与孔板长期精度比较:威力巴和孔板相比能保持长期的高精度。 Verabar flowmeter and orifice plate long-term accuracy comparison: Verabar and orifice plate can maintain high accuracy for a long time. This is because the unique structure of Verabar is not affected by abrasion, impurities and grease, there are no moving parts, and the integrated structure avoids signal leakage between high and low pressure chambers; on the contrary, the use time of the orifice plate is long , The accuracy will drop sharply, regular inspection and cleaning are needed, which will lead to many reasons for the decline in the accuracy of the orifice plate. Among them, the biggest impact is the change of the orifice plate geometry during long-term operation, and the acute angle becomes blunt. It was announced after the test that the wear radius increased by 0.04mm per year during the first two or three years of operation, but stabilized after five or six years. As the acute angle becomes blunt, the orifice flow coefficient will become smaller!); During the process of starting and stopping, because the condensed water is easy to be stored in the steam pipe, water hammer is generated during the process of starting and stopping the steam pipe, which causes the orifice plate to deform and even become a bell mouth. All this shows that the orifice plate differential pressure steam flow meter is difficult to guarantee its original design measurement accuracy. 2. Verabar flowmeter and orifice flowmeter installation cost comparison: Verabar and orifice plate save a lot of installation costs. In the installation process of Verabar, only simple welding is required. The welding workload ranges from a few centimeters to a dozen centimeters, which is basically independent of the diameter of the pipeline. Compared with the orifice plate, a welding station with twice the circumference of the pipeline is required. The cost is much smaller. For example, installing Verabar on DN250 pipelines requires only 10cm welding; the same pipelines require 160cm welding to install the orifice plate, compared to Verabar saving at least 60% of installation costs. According to experience, the larger the diameter of the pipeline, the more the Verabar will save on installation. 3. Comparison of operating costs between Verabar flowmeters and orifice flow meters: Verabar and orifice plates save a lot of operating costs. Compared with the orifice plate, the long-term operating cost of Verabar is very low, and the electricity cost saved in less than one year of operation can recover the purchase cost. Verabar uses a non-restrictive throttle design, which reduces the permanent pressure loss of the orifice plate by at least 95%. It is an efficient, energy-saving, uniform velocity flow probe. (For details, see the calculation of pressure loss comparison below) 4. Comparison of pressure loss of Verabar flowmeter and orifice flowmeter: Throttle flowmeter is a typical differential pressure flowmeter, which is currently used in industrial production. One of the most commonly used flow meters for measuring gas, liquid and vapor flow. The theoretical basis of its measurement is: In a fluid-filled pipe, a resistance member (throttle member) with a flow area smaller than the cross-sectional area of the pipe is fixedly placed. When the fluid in the pipe passes the throttle member, it will cause local contraction. The flow velocity at the constriction increases and the static pressure decreases. Therefore, a certain pressure difference will occur before and after the throttle. For a certain shape and size of the throttle, a certain pressure measurement position, a straight pipe section before and after, and certain fluid parameters, the relationship between the differential pressure △ P before and after the throttle and the flow rate Q is in accordance with Bernoulli's equation. This flowmeter inevitably creates permanent pressure loss in the pipeline. Taking the orifice plate as an example, the main reason for the pressure loss of the fluid is the formation of vortices in the front and back of the orifice plate and the friction along the fluid. It makes part of the total mechanical energy of the fluid irreversibly turned into thermal energy and disappears in the fluid.
采用了子弹头形的革命性设计，使得其不仅在流量测量上保持了高精度、高强度和大量程比，还使得管道压损大大降低。 The Verabar flowmeter uses a bullet-shaped revolutionary design, which not only maintains high accuracy, high strength and a large range ratio in flow measurement, but also greatly reduces pipeline pressure loss.
Comparison of pressure loss between Verabar and orifice plate:
Empirical formula for orifice plate pressure loss:
When β = 0.6, PPLo = 0.6 × △ P
When β = 0.7, PPLo = 0.5 × △ P
Among them: β ------- the hole diameter ratio △ P ------ the differential pressure PPLo produced by the orifice plate ----- the pressure loss produced by the orifice plate can be obtained through experiments. The pressure loss is approximately: PPLv = 0.03 × △ P
Because the differential pressure △ P of Verabar is an order of magnitude smaller than the differential pressure ΔP of the orifice plate, and the proportion of pressure loss is an order of magnitude smaller, the Verabar pressure loss is very small compared to the orifice plate pressure loss.
Let's write the expression of pressure loss:
The power loss caused by the pressure loss of the throttle is calculated as:
Hp '= Q × PPL
Among them: Q ------ fluid volume flow rate PPL ---- pressure loss caused by the throttle piece. In order to make up for the unrecoverable pressure loss caused by the throttle piece, we will add a pressure pump afterwards. The efficiency of the pump is assumed to be η.
Then: Hp = Q × PPL ÷ η
Among them: Q --------- fluid volume flow AM3 / S
PPL ------ Pressure loss caused by throttle KPa
η ------ Dimensional constant Hp of motor efficiency -------- Power loss KW
Example: Take the measurement of steam as an example, suppose a measuring point, the measuring medium is superheated steam, the pipe diameter is Φ325 × 13mm, the pressure is 3900KPa G, the temperature is 450 ℃, and the steam density is 12.511Kg / M3 at this temperature and pressure When the medium flow rate is 50T / H, the differential pressure produced by Verabar is 5.600 KPa.
Pressure loss caused by Verabar: PPLv = 0.03 × △ P = 0.03 × 5.600 = 0.168 KPa
According to the above formula, the power loss: Hp = Q × PPL ÷ η
Because the density of superheated steam is 12.511Kg / M3 under working conditions, the volume flow of the medium under working conditions (3900KPa G, 450 ℃) is:
Volume flow rate = mass flow rate / medium density Q = 50 × 1000 ÷ 12.511≈3996.5M3 / H = 1.110M3 / S (3900KPa G, 450 ℃)
Assuming motor efficiency η = 0.8
Then: the power lost by Verabar is Hp = 1.110 × 0.168 ÷ 0.8 = 0.233 (KW)
Assuming that it runs 365 days a year, operates 24 hours a day, and the electricity cost per kilowatt-hour is 0.8 yuan, then the energy consumption of Verabar for one year is converted into electricity costs: ￥ / year = 365 × 24 × 0.233 × 0.8≈1633 ￥ / year Another same measuring point is measured with orifice plate. Under the same conditions, the pressure difference of the orifice plate is 30Kpa, the orifice plate's β = 0.7, and the pressure loss caused by the orifice plate: PPLo = 0.5 × 30 = 15.0KPa
The percentage reduction of the permanent pressure loss of Weili Babie orifice plate is: (15.0－0.168) ÷ 15.0 × 100% = 98.88%
Obviously, it is an efficient, energy-saving, uniform velocity flow probe.
According to the above formula, the power lost by the orifice plate is:
Hp = 1.110 × 15.0 ÷ 0.8≈20.813 (KW)
Running 365 days a year, 24 hours a day, the electricity cost per kilowatt-hour is 0.8 yuan, then the energy consumption of a perforated plate is converted into electricity cost: ￥ / year = 365 × 24 × 20.813 × 0.8≈145858 ￥ / year, then Every one year of operation, the operating cost saved by the Verabarbi orifice plate is: 145858-1633 = 144225 yuan / year Verabar flowmeter products have a wide range of measurement media, high measurement accuracy and simple maintenance. I believe its market will have better prospects.
Verabar flowmeter is also based on the principle of differential pressure flowmeter. Verabar is a differential pressure, average velocity flow sensor. Flow measurement is performed by sensing the differential pressure generated in the flowing fluid. It consists of a probe, a differential pressure transmitter and a flow totalizer. The unique structure is not affected by wear, impurities and grease, there are no moving parts, and the integrated structure prevents signal leakage between high and low pressure chambers. Verabar flowmeter flow measurement system consists of secondary instruments such as throttling device (differential pressure generator), differential pressure transmitter and flow totalizer. With the rapid advancement of electronic technology, the accuracy and sensitivity of secondary instruments such as transmitters and totalizers have undergone qualitative changes, reaching a very high level. Verabar probes, differential pressure transmitters, and secondary instruments such as totalizers constitute the world's highest level differential pressure flow measurement system.
Verabar flowmeter works: When fluid flows through the probe, a high-pressure distribution area is generated in the front of the probe. The pressure in the high-pressure distribution area is slightly higher than the static pressure of the pipeline. According to the principle of Bernoulli's equation, when the fluid flows through the probe, the speed increases, and a low-pressure distribution area is generated at the rear of the probe. The pressure in the low-pressure distribution area is slightly lower than the static pressure of the pipeline. After the fluid flows through the probe, a partial vacuum is created at the back of the probe, and vortices appear on both sides of the probe. The cross-sectional shape of the average velocity flow probe, the surface roughness, and the location of the low pressure pressure taking hole are the key factors that determine the performance of the probe. The stability and accuracy of the low-voltage signal play a decisive role in the accuracy and performance of the average speed probe. Verabar's average velocity flow probe can accurately detect the average differential pressure generated by the average velocity of the fluid. It has multiple pairs of pressure taking holes arranged according to certain criteria in the high and low pressure regions, making it possible to accurately detect the average flow velocity.
Verabar, like other differential pressure flow meters such as orifice plates, follows Bernoulli's equation.
Among them: Q = volume flow in the pipeline K = flow coefficient C = flow constant DP = differential pressure Verabar flowmeter measurement system performance index produced by differential pressure generator:
Measurement accuracy: ± 1.0% Repeat accuracy: ± 0.1
Maximum pressure: usually 10MPa, especially up to 40MPa
Applicable temperature:-100 ℃-500 ℃ Special up to 800 ℃ Range ratio: greater than 10: 1
Lower measurement limit: (mmH2O) Gas: 2.54 Liquid: 25.4 Vapor: 38.1
Upper limit of measurement: Different models have different strengths and their upper limits are different. Verabar has been widely used in square and round pipes of various materials, with pipe diameters ranging from 38mm to 14000mm. Under full tube conditions, measure the flow rate of various single-phase gas, liquid and vapor media.
特点： 1、子弹头形状：子弹头形的截面，不但使压力牵引降到最小，而且使流体分离得以固定2、测量信号稳定、量程比大：表面粗糙处理和防淤槽控制附面层，在各种流速下，探头表面的流体都处于紊流状态，可以获得稳定的信号，保证了较宽的量程。 Verabar flowmeter features: 1. Bullet shape: bullet-shaped cross-section, not only minimizes pressure traction, but also fixes fluid separation. 2. Stable measurement signal, large range ratio: rough surface treatment and anti-fouling tank control. With a surface layer, the fluid on the probe surface is in a turbulent state at various flow rates, which can obtain a stable signal and ensure a wide range. 3. The probe pressure hole is essentially anti-blocking: the low pressure pressure hole is provided on the back of the probe side, which completely eliminates the effect of the eddy current pulsation on the probe tail on the differential pressure value, ensures the stability of the low pressure signal, and prevents the low pressure pressure hole The blockage solves the blockage problem of the round probe and the rhombus probe, and opens a new way for the measurement of dirty fluids such as blast furnace gas and flue. 4. Unique high-strength bullet-type single-chip dual-cavity structure: Verabar uses a complete metal structure and a single-chip dual-cavity structure probe made of 316 stainless steel, which improves the strength and avoids a multi-chamber structure flowmeter. The leakage between the multi-chambers will not reduce the accuracy due to edge deformation like the orifice plate, which ensures long-term high accuracy. 5. The pressure taking hole has small pressure fluctuation and high precision: read the high pressure average signal when the pressure taking hole is facing the fluid, and read the low pressure average signal at the low pressure pressure taking hole at the two sides behind the probe and before the separation point of the fluid and the probe. The probe passes through the entire section through which the fluid flows, and takes pressure from multiple pressure taking holes. The distance between the pressure taking is obtained by integrating the area. The measured signal reflects the true signal of the average speed. It is also very accurate, and the accuracy of other single-point pressure-receiving flow meters is only about 10% in actual application. 6. Extremely low pressure loss: the bullet-shaped cross section produces the least resistance, so the permanent pressure loss is the lowest, accounting for only 3% of the differential pressure. Compared with the orifice plate, the energy consumption is reduced by more than 95%. The energy saved in the year can recover the entire investment. 7, extremely easy to install and maintain: Installation is very easy, just need to make a small hole in the pipeline, a small flange can be installed, the installation cost is very low, and the service life exceeds the life of the pipeline, and generally does not require maintenance. 8, can measure a variety of media, a wide range of applications: can measure a variety of single-phase gas, liquid and steam media flow.