LWGY One-piece type cone flowmeter

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Specifications

One-piece type cone flowmeter

Product Statement

Product Introduction
Cone flowmeter is new type of differential pressure flowmeter.

Since American company, McCrometer released, the cone flowmeter is widely used. It could measure every kind of reynold number,and could meet the application condition of all kinds of medium..

The principle of operation is same as other kinds of differential pressure flowmeter that all are based on the conservation of energy of the sealing pipe. Yet due to the unique design structure which enlarge the measurement range of flow, and avoid the limiation of classic differential pressure flowmeter.

So the performance is better. After a long use to prove, comparing with the general differential pressure flowmeter,

,the cone flowmeter has the advantages of high accuracy for the long term, good repeatability, less limitaion of installation conditions, wear resistance,wide measurement range.

The cone flowmeter hangs a cone throttling element, and the element obstacles the flow of the medium, and remould the doppler waveform, which could immediately form the low pressure zone at the downstream of the cone element.

There is a differential pressure between the positive pressure of the upstream of the pipe and the nagative pressure of the downstream after the throtting element throttles, and the posivie pressure and the negative pressure was taken out. The posive pressure port is situated the upstream of the pipe, and the negative pressure is situated the end of the cone.

Through measuring the differential pressure between them, and based on the bernoulli equation, the flowmeter in the pipe could be calculated. The cone is situated at the central of the pipeline, which could optimize the doppler waveform of the medium, so the measurement accuracy is high, and which has the low requirement for the straight pipe section of the upsrteam and downstream of the instrument.

The cone flowmeter could measure the medium inclucing water, stream, air, gas, nitrogen, coke oven gas etc. The conditon of the flow could be from the very low temperature to the supercritical state.

The highest working temprature is 700°C,and the largest pressure is 40.5Mpa.

Working mechanism
The cone flowmeter is differential type one, and the mechanism is same as other general differential pressure flowmeter. All are based on the bernoulli”s law.

Under the condition of stable flowfield, the flow speed in the pipe and the square root of the differential pressure is directly proportional. The upstream pressure is P1, the downstream pressure is P2, and the producing the defferential pressure is

Basic Parameter

Explosion-proof grade: ( I a )ⅡCT2 - T5 intrinsically explosion proof
The surrounding humidity: relative humidity: 45 ~ 85%

Output signal: 4 ~ 20mA((load resistance ≤500Ω); HART digital singal
β value range: 0.45 ~ 0.85

Range span: normal range1:15, the range after expansioin:1: 30

Repeatability: ±0.1%
Straight pipe section requirement: upstream1-3D, downstream0.5-1D

Structure features
The flow formula of the cone flowmeter is same as the other diferential pressure flowmeter. Yet the geometry is absolutely different. It is throttled by a cone hanged in the centre of the pipe which forces the fluid centered the center of the pipeline flows surrounding the cone.

The goemetry of the circular cone has much more advantages compared with the traditional throttle element. It takes for many years for the cone shape design and test, providing the best performance under different inviroment.

For understanding the features of the cone flowmeter, it must understand the distribution feature of the velocity in the pipe. As figure shows, if the fluid in the pipe does not be obstacled and interfered by any other factor, it could form the ideal flow field.

Through the pipe centreline to silver the pipe to look the ideal flow field, the velocity distribute: the velocity closing zero against the pipe skin, the more closing to the centre of the pipe , the larger the velocity is.

The velocity in the centre of the pipe is the most( due to the friction force decrease the speed of the fluid flowing through the pipe skin.)

Because the cone hang the centre of the pipe, which directly has mutual effect with the high speed centre part of the fluid, to force the high speed core and low speed fluid near the pipe skin equably to change.

Yet other differential flowmeters opening pore at the centre do not have this function. This is one of the many advantages of the inner cone flowmeter, so even if the velocity decrease, the cone flowmeter could also produce the accurate differential pressure by the continuously mutual effect between the fluid and the highest velocity of the pipe centre. Yet the traditional differential pressure flowmeter could not measure so long ago.

All the differential pressure instruments are based on the ideal fluid state. And in fact this state does not exist in the actual application. Any change of pipe installation such as elbow, valve, reducing down, hole enlargement, pump, tee coupling etc. all could break the ideal liquidity. So the general flowmeter is very difficult to obtain the accurate measurement value under the disturbed flowfield.

Yet the cone flowmeter overcome these shortcomings. Because the effect of the cone shape and position renew to arrange the distribution of the velocity to cause fluid field to idealize.

The practice has proved, under the very wicked installation condition(such as near the cone upstream, there are two elbows which are not at the same surface), the cone flowmeter could make the speed distribution to be flat and symmetrical, so that ensuring the measurement accuracy.

The property and advantage.
1.High accuracy: the accuracy of the flowmeter could be reading: ±0.5%
2.Good repeatability: overmatching ±0.1%

3.Low installation requirement: the before 0-3D straight pipe section and back 0-1 straight pipe section of the flowmeter could guarantee the measurement accuracy. The experiment could improve that the cone flowmeter could near the singe-bending pipe or double-bending pipes and has very little affect of the accuracy.

Long stability: there is no sudden wave motion when the fluid flow the cone, but to form a boulding layer along the cone, and lead the fluid to leave the postcornu of the cone.

This make the included angel not be worn by the uncleaning fluid. The β rate does not change for a long time, and guarantee the long accurate measurement.
Stable signal: every kind of differential pressure instrument has “signal wave motion”. This means even if the fluid is stable, the signal produced by the throttle element, there is a certain amount wave. For the standrad pole plat, the back of the plate produces longer vortex,

These longer vortex is more longer, and these long vortex make hole plat to produce low frequency and substantial signal, which severely interfere the acurracy of the differential pressure reading. And when the fluid flow over the cone flowmeter, it come into being a very short vortex, and these vortex make the cone flowmeter to produce high frequency, and low-amplitude signal, this result the cone flowmeter could produce stable signal. The changing of these two kinds of signals are shown in the diagram.

6. Wide range with low pressure loss: Due to without the sharp-edged orifice, the permanent pressure loss caused by the cone flowmeter is invariable and less than the hole plate. In the all kinds of differential pressure flowmeter, only the pressure loss of the inner cone flowmeter is near to the venturi. At the same time, the very stable signal make the lower limit of the differential pressure range very much lower than the general ones, so the range could be expanded to more lower limit, normally the range ratio is 15:1, and if the reynolds number lower 8000, it could still maintain the signal linearity. If applying the curve modification, it could still measure under the much lower reynolds number condition and keep the good repeatability.

7. βvalue has wider scope; the unique goemetrical shape of the cone flowmeter permit to have wide β value scope. And the standard β values are 0.450,0.550,0.650,0.750,0.850, and the special β value could be customized for guarantee the users’special differential pressure output( no need to add the fee and also having no effect for the delivery.)

8.The pipe width range: the cone flowmeter has two kinds of basic form, i.e. the pipe type ande plug-type. The size is from15mm to 1600mm.
9.Without stagnation zone

The installation mode

The measurement system
The signal produced by the primary instrument must be measured by the differential pressure transmitter, and then go into the flow totalizer or flow computer to process. For the much bigger change of the temperature pressure or to measure the medium requiring more higher, it sometimes need the temperature and pressure modification. Our company could supply these instruments and also could program and demarcate before the instrument go out of the factory.

The specifications

  The installation size:

The flange size is decided by the standard GB/T9119-2000