Throttle flow meter decade development history

Throttle flow meter because it can withstand harsh conditions, the cost is low, use has been more than a hundred years, accumulated a large amount of data, there are more mature international and national standards, and can be dry standard, long-term accounted for the first flow meter market. However, its biggest drawback is that it requires a longer straight pipe section to achieve higher accuracy. In particular, after ISOTC30 announced the new standard ISO5167 in 2003, a longer straight pipe section was required to achieve higher accuracy and make it contradictory. More prominent, it is urgent to develop a new type of throttling flow meter. This type of instrument does not require long straight sections and still maintains high accuracy.

1) Annular channel flowmeter: In 1986, American McCrometer Company introduced the inner cone type flowmeter, which is mainly used to solve the type of contaminated fluid such as the measuring furnace and coke oven gas. In the application, it found that the annular passage has the rectification function in the straight pipe section. Insufficient conditions still have higher accuracy characteristics. In the past few years in China, due to overheated propaganda and misuse, it caused many major accidents and caused a sharp drop in the market, ruining its development prospects. However, the rectification advantages of the internal cone flow meter should still be affirmed and should not be blocked. As long as some structures are improved, it is still a good flow meter.

2) Adjust the orifice plate: The IS0TC30 has always recommended the use of a flow regulator in order to achieve high accuracy in flow measurement and to reduce the length of the necessary straight pipe segment. However, the flow regulator itself needs a 2D length, and before and after installation requires 3 to 4D, and the on-site application is still difficult. In 2002, Rosemount Corporation in the United States first introduced a four-hole orifice adjustment orifice that combines a flow regulator and a throttling element. When the length of the forward straight segment is 5D, the accuracy can reach ±0.5%; for 2D Accuracy up to ±1%. The concept of this kind of flow meter was pioneered.

3) Balanced flow meters: Following the adjustment of the orifices, A Flowtek launched the "balanced flow meters" in 2004 and entered China in 2007. It is said that the length of the straight pipe before and after only 0.5D, accuracy can reach ± ​​0.5%. This kind of propaganda seems to mislead the user, because it has a long instrument. Before the throttle (Figure 5B), there is a pipe no less than 5D in length. It is to occupy the length of the straight pipe, just to say between the two flanges. The distance is obviously unreasonable, and it lacks the proper number of tests to verify.

4) Rectifier-type flow meter: A company in Tianjin, China in 2008 conducted nearly a year of research and development, testing, and its structure is different from the balance of the United States A Flowtek company. Test data shows that when the straight section is 2D, the accuracy can reach ±1%. If it is 5D, the accuracy can reach ±0.3%. The value of β is recommended to be between 0.5 and 0.65.

5) Various types, performance is difficult to distinguish. The above throttling flowmeters (adjustment orifice plate, balanced type, and rectification type...) all have simple and reliable structure, simple and easy to process, and have a low requirement for the straight pipe section before use and maintain high The advantages of accuracy. It is still difficult to say which product has a significant advantage and is proud of it, let alone a unique one.

In the past seven or eight years since the key to popularization and application, the new type of throttling flow meter has developed rapidly. With the hype of manufacturers, it has greatly replaced the trend of standard throttling meters. But it is still a new thing in the end, lack of experience in research and development, production and application, disorderly production and abuse is bound to lay hidden accidents, (2005 Dalian cone accident should be a lesson from the past). This type of speculation has attracted the worries of industry experts in the pursuit of profiteering. It is necessary to formulate standards as soon as possible on the premise of affirmative innovation. The following recommendations are made for this purpose:

1. The standardization of throttles optimizes the various “porous orifice” chokes that are currently being introduced. This is the only way to simplify test items.

2. Accumulation of Test Data Standards The development of standards for throttling flow meters took decades and accumulated thousands of data from laboratory tests to establish standards. Must not be arbitrary, behind the door to establish standards, must be based on the test.

3, the impact of resistance test test must first be carried out in the standard laboratory, and then need to use different data in different resistance parts, different length of installation, to illustrate the length of the straight pipe to ensure a higher degree of accuracy.