Vortex Gas Flowmeters/Counters VRSG-1 General specification

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general specification

Introduction

Purpose of the device

Vortex Gas Flowmeter/counter VRSG-1 gives a capability to measure volume of non-aggressive combustible and inert gases with the volume reduction to normal condition (760 mm of h.c. and +20°C ) according to GOST (state standard) 2939 "Gases. Conditions for Volume Determination".

It can be possible to use the Flowmeter/counter to control volumatic gas flow rate reducted to normal condition, temperature and working gas pressure in a pipeline as well as total run time of the device.

The gas volume reduction to normal condition is provided automatically: three separate converters ( of flow rate, pressure and temperature) measure gas flow simultaneously with the following calculations.

It is possible to supply a flowmeter /counter for different kinds of working gas at customer's request.

Features

No movable parts
High accuracy of measurement in wide range of rates
Simple and easy to install
Simple and easy to operate
Automatic correction according to density

Principle of operation

Principle of operation of the flowmeter/ counter VRSG-1 is based on measuring of vortex generation frequency in a gas flow behind fixed bluff bodies. When a columnar obstacle is installed in a fluid flow inside a pipeline, vortices are generated on the downstream side of the obstacle alternately on both sides. These vortices are known as Karman vortices. Vortex generation frequency is proportional to volumatic gas flow rate.

Measurements of vortices shedding frequency are provided with the help of a hot-wire sensor located in the canal which connects the opposite sides of the bluff body.

In order to reduce measurable gas flow rate to normal condition ( compensation according as density) signals from pressure and temperature converters are used.

High accuracy and quality

Frequency vortex signal, microprocessor and individual graduation of the flowmeter/counter make it highly accurate and interference resistant in the most difficult conditions. High accuracy remains permanent in the whole range of rate measurements. The frequency vortex signal provides long-term stability of indications, reproducibility and no zero drift.

Simple and easy to use

Some features of the device ( wear-proof parts, easy to get information) help to reduce expenses on setting up and maintenance.

The flowmeter/counter does not make any obstacles for a gas flow inside a pipeline so that there is no need of a by-pass canal and it makes the device cheaper to use.

In order to transfer measurable parameters to a central computer the flowmeter is completed with RS-232 or RS-485 interface device (at customer's choice).

Functional features

Working gas - natural gas according to GOST 5542, methane according to OST 51.40-74, other combustible gases, air, inert gases;
Working gas absolute pressure - 0,05-1,7 MPa;
Working gas temperature - from - 35 to + 45 °C
Air temperature -
Primary Converter - from - 35 to +50° C
Block of signal processing and indicating - from +10 to 50° C;
Internal diameters - 50, 80, 100, 120, 150, 180 and 200 mm
Measurable gas flow velocity range -0,1-45m/sec;
Time interval between verifications -2 years;
Length of straight runs: no less than 20 ID before and 5 ID after the flowmeter/counter; if there is local resistance the length of the straight runs gets longer ( turbulizator using makes it shorter up to 10 ID before the flowmeter/counter)
Pressure loss on bluff body: no grater than 50 Pa;
Limit of main relative errors:
For the volumatic gas flow rate, no grater than:
±1% for Q_min...0,2 Q _max;
± 0,8% for 0,2 Q_max...Q_max;
for the working gas volume with the reduction to normal conditions, no grater than:
±1,3% for Q_min...0,2 Q_max;
±1% for 0,2_max...Q_max;
Explosion-proof device -electric spark-proof circuit satisfying mark 1ExibIIBT4
Power supply: 220(+27-30)V, 50Hz

Assembling and installation

The Primary Converter can be installed inside horizontal, vertical or inclined pipeline in an unheated room or outside.

Type of connection between the primary converter and a pipeline - flange.

Electronic block of signal processing and indicating ( BSPI) must be installed in a heated room ( or in a heated box) on a vertical surface ( a wall) using fastening brackets. The distance between primary converter and BSPI must be no greater than 300 m. Power supply voltage must be 220V/50Hz and an automatic circuit-breaker with operate current no less than 2 A must be used.

Description

Parts of the flowmeter/counter

The flowmeter/counter consists of a primary converter (PC), a block of signal processing and indicating (BSPI) and cables.

The primary converter includes:

vortex converter of volumatic flow rate;
primary pressure converter (PPC);
primary temperature converter (PTC);
block of signal preamplification (BSP).

Vortex converter of volumatic flow rate looks like a bluff body with a built-in hot-wire sensor. Primary pressure converter is a tensoresistive pressure probe. Block of signal preamplification is installed on a surface of the primary converter.

VRSG-1 can be completed with a registrator of mean-hours and mean-twenty-four-hours parameters ( PI-1) which has an output for EPSON- compatible printer connection and standard interface device RS-232(485) to provide data transfer to PC; software to record transferring parameters on PC; or power transformer of standard interface.

Construction and operation

Primary converter

The primary converter looks like a pipe section with flanges. There are three holes on the external surface of the pipe section where a bluff body, pressure and temperature probes are located.

The bluff body looks like a cylinder of a special form. There is a canal perpendicular to the gas flow direction which connects the opposite sides of the bluff body. Hot wire sensor which can register vortex shedding frequency is located in the canal.

Pressure and temperature probes are located at the same plane as the bluff body is but a little bit downstream. The board of the block of signal preamplification (BSP) is located on the external surface of the primary converter. The flow rate, pressure and temperature probes as well as the BSP board are covered with the help of the one cap. There is a terminal-block with a cable input device on the side surface of the primary converter.

Block of Signal Processing and Indicating (BSPI)

From the designer's point of view the BSPI is a calculator which contains a power unit, a flame-proof barrier board, a normalizing amplifier board, a calculator board, an indicating board with a digital display.

The signals which are proportional to the volumatic flow rate, temperature and pressure after the preamplifier with the help of a cable apply to the flame-proof barrier board.

The flame-proof barrier board is used for prevention of an electric spark appearance in the case of the device damage. So it provides the necessary level of explosion-proof.

After the flame-proof barrier board the signals apply to the normalizing amplifier board. The amplifier transforms the primary signals to the standard form which is necessary for the calculator work.

Then the signals apply to the calculator board. Using the three measured signals the calculator determines current volumatic flow rate and gas volume with the reduction to normal condition (T=293,15 K, P=101325 Pa). Also the calculator controls the work of the display. The display gives a possibility to observe the gas volume and time of the device work as well as to on-line control the working gas parameters (volumatic gas flow rate with the reduction to normal condition, pressure, temperature) and to indicate breakdown signals (the data of the indicator are the certified tool of the gas volume registration). Regime of the indicator work can be chosen with the help of the button "Regime". When the power is off data from the counter can be stored in a memory of the device during an unlimited long period of time.

Due to standard interface RS-232 (485) the flowmeter/counter can transfer the following parameters:

gas temperature in a pipeline, ^оС;
gas pressure in a pipeline, MPa;
volumatic gas flow rate in a pipeline under normal condition, m³/h;
total gas volume, Nm³ (N - normal).