Now most steam metering meters on the market are vortex flowmeter, vortex steam flowmeter national standard measurement accuracy is level accuracy, so many customers in the use of steam metering accuracy is very poor, what is the reason? Today for you to summarize the steam flowmeter measurement is not accurate reasons.

1. Analysis of steam medium in field measurement:

1. Superheated steam: steam is a special medium. In general, steam refers to superheated steam. Superheated steam is a common power source used to spin steam turbines, which in turn turn generators or centrifugal compressors. Superheated steam is obtained by heating saturated steam. It does not contain liquid droplets or liquid mist, belongs to the actual gas. The temperature and pressure parameters of superheated steam are two independent parameters and its density should be determined by these two parameters.

After long distance transportation, superheated steam, with the change of working conditions (such as temperature and pressure), especially in the case of low superheat, will change from superheated state into saturated or supersaturated state because of the decrease of heat loss temperature, and become saturated steam or supersaturated steam with water droplets. Saturated steam suddenly large decompression, liquid adiabatic expansion will also be transformed into superheated steam, so that the formation of vapor-liquid two-phase flow medium. It makes the measurement difficult and leads to inaccurate measurement.

2, saturated steam: without overheating treatment of steam is called saturated steam. It is a colorless, odorless, uncombustible, and non-corrosive gas. Saturated steam has the following characteristics.

(1) There is a one-to-one correspondence between the temperature and pressure of saturated steam, and there is only one independent variable between them.

(2) Saturated steam is easy to condense, and if there is heat loss in the transmission process, droplets or liquid mist will form in the steam, and lead to the reduction of temperature and pressure. Vapor containing droplets or mist is called wet vapor. Strictly speaking, saturated vapors contain more or less liquid droplets or mist biphase fluid, so different states cannot be described by the same gas state equation. The content of droplet or mist in saturated steam reflects the quality of steam, which is generally expressed by the parameter dryness. The dryness of steam is the percentage of dry steam per unit volume of saturated steam, expressed as "x".

(3) Accurate measurement of saturated steam flow is difficult, because the dryness of saturated steam is difficult to guarantee, generally without temperature and pressure compensation steam flowmeter can not accurately detect the flow of two-phase fluid, steam pressure fluctuation will cause the change of steam density, flowmeter value will produce additional error. Therefore, in steam measurement, we must try to maintain the dryness of the steam at the measuring point to meet the requirements, and if necessary, compensation measures should be taken to achieve accurate measurement.

Considering the influence of steam temperature and pressure on steam flow, we should choose AK-LUGB-WY series steam flow meter with temperature and pressure compensation when choosing steam flow meter, so that we can measure steam flow correctly.

Ii. Analysis of installation problems of flowmeter measured on site:

The correct installation of the instrument is an important link to ensure the normal operation of the instrument. If the installation is not proper, the accuracy of the instrument will be affected, the service life of the instrument will be affected, and even the instrument will be damaged.

Steam flowmeter installation environment requirements:

1. Avoid strong electric devices, high frequency devices, and strong switching power devices. The meter's power supply is separated from these devices as much as possible.

2. Avoid the direct influence of high temperature heat source and radiation source. If it must be installed, it must be insulated and ventilated.

3. Avoid high humidity environment and strong corrosive gas environment. Ventilation measures should be provided if installation is necessary.

4. Vortex street flow meter should be avoided as far as possible installed on the pipeline with strong vibration. If it must be installed, pipe fastening devices shall be installed in 2D upstream and downstream of the pipe, and anti-vibration pad shall be added to strengthen the anti-vibration effect.

5. It is best for the instrument to be installed indoors, and waterproof should be paid attention to when installed outdoors. Special attention should be paid to bending the cable into a U shape at the electrical interface to avoid water entering the amplifier shell along the cable.

6. Adequate space should be left around the installation point of the instrument for cable installation and regular maintenance.

1. The inner diameter of upper and downstream piping should be the same. If there is any difference, then the relation between the inner diameter of piping Dp and the inner diameter of vortex meter Db should be as follows: ≤Dp≤1.05Db

2. The upper and downstream piping should be concentric with the body diameter of the flow meter, and the different coaxiality between them should be less than 0.05Db

3. The sealing gasket between the instrument and the flange shall not be convex into the pipe during installation, and its inner diameter shall be 1-2mm larger than the inner diameter of the meter

4. Installation design of pressure hole and temperature hole. When temperature and pressure transmitters need to be installed in the pipeline under test, pressure holes should be set at 3-5 d downstream, and temperature holes should be set at 6-8D downstream). D is the nominal caliber of the instrument, unit: mm

5. The meter can be installed horizontally, vertically or at an Angle on the pipe.

6. When measuring gas, install the instrument in the vertical pipe, the gas flow direction is not limited. But if the pipe contains a small amount of liquid, in order to prevent liquid into the meter measuring tube, the air flow should be bottom-up.

7. When measuring liquids, in order to ensure that the tube is filled with liquid, the direction of liquid flow should be ensured from the bottom up when the meter is installed in a vertical or inclined pipe. If the pipe contains a small amount of gas, the meter should be installed at a lower part of the line to prevent gas from entering the meter measuring pipe.