be lower than the given minimum flow, the liquid will accumulate in the buffer tank to be discharged into the meter when the level is sufficient to ensure the minimum flow.

 To limit the frequency of alternating opening and closing, the passage of the liquid is opened when the level of liquid in the reservoir reaches a chosen maximum level. This maximum level will correspond to a flow in the meter, lower than the maximum flow given by the gauge of the meter. It will be understood that the opening level must not induce a flow greater than the maximum flow for which the meter is calibrated1 but that, in any case, the buffer tank must be provided high enough to accept the maximum flow to be counted without overflowing , and that the spacing of the openings assumes that the volume debited during an opening period is as large as possible. The maximum flow here is the maximum flow that the meter is supposed to count.

 In another aspect, the invention provides a device for measuring liquid flowing, at random flow rate, in a pipe, using a meter whose measurements are not reliable at flow rates lower than a minimum flow rate. given, characterized in that it comprises, inserted in the pipeline, upstream of the meter, a buffer tank provided, in the lower part, with a discharge valve towards the meter, with closed and full open positions, three floats located on stepped levels and designated consequently below by lower, middle and upper floats, each float with an active state where it receives liquid a preponderant Archimedes thrust, and a passive state where its weight is preponderant, the lower float being arranged to, in its active state, maintain the valve in the fully open position, the middle float being coupled to the valve so as to urge it, in active state, towards its fully open position and, in not state sif, towards its closed position, and to take up and down positions in respective correspondence with the full opening and closing positions of the valve, while the upper float is arranged to, in passive state, maintain the median float in low position.

 Given the comments relating to the process of the invention, it is understood that the passage of the float to its passive state, following the emptying of the buffer tank, causes the discharge valve to close, and thus defines the level corresponding to the minimum flow in the counter, and that the passage of the upper float to its active state due to the filling of the buffer tank causes the full opening of the discharge valve.

 Preferably, the valve is equipped, at the outlet, with a calibrated annular diaphragm, above a pressure balancing chamber in communication with the buffer tank by a tube opening at a level higher than that of the upper float, thus than a vent, whereby the liquid level in the buffer tank determines the flow in the relief valve.

 Balancing the pressures between the chamber downstream of the diaphragm and the surface of the liquid in the buffer tank allows a one-to-one relationship between the level of liquid in the buffer tank and the flow rate in the discharge valve provided with its calibrated diaphragm. The levels of the high and low floats, above the diaphragm, therefore determine in a precise and calculable manner the flow rates at the opening and at the closing of the valve. This downstream chamber is provided to facilitate the admission of liquid into the downstream piping without clogging.

Secondary characteristics and advantages of the invention will become apparent from the description which follows, by way of example, with reference to the accompanying drawings in which
Figure 1 is a sectional elevation of a device according to the invention
Figure 2 is a section of a discharge valve in the closed position
Figure 3 is a section of the relief valve of Figure 2, in the fully open position
Figure 4 is a schematic representation of the device, during filling
FIGS. 5A and 5B schematically represent the device when the discharge valve is opened
FIG. 6 schematically represents the device during discharge
FIGS. 7A, 7B and 7C schematically represent the device when the relief valve is closed.

 According to the embodiment chosen and shown in Figures 1, 2 and 3, the device according to the invention is inserted in the condensate return circuit of a building heating substation connected to an urban distribution network steam. This circuit conventionally comprises a condensate collection pipe 3, in series with a volume counter 5 and a return pipe 9; this leads to a cover from which pumps return the condensate to the boiler room which produces the steam.

 The device according to the invention comprises a buffer tank 1, provided at its lower part with a discharge valve 2, with opening stroke closing vertically1 with an axial control rod 10, held vertical by an iota guide ring, fixed at the walls of the tank 1.

 Immediately downstream of the valve 2 is disposed a balancing chamber 4, of large section in front of that of the valve 2, and which ends in a truncated cone to connect to the inlet pipe of the meter. In the upper part of the balancing chamber, there is a pipe 6 which is communicated by a nozzle 7 with the upper part of the buffer tank. Tubing 6 extends upward toward a vent.

 The interior of the balancing chamber 4, which is of sufficient cross section not to be filled with liquid when condensates flow through the open valve 2, is in pressure equilibrium with the gas phase above the liquid level in the tank 1. In the case shown, the pressure in the balancing chamber 4 and above the liquid level in the buffer tank 1 is atmospheric pressure, due to the presence of the vent 8 It will be understood that the presence of the vent 8 is only justified if one operates at atmospheric pressure.

 Incidentally, the nozzle 7 would act as an overflow if accidentally the level of condensate in the buffer tank 1 rose excessively.

 In the buffer tank 1 are arranged three floats designated according to their level in the tank by lower floats 30, median 35 and upper 40. These three floats 30, 35, 40 are pivotally mounted around horizontal axes 31, 36, 41 respectively held in position on the walls of the buffer tank 1, at the end of arms 32, 37 and 42 respectively.

 Depending on the level of condensate in the buffer tank, the floats can be in passive state 1 where their weight outweighs the buoyancy, or in active state where the buoyancy outweighs the weight of the floats. Practically, so that the forces developed in the two states are of the same order of magnitude in absolute value, the volume of the floats will be such that the buoyancy of Archimedes on a fully submerged float will be double the weight of the float. In other words, free, a float will immerse half of its volume.

 It will be noted that the state of a float does not rigidly determine the position it takes. As will be seen below, a float can be in the active state and locked in the low position, and be in the passive state and locked in the high position.

 The arm 37 of the median float 35 passes, with play, between two horizontal pins 12 inserted in the control rod 10 forming a fork. The float 35 and its axis 36 are placed on either side of the rod 10.

 By pressing the arm 37 on the pins 12, the float 35, in the passive state, will urge the rod 10 downwards, and, in the active state, will urge this rod 10 upwards. The relief valve 2 has a closed position, corresponding to a low position of the control rod 10, and a fully open position, corresponding to a high position of the rod 10, where a stop pin. 13 comes to bear against the guide ring 10a.

The float 35 will present, together with the control rod 10, a low position corresponding to the closing of the valve 2, and a high position corresponding to the full opening of this valve 2.

 The discharge valve 2, in the example described here, as best seen in Figures 2 and 3, respectively representing this valve in the closed and fully open position, has a cylindrical body 20 with vertical axis, with a bore 20a , this cylindrical body 20 being welded into the bottom wall of the buffer tank 1. A cap 21 comes to rest in the closed position, FIG. 2, on the upper edge of the body 20, and has at its upper part a blind tapped hole in which is screwed axially the threaded lower part of the control rod 10.

 In the lower part of the cap 21 is fitted a sleeve 22, made of polytetrafluoroethylene, with a cylindrical wall capable of leaktight sliding in the internal bore 20a of the valve body 20. In this cylindrical wall are provided two lights, here oblong, 23 and 23 ', hidden when the valve 2 is in the closed position (figure 2) and fully exposed (figure 3) when the valve 2 is in the fully open position, with the stop pin 13 resting on the iota guide ring.

 Furthermore, the outlet orifice of the valve body 20 here has a removable diaphragm 24, held in place by tightening an outlet nozzle 25, screwed into the body 20.

 The diaphragm 24 constitutes the narrowest passage of the valve 2. It will be calibrated so as to determine discharge rates chosen under hydrostatic pressures corresponding to the condensate levels in the buffer tank 1 which cause the opening and closing of the valve 2.

 We will see below how the structure of the floats 30, 35, 40 and the level of their axes 31, 36, 41 determine the levels of condensate causing the opening and closing of the valve 2.

 As the pressures in the balancing chamber 4 and in the buffer tank 1 above the condensate level are equalized through the pipe 6, the pressure drop across the diaphragm 24, the valve 2 being in the fully open position , will be equal to the hydrostatic pressure of the condensates above the diaphragm. The pressure drop corresponds to what is called dynamic pressure in hydrodynamics.

 If the viscosity of the condensates is neglected, the flow rate through the open discharge valve is therefore strictly linked to the level, taken above the diaphragm 24 of the condensates in the buffer tank.

 Also the closing level will determine a flow rate at least equal to the minimum reliability flow rate of the counter 5, while the opening level will determine a flow rate close to the maximum flow rate for which this counter 5 is provided, but lower than this. Indeed, it would not be necessary that, at the opening of the valve 2, the original flow exceeds the maximum, but moreover, it would not be necessary that, if the condensates arrive by the collecting pipe 3 at the maximum flow , the level is established in the buffer tank 1 too above the level which causes the opening and in particular reaches the nozzle 7 for the connection with the balancing chamber 4.

 Returning to FIG. 1, the arm 32 of the lower float 30 is provided with a spout 33 which cooperates with a tongue 11 fixed longitudinally on the control rod. When the float 30 is in the passive state, the spout 33 moves away from the tongue 11. When the float 30 is in the active state, the spout 33 comes to bear on the tongue 11 when the rod 10 is in position low and the valve 2 in the closed position, and comes to hang under the lower edge of the tongue 11 when the rod 10 is in the high position and the valve 2. in the fully open position; thus when the valve 2 is open, the spout 33 prohibits its closing, as long as the float 30 is in the active state.

 The arm 37 of the median float 35 is extended, beyond the axis 36 relative to the float, by a circular sector 38, with a cylindrical blade 38a. The arm 42 of the upper float 40 has a hook 43 which cooperates with the limb 38a of the sector 38. When the float 40 is in the active state, the hook 43 is away from the limb 38a.

When the float 40 is in the passive state, the hook 43 engages under the lower edge of the blade 38a, corresponding to the lower radius of the circular sector 38, when the median float 35 is in the low position, while it bears on the blade 38a when the median float 35 is in the high position, or at an intermediate position between the low position and the high position.

 Thus the cooperation of the hook 43 and of the limb 38a prohibits the passage of the median float 35 from its low position to its high position, and therefore the opening of the valve 2, as long as the float 40 is in the passive state, without however causing closing the valve 2 if the latter is open as long as the spout 33 is engaged under the tongue 11.

 Figure 1 shows the device after closing the valve 2. The lower float 30 is in the passive state, the spout 33 slightly apart from the tongue it.

The median float 35 is in the passive state at its low position 1 and confirms, by pushing on the lower pin 12, that the valve 2 is closed. The float 40 is in the passive state, and the hook 33 is engaged under the limb 38a of the arm 37 of middle float 35.

 Condensates arriving through the collection pipe 3, the level of condensates rises in the buffer tank 1, as shown in FIG. 4. The lower float 30 is in passive state, and the spout 33 bears on the tongue 11. The float 35 is also in the active state, but is locked in the low position by the engagement of the hook 43 under the limb of the circular sector 38; the float 40 is in passive state.

 As shown in FIGS. 5A and 5B, when the level of the condensates in the buffer tank 1, rising, changes the float 40 from its passive state to its active state, the hook 43 emerges from the limb of the circular sector 38 (FIG. 5A). The float 35 in the active state, then released, quickly switches to the high position 1 causing the full discharge valve 2 to open (FIG. 5B).

The float 30, also in active state, engages the spout 33 under the lower edge of the tongue 11, which accompanied the control rod 10 in its ascent. The content of the buffer tank 1 is poured, at a flow rate close to the maximum, through the valve 2, into the counter 5.

 If the condensate flow arriving in the buffer tank 1 via the collection pipe 3 is intermediate between the maximum flow rate and the minimum which causes the valve 2 to close, the level of condensate in the tank buffer is established at a level intermediate, as shown in Figure 6. The upper float 40 is in the passive state, as well as the median float 35. The lower float is always in the active state, and the spout 33, engaged under the tongue 11, maintains the control rod 10 in the high position, and the discharge valve 2 remains open while the float 35 is held in the high position so that the hook 43 bears on the blade of the circular sector 38.

When a reduction in condensate flow in the collection pipe 3 causes a drop in level in the buffer tank 1 such that the lower float 30 changes from its active state to its passive state, the valve 2 closes by a process with three linked steps, shown in Figures 7A, 7B, 7C;
The float 30 passing from its active state to its passive state, the spout 33 emerges from the lower edge of the tongue 11 (FIG. 7A) and unlocks the fully open position of the valve 2. The float 35, in passive state, urges down the control rod 10, to close the relief valve 2 (Figure 7B). This step is very quick. When the float 35 has reached the low position, the float 40, in the passive state, engages its hook 43 under the limb of the circular sector 38 (FIG. 7C) thus locking the float 35 in the low position. We are thus brought back to the state corresponding to FIG. 1.

 It will be understood that the operation of the device would not be altered if the hook 43, fixed to the arm 42 of the float 40 was engaged above a tongue similar to the tongue 11 and fixed to the upper part of the control rod 10, instead of engaging under the blade 38, so as to prevent the ascent of the control rod 10 under the action of the float 35 in the active state, as long as the float 40 is in the passive state. Furthermore, this hook 43 would bear against the added tongue when the control rod is in the high position. Indeed, as we have. seen, the float 35 and the rod 10 are jointly in the high position or in the low position, due to the coupling of the arm 37 between the pins 12.

 It will be appreciated that thus the flow rates in the meter 5 will be either zero or greater than a minimum, chosen because of the reliable operating conditions of the meter, and jointly determined by the opening of the diaphragm 24 (FIGS. 2 and 3) and the transition level between the active and passive states of the lower float 30, above the diaphragm. Furthermore, the opening of the discharge valve 2 occurs at a level corresponding to the transition between the passive and active states of the upper float, such that the resulting flow remains within the reliability range of the counter 5; it is also ensured that the level in the buffer tank will only slightly exceed the previous transition level, insofar as the installation has been properly calculated and where, consequently, the condensate flow will not exceed not the maximum flow expected.

 It will be noted that, in the preceding description, the lower float 30 operates as a lower level detector and that the upper float 40 operates as an upper level detector, while the median float 35 acts as the control of the discharge valve 2 qu 'it puts in the fully open position in a first state, and in the closed position in a second state. When the upper float or detector 40 goes into active state, it puts the median float or control means 35 in first state, with the valve 2 put in the fully open position.

When, as a result of the flow of liquid to the counter 5, the level drops and the float or lower level detector 30 goes into passive state, it puts the control means 35 (median float) in its second state, with valve 2 in the closed position.

 It therefore appears that an equivalent device would be obtained by replacing the lower 30 and upper 40 floats with level detectors, for example electric or electronic, and the middle float 35 with an all-or-nothing control means coupled to a shut-off valve. controlled discharge, such as a rocker and a solenoid valve, with the difference however that the equivalent measuring device should be connected to an energy source, while the device with three floats borrows its operating energy from the current of water that 'he pilots.

 Of course, the invention is not limited to the examples described, but embraces all the variant embodiments thereof, within the scope of the claims.

 In particular, the device can operate under a working pressure which differs from atmospheric pressure.

The method and the device are applicable to the volume measurement of other liquids than steam condensates, since these are not suspensions the storage of which may cause sedimentation or phase segregation.

Claims (12)

 1. Method for measuring the volume of liquid flowing, in random flow, in a pipe (3, 9), using a counter (5) whose measurements are not precise enough at flow rates less than one given minimum flow rate, characterized in that there is on the pipe (3), upstream of the meter (5), a buffer tank (1), and the passage (2) of liquid is cut in the pipe between the buffer tank (I) and the meter (5) when the liquid level in the buffer tank (1) is insufficient to induce a flow in the meter (5) greater than the given minimum flow.  2. Method according to claim 1, characterized in that one opens the passage (2) of liquid between the buffer tank (1) and the counter (5) when the liquid level in the buffer tank (I) reaches a maximum level chosen.  3. Method according to claim 2 wherein the meter (5) is calibrated for a maximum flow, characterized in that the maximum level is chosen such that the resulting flow in the meter (5) is at most equal to the aforementioned maximum flow .  4. Device for measuring liquid flowing, at random flow rate, in a pipe (3, 9d, using a counter (5) whose measurements are not precise enough at flow rates lower than a minimum flow rate given, characterized in that it comprises, inserted in the pipe upstream of the counter (5), a buffer tank (1) provided, in the lower part, with a discharge valve (2) towards the counter (5), with closed and full open positions, three floats located at stepped levels and designated accordingly below by lower (30), middle (35) and upper (40) floats, each float in an active state where it receives of liquid a predominant Archimedes thrust, and a passive state where its weight is preponderant, the lower float (30) being arranged to, in its active state, maintain the valve (2) in the fully open position, the median float ( 35) being coupled to the valve (2) so as to urge it, in active state, towards its full position e opening and, in passive state, towards its closed position, and to take the high and low positions in respective correspondence with the full opening and closing positions of the valve (2), while the upper float (40) is arranged to, in passive state, maintain the median float (35) in the low position.  5. Device according to claim 4, characterized in that the valve (2) is equipped, at the outlet, with an annular diaphragm (24) calibrated, above a balancing chamber (4) of pressure in communication with the buffer tank (1) by a tube (6) opening at a level (7) higher than that of the upper float (40), whereby the level of liquid in the buffer tank.  (1) above the diaphragm (24) determines the flow rate in the relief valve (2).  6. Device according to claim 5, characterized in that the tube (6) which connects the balancing chamber (4) to the buffer tank (1) communicates with a vent (8) for venting.  7. Device according to one of claims 5 and 6, characterized in that the liquid level above the diaphragm (24) which corresponds to a transition between the active and passive states of the lower float (30) determines a flow at less equal to the given minimum flow rate of reliability of the meter.  8. Device according to any one of claims 5 to 7, where the meter (5) is dimensioned for a maximum flow rate, characterized in that the level of liquid above the diaphragm (24), which corresponds to a transition between the passive and active states of the upper float (40), determines a flow rate lower than the aforementioned maximum flow rate, but close to the latter.  9.'A device according to any one of claims 4 to 8, -characterized in that, the relief valve (2) having a valve (22) which passes from the closed position to the fully open position by an upward vertical stroke , and a rod (10) fixed axially on the valve (22), the three floats (30, 35, 40) are held at the end of respective arms (32, 37, 42) pivotally mounted around horizontal axes (31, 36, 41) fixed to the buffer tank (1), and the control rod (10) is provided with a pair of stepped pins (12) forming a fork through which the arm (37) of the middle float (35) passes , between axis (36) and float (35).  10. Device according to claim 9, characterized in that the arm (32) of the lower float (30) is provided with a spout (33) arranged for, in the active position of the float1 to hang under a lower edge of a tongue (11) fixed longitudinally on the control rod (10) of the valve (2), the latter being in the fully open position, while, the valve (2) being in the closed position, the spout (33) door against the tongue (it).  11. Device according to one of claims 9 and 10, characterized in that the arm (37) of median float (35) is extended, beyond its axis (36), by a circular sector (38) centered on this axis with a blade (38a) and a radial lower edge, while the upper float arm (42) (40) has a hook (43) arranged for, the upper float (40) being in the passive state, s '' Engage under the lower radial edge of the circular sector (38) when the median float (35) is in the low position, and bear against the limb (38a) of this sector (38) when the median float (35) is in the high position .  12. Device for measuring liquid flowing, at random flow rate, in a pipe (3, 9) using a counter (5) whose measurements are not precise enough at flow rates lower than a flow rate given minimum, characterized in that it comprises, inserted in the pipe upstream of the meter (5), a buffer tank (1) provided, in the lower part, with a discharge valve (2) towards the meter (5) with closed and fully open positions, two level detectors arranged in stages and designated accordingly below by lower (30) and upper (40) detectors, each with an active state where it is immersed in the liquid, and a passive state, and a control means (35) coupled to the valve (2), with a first state where it puts the valve (2) in the fully open position, and a second state where it puts it in the closed position, the lower (30) and upper (40) detectors being coupled to the control means such that the upper detector (40) passing through the active state puts the control means (35) in its first state, while the lower detector (30) puts the control means (35) in its second state.