RU2649U1 - INSTALLATION FOR CALIBRATION OF STANDARD IRIS - Google Patents

Abstract

An installation for calibrating standard measuring orifice plates, containing a source of compressed gas, a gas line with a standard orifice, a standard flowmeter, a medium-pressure regulator, consisting of a housing inside which a rod with measuring weights is placed, the lower end of which enters the working chamber, which is connected by a channel with a gas line to the entrance to the standard diaphragm, characterized in that the bypass to the standard diaphragm is connected to a medium differential pressure adjuster, in the casing of which has a discharge cavity, a communicated channel with a gas line at the exit of the standard diaphragm, and a working chamber connected by a channel with a gas line at the entrance to the standard diaphragm, a rod with measured weights is placed, liquid level sensors are installed in the wall of the discharge cavity, the electrical outputs of which are connected to the electronic unit, the output of which is connected with a control winding of a two-position solenoid valve, one of the inlet nozzles of which is connected with a pressure source, the other with a drain line, the outlet of the solenoid valve is in communication with azgruzochnoy body cavity in mating with the stem upper portion of the housing from the discharge cavity two annular grooves are made, the top of which communicates with the discharge manifold, and the lower groove - with a working chamber communicated with the gas manifold channel at the inlet to a standard diaphragm.

Description

INSTALLATION FOR CALIBRATION OF STANDARD IRIS

The invention relates to the field of test equipment, in particular, for calibrating standard diaphragms in a pulsating gas flow.

Standard diaphragms are one of the most common means for measuring gas and liquid flow in various industries, so it is very important to ensure high accuracy in measuring gas and liquid flow in conditions close to operational. It is known that due to the uneven supply of compressors, pulsations of the gas flow occur, leading to an additional error in measuring the gas flow. The magnitude of this error depends on both the relative amplitude of the pressure drop oscillations and the parameters of the connected gas lines 1,2. In this regard, standard diaphragms must be calibrated taking into account actual operating conditions, in particular in the presence of pressure fluctuations.

There are various devices for calibrating standard apertures, based on the use of standard sensors installed in series with the tested standard aperture 3.

Closest to the proposed technical solution is a device for calibrating pressure sensors 4.

The device comprises a resonance tube connected to a pressure source with sockets for control and calibrated sensors, a pressure pulsation valve connected to the resonance tube and a medium pressure regulator made in the form of a glass with a window, inside of which a piston with measured weights is placed on the hydrostatic supports at the upper end, axial and radial channels at the lower end, the glass window is connected to a collector connected via a switch to one of two output channels with throttle valves in communication with mosferoy in

MPK001127 / 00

 nine

one of which is pneumatic resistance between the switch and the butterfly valve.

The disadvantage of this calibration device is the inability to set the constant component of the pulsating differential pressure across a standard diaphragm.

The task is to create such a setup for calibrating standard diaphragms, which will reduce the error in calibrating standard diaphragms in conditions close to operational.

The problem is solved in that in the installation for calibrating standard diaphragms containing a source of compressed gas, a gas line with a standard diaphragm, a reference flowmeter, a medium pressure adjuster, consisting of a housing inside which a rod with measured weights is placed, the lower end of which enters the working chamber, communicated by a channel with a gas line at the entrance to the standard diaphragm, according to a utility model, a bypass to the standard diaphragm is connected to a medium differential pressure switch, in the housing of which there is a a loading cavity connected by a channel with a gas main at the outlet of the standard diaphragm and a working chamber connected by a channel with a gas main at the entrance to the standard diaphragm has a rod with measured weights; liquid level sensors are installed in the wall of the discharge cavity, the electrical outputs of which are connected with an electronic unit, the output of which is connected to the control winding of a two-position solenoid valve, one of the inlet nozzles of which is connected to a pressure source, the other to a drain line, the outlet pieces p of the electrovalve is communicated by a channel with a discharge cavity of the housing, in the upper part of the housing associated with the rod on the side of the discharge cavity there are two annular pro-points, the upper of which is connected to the drain line, and the lower pro-point to the working chamber in communication with the gas pipeline at the entrance to the standard aperture.

mode, in Fig.Z - the dependence of the gas pressure at the inlet of the standard diaphragm on time and in Fig.4 the dependence of the error of measuring the gas flow from the amplitude of the pulsations of the differential pressure across the diaphragm.

The installation for calibrating standard orifice plates contains a constant pressure adjuster at the inlet of the standard orifice plate, which consists of a housing 1, inside of which there is a rod 2, which enters from below into the working chamber 3 and is loaded from above with measured weights 4. Axial and radial channels are made at the lower end of rod 2 communicating through the pipeline 5 the working chamber 3 of the housing 1 with the atmosphere. The working chamber 3 of the housing 1, in addition, is connected by a channel 6 with a gas line 7 at the entrance to the standard diaphragm 8. To prevent dry friction of the rod 2 against the walls of the housing 1, a gas-static bearing 9 is placed in it. The movement of the rod 2 is limited by a stop 10. The installation also contains a medium differential pressure adjuster, which consists of a housing 11, inside of which a rod 12 is placed, which enters from below into the working chamber 13, and from above is loaded with measured weights 14. At the lower end of the rod 12 there are axial and radial channels communicating through the pipe 15 neither the bottom working chamber 13 of the housing 11 with the atmosphere. The working chamber 13 of the housing 11, in addition, is communicated by a channel 16 with a gas highway 7 at the entrance to the standard diaphragm 8. In the housing 11, on the side of the end of the rod 12 with measured weights 14, a discharge cavity 17 is made, connected by the channel 18 with the gas highway 7 at the exit from the standard diaphragms 8. In the wall of the discharge cavity 17, liquid level sensors 19 and 20 are installed, the electrical outputs of which are connected to an electronic unit 21, for example, RP4-U, the output of which, in turn, is connected to the control winding of the on-off electro-valve 22. One of Khodnev fittings solenoid 22 communicates with the pressure fluid manifold 23, the other input fitting - a drain manifold. The outlet fitting of the solenoid valve 22 is communicated by channel 24 with the discharge cavity 17 of the housing 11. In the part 12 of the housing 11 connected to the rod 12, annular grooves 25 are made from the side of the discharge cavity 17, the upper groove being communicated by the channel with the drain line and the lower groove with the working chamber

13 of the housing 11. To exclude dry friction of the rod 12 against the walls of the housing 11, a gas-static bearing 26 is placed in it.

A capacitance 27 is connected to the gas line 7 at the outlet of the standard diaphragm 8, the output of which is in turn connected to a standard flow meter 28. To control the average pressure level at the entrance to the standard diaphragm 8, a pressure gauge 29 is connected to measure the pressure drop fluctuations on the standard diaphragm 8 a differential pressure sensor 30 is connected. A bypass valve 31 and a pressure oscillation generator 32 with a valve 33 are installed at the inlet of the standard diaphragm 8. By the valves 34 and 35, gas-static bearings 9 and 26 are connected I am gas under pressure from a source of compressed gas 36.

Calibration of the measuring diaphragm is performed in the following sequence. Prior to testing, the rod 2 of the medium pressure level setter and the rod 12 of the medium pressure differential setter are loaded with measured loads of the mass of Mgrch and Mgr2

respectively:

Rsr $ ШТ1

 WGM | (1)

ARSr 8ShT2 Mf2 pMShT2 (2)

where PCP is the specified average pressure at the inlet to the diaphragm; And Рср is the given average pressure drop across the diaphragm;

$ pcs1 - cross-sectional area of the rod 2;

8Sh72 - the cross-sectional area of the rod 12;

МШТ1 - mass of rod 2 with fasteners.

it is controlled by a system for maintaining a given level, including level sensors 19 and 20, an electronic unit 21 and a two-position solenoid valve 22 with a fluid pressure source 23. The functioning algorithm of the fluid level control system is constructed in such a way that, regardless of the pressure in the discharge cavity 17, the fluid level is maintained between level sensors 19 and 20. When the level of the sensor 19 is reached, the liquid supply from the pressure line 23 is stopped, and when the liquid level drops below the level of the sensor 20, the two-position The pressure valve 22 communicates the cavity 17 with the pressure fluid line 23. Thus, the liquid level in the discharge cavity 17 is maintained between the levels of the level sensors 19 and 20.

The average pressure regulator at the inlet to the standard diaphragm works as follows: when the pressure at the inlet to the standard diaphragm S increases, the pressure in the working chamber 3 increases, which leads to the rod 2 being pushed up; this increases the area of the bore of the radial holes in the rod 2, increases the gas flow into the atmosphere and the pressure at the inlet to the diaphragm 8 is restored. When the pressure at the inlet to the standard diaphragm 8 decreases, on the contrary, the area of the radial openings decreases, and accordingly the gas flow to the atmosphere decreases, which leads to the restoration of the pressure Рср to the initial

level. To prevent self-oscillations of the rod 2 introduced a long pipe 5.

The controller of the average differential pressure works as follows: when the differential pressure increases on the standard diaphragm 8, the buoyant force acting on the rod 12 increases, the latter moves up; this increases the area of the bore of the radial holes in the rod 12, increases the flow of gas into the atmosphere and the pressure drop across the diaphragm 8 is restored. With a decrease in the pressure drop across the standard diaphragm 8, on the contrary, the area of the radial openings decreases, and accordingly, the gas flow into the atmosphere decreases, which leads to the restoration of the pressure drop across the diaphragm 8 to the initial level. To prevent self-oscillation of the rod 12,

as well as in the medium pressure switch, a long pipe 15 is introduced.

When calibrating the diaphragm in static mode, valve 31 opens, valve 33 is closed. The gas flow passing through the standard diaphragm 8, creates a pressure drop AR. A pressure gauge 29 controls the average pressure at the entrance to the standard orifice 8, and the gas flow rate through the orifice 8 is determined by the reference flow meter 28, which corresponds to the pressure drop set by the measured weights 14. By setting a series of P values, by changing the mass of the measured weights 14, a number of gas flow rates are measured and built flow characteristics of the diaphragm 8 in the absence of pulsations of the gas flow (figure 2).

To calibrate the diaphragm under conditions of a pulsating gas flow, oscillations excited by the generator 32 and amplitude-controlled by valves 31 and 33 (Fig. 3) are superimposed on the constant pressure component.

At the same time, differential pressure fluctuations occur on the standard diaphragm 8, which are measured by the sensor 30. Due to the inertia of rods 2 and 12 with measured weights 4 and 14, they do not have time to equalize the pressure fluctuations at the inlet to the diaphragm 8 and the pressure differential fluctuations on it. At the same time, the average values of the pressure Рср and the differential pressure ARСр

on standard diaphragm 8, implemented before the excitation of pressure differential oscillations.

The pulsating gas flow from the output of the standard diaphragm 8 is supplied to the reference flowmeter 28 through the tank 27, the volume of which is selected based on ensuring complete damping of pressure fluctuations in it. Thus, the reference flow meter 28 will record, as in the first case, the stationary gas flow, with accuracy determined by the passport data.

Selecting the amplitude Adr from the measured pressure drop determines its relative value:

ADR ADR (3)

Since, due to pressure pulsations, the characteristic diaphragm 8 deviates, the error in measuring the gas flow will be equal to:

AQ Q6.n. - Qn. (4)

where and Qn. - gas flow rates determined by the reference flow meter 28 under the conditions of a stationary gas flow through the standard diaphragm 8 and in the presence of pressure pulsations at the same values of Pav

and ARsr defined by medium pressure adjusters and

differential pressure.

With a known value of AQ, the relative error in measuring the gas flow is determined:

BEFORE (5)

Ob.p.

Thus, by setting a series of values of the amplitudes of the oscillations of the differential pressure, a dependence of the additional measurement error ISQI on the relative amplitude of the oscillations of the differential pressure A can be constructed (Fig. 4).

The presence of such a characteristic (see Fig. 4) makes it possible to distinguish the lower limit of the allowable amplitudes of the pressure differential oscillations at the standard diaphragm 8 Adr, at which the additional error in measuring the gas flow due to pulsations will not exceed the predetermined value 5QIAon.

In addition, with known fluctuations in the pressure drop across the standard diaphragm, an additional error in measuring the gas flow due to pressure pulsations in the gas main can be taken into account with a certain probability. Application of the proposed installation will improve the accuracy of calibration of flow sensors taking into account fluctuations in the working environment, i.e. in conditions as close to operational as possible.

LITERATURE:

1. Shumilovsky NN, Sitnitsky Yu.I. Measurement of pulsating flows. Lviv, 1947.

2. Drobysheva NA, Nikiforov A.N. et al. Measurement of non-stationary costs using narrowing devices: Overview. - M, 1984.

3.Kremlevsky P.P. Flowmeters and counters of quantity.-L, 1975.

4. A.S. 1739230, G01L27 / 00, BI N21.1992.

Vice Rector for Research of the Samara State Aerospace

University D U W UUleg ° Aaev D-EAutorys FORMULA

Claims (1)

An installation for calibrating standard measuring orifice plates, containing a source of compressed gas, a gas line with a standard orifice, a standard flowmeter, a medium-pressure regulator, consisting of a housing inside which a rod with measuring weights is placed, the lower end of which enters the working chamber, which is connected by a channel with a gas line to the entrance to the standard diaphragm, characterized in that the bypass to the standard diaphragm is connected to a medium differential pressure adjuster, in the casing of which has a discharge cavity, a communicated channel with a gas line at the exit of the standard diaphragm, and a working chamber connected by a channel with a gas line at the entrance to the standard diaphragm, a rod with measured weights is placed, liquid level sensors are installed in the wall of the discharge cavity, the electrical outputs of which are connected to the electronic unit, the output of which is connected with a control winding of a two-position solenoid valve, one of the inlet nozzles of which is connected with a pressure source, the other with a drain line, the outlet of the solenoid valve is in communication with azgruzochnoy body cavity in mating with the stem upper portion of the housing from the discharge cavity two annular grooves are made, the top of which communicates with the discharge manifold, and the lower groove - with a working chamber communicated with the gas manifold channel at the inlet to a standard diaphragm.