The introduction of nozzle flowmeter and its application
Nozzle flowmeter, also known as standard nozzle flowmeter, nozzle, and the standard orifice, venturi tube flowmeter, venturi nozzle as standard throttle device belongs to China national standards. Henan SIKE measurement and control technology co., LTD. nozzle flowmeter Product accords with national standard GB / 2623-2623, so like the standard orifice plate without real flow calibration, as long as according to the national standard design and price can meet the design accuracy, if users need can accurately provide: common flow work, medium, temperature, pressure, process pipe diameter of these parameters. Standard nozzle throttling device with differential pressure transmitter, can measure the rate of flow of liquid, steam, gas. Nozzle flow meter is to measure flow differential pressure generator, cooperate with all sorts of differential pressure gauge or differential pressure transmitter to measure all kinds of fluid flow in pipes. Mainly used in petroleum, chemical, metallurgical, power, light industry and other departments.
Because the nozzle flowmeter has high temperature and high pressure resistance, impact resistance, long service life, etc, are still widely used in industry nozzle flowmeter for steam flow measurement. In the process of actual use, in many cases, the straight pipe length is difficult to meet the standard requirement, which bring great influence on measuring readiness. With the development of oil and gas add, high pressure gas transmission and high pressure large flow gas flow measurement, need to take a reason of flow meter and standard device, critical flow nozzle flowmeter in solving the problem of high pressure large flow gas flowmeter has played an important role, and has been widely applied.
Nozzle flowmeter played an irreplaceable by other gas flow standard, as a kind of gas meter, there are many advantages of differential pressure flowmeter do not match.
1, the advantage of the nozzle flowmeter
The working principle of the first, have a very clear can be expressed in one and a half experience formula, the outflow in the primary standard device calibration coefficient can be applied to different operating conditions without losing its accuracy; And with good reproducibility, can undertake online measurement, easy to automatic control. General always preferable in throttle flowmeter using orifice meter, in fact, in a period of time, has become the standard orifice flowmeter throttle device, actually standard throttling pieces such as ISA1932 nozzle, venturi tube did not cause enough attention (the early nozzle type products of handbags processing technology limited), make the didn't get full play to its unique advantage. Therefore, we should attach importance to the nozzle flow meter application. It has advantages of orifice meter, but also for nozzle profile throttling, no sharp edges, the administrative structure high velocity impact and abrasion resistance, so its flow characteristic can maintain long-term stability, no orifice passivation, sharp edges and verification cycle is long, and the pressure loss is small. So the nozzle flowmeter should be than throttling orifice plate is superior.
Secondly, from the upstream end velocity distribution, the influence of nozzle straight pipe upstream side so don't need to be very strict, and its flow rate value only depends on the fluid parameters, upstream of the nozzle is not affected by changes in downstream pressure. Through nozzle mass flow rate and inlet stagnation pressure is linear relationship, do not need to measure differential pressure, also do not need to be dramatic changes in the velocity of support to measure static pressure, the pressure measurement accuracy is greatly improved, to improve accuracy of measurement.
Finally, very wide scope of work, such as temperature, pressure, flow field of the scope of almost unlimited, compact size, as a standard flow, at the same flow rate measurement range, regardless of size, price than the same accuracy of gas flow standard device, such as small and cheap.
2, the integration of fixed value nozzle flowmeter
Nozzle flowmeter applied less an important reason is that its profile processing technology is complex, a nozzle to prepare a few templates, for guarantee machining accuracy and inspection.
To commercialize the throttling parts, many years ago, some experts have proposed the fixed value of throttling originality, a fixed value throttling piece is only under a nominal pipe diameter to make three kinds of throttle aperture throttle parts (β=0.4、0.5、0.6), such integration constant value nozzle flowmeter, like mechanical parts, can form batch production. Not only easy to guarantee the machining precision, reduce cost, also facilitate measurement supervision.
There is a serious problem, which is currently in use of a large number of orifice plate and the nozzle, the straight pipe length does not meet the standard requirements, and within the scope of the 10 d, concentricity, roundness, roughness or risk standard requirements, large additional error caused by, therefore bring processed straight pipe, it is very necessary. So, the integration of custom nozzle flowmeter is mainly used with straight pipe before 10 d, can completely satisfy the gas flowmeter, including the accuracy of the technical requirements.
Above this article easy to nozzle flowmeter is presented and the application shows that due to the instrument of solid structure, calibration cycle is long, the decrease maintenance colleagues, greatly reduce the operation cost; Has a good technical and economic indicators, there is reason to think that can be used as one of the key selection of instrument of measuring gas flow. This is not only a professional consensus, will also become the consensus of the masses of users.