Do you know what influence the K coefficient of DN125 pipeline steam flowmeter has on the flow calculation?

The steam flowmeter will be divided into a variety of different caliber models and selections, but do you know how the K coefficient of the large-diameter DN125 pipeline steam flowmeter affects the flow calculation during the use process? The editor intends to use this article to take you to explore one or two.

The DN125 pipeline steam flowmeter is a throttling device of a process flow detection instrument. It is composed of a standard orifice plate and a multi-parameter differential pressure transmitter (or a differential pressure transmitter, a temperature transmitter, and a pressure transmitter). The differential pressure flow device with high turndown ratio can measure the flow of gas, steam, liquid and lead. It is widely used in process control and measurement in the fields of petroleum, chemical industry, metallurgy, electric power, heating, water supply and so on. Because of its long history of application, it has established a complete database table of design, calculation, specification, and model selection and formed a standard specification in use. In engineering design, orifice plate is widely used as a standard throttling element, and it is the first choice for engineers to design flow detection.

Measuring principle of DN125 pipeline steam flow meter:

The orifice plate is used for process flow detection and is a throttling element manufactured based on the ideal fluid transmission characteristics in fluid mechanics.

Bernoulli equation of ideal fluid: Z1+P1/ρ1g+V12/2g= Z2+P2/ρ2g+V22/2g+hf

Z1 and Z2 are the pressure heads produced by the vertical height between the front and back pressure points of the throttling element and the reference platform;

P1 and P2 are the static pressure of the medium in the pipeline before and after the throttling element;

V1, V2 are the average flow velocity of the medium before and after the throttling element;

ρ1, ρ2 are the density of the medium before and after throttling, the ideal fluid can be regarded as the density before and after throttling does not change to ρ;

hf is the fluid head loss caused by the throttling element, which can be ignored during the standardized installation of the standard throttling element.

According to the above formula and symbol definition, we can get:

(V22 —V12)/2g=(P1 —P2)/ρg + (Z1 — Z2)

According to the law of conservation of fluid flow, the fluid flow before and after the throttling element is equal:

Q1=Q2; Q1=V1S1, Q2=V2S2,

It can be concluded that the average flow velocity of the throttling element is: V2 = V1 S1/ S2

In the formula, S1 and S2 are the flow cross-sectional area of the pipeline and the throttling element respectively, which can be calculated from the pipeline diameter and the size of the orifice plate opening.

From this, the average flow velocity of the fluid before the throttling element can be obtained:

V12= [( P1-P2)/ρg + (Z1-Z2 )] 2g S22/(S12-S22 );

In actual use, the vertical distance from the front and rear pressure points of the throttling element to the reference platform remains the same, so

(Z1 — Z2) =0 Thus the above formula can be simplified to:

V1 =√(P1 —P2 )√(2S22/(S12- S22)ρ

=K√(P1 —P2);

In the formula, K=√(2S22/(S12-S22)ρ keeps basically constant in the use of the standard orifice plate after installation, which can be regarded as a constant as the flow coefficient, which is calculated in the engineering design calculation.

It can be seen from the above formula that the fluid velocity is proportional to the square root of the pressure difference before and after the throttling element. As long as we detect the pressure difference before and after the throttling element, the average flow velocity of the medium can be obtained, and the volume of the fluid can be calculated from this. Flow rate, this is the principle that the orifice plate can measure the fluid flow rate.

The influence of errors in the use of DN125 pipeline steam flowmeter:

    It can be seen from the measurement principle of the above DN125 pipeline steam flowmeter that the square root of the pressure difference before and after the orifice is proportional to the flow rate of the fluid under the assumption that some conditions remain constant. Therefore, in actual engineering use, whether this restriction can be kept constant is the primary factor to ensure the accuracy of the DN125 pipeline steam flow meter measurement. For this reason, we need to carry out corresponding work in the design, installation and use and maintenance.

Influence of K:

    In order to ensure that the flow coefficient K remains constant, the density of the medium is required to be accurate in the engineering design. Therefore, the temperature, pressure, density, composition and other parameters of the fluid during normal use should be provided during the selection of the orifice plate. If these parameters deviate too much from the selection parameters in actual use, the flow coefficient needs to be revised numerically. The production of most devices wil

l be carried out in accordance with the parameters of the engineering design, and the online flow process detection is not very demanding on the accuracy of the parameters, so this revision of the orifice plate flow coefficient is rare in actual production. If the DN125 pipeline steam flowmeter is used in the measurement and inspection of materials, it is necessary to take compensation measures for the fluid flow coefficient. The most common method is to use temperature and pressure compensation measures to revise the flow coefficient value.

Do you know what the impacts are now? As long as you encounter a problem, even if you solve the problem with empathy, I believe that the problem is not a problem. No matter how different the caliber is selected, there will always be a solution to it. What other problems need to be consulted, please feel free to call 400-0117-885 online Advisory Service.