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technical article
Application of intelligent precession vortex flowmeter
2012-1-27 19:46:44

One. Overview of Smart Precession Vortex Flowmeter

采用先进的微处理技术,具有功能强、流量范围宽、操作维修简单,安装使用方便等优点,主要技术指标达到国外同类产品的先进水平。 Intelligent precession vortex flowmeter uses advanced micro-processing technology, which has the advantages of strong function, wide flow range, simple operation and maintenance, convenient installation and use, etc. The main technical indicators reach the advanced level of similar foreign products.

Can be widely used in petroleum, chemical, power, metallurgy, coal and other industries to measure the flow of various gases and liquids.

two. Application range of precession vortex flowmeter

① Orifice flowmeters can no longer meet the most basic measurement requirements in certain specific situations.

In the field of natural gas flow measurement, there are often some special users, which are mainly manifested as: instantaneous flow is small or the fluctuation of the flow is large. If the traditional orifice plate flow meter is still used for flow measurement in this case,

Then it is very likely to violate the relevant technical standards [1, 2]. For example, the requirement "the flow rate in the pipeline should not change with time, or actually only slight and slow changes with time" For the orifice plate flow meter using flange pressure

It also requires "ReD≥1260 2D" and so on. Once these basic conditions of use are exceeded, the measurement accuracy of the orifice plate flow meter will be impossible to talk about. In addition, in this special case, the selection of display instruments is also a Quite troublesome

In case of improper matching, it is inevitable to indicate or record an excessively poor value.

② Strict control of production management costs is an urgent requirement for the survival and development of modern enterprises.

Today, various enterprises and counties are experiencing the severe baptism of the market, and the production cost is bound to close the life and death of the enterprise. Therefore, on the premise of meeting the basic requirements of the flowmeter, the choice of both can save static investment and reduce dynamic costs

The new meter is also on the agenda of decision makers.

Three. Characteristics of precession vortex instrument

具有以下几个主要特点: Compared with the traditional orifice plate flowmeter, the intelligent precession vortex flowmeter has the following main features:

①Mechanical and electrical integration is realized, and the daily measurement process does not need manual watchkeeping;

② The process installation conditions are not harsh, and the upstream and downstream straight pipe sections of the instrument can be greatly shortened compared to the orifice flowmeter;

③ The system's measurement accuracy can meet the current trade measurement requirements (≤2%) ">;

④ The flow measurement range is wide (qmax / qmin = 15 ~ 20 ">), and it can work effectively in the small flow area where the orifice flowmeter cannot reach;

⑤ Small size and light weight, convenient for offline calibration;

⑥ The measurement signal can be displayed locally or remotely transmitted as required;

⑦No moving parts, so there is no mechanical wear of the instrument for general measurement;

⑧Instrument management personnel do not need professional training, and measurement parameters such as flow, pressure, and temperature can be read directly from the meter head without conversion.

⑨It is only necessary to periodically replace the battery (micro power consumption) "> and the parameters of the measured medium.

Any type of measuring instrument has its special characteristics, and the intelligent precession vortex flowmeter is no exception. In order to make this kind of instrument better serve the flow measurement work, the practical experience from the production site shows that the following aspects

The matters needing attention should attract sufficient attention from the relevant management and use departments.

Four. Matters needing attention when using precession vortex flowmeter

Any type of measuring instrument has its special characteristics, and the intelligent precession vortex flowmeter is no exception. In order to make this kind of instrument better serve the flow measurement work, the practical experience from the production site shows that the following aspects

The matters needing attention should attract sufficient attention from the relevant management and use departments.

① Pay attention to instrument selection. After the type of instrument has been selected (for example, intelligent precession vortex flowmeter), the selection of instrument specifications and its supporting components is very important. In a word, choose well before you can make good use of it. to this end,

In the selection process, two basic principles should be grasped; namely: one must ensure the accuracy of use, and the other must ensure production safety. To do this, three selection parameters must be implemented, namely the maximum, minimum, and commonly used instantaneous flow (main

To be used for the size and specification of the selected instrument), the design pressure of the measured medium (mainly used to select the nominal pressure level of the instrument), and the working pressure (mainly used to select the pressure level of the instrument pressure sensor).

② Perform calibration before use. On the one hand, considering the current on-site verification of such instruments, there are still such difficulties. In addition, if the purchase intention is to prepare the instrument for more important measurement occasions, such as large flow

The measurement points of trade measurement or measurement disputes are prominent, and the application site does not have the conditions for online calibration of the flow. In this case, the table can be easily judged only by a piece of factory certification provided by the manufacturer at the time of purchase. All

Qualifying performance is a bit premature. Therefore, in order to ensure the reliability and accuracy of the measurement results of the instrument in the future work process, it is necessary to send it to the department with the capability and qualification for verification in this area before the formal installation.

System verification over full flow range.

③ Do a good job of process installation Although this type of instrument does not have too many special requirements for process installation and use environment, any type of flow measurement instrument has a commonality, that is to avoid vibration and high temperature environment interference components away from the flow state as much as possible (Such as pressure

Shrinking machine, separator, pressure regulating valve, big and small heads and manifolds, elbows, etc.), keep the inner wall of the straight pipe section in front and back of the instrument smooth and straight, and ensure that the measured medium is a clean single-phase fluid.

④ Strengthen later management Although this kind of instrument has various automatic disposal functions and micro power consumption characteristics, it still needs to be strengthened after operation. For example, in order to ensure the accuracy and reliability of the meter's long-term work (to avoid accidental outages and data loss

Lost), the system calibration should be performed regularly (every 1 to 2 years), the header data should be copied (daily or weekly), the media parameters should be changed (monthly or quarterly), and the battery status should be checked from time to time. Seals and so on.

⑤ Pay attention to internal maintenance. If the measuring cavity and its components need to be regularly inspected or cleaned due to dirty soil or other reasons, then one point must be paid special attention to: For the vortex flowmeter of the same specification, its vortex

The core components such as generator and fluid cannot be interchanged. Otherwise, the meter's metering coefficient must be re-calibrated and the temperature and pressure sensors must be calibrated.

Fives. 存在问题 Problems with precession vortex flowmeters

① The setting of the cut-off frequency is arbitrary. The cut-off frequency is set by the user to determine the starting flow of the meter according to the production changes on the measurement site. If the cut-off frequency is set too high, the starting flow of the meter will increase accordingly.

For this reason, the leakage of the flow may occur; if the cut-off frequency is set too low, the sensitivity of the meter will increase accordingly, and some weak vibration or stray signals from the outside may cause the situation where the measured medium does not pass. under

The meter starts to operate, so over-counting of the flow is inevitable. These two phenomena have been encountered in the company where the author is located, and until recently, a suitable solution has not yet been found.

② More sensitive to interference signals such as noise or vibration. If a strong magnetic field exists near the measuring instrument or there is obvious noise or disturbance upstream of the measuring end of the instrument (for example, howling caused by throttling or flow direction change)

And other mechanical vibrations), then the operation of the instrument will be affected to a certain extent. In other words, the anti-interference ability of this instrument needs to be further improved.

③ No historical record of measurement parameters. Because flow measurement is an important basis for process control, cost assessment or trade settlement, sometimes due to the decline in product quality, production costs, or large losses, it is inevitable to have different historical records.

The periodical measurement data is compared and analyzed. At this time, the historical records of pressure, temperature, and instantaneous (cumulative) flow need to be called. If you do not take regular manual entry or secondary development of this instrument (for example, the timely measurement of the field data)

Remote transmission and automatic recording), then the required information no longer exists.

In addition, the instrument also has the following problems: due to the short time to market, the reliability and stability of the instrument has yet to be tested in various complex conditions; the sensitivity of the measurement accuracy to the flow regime and the media contamination has yet to be determined. Experimental research

Research; on-site verification methods need to be further explored. In this sense, the instrument is currently mainly applicable to those less important measurement occasions, such as small and medium flow and internal transfer measurement.

In recent years, new measuring instruments suitable for different media and working conditions have come out one after another, and the intelligent precession vortex flowmeter is one of them. It is a speed type flow meter developed and put on the market in recent years, which can be applied to a variety of gases

Flow measurement, and realizes online automatic compensation of dynamic parameters such as pressure, temperature and compression coefficient. It is also because the table has certain characteristics but a short application history. At the same time, considering that the user has not performed a more systematic

Summary of practice. In view of this, the author summarizes the use of this instrument by this enterprise as a reference for the relevant departments in the selection and use of the instrument.

1 Select background

① Orifice flowmeters can no longer meet the most basic measurement requirements in certain specific situations.

In the field of natural gas flow measurement, there are often some special users, which are mainly manifested as: instantaneous flow is small or the fluctuation of the flow is large. If the traditional orifice plate flow meter is still used for flow measurement in this case, then

It is likely to violate the provisions of the relevant technical standards [1,2]. For example, the requirement that "the flow rate in the pipeline should not change with time, or actually have only slight and slow changes with time" is also required for orifice plate flow meters that use flange pressure.

"ReD≥1260 2D", etc., once these basic conditions of use are exceeded, the measurement accuracy of the orifice plate flowmeter will be impossible to talk about; in addition, in this special case, the selection of the display instrument is also quite expensive. Setbacks, if

If the match is not correct, it is inevitable to indicate or record an excessively poor value.

② Strict control of production management costs is an urgent requirement for the survival and development of modern enterprises.

Nowadays, various enterprises and counties are experiencing the severe baptism of the market, and the production cost will inevitably affect the survival of the enterprise. Therefore, under the premise of meeting the basic requirements of the flow meter, choose a new type that can save static investment and reduce dynamic costs.

Meters are also on the agenda of decision makers.

2 Instrument Features

Compared with the traditional orifice plate flowmeter, the intelligent precession vortex flowmeter has the following main features:

①Mechanical and electrical integration is realized, and the daily measurement process does not need manual watchkeeping;

② The process installation conditions are not harsh, and the upstream and downstream straight pipe sections of the instrument can be greatly shortened compared to the orifice flowmeter;

③ The system's measurement accuracy can meet the current trade measurement requirements (≤2%) ">;

④ The flow measurement range is wide (qmax / qmin = 15 ~ 20 ">), and it can work effectively in the small flow area where the orifice flowmeter cannot reach;

⑤ Small size and light weight, convenient for offline calibration;

⑥ The measurement signal can be displayed locally or remotely transmitted as required;

⑦No moving parts, so there is no mechanical wear of the instrument for general measurement;

⑧Instrument management personnel do not need professional training, and measurement parameters such as flow, pressure, and temperature can be read directly from the meter head without conversion.

⑨It is only necessary to periodically replace the battery (micro power consumption) "> and the parameters of the measured medium.

3 working principle

①Composition structure

主要由壳体(文丘利管)">、旋涡发生体、导流体、频率感测件(压电晶体)、微处理器、温度及压力传感器等部件组成,其外型结构如图1所示。 Intelligent precession vortex flowmeter is mainly composed of housing (venturi tube), vortex generator, fluid guide, frequency sensing element (piezoelectric crystal), microprocessor, temperature and pressure sensor, etc. The structure is shown in Figure 1.

②Working principle

l a vortex generator; 2—shell; 3—> temperature sensor input; 4 pressure sensor input; 5—signal output;

6 a piezoelectric crystal; 7 a temperature sensor; 8 a pressure sensor; 9 a outlet fluid

Figure l "> Structure of precession vortex flowmeter

When the measured medium reaches the upstream inlet of the instrument along the central axis of the pipe, the fan blades fixed at the end force the fluid to rotate first, and then a vortex is formed by the vortex generator. Due to the kinetic energy of the fluid itself, the vortex flow continues

Continue to rotate forward in the Venturi tube. When the fluid reaches the contraction section of the Venturi tube, the vortex flow energy increases and the flow velocity increases due to the throttling effect. After entering the diffusion section, the fluid is forced due to the return flow. Perform a second rotation. produce

After the vortex frequency is detected, converted by the frequency sensing element (piezoelectric crystal), and amplified, filtered, and shaped by the preamplifier, the vortex frequency is transformed into a pulse proportional to the velocity of the measured medium. Signal, then

After that, it is sent to the microprocessor for integration processing with the detection signals such as temperature and pressure. Finally, the measurement results are displayed on the LCD (instantaneous flow, accumulated flow, temperature, and pressure data under standard conditions).

4 Usage

① Overview In order to solve the problem of civil gas measurement in small towns (small daily gas supply and large fluctuations in flow), from August 1997 to now, a company has used Jiangsu Jinhu Dongxiang Instrument Co., Ltd. Production of intelligent precession

There are more than 50 vortex flowmeters. The flow measurement range of the point of use is between 100 and 3000m3 / d, and the air supply pressure is ≤ 1.0MPa. The minimum specification is DN25 and the maximum specification is DN50.

②Medium conditions The tested media are basically purified natural gas, with methane (CH4) content ≥95%, carbon dioxide (C02) and nitrogen (N2) content ≤5% ">, and hydrogen sulfide (H2S) content ≤30mg / m3, relative density (Cr) is 0.55 to 0.58 ">.

③ The use of the meter is stable and reliable as long as the meter is selected properly and the flow is stable and there is no obvious interference. At a certain measurement point, the measurement results are in good agreement with the orifice plate flowmeter in series comparison.