Gas flow metering devices
- SG-1, SGBM-1,6
- Gallus 2000 G1.6, G2.5, G4
- NPM-G1.6, NPM-G2.5, NPM-G4
- BK-G1.6, BK-G2.5, BK-G4
- SGK-1,6, SGK-2,5, SGK-4
- SGK-1.6, SGK-2.5, SGK-4 (T) *
- Helios G1.6 Helios G2.5 Helios G4
- SGB-G2.5, SGB-G4-1
- SGB-G2.5 Signal, SGB-G4 Signal
- SGM-2 G4, SGMN-1 G6, SGMN-1M (1)
- Metrix g6
- BK-G6 (T), BK-G10 (T), BK-G16 (T), BK-G25 (T)
- UBSG-001 G6, UBSG-001 G10, AGAT-G16, AGAT-G25
- Metrix g10
- RGA, RGA-Ex, G10, G16
- G10, G16, G25, G40
- Metrix G16, Metrix G25
- VK-G40, VK-G65
- Metrix G40, Metrix G65
- RVG G16-G250
- Delta G16-G650
- RSG "Signal"
- TZ / Fluxi G65-G6500
- TRZ (G65-G4000)
- STG 100-1600
- SG-16 (MT) 100-4000
- Turbo Flow GFG-ΔP Series
- Turbo Flow GFG-F Series
- Turbo Flow TFG Series
- PURG-100, PURG-200, PURG-400
- PURG-800 (-EC), PURG-1000 (-EC), PURG-1600 (-EC), PURG-2500 (-EC)
A membrane counter (diaphragm, chamber) is a gas meter, the principle of which is based on the fact that using various movable converting elements, the gas is divided into fractions of the volume, and then they are cyclically summed.
The diaphragm counter (Fig. 8.10 ) consists of a housing 1, a cover 2, a measuring mechanism 3, a crank mechanism 4, connecting the movable parts of the diaphragms (membranes) with the upper valves 5 of the gas distribution device, valve seats (lower part of the distribution device) and the counting mechanism . The case and cover of the meter can be:
- - steel, stamped coated against corrosion and sparking. Compound stamped steel body and lid is performed via the sealing material and the clamping band 6 (see Figs.. 8.10 ), which provide a tight fit of the two parts to each other;
- - aluminum, cast. The case and counter cover in aluminum design are hermetically sealed using special gaskets and a set of screws, one of the screws is sealed.
Parts and components of the measuring mechanism for membrane meters are made of plastic. The use of plastic measuring mechanisms significantly reduces the cost of production, increases resistance to chemical components in gases, significantly reduces the coefficient of friction in moving parts of the meter.
Depending on the design and volume of the measured gas, the measuring mechanism may consist of two or four chambers. Schematic diagram of the diaphragm counter is shown in Fig. 8.11 .
|Position of counter cameras||Camera 1||Camera 2||Camera 3||Camera 4|
|but||Devastated||Fills up||Is empty||Filled with|
|b||Is empty||Filled with||Fills up||Devastated|
|in||Fills up||Devastated||Filled with||Is empty|
|g||Filled with||Is empty||Devastated||Fills up|
The counter works as follows:
a) the measured gas flow through the inlet pipe enters the upper body cavity and then through the open valve into the chamber 2. An increase in the gas volume in the chamber 2 causes the diaphragm to move and gas is displaced from the chamber 1 to the outlet from the slot of the valve seat and then to the outlet of the meter. After approaching the diaphragm lever to the wall of the chamber 1, the diaphragm stops as a result of switching valve groups. The movable part of the valve of chambers 1 and 2 completely covers the valve seats of these chambers, disabling this chamber unit.
b) The valve of chambers 3 and 4 opens the gas inlet from the upper cavity of the meter body into the chamber 3, fills it, which causes the diaphragm to move and gas to be forced out of the chamber 4 into the outlet pipe through slots in the valve seat. After approaching the diaphragm lever to the wall of the chamber 4, the diaphragm stops as a result of shutting off the valve block of the chambers 3, 4.
c) The valve of the chambers 1, 2 opens the gas inlet from the upper cavity of the meter body into the chamber 1. When gas is supplied to the chamber 1, the diaphragm 1, 2 moves, displacing the gas from the chamber 2 into the outlet through the slots in the valve seat. After approaching the diaphragm lever to the wall of the chamber 2, the diaphragm stops as a result of turning off the valve block of the chambers 1, 2.
d) The valve of the chambers 3, 4 opens the gas inlet from the upper cavity of the meter body into the chamber 4. When gas is supplied to the chamber 4, the diaphragm 3, 4 moves and displaces the gas from the chamber 3 into the outlet pipe through the slots in the valve seat. After approaching the diaphragm lever to the wall of the chamber 3, the diaphragm stops as a result of shutting off the valve block 3, 4.
The process is repeated periodically. The counting mechanism counts the number of strokes of the diaphragms (or the number of cycles of the measuring mechanism n). For each cycle, the volume of gas Vc is displaced, equal to the sum of the volumes of chambers 1, 2, 3, 4. One full revolution of the output axis of the measuring mechanism corresponds to 16 cycles.
It is necessary to remove the meter from the gas pipeline (here not everyone can restore seals on union nuts) !!!!!!
The essence of the methods is upsettingly simple - inside the outlet pipe, it is necessary to break the tightness of the connection between the plastic insert and the meter body. I simply bent the plastic slightly inside with a screwdriver and tamped the rubber seal ring with tweezers and deleted its result, exceeded all expectations, the counter twists half as much.
As I understand it, meters of this type are very sensitive to the pressure drop in the gas input-output after this procedure, you can put a part of the sealant in place, otherwise I didn’t turn the poor fellow when I turned on the gas stove ....
I began to count only with the gas boiler turned on. So that is all. After that, we put the counter in a regular place and restore the seals.
In a turbine gas meter (Fig. 8.13 ), under the influence of a gas stream, the turbine wheel is driven into rotation, the speed of which is directly proportional to the flowing volume of gas. The turbine speed through a reduction gear and a gas-tight magnetic coupling is transmitted to a counting mechanism located outside the gas cavity, showing (increasing) the total volume of gas under operating conditions that has passed through the device.
1, 10 - measured cross section; 2 - inclusion of pressure; 3 - magnetic clutch; 4 - counting mechanism; 5 - RT-100 heat measuring probe; 6 - control thermometer; 7 - output channel; 8 - pulse sensors; 9 - turbine wheel; 11 - displacing body.
A permanent magnet is fixed on the last gear wheel of the gearbox, and two reed switches near the wheel, the contact closure frequency of the first is proportional to the speed of rotation of the turbine rotor, i.e., the gas flow rate. When a powerful external magnetic field appears, the contacts of the second reed switch close, which is used to signal unauthorized interference.
Structurally, turbine meters manufactured in Russia are a pipe segment with flanges, in the flowing part of which the inlet flow straightener, a turbine assembly with a shaft and rotational bearings and a rear support are arranged in series with the flow. A unit of a plunger oil pump is installed on the meter housing, with the help of which liquid oil is supplied through the tubes to the bearing area. On the turbine casing there are places for installation of equipment sensors (for measuring pressure, temperature, pulses).
According to the degree of automation of the measurement process and the processing of measurement results, turbine meters are available in the following configuration options:
- - for separate measurements of variables of controlled parameters with arbitrarily selected means of processing the measurement results (manual calculating devices, microcalculators, etc.);
- - for semi-automatic measurements of variable controlled parameters with computing devices for processing measurement results and devices with manual input of conditionally constant parameters or manual correction of measurement and calculation results;
- - for automatic measurements of all controlled parameters with computing devices for processing measurement results.
In connection with the increase in the types of equipment, there was a need for measuring instruments that would have a relatively large throughput and a significant range of measurements with relatively small overall dimensions. These conditions are met by rotary gas meters, which additionally have the following advantages: lack of electricity demand, durability, the ability to control the serviceability of the pressure drop across the meter during its operation, and insensitivity to short-term overloads. Rotary meters are widely used in public utilities, especially in heating boiler rooms, as well as in small and medium enterprises.
Rotary (rotary) counter - a chamber gas meter, in which eight-shaped rotors are used as a converting element.
Fig. 8.12 Rotary gas meter type RG
11 - case; 2 - rotor.
The rotary gas meter type RG consists of a housing 1, inside of which two identical eight-shaped rotors 2 of the transmission and counting mechanisms rotate, connected to one of the rotors. The rotors are driven into rotation by the pressure difference of the gas entering through the upper inlet pipe and exiting through the lower output pipe. During rotation, the rotors run around their side surfaces. The synchronization of rotor rotation is achieved using two pairs of identical gears mounted on both ends of the rotors in the end boxes outside the measuring chamber-housing. To reduce friction and wear, the gears of the rotors are constantly lubricated with oil poured into the end boxes.
The volume of gas displaced in half a revolution of one rotor is equal to the volume bounded by the inner surface of the housing and the side surface of the rotor, which occupies a vertical position. For a complete revolution of the rotors four such volumes are displaced.
In the manufacture of rotary meters, special attention is paid to the ease of movement of the rotors and the reduction of unaccounted gas leaks through the meter. The ease of movement, which is a qualitative indicator of low friction in the mechanism, and consequently, low pressure loss in the counter, is ensured by installing rotor shafts on ball bearings, minimizing friction in the gearbox and counting mechanism, as well as a rational choice of design dimensions and rotor speed. Reducing gas leaks is achieved by careful processing and mutual adjustment of the inner surface of the housing and the friction surfaces of the rotors. The gap between the housing and the rectangular platforms located at the ends of the largest diameters of the rotors ranges from 0.04 to 0.1 mm, depending on the type of meter. In the manufacture of meters, special attention is paid to the static balancing and processing of rotors.
Vortex flow meters are called flow meters based on the dependence on the flow rate of the pressure fluctuations that occur in the stream during the process of vortex formation or stream oscillation or after an obstruction of a certain shape installed in the pipeline or special swirling of the stream.
Vortex flowmeters got their name from the phenomenon of disruption of vortices that arise when an obstacle flows around a liquid or gas stream, usually in the form of a truncated trapezoidal prism (Fig. 8.9 ). Behind the body of the flow is a sensitive element that perceives vortex oscillations.
The advantages of vortex flowmeters include: the absence of moving parts, the independence of the readings from pressure and temperature, a large measurement range, a frequency measuring signal at the output, the possibility of obtaining universal calibration, a relatively low cost, etc.
The disadvantages of vortex flowmeters include significant pressure losses (up to 30–50 kPa), limitations on the possibilities of their use: they are not suitable at low flow rates for measuring the flow rate of contaminated and aggressive media.
Acoustic meters are flowmeters based on the measurement of a particular effect that occurs when oscillations pass through a stream of liquid or gas and depend on the flow rate. Almost all acoustic meters used in practice operate in the ultrasonic frequency range and are therefore called ultrasonic.
Most industrial ultrasonic flow meters use effects based on the movement of acoustic vibrations in a moving medium. They serve to measure the volumetric flow, because the effects that occur when acoustic vibrations pass through the flow of a medium (liquid or gas) are related to the speed of the medium. In fig. 8.8 shows the primary transducers of ultrasonic flow meters.
To enter acoustic vibrations into the stream and to receive them at the outlet of the stream, emitters and oscillation receivers are necessary - the main elements of the primary transducers of ultrasonic flow meters. When certain crystals (piezoelectric elements) are compressed and stretched in certain directions, electric charges are formed on their surface, and vice versa, if a potential difference is applied to these surfaces, then the piezoelectric element will stretch or contract depending on which of the surfaces has more voltage, - the opposite piezoelectric effect. These effects are based on the method of converting a variable electric potential difference at the crystal faces to acoustic (mechanical) vibrations of the same frequency (for emitting vibrations) or vice versa - converting acoustic vibrations into a variable electric potential difference at the crystal faces (for a vibration receiver).
The advantages of ultrasonic flow meters are a wide range of flow measurement and the possibility of using microprocessor technology. The main disadvantage of ultrasonic flow meters is their sensitivity to solid and gaseous inclusions.