The sensor of Fuji FCX-series smart transmitter is a silicon micro-capacitance type, which converts the measured parameters into electrostatic capacitance, and then obtains the measured differential pressure or pressure value by measuring the silicon capacitance.
Answer: The wet temperature of the fuji flange transmitter is mainly determined by the properties of the filling liquid in the flange diaphragm. When the temperature of the measured medium exceeds the upper limit of the rated liquid temperature of the instrument, two situations will occur.
1) The volume of the filling liquid expands or even evaporates due to heating. If the expansion is too large and the pressure exceeds the allowable value, the isolation diaphragm will be permanently deformed, and the filling liquid will be squeezed out from the joint and the weld.
2) The filling fluid is an oily substance that contains more or less gas in it. In addition, the closed system before filling can not be pumped into absolute vacuum, and there is gas. Although they are small in amount, due to the large thermal expansion coefficient, if the temperature is too high, the isolation diaphragm will also be permanently deformed. To sum up, if the temperature of the measured medium exceeds the upper limit of the rated range of the instrument, the technical performance of the instrument will be changed in the lighter case, and the instrument will be damaged in the severe case. Therefore, when purchasing an instrument, it must be considered that its wetted temperature cannot be lower than The maximum temperature of the measured medium.
If the temperature of the measured medium is lower than the lower limit of the rated temperature of the instrument, the filling liquid will freeze and cannot move. In this way, when the pressure of the measured medium changes, the output change of the instrument will be relieved or even unchanged. But generally the instrument will not be damaged, when the temperature of the measured medium returns to normal, the instrument will work normally again.
Answer: No, if the fuji flange transmitter works at high temperature, the volume of the filling liquid in the flange diaphragm box will expand. If the filling liquid is mixed with air during the filling process, since the expansion coefficient of the air is much larger than that of the filling liquid, the volume expansion will be more severe, so that the outer drum of the isolation diaphragm will be seriously deformed or even permanently deformed. However, if the pressure of the measured medium is very high, they act on the isolation diaphragm, so that it cannot be drummed, so even if the temperature of the measured medium is higher, it will not affect the instrument. Therefore, the two parameters of pressure and temperature are related. Both high temperature and high vacuum cause the greatest harm to the instrument, otherwise they can cancel each other out. The two parameters of 0.13KPA abs and 300°C mentioned in this question cannot exist at the same time. If the instrument is to work at 300°C, the working pressure cannot be negative and must be above atmospheric pressure. If the instrument is to work under a high vacuum of 0.13KPa abs, the temperature must be much lower than 300°C.
Answer: Because the P meter in the atmosphere = P absolute - P0 (atmospheric pressure), if the pressure gauge is moved to a vacuum, the absolute pressure is measured, then P absolute = P meter + P0, so the pressure gauge indicates an increase.
7. What are the operating steps for the initial start-up of the differential pressure transmitter for measuring steam flow?
A: You should follow the steps below:
1) Check whether each cutting door, pressure guiding pipe, union, etc. are firmly connected;
2) Check whether the secondary cutting and sewage cutting are closed, and whether the balance cutting is open;
3) Open the cutting a little, and then check the pressure guiding pipe, cutting door, union, etc. If there is no leakage, open the cutting all the way;
4) Turn on the sewage felling respectively, and close the sewage felling after the sewage is discharged;
5) Unscrew the plug of the differential pressure chamber to remove the air in it;
6) The differential pressure transmitter can be started only after the pressure guiding pipe is filled with condensed water;
7) To start the differential pressure transmitter, press to open the positive pressure valve, close the balance valve, and open the negative pressure valve.
8. What is the zero point adjustment and zero point migration of the pressure or differential pressure transmitter?
Answer: Zero point adjustment: refers to the zero point adjustment when the input pressure or differential pressure is zero, but the output is not zero; Zero point migration: refers to the adjustment of the output to zero when the input pressure or differential pressure is not zero.
9. There are static pressure, dynamic pressure and total pressure. What is the relationship between them? What pressure does the pressure change measure?
Answer: total pressure = dynamic pressure + static pressure, the pressure change is static pressure.
10. Describe the correct pressure-taking position of liquid, gas and steam pressure measuring instruments?
Answer: When measuring gas: In order to make a small amount of condensate in the gas flow back to the process pipeline smoothly, instead of flowing into the measuring pipeline and the instrument, the pressure-taking port should be in the upper half of the pipeline; When measuring liquid: In order to let the liquid A small amount of gas precipitated in the inside can be returned to the process pipeline smoothly without entering the measuring pipeline and the instrument. There is stable condensate in the pipeline, and it also prevents the solid medium at the bottom of the process pipeline from entering the measuring pipeline and the instrument.
11. Explain the meaning and relationship of absolute pressure, atmospheric pressure, gauge pressure and vacuum degree.
Answer: The pressure under absolute vacuum is called absolute zero pressure, and the pressure expressed on the basis of absolute zero pressure is called absolute pressure. The gauge pressure is the pressure expressed on the basis of atmospheric pressure, so it is exactly 0.1MPa different from the absolute pressure by one atmosphere. If the absolute pressure of the measured fluid is lower than atmospheric pressure, the pressure measured by the pressure gauge is negative pressure, and its value is called vacuum degree. Absolute pressure = atmospheric pressure + gauge pressure.
12. What are the characteristics of the smart transmitter?
Answer: 1) The temperature characteristics and static pressure characteristics are greatly improved;
2) High precision;
3) The adjustable range ratio is large;
4) With remote control setting function;
5) It has self-diagnosis function.
13. Is there any relationship between reading the input signal of the smart transmitter with the communicator and the setting range of the transmitter?
Using the input signal, the static pressure error of the transmitter can be detected. Can the change trend outside the measurement range be observed?
A: It doesn't matter; you can.
14. What is the HART communication protocol? What is DE communication protocol?
Answer: HART protocol: The digital signal is superimposed on the analog signal, and the two can be transmitted at the same time. DE protocol: The digital signal and the analog signal are transmitted separately. When the digital signal is transmitted, the analog signal needs to be interrupted.
15. What is the damping of the transmitter?
Answer: That is, the response speed of the output of the transmitter with the change of the measured parameter.
16. Why is the accuracy of flange transmitters lower than that of ordinary transmitters?
Answer: Because the flange transmitter has one more remote flange membrane box and one more conversion link than the ordinary transmitter, the error increases the conversion error of the flange membrane box on the basis of the original error.
17. What are the two types of pressure switch contacts? Answer: Normally open and normally closed
18. What is the difference between flange transmitter and ordinary transmitter?
In an ordinary transmitter, the measured medium enters the transmitter measurement chamber through the pressure guiding pipe. If the measured medium is a viscous liquid, the pressure guiding pipe is easily blocked. Now use the capillary instead of the pressure guiding tube, and the blockage phenomenon will not exist. Because the capillary is sealed, the filling liquid in it is selected, and the chemical and physical properties are stable. It is not easy to freeze and vaporize like the medium in the pressure guiding tube, so it is not necessary to fill the isolation liquid like ordinary transmitters. Install auxiliary equipment such as isolators and condensers. In this way, the measurement accuracy can be improved and the maintenance effort can be reduced.
19. What is the composition and working principle of the smart transmitter?
Answer: Smart transmitter, it consists of two main parts: composite sensor and microprocessor. The composite sensor is to generate three sensors of differential pressure, temperature and static pressure on a single crystal silicon wafer by the diffusion process of integrated circuit. Complete accurate pressure and differential pressure calculation; then output 4~20mADC DC signal through D/A conversion
20. What is the range ratio of the transmitter?
Transmitter turndown ratio: maximum measurement range/minimum measurement range
21. What properties should the filling fluid in the transmitter capsule have? What is the difference between silicone oil and fluorine oil?
Answer: The bellows needs to be filled with filling liquid to transmit pressure. The requirements of the transmitter for the filling liquid are: small thermal expansion coefficient, no freezing at low temperature, no volatilization and no vaporization at high temperature, and its viscosity does not change due to temperature changes. There are major changes, so that the performance of the instrument can be stable. Usually the capsule is filled with silicone oil or fluorine oil. Silicone oil can be divided into low temperature silicone oil and high temperature silicone oil. The lowest temperature of low temperature silicone oil can reach -40℃, and the highest temperature of high temperature silicone oil can reach 315℃. According to the different operating temperature of the transmitter, use different grades of silicone oil. Fluorine oil is an inert liquid with inactive chemical properties, so it is used in transmitters for measuring oxygen or chlorine. Its operating temperature is between -45 and 250 °C, its viscosity is low, and its price is higher than that of silicone oil.
22. What is the degreasing treatment?
Answer: During the processing of the parts of the transmitter and the filling of the diaphragm box, it is inevitable to encounter substances such as grease. Degreasing treatment is to remove the grease in the bellows parts and the high and low pressure measurement chambers, so that they do not contaminate the measured medium. Degreasing treatment is often used in transmitters for measuring oxygen, chlorine or food and beverages. Because oxygen will explode in contact with oil, chlorine is also an active chemical element, and beverages cannot be contaminated, so the membrane box should be cleaned.
23. Can the flange transmitter with carbon steel flange be used to measure corrosive media? why?
Answer: The flange of the flange transmitter is not in contact with the medium, only the isolating diaphragm is the liquid contact surface, so as long as there is no corrosive gas in the surrounding environment, carbon steel flanges can also be used to measure corrosive media .
24. Are the upper and lower limits of the working pressure limited in the static pressure indicators of the flange transmitter? why?
Answer: The working pressure of the flange transmitter is limited by the upper and lower limits. But generally people only pay attention to its upper limit of use pressure, while ignoring its lower limit of pressure, thinking that any amount can be used. In fact, this is wrong. The lower limit operating pressure of the flange transmitter is also specified, and it usually cannot work in a negative pressure state, especially in a high vacuum state. In high vacuum, the outer drum of the isolation diaphragm is easily damaged, so it cannot be without restrictions.
25. The difference between absolute pressure transmitter and gauge pressure transmitter.
The absolute pressure transmitter measures the absolute pressure of the medium in the equipment, which has nothing to do with the atmospheric pressure, while the gauge pressure transmitter measures the pressure based on the atmospheric pressure, which is related to the atmospheric pressure. In terms of structure: the other side of the pressure measuring element of the absolute pressure transmitter is absolute vacuum, and the other side of the pressure measuring element of the gauge pressure transmitter is the atmosphere.
