Vortex flowmeter EMIS-VIHR 200

The vortex flowmeters EMIS-VIHR 200 are applied to measure the flow rate of gas, steam and liquid. The application of flowmeters is mostly effective if:

• the flow of steam or gas contains considerable amount of liquid.
• gas in the pipeline contains solid mechanical inclusions, and the installation of a filter is not allowed or economically unprofitable.
• It is essential to provide maximum security for high temperature and corrosive mediums.
• The parameters of process flow, pressure, temperature, density can change,even abruptly, while measurement.

Vortex flowmeter common tasks:

• Fiscal metering of steam in the boiler houses or process control
• Fiscal metering of natural gas in the large industrial facilities
• Compressor performance monitoring and pressure air consumption record
• Flow measurement of commercial industrial gas
• Burner rate  measurement
• Liquid flow for process control

With each passing day the conditions of process control instruments industry rivalry become complicated and stiffened. Lately the base methods of measurement list has not changed and remains the same. Mass flowmeters have effected the revolutionary breakthrough. The price and quality have stopped being competitive advantages but become the mandatory requirements of equipment selection.

Today the digital signal processing appliance using spectrum analysis is the upcoming direction in flowmeters production due to high level of microprocessor engineering development. Digital flowmeters have a number of advantages over the analogue ones. Such Russian engineering products appeared on the domestic market in 2013 year. The digital electronics has become widespread based on the vortex and ultrasonic flowmeters.

This articles discusses the fundamental principles of flow measurement using modern software and hardware ; Also the major advantages yielded as the result of the digital signal processing and the mathematical algorithms allowed to bring a vast improvement of the equipment attribute characteristics are listed below.

Digital electronics of the vortex flowmeters EMIS- VIHR 200 (V.8) is designed based on the powerful digital signal processor «Blackfin» by «Analog Devices» company with high speed of operation. The high-performance processor is enabled to process the sensor signal used frequency analysis mathematical techniques in real-time mode to achieve the brilliant results of measurement accuracy.

The procedure of automatic signal spectrum analysis provided for on-line continuous flow measurement process control is performed in the processor. Diagnostic codes are displayed automatically in case of cavitation or chaotic whirl formation. Measurement process monitoring is ensured by flow self-diagnostic function. The device is capable to perform self-check of its internal electronic units of signal processing by operator command or on schedule. Diagnostic codes are displayed automatically in case of electronics disturbance detection. Vibration and temperature sensors are installed on the flowmeter processor board for remote control ofoperating conditions of the device. Temperature sensor values are continuously recorded.

Digital signal processing provides device monitoring in liquid and gaseous medium.

The electronics applied (V.8) protects all metrological coefficients by the «digital seal» method. It means that the device based upon its metrological coefficients calculates the certain number named «metrological sum». Metrological sum is unique for any number of metrological coefficients values and permits definitely to determine the tampering in adjusting device.

The vortex flow transducers equipped with the digital electronics have the advantage of simpler ones in the followings:

• mean time between errors of the flowmeters is 75 000 hours;
• environmental protection according to GOST 14254 corresponds to IP67;
• Explosion protection of «intrinsically safe electrical circuit» and explosion-proof enclosure.

The functionality and the efficiency of the flowmeters digital electronics are achieved by the user-friendly graphical interface of the program- integrator powered by Windows. The program- integrator provides wide possibilities of the measurement process quality audit because of the signal processing technology by the direct and inverse Fourier transformation: graphical display of flowmeter signal spectrum confirmed the metrological measurement reliability; graphical display of flowmeter signal spectrum provides to detect the sources of noise vibration generated a negative impact on flow measurement.

The program permits to switch immediately on and adjust desired digital filter and provide the best «signal/noise» ratio. Digital filtering based on a signal spectrum analysis provides to increase resistance to vibration and to enlarge flow measurement range kept metrological characteristics.

Key functional of the program- integrator is the following. Forward filters are intended to protect from unwanted permanent actions (vibration, different noises); electronics of V.8 version has 4 band-pass tunable filters and 1 network pickup filter (50Hz). The spectrum below (Figure 1а) represents the coverage of the valid signal (on a frequency of 200 Hz) by the noise (on a frequency of 50 Hz), and the device displays false flow. The noise nature is unknown or it is not possible to neutralize. To reduce its influence, it is necessary to adjust the forward filter in the range of 44 - 65 Hz, the noises should decrease by factor of 100 (Figure 1b).

Band-pass filters are not width limited. They can be combined. The electronics and the program have the median filter intended to remove unwanted random actions (in case of acoustic noise of mechanical origin, e.g. due to vibrations). This filter intends to keep instrumental data stable. The filter capability to operate automatically is its fundamental advantage.

The electronics of V.8 gives the opportunity to determine device status with the self-diagnostic function. The program has the indicators on the right panel: green indicator means that the subsystem operates properly, red indicator – the subsystem fails. To receive more detailed description and recommendations it is necessary to wake up the indicator with the mouse cursor. So the primary flowmeter diagnostic can be provided with the computer or notebook connected by RS-485 or USB.

Flowmeter electronics functionality

Setting Saver function. This function provides of flowmeter settings. This function gives the opportunity to receive factory flowmeter settings and adjust it in accordance with providing for particular medium conditions without flow transducer removal. The electronics and the program- integrator functionality provide to record the spectrum and email it to the manufacturer's service center. Spectrum operation record. This function provides to record the device operation in file and recall the file recorded before. This function gives the opportunity to send data to the service center for measurement evaluation. This record will help the manufacturer to give the unique estimates of the device settings and recommended guidelines. Moreover, it is possible to create the settings file for Your device and working nudium. Important to note that the device should not be removed and interrupt measurement process.

Also the function gives the opportunity to detect the status of the flowmeter wetted part (contaminating impurity and others). To perform that the reference file should be recorded (after the flowmeter installation on the pipe). It gives the opportunity to compare device operation with reference file and detect wetted part status.

So the flow transducer perceives the signals from the sensor (piezoelectric, thermoanemometric, infrasonic and others) and boosts, filters and processes it.

Simple structural arrangement of signal processing is below (Figure 2):

Customary the signal processing is performed by analogue methods used RLC-filters and operating amplifiers. Later the signal is normalized with the help of the instrumentation amplifiers or the comparator unit and the microcontroller.

Advanced measurement procedures in the modern flowmetering is a digital signal processing. In this case a primary real-world signal is normalized and then processed in the electric one with the help of the analogue-digital convertor. It is possible to use 1- bit conversion used the comparator unit. Here the microcontroller counters only the pulse number per unit.

If the signal is close to the sinusoidal wave that is possible for average and high fluid velocity, the signal crossover frequency through threshold level corresponds the flow. But if the «signal/noise» ratio is dropped that is unpreventable for low flow velocity and under elevated vibration the signal becomes far from the sinusoidal wave and the false responses take place. The comparison of simple digitization effects on the high and low flows is below (Figure 3).

The application of powerful computational capabilities provides to perform the complex mathematical algorithms to enlarge turndown and improve the metrological metering component. One method of mathematical signal processing is Fourier transformation.

At its simplest sensor input signal is transformed from the time domain into the frequency domain used fast Fourier transformation (FFT). Spectrum dominant frequency is considered to be valid signal frequency. Whirl formation frequency can be calculated more precisely and steadily used direct and inverse Fourier transformation. Therefore, desired spectrum component and the zero components " lobe " near got by the direct Fourier transformation are transformed into the time domain with the help of inverse Fourier transformation (IFT). Received output signal is close to sinusoidal wave and can be processed by the time calculation between signal crossover through threshold level. This method is below (Figure 4).

The advantages of the digital signal processing flowmeters are:

• Noise filtering capability;
• Spectrum scanning capability;
• Alarm status diagnostic capability (cavitating and unwanted whirl formation);
• Signal control used the frequency scale to determine the overrange;
• Metrological range tuning according to the process conditions (temperature, pressure, viscosity effectiveness, density).
• Feedback coupling capability. It provides to detect the output circuit integrity.

Digital signal processing gives the opportunity to calibrate the device (see Figure 5). The correction table is stored in the digital form and can be easy recovered.

So scientific and innovative approach to the measurement enlarges vortex flowmeter functionality without device cost increase.

Installation

EMIS-VIHR Mounting kit
Installation kit (counter flanges, gaskets, bolts, nuts, washers)

Flanged disassembling joint EMIS-VIHR 200.
for easy and safety installation of vortex flowmeters EMIS-VIHR 200

Flow conditioner EMIS-VECTA 1200
reduces requirements for the straight meter run length at the installation site of EMIS-VIHR 200

Power unit EMIS-BRIZ
to power the vortex flowmeter

Cable set
to connect EMIS-VIHR flowmeter

Filters & Functional Equipment

Liquid filter EMIS-VEKTA 1210
to improve performance and service life of flowmeter by filtering liquids from impurities of solid particles, dust, rust

Filter-Separator EMIS-VEKTA 1212
to filter out steam and gas inclusions from liquid to improve metrological characteristics

Interface converter RS-232/RS-485/USB EMIS-SYSTEMA 750
For data communication between flowmeter and PC or other digital devices