Recently, many customers have received frequent calls to ask if we can replace the orifice flowmeter vortex flowmeter? Now we are on these two

Can a variety of products substitute for everyone?


I. About Vortex Flowmeter Products

The basic structure of the vortex flowmeter consists of vortex generators, detection elements, and signal processing amplifiers.

The body of the street has reached a fairly complete level of research. The body is a triangular body. The detection element has a thermistor, and

Variations, piezoelectric crystals, differential capacitance, ultrasound, etc. Many of the signal processing sections have been computerized. Vortex flowmeter has an installation side

It can be installed directly on the pipeline, small size, strong interchangeability, long-term running accuracy, applicable to most liquids, gases

And steam measurement. At present, the sales volume of vortex flowmeters in the world market is increasing by about 30% every year.

Second, on the orifice flowmeter products

Orifice flow meter is a standard orifice plate and multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter and pressure transmitter)

Comprised of high-range differential pressure flow devices, which can measure the flow of gas, steam, liquid and natural gas, and the orifice plate throttling device consists of

Due to its advantages of simple structure, low cost and reliability, it is suitable for all media measurements, and it is supported by the development of differential pressure transmitters.

Rapidly, it made up for its own deficiencies. Widely used in petroleum, chemical, metallurgy, electric power, heating, water supply and other fields

Process control and measurement. At present, the technological development level of the orifice plate flowmeter is still based on the empirical formula for determining, 1980 International

The standardization organization combines the two standards of R541 and R781 into the standard ISO5167 (1980).

Third, the two products comprehensive performance evaluation

Vortex flowmeter (Vortex Street) has only 3 static seal points, it is not easy to leak, there is no flow dead zone, no heat insulation,

It is not affected by the severity of fluid, temperature, pressure, and viscosity, and the flow coefficient does not change for a long time.

Orifice plate flowmeter (referred to as the orifice plate) is composed of a pressure-reducing device for a throttling piece and a differential pressure transmitter. The pressure-conducting tube needs to be used in a place where it is prone to freezing.

With heat-tracing measures, a flow measurement loop static sealing point is about 20, there are the following problems in use:

Easy to freeze, easy to plug, easy to leak, heat-prone to cause aging of the differential pressure transmitter device, in some occasions need to add isolation fluid pressure tube, due to heat

Or process operation is not stable, positive and negative pressure tube isolation liquid line is often not equal, resulting liquid column difference, so that the flow rate indication is not accurate.

All these will change the flow coefficient, reduce the measurement accuracy, shorten the pressure tube and install the differential pressure transmitter directly on the pipeline.

But there are still dead areas of the flow.

However, when vortex street is used in a vibrating environment, it will make flow measurement inaccurate. At present, the market has launched a vibration-resistant vortex street to overcome the vibration

Impact on the inaccurate flow measurement.

(1) Initial investment

An imported vortex street is about 20,000 yuan (DN15-DN50), and a throttling device includes differential pressure transmitter, orifice plate and

Flanges, pressure pipes, valves, insulation boxes or protection boxes also need 15,000 yuan. From a long-term perspective, the adoption of vortex street is still

Calculated.

(2) Installation cost

The vortex street is simple to install, only need to ensure that the flow meter has a certain straight pipe section before and after, the orifice plate straight section, concentricity, pressure guiding pipe,

Transmitters and incubators have certain installation requirements and installation costs are several times that of vortex.

(3) Maintenance costs

In addition to the periodic calibration required on the measurement, the vortex street will generally not fail, but the orifice plate will be otherwise.

Irrigation isolation fluid, replacement of pressure guiding tubes, valves, insulation, cleaning orifices, etc., have a certain amount of maintenance. If 200 sets of flow orifices measure back

Road (heat insulation required), every two years, thermal insulation system transformation will have to invest a certain maintenance fee, which does not include differential pressure transmitter

The update, orifice update costs. You can buy a certain amount of imported vortex street.
(4) Operating costs
1, steam consumption costs such as 200 sets of flow orifice plate measurement loop (heat insulation required heating), each with hot steam consumption 0.02t/h, if the average annual calculation by 4300 hours, steam costs 40 yuan / ton, the annual need The cost of steam consumption is approximately RMB 688,000 and the annual cost per circuit is RMB 0.344 million.

2, energy costs

Vortex has a smaller pressure loss than the orifice plate, about 1/15 of the orifice plate. Therefore, long-term operation requires less energy consumption for pumps and fans. Orifice plate

15 times that of vortex street. When used for gas or steam flow measurement, due to the small density, the volume flow of the same pipe is large and the pressure loss is more

It is serious and the energy cost is higher.

3, leakage of sewage charges

Sewage discharge charges are regarded as the number of discharges, which is generally about 20 times per year. The discharged sewage and materials pollute the atmospheric environment and the sewage exceeds the standard.

The environmental protection department will also impose fines on it.

(5) Long-term operation accuracy

The orifice plate design system accuracy is 1.5%-2.5%, due to the linear relationship between differential pressure and flow rate, when the flow rate is lower than 30%, the error increases.

Large, the gas is too serious, on the other hand, due to the long-term wear of the media, the acute angle becomes dull and changes the flow coefficient.

It is an important reason that affects accuracy.

Due to the special structure of vortex street, the accuracy is almost constant when the accuracy is actually determined (approximately 0.5%-1% measured value).

(6) Interchangeability

The same vortex street can measure the flow of gas, liquid and steam, electronic circuit boards and sensitive components for different caliber flowmeters.

There are general purpose, signal output usually has three forms: pulse, analog and digital signals. Can be cut by the circuit board switch

Change, the user can switch to another output signal at any time according to their needs. Changing the range is also easy. For analog output,

Just change the input pulse frequency line.

The aperture plate is not the same, the aperture is designed for a specific medium, and the interchangeability is poor. It is also difficult to change the range. The hole needs to be recalculated.

board.

(7) Turndown ratio

Since the output frequency of the vortex street is linear with the flow rate, the flow rate ratio can reach 20:1-80:1. For example, some vortex street flows

The measuring range of measuring gas and steam is 80:1, the measuring liquid has a ratio of 40:1, and it can adapt to the measurement range of the process flow.

Large requirements, accuracy can still be guaranteed.

The differential pressure flowmeter has a non-linear relationship between differential pressure and flow rate. Measurements at low flow rates are inaccurate and the turndown ratio is only 3:1-5:1. If you expand

With a large number of steps, you must try to improve the accuracy of the differential pressure transmitter.

(8) Reliability

There is now a more reliable vortex street. It has two electronic circuits, two sets of sensitive elements, and a single pair of surfaces.

It can be used for important flow measurement occasions, and it is difficult for differential pressure flowmeters to do this.

(9) Energy-saving effect

Such as the amount of steam is 120t/h, the pressure is 3.9Mpa, and the temperature is 445oC. If the steam is measured with the orifice, the pressure loss is

0.03-0.05Mpa, if calculated by 0.03Mpa, the power consumption of this orifice plate is 82kW, which consumes 59 power per year for 300 days a year.

Million kW/h conversion standard coal is 68.5t. If vortex street energy consumption is only 1/15-1/20 of the orifice plate, if it is 1/20, then only

Coal consumption is 3.34 tons, which only accounts for 3.33% of the energy consumption of the orifice plate.

(10) Influence of flow characteristics of primary components on the control system

Since the output frequency of the vortex street is linear with the flow rate, when it is a control system with the regulator valve and regulator stage, it is equivalent to a

A hysteresis link with a negligible time lag and time constant can be regarded as a proportional link. The characteristics of the generalized object are completely determined by

The other parts of the loop have little effect on the control system.

The orifice plate is not the case, since its output is linear with the flow rate, the loop gain varies with the flow rate, although the control valve is used.

The flow characteristics compensate the linear effect of the generalized object, but the effect is not obvious. Therefore, it is necessary to introduce a squarer, and the introduction of a squarer

Although the characteristics of the generalized object do not change with the operating point, the quality of adjustment is obviously changed, but the response is fast and sensitive at small flow rates.

It is easy to cause the system and the adjustment error increases.


To sum up: Vortex Street is a viable alternative to orifice plates in many flow measurements. It saves money and effort, and it does give flow measurement many benefits.


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