1、 Product usage and scope of application

This patented product - annular orifice plate is suitable for various fluid (gas, steam, liquid) media, such as saturated steam, superheated steam, compressed air, various types of coal gas, furnace exhaust gas, cooling water, heavy oil, residue oil, fuel oil, condensate, various corrosive chemical solutions, etc. In addition to the simple structure, firmness, and easy installation and use of standard orifice plates, it also has the following advantages:
(1) More suitable for measuring saturated steam, superheated steam, as well as dirty fluids such as gas and cooling water
The pipelines that transport water vapor often contain impurities such as rust, while gas and cooling water pipelines contain more impurities. Due to the fact that the impurity flow rate is lower than the main flow rate and flows close to the inner wall of the pipe, if a standard orifice plate is used to measure its flow rate, the impurities will settle and accumulate in the upstream and downstream of the orifice plate due to the flow in the middle and obstruction at the periphery of the orifice plate. This not only affects the flow velocity distribution of the fluid passing through the orifice plate, but also blocks the pressure tapping hole in the stagnant area, affecting normal operation; The structure of blocking in the middle and surrounding circulation of this product ensures that impurities are unobstructed, without affecting the flow rate or easily blocking the pressure tapping holes in the smooth flow area, thereby improving measurement accuracy and work reliability, and reducing the maintenance workload of instrument workers.
On the other hand, the steam pipeline cannot avoid stopping the steam, and the steam condenses into water. For the standard orifice plate, the structure of "middle circulation and peripheral obstruction" causes the condensed water to accumulate on both sides of the orifice plate (the "drainage holes" on the orifice plate are small and easy to block, and cannot work). When passing the steam, the accumulated water before and after the orifice plate must be carried away by the steam in order to generate the correct static pressure difference before and after the orifice plate. This process can take several tens of minutes, resulting in significant measurement errors, especially when the steam is frequently stopped, the error can reach more than 50%.
For this product, the special structure of the annular orifice plate with "peripheral circulation and intermediate obstruction" allows the condensed water formed by steam to flow away in a timely manner when the steam is stopped. When the steam is restarted, it quickly generates the correct static pressure difference before and after the orifice plate, without additional errors caused by steam stoppage. Therefore, it can be said that this product is more suitable for measuring saturated steam and superheated steam than standard orifice plates, especially in situations where steam is frequently stopped.
(2) More adaptable to flow measurement of high temperature and high pressure fluids
High temperature fluids, such as steam, gas, high-temperature air, or fuel oil, when using ordinary orifice plates, the periphery of the orifice plate is fixed in the groove of the ring chamber or flange. Often, the temperature expansion coefficient of the orifice plate (made of stainless steel material) is greater than that of the groove (made of carbon steel material). The orifice plate assembled at room temperature works at high temperatures, and the expansion amount of the orifice plate is greater than that of the groove, while the outer periphery of the orifice plate is restricted. The excess expansion amount can only be accommodated by the deformation of the inner hole of the orifice plate (forming a horn mouth), and the shape of the inner hole of the orifice plate is destroyed, significantly changing the outflow coefficient and affecting measurement accuracy.
The two sides of a regular orifice plate play a sealing role at the same time. When measuring high-pressure fluids, high requirements are placed on the sealing surface of the orifice plate. Sometimes, a lens pad orifice plate is also used, which increases the price of this throttling device exponentially. The replacement of seals during each maintenance greatly increases the maintenance cost and burden on users.
The patented product - a circular orifice plate for measuring high-temperature fluids, has a free state around the measuring plate, and the temperature expansion only changes the external dimensions (which can be accurately calculated), without changing the edge sharpness and shape. Therefore, it does not change the outflow coefficient and does not affect the measurement accuracy. When measuring high-pressure fluids, the measuring plate is located inside the pipeline and is independent of the static pressure, resulting in low processing costs; Only the size, material, and welding form of the pipes and flanges need to be considered, so it will not significantly increase the product price. The price of the annular orifice plate used for high pressure is lower than that of the high pressure standard orifice plate of the same specification.
(3) More reliable and accurate in measurement compared to circular and eccentric orifice plates
In the past, people commonly used circular orifice plates and eccentric orifice plates to measure dirty fluids. These orifice plates cannot reduce the possibility of pressure tapping hole blockage, and due to low machining accuracy and difficulty in achieving geometric similarity, the measurement accuracy is not high. The annular orifice plate is not only less likely to block the pressure tapping hole, but also, due to its simple geometric shape, can be precision machined and assembled, making it easy to improve measurement accuracy. From this, it can be seen that this product can completely replace circular hole plates and eccentric hole plates.
(4) Produce corrosion-resistant types at a lower cost and measure the flow rate of corrosive fluids
Due to the special structure of this product, materials with strong corrosion resistance (such as plastic) can be used, with low cost and a wide range of temperature and pressure adaptability. In some situations where the flow rate variation range is not more than 4 times, the price of using an electromagnetic flowmeter is too high. Therefore, the corrosion-resistant annular orifice plate of this product can be selected.
(5) Due to its simple external shape, this product is easy to make into a jacket insulation type
Passing steam inside the jacket can prevent the measured fluid (such as heavy oil, residual oil, etc.) from condensing or adhering in the measuring pipe section; By using coolant, it can prevent easily vaporized liquids from forming a gas-liquid two-phase flow (such as liquid ammonia) when passing through the flow plate. In terms of structure, it is simpler, cheaper, and has more specifications than metal tube rotor flow meters.
(6) Adopting a pressure equalization ring structure reduces the sources of measurement errors
The differential pressure transmitter is introduced by taking the average static pressure of the cross-section of the pressure tube at the upstream and downstream of the flow plate, which reduces the influence of velocity distribution distortion caused by local resistance in the upstream on accuracy, and the actual accuracy is closer to the basic accuracy.
(7) Lower requirement front and rear straight pipe sections
The throttling element (annular orifice plate) itself has a measuring tube, which is better than welding the standard orifice plate directly to the process pipeline, welding slag easily entering the tube, or both having a joint to generate disturbance vortices. Generally, the first 3DN and then 2DN can meet the measurement requirements. If there is a 90 ° bend or half open valve upstream, at least 5DN and 3DN equal diameter straight pipe sections should be maintained to improve measurement accuracy. In the 1930s, American scholar Howell first proposed that in the 1960s, the National Engineering Laboratory (NEL) in the UK conducted some experiments on it. The experimental data showed that under severe rotational flow, the outflow coefficient of the standard orifice plate changed by 25%, while the variation of the annular orifice plate was less than 1%. This indicates that the annular orifice plate does not require a long straight pipe section and can work under harsh pipeline conditions. This is another major advantage of the annular orifice plate, in addition to its ability to work in dirty gas media.
(8) Adopting an integrated structural form to reduce pipeline laying
The integrated annular orifice flowmeter is a flowmeter that combines an annular orifice throttling device with a differential pressure transmitter. It not only brings great convenience and benefits to installation, but also eliminates the need for users to lay installation pipelines and is less prone to malfunctions: simple installation, compact structure, and low maintenance. Equipped with an intelligent differential pressure transmitter, the range can be easily adjusted with the help of a "manual controller". By using digital communication, the range can be expanded to 1:13.
Note that during installation, if the measuring medium is gas, the meter head should be installed facing upwards. If the measuring medium is liquid or vapor, the meter head should be installed below.
(9) By using a differential pressure transmitter with a remote transmission membrane box, the flow rate of dirty fluids such as coal powder and residual oil can be measured