FR2524979A1 - Outflow control appts. for compressed gas in vessel - has manometer, analogue or digital calculator and display panel with regulators - Google Patents

Abstract

The control appts. makes measurements on a vessel (V) into which compressed gas is introduced, then expelled. The vessel is connected to a compressor by a pipe. There are cut-out valves at the input and/or the output of the vessel. The control appts. is contained in a box connected to the vessel by a coupling pipe attached to a suitable pressure inlet of the vessel. The coupling pipe opens into a manometer with two contacts - one for minimum and one for maximum pressure. The two contacts are adjustable, the pressure fork being chosen in the range where measurements are to be made. The manometer emits an electrical signal at each crossing towards the bottom or top limits of the pressure fork. The signals are fed to a calculator which determines the outputs produced up stream and consumed downstream of the vessel and/or the resultant of the two. The calculator is connected to a panel having a display system with a zero reset button and a regulation button dependent on the characteristic parameters of the vessel and its associated pipes and fittings. The calculator may be for analogue or digital function usage.

Description

Technical area.

The invention relates to an apparatus for controlling the flow of compressed gas into an enclosure from which conduits of a circuit originate, a gas introduced into it and then expelled, said chamber comprising isolation valves.
at the entrance and / or exit and a pressure tap.

Problem.

 In fact compressed gas, we will consider here the most general case of compressed air, widely used in industry as a source of power for production machine and control device and / or regulation.

However, the applications of the apparatus of the present invention may be of interest to all kinds of various compressed gas networks.

 It is a question of periodically checking the flow rates of gas produced and / or consumed, which generally pass through a fugitive volume buffer tank where the measurement can be made. This tank can be isolated either at the intake or at the exit. This control can also be done on any isolated section of the circuit. The interest of these measures, especially if they can be practiced simply, is to check the good state of the apparatus of gas production, the appliances which consume it and the circuit which is between the two.

State of the art and disadvantages.

 Some installations are equipped with counters that can be rotary, volumetric or dynamic type (partial expansion through a calibrated orifice).

 In the most general case, the precise measurements of the produced or consumed flow require the temporary implementation of devices of the depressive type which determine the speed of passage of the air or the gas relax in the open air after passing through. a caliber orifice.

These techniques follow standard procedures and they implement an imposing apparatus. They are hardly accessible to the user who must, therefore, call on specialists (receiving organization or manufacturer) each time he wants to check the flows involved in his network.

 Apart from the cost of these vacations, a major disadvantage is that such measurements require the disconnection, so out of production, of all or part of the network concerned for an extended period of time.

 Otherwise, the user can still measure these flows by calculation from the filling time of a known volume capacity in a given pressure range. This simple but empirical method presupposes experimental errors that may be significant and, in particular, because it is difficult to trigger a stopwatch at the precise moment when the needle of a manometer indicates the limit values of the pressure selected. for the measurement.Also reliable and precise is the pressure gauge, an error of a half-division on a device graduated fifth supposes a possible error of 0,2 bar is 20% if the measurement is carried out on a range of 1 bar = dp; if 1C, if it is 2 bars At this error, it will of course be the one that is due to the precision of the device.

 The ot of the device of the invention is essentially to make available to the user a light and mobile device of a simple and convenient empl @ i that allows him at any time and quickly @ test, to auscultate its network, both in terms of production and consumption, to diagnose, in comparison with normal operating conditions, any change in flow rate in the installation which generally indicates a fault. The device therefore has the function of alerting the user so that he can intervene preventively before the failure occurs without notice.

 It is therefore seen that the apparatus of the invention aims to eliminate the disadvantages listed above.

Presentation of the invention.

The apparatus of the invention is characterized primarily by the combination in and around a box
a) a connecting pipe to the pressure tap, b) a pressure gauge detecting the pressure variations in a determined and adjustable f-urchette by emitting an electric signal at each crossing down and up of limits of said oven, c) a computer receiving signals from the gauge apparatus for calculating the flow rates produced upstream of the enclosure. consumed downstream and / or the resultant of the two, thanks to integration circuits parameters specific to the enclosure and its tu ;; batteries and related devices, by the maneuvering of a particular adjustment with control by display of said setting and a device for resetting the display after each measurement, d) a device for displaying the result of the control.

(e) a supply of electrical current to the appliances specified in (c) and (d).

 When fired, the measuring apparatus is a conventional pressure gauge whose displacement of a mechanical member as a function of pressure acts on electrical contacts whose position is adjustable and detectable in front of indexes and which sends a signal to each of the two limits. upper and lower pressure signals that are processed in the comer to determine the time #t that elapses between the emission of the two signals.

 More specifically, the calculator can have two main forms of realization.

 n using an analog function, the computer combines a) a capacitor which is charged during the time of the measurement determined by the two signals emitted by the manometer, a voltage proportional to this time, b) an oscillator whose frequency is inversely proportional to the charge voltage of the capacitor and proportional to a previously adjustable voltage with the aid of a control potentiometer to introduce a determined coefficient (coefficient K) which follows the characteristics of the installation where the measurement is practiced to combine in said oscillator the two received values in a frequency proportional to the characteristics introduced from the installation and inversely proportional to the capacitor charge voltage, that is to say the time separating the two signals emitted by the manometer, c ) a frequency-to-voltage converter that sends a voltage proportional to the flow rate to a display system, d) an inverter e between the potentiometer and the display system allowing - either to directly display the coefficient K depending on the characteristics of the installation - or to send to the oscillator the voltage corresponding to the flow, e) a switch that allows to reset the display by sending an adequate voltage to the oscillator.

 Using a numerical function, the computer combines a) a quartz clock measuring the time separating the two signals emitted by the pressure gauge by emitting a certain number of proportential pulses at this time, b) a counter of the number of these oscillations, c) a memory where is stored a value inversely proportional to the measurement time (number of oscillations received from the counter), d) a digital-analog converter receiving the pulses of the memory at the end of measurement and a voltage proportional to the characteristics of the installation from an adjustment potentiometer, said converter sending a characteristic voltage of the flow rate to the display, e) a variable potentiometer making it possible to adjust and, thanks to an inverter, either to directly display a voltage depending on the characteristics of the the installation, either to introduce this voltage directly into the digital-analog converter which combines with the impulses memory and whose output, after appropriate operation of said inverter, is connected to the display, f) a switch that resets the counter by sending a suitable voltage, thereby having the effect of zero display.

Solution to the problem, benefits and industrial result.

 It should be noted that the apparatus operates in a differential manner, that is to say that, for a given installation comprising a producer machine and various receiver and consumer organs, the first operation is to establish a state of the volumes produced or consumed by the network elements assumed to be in good working order. By difference, the user can then, at any time, determine by a control operation the changes in flow that may occur at one or more organs of the circuit, whether receiver or producer of compressed air, provided of course to consider the same reference volumes for differential control.

Therefore, the precise knowledge of a reference capacity or volume does not intervene a priori provided that it is the same from one control to another. Only temperature corrections are to be taken into account - by reference to the ambient temperature of the air drawn by the network, if we want to make the volume comparison measured at the suction conditions (it is assumed that same place the atmospheric pressure does not vary), - or more simply by reference to the temperature that prevails in the reference capacity, ignoring the various treatments that this air will have undergone (cooling).

 It should be noted, however, that a variation of 10 over a reprofiling temperature of 30 represents a volume or flow variation of the order of 3, which must be taken into account when the comparisons require it.

 The device allows adjustment avoiding the use of correction charts.

 Finally, it is noted that the apparatus allows measurements of absolute value flow as soon as the reference volumes are precisely determined and the corrections made. Similarly, knowing the flow rate of the compressor will make it possible to determine the volume of the reference capacity (storage tank closed by a valve). But also that of all the sections or meshes of the network, the receivers being out of service, and by difference the capacity of @ network out tank if it is necessary.

 Conversely, the knowledge of these volumes makes it possible to determine the consumption of all or part of the receivers, the producer member (compressor) being isolated. The device avoids the prolonged unavailability of the installation during the control.

 The invention will be better understood from the following description which gives a non-limiting example of practical realization and that is illustrated by the accompanying drawings.

Brief description of the figures.

 Figure 1 is a schematic view of the entire apparatus of the invention and pneumatic circuit on which it must perform and measurements.

 Figure 2 is a diagram p2 'block synoptic of a first v ri @ nte the calculator using a numerical function.

 Figure 3 is a block diagram of a second variant of the processor using an analogical function.

The apparatus of the invention is intended to perform measurements in a chamber d @ nt the v @ l @ me is marked by V. which is connected to a compressor (1) by a pipe (2) to supply equipment ( 4) to which the enclosure
V is connected by the cond @ ite (5). Valves (3) and (6) allow one to be solved in one direction or in the other or both. 'Speaker V. Naturally the speaker
V may be constituted by any section or mesh of the network likely to be isolated by two valves.

 The apparatus of the invention is contained in a c-ffret (7) which is connected to the enclosure V by a connecting duct (8) attached to a suitable pressure tap of the enclosure V. The duct (8) ) leads to a pressure gauge (9), which can be a manometer with two contacts. one for the minimum (1 @), the other for the maximum pressure (11). It can also be a double pressure switch with a minimum contact and a maximum contact. It can be any device capable of controlling the meter of the device by measuring a pressure difference. The two contacts of minimum and maximum are adjustable or not; the range of the pressures is chosen in the zone where n makes the measurement. The contacts (10) and (11) are connected respectively by the Wines (12) and (13) to a cauler (14) which will be described in more detail later.

 The filter (7) further comprises a current source (16) which is connected by a line (17) to a keyboard housing (18) even connected by the lines (19) to the computer (@ 4). The table (18) comprises a display system (20), a reset button (21) and a setting knob (22) of the coefficient K depending on the characteristics of the installation.

 Before going further in the description, we will explain the theory and operation of the device that will better understand the functions of the calculator that will be described next.

The reference capacity V which contains, for example air under the conditions of absolute pressure
P2 and T2 absolute temperature, is empty for a time t to power equipment (4) whose consumption is Q m3 / min. At the end of time t, the conditions of pressure and temperature became pl and T1.Measured at ambient conditions pO, TO, which prevail at the suction of the compressor of supply, the volumes of air stored at the end and beginning of operation express themselves by
V01 = V (1)
p2 T0
p2 T0
V02 = V (2)
p0 T2 and the flow rate thus consumed during the time t by
V02 - V01 T0 (P2 - PI)
Q = = I / t V
P0 T2 TI
If we consider that the temperature T in the capacity is constant during the operation (T2 = T1 = TO) and by posing p2 - pl = & we obtain the formula #p T0
Q = 1 / t V
Po T which measures the consumption of the air taken in the reference capacity between p1 and p2 reduced to the suction conditions pO, TO.

If p2 and p1 are values chosen on either side of the nominal pn pressure of the network and such that the value of pn is their mean, we can say that
Q measures the average consumption brought back to 12 suction temperature of the device 4 to the pn pressure.

 one will see that the man-meter (9) measures the pressures pl and p2.

In other words, the device measures the flow
V # p To 60 free air
Q (m3 / min) = xx
P0 T t (sec)
As we have just seen, that in the apparatus the pressures p1 and p2 are determined, we can summarize these formulas by
Q (m3 / min) = 60K = t by setting K = V # p T0 (m3)
p0 t being understood, as we have seen that T2 = T1 @ = = T0.

We are thus reduced to measuring the flow rate in M3 / min by the measurement of 60K
7.

K is a fixed value that is set on the device and t is the value in seconds measured by the device.

 It can be seen that it is important to be able to adjust the apparatus with regard to the coefficient K representative of the enclosure and the apparatus where the measurement is made, which can be done using an inverter which directly connects the potentiometer relative to the control knob (22) with the display system (20) and feeds the data into the calculator (@). This is designed to measure the time t between the two reference pressures pl and p2 determined by the pressure gauge (9).

We will now describe the operating principle of the calculator (1)).

Referring to Figure 2 which provides a numerical solution. electrical signals relating to the pressure p1 and p2 are recognized which actuate a contactor (24) which is responsible for sending a time signal from a clock (25) to send them to a pulse counter (26). which by a memory address (27), stores them in the memory (28) .The content (29) of the memory (28) is sent to a digital-to-analog converter (30) which by the line (31) receives a voltage delivered by the variable potentiometer (P1) connected to the adjustment knob (22) and which introduces the coefficient K relative to the installation mentioned above. There is an inverter (33) which, in the position shown in dashed lines in FIG. 2, makes it possible to display said coefficient K directly on the display system (20) by operating the variable potentiometer (21) via the line ( 32). When the inverter
(33) is in the position shown in solid lines in FIG. 2, it makes it possible to display in (20) the value which has been calculated by the computer of the invention at the output of the digital-analogue converter (30) which combined the memory contents (29) with the value of
K received by the line (31) .The settings are provided so that the display (2G) directly gives flow rates in m3 / min.

There is provided a reset contactor (34) which sends a voltage to the meter to determine the reset
at zero of the display (20).

 In the version using an analog function, shown in Figure 3> the switch (35) is actuated by the two pressure limits p1 and p2 of the pressure gauge (9). By means of a constant current source (36), it charges a capacitor C4 which. after opening the contactor (35) discharges into the oscillator (40).

On the other hand, the variable potentiometer pl makes it possible to adjust the coefficient K by sending a suitable voltage in the line (38) where the inverter (37) is in the position shown in dotted lines, said coefficient being displayed in FIG. 20. When the inverter (37) is in the position shown in solid lines, this same voltage representative of the coefficient K is sent through the line (39) in the scripper (4u).
voltage vl = α t, 8 t being the time separating the passage between the two pressures pl and p2 and α a proportionality constant; it also receives a voltage representative of K so that it emits in the line (41) a frequency f = 60K. This frequency is sent via the line (41) to the voltage-frequency converter (42), which in the line (43) has a voltage Vs which is representative of the flow rate in m3 / min displayed in (20).

There is provided a reset contactor (44) connected to the button 21 which sends a determined voltage in the oscillator (40) via the line (45) and which G for
effect of returning the display (20) to zero so that it is ready for a new measurement.

Claims (5)

REVssNDICATIONS  1. Apparatus for controlling the flow of compressed gas into a chamber V from which pipes (5) of a circuit, gas introduced and then expelled, said chamber including isolation valves to the inlet (3) and or at the outlet (6) and a pressure tap, characterized by the combination a) of a connecting pipe (8) to the pressure tap, b) of a pressure measuring device (9) detecting the pressure variations in a determined and adjustable range by emitting an electric signal at each crossing downwards and upwards of the limits of said range; c) a calculator (14) receiving the signals from the manometer (9) for calculating the flows produced upstream of the enclosure V, consumed downstream and / or the resultant of the two, thanks to parameters integration circuits specific to the enclosure and its pipes and related apparatuses (4), by the operation of a particular setting (22) with control by affiliation ichage (20) of said setting and a reset device (21) of the display after each measurement, d) a display system of the result (20) of the flow control e) of a power source electrical supply (16) of the apparatuses in b), c) and d).  2. Control device, as defined in claim 1, characterized in that the pressure gauge (9) is a conventional pressure gauge whose displacement of a mechanical member as a function of pressure acts on contacts electrical devices (10-11) whose position is adjustable and recognizable in front of indexes and which sends a signal to each of the two upper and lower pressure limits, which signals are processed  in the computer (14) for determining the time t which elapses between the emission of two signals.  3. Apparatus as defined in claim 2, wherein the calculator (14) makes it possible to integrate beforehand a coefficient K determined in advance for each enclosure V eW its associated piping  (4), K being representative of the range of the pressure variation measured, the volume of the chamber and the temperature at which the chamber is carried.  4. Apparatus, as defined in any one of claims 1 to 3 2 aracterized by the fact that it uses an analog function and Q 'for this purpose, the calculator combines a) a capacitor C4 which is charge, during the measurement time determined by the two signals emitted by the pressure gauge (9), a voltage proportional to this time, b) an oscillator (40) whose frequency is inversely proportional to the charging voltage of the capacitor C4 and proportional to a voltage, previously adjusted using a variable potentiometer P1 setting to introduce a determined coefficient (K coefficient) quirepreselhe characteristics of the installation where one practices the measurement to combine in said oscillator (40) the two values received in a frequency proportional to the  introduced characteristics of the installation and inversely proportional to the charge voltage of the condensate Teur, that is to say, the time separating the two signals P1, P2 emitted by the pressure gauge (9) c) a frequency-voltage converter (42) which sends a voltage proportional to the flow rate to a display system (20), d) an inverter (37) between the variable potentiometer, the display and the converter (42) for either directly displaying the K coefficient depending on the characteristics of the installation, or for sending to the oscillator (40) the voltage corresponding to the Q rate. e) a switch (44) which resets the display by sending an adequate voltage to the oscillator (4).  5. Apparatus as defined in any one of claims 1 to 3 which uses a digital function and whose calculator combines a) a quartz clock (25) measuring the time separating the two signals P1 and P2 emitted by the pressure gauge (9) emitting a certain number of pulses pr @ proportional to this time, b) a counter (26) of the number of these osci @ tions, c) a memory (28) where is stored a value inversely proportional to the measurement time (number of oscillations received from the counter) d) a digital-analog converter (30) receiving the pulses from the memory (28) at the end of the measurement and a voltage proportional to the characteristics of the installation from a potentiometer setting, said converter (30) sending a characteristic voltage of the flow to the display (20), a variable potentiometer Pl for adjusting and, through an inverter (33) - to directly display a voltage dependent on charact system of the installation, - either to introduce this voltage directly into the digital-analog converter (SO) which combines it with the pulses of the memory (26) and whose output, after appropriate operation of said inverter (33), is connected to the display (20), f) a switch (34) which enables the counter (26) to be reset by sending a suitable voltage thereto, thereby causing the display (20) to be reset to zero.