The function of the pressure transmitter is to measure the liquid level, density, and pressure of liquids, gases, or vapors. The pressure signal is then converted to a 4-20 mA DC signal output for measurement by secondary instruments such as alarm meters, recorders, and regulators. , instructions and process adjustments.
When the customer bought back the pressure transmitter installed in the field, the pressure and differential pressure transmitter reflected the phenomenon that the process parameters were incorrect: There were problems with the pressure tube plugging, throttling device, condensation tank, and pressure tube installed. The normative issues, electromagnetic interference problems, maintenance problems, and so on. Because many flow, liquid level, and pressure of our factory are involved in automatic control, some pressure and differential pressure also participate in the shutdown control. If the measurement accuracy is not high, it not only affects the accuracy of automatic control. It will also affect the stability of production. This puts forward higher requirements for the accuracy and stability of our metering measurement.
Here are some of the main problems encountered in the use of pressure transmitters produced by our company:
First, the installation problem
In steam flow measurement, steam mainly involves two kinds, one is external steam supply, and the other is superheated steam of boiler. External steam supply is steam after desuperheating and decompression. The temperature is not high, and a large amount of water is added. It is not used when it is needed, and the steam flow rate is changed according to the user's requirements. In the actual flow measurement process, sometimes the flow is too large sometimes the flow rate is small, very unstable, often need to carry out the sewage, the transmitter after each sewage discharge measurement is accurate, but the steam pipe discharge more times, and easily lead to Steam leaks at each contact point on the pressure pipe. In measuring the use of superheated steam, the biggest problem was found to be shutdown, which caused a deviation in the flow rate after restarting, resulting in inaccuracies, and sometimes there was still a slight flow after stopping. The general transmitter installation position is lower than the measuring pipe. However, in the actual installation, the condensation tank and the transmitter outside the steam flow rate are higher than the measurement pipeline, and the pilot pressure pipeline that is laid down from the throttle device and is laid down at least 1 meter is too short. The superheated steam flow rate of the boiler also has the problem of inconsistent height between the condensing tank and the measuring pipeline, resulting in unbalanced condensate height and static pressure difference.
Second, the pressure tube plugging problem
In pressure measurements, sometimes the indicated pressure does not change with operating conditions. After the sewage valve is opened, there is only a small amount of sewage, and no water flows out. This is because the water quality or compressed air will have a small amount of floating dust and will enter the pressure tube as the water flows. Over time, the wall of the pressure tube will corrode and foul.
Third, the transmitter device itself failure
In the measurement of lubricating oil pressure, the lubricating oil pressure signal participates in the stop interlock control. The signal measured by the lubricating oil pressure transmitter is transmitted to the computer and displayed on the one hand. On the other hand, the signal is also compared through the program. When the pressure is lower than 0.06 MPa, an out-of-oil shutdown signal is sent out to stop. The sudden drop in lubricant pressure caused by the 1# machine caused a tripping accident and the loss was huge. From the lubricating oil pressure signal trend chart, we can see that the pressure is a straight line drop and cause tripping. After checking the transmitter, the internal module of the transmitter is found to be damaged. Although we conduct regular verification of the transmitter every year, the test is qualified for production. Since the transmitter has been running for several years, its accuracy, sensitivity, stability and other performance indicators will gradually decrease, and the internal diaphragm and integrated block will also be damaged and malfunction.
Fourth, there is interference problem
In the measurement of the compressor discharge pressure, the exhaust pressure signal fluctuates greatly. After verifying the transmitter, it meets the accuracy requirements and eliminates the fault of the transmitter itself. Check that the pressure-transmitting tube and the connector are not damaged or leaking, and the connection of the signal cable is in good contact. But the direction of the cable is introduced into the control room through the cable tray next to the high distribution room. There is a lot of electromagnetic interference around.
Commercial Vehicle Filter Assembly
In order to make the lubrication system oil flow unimpeded, avoid impurities scratch, hair parts surface, oil before sending to the friction surface, must be strictly filtered. In order to achieve satisfactory filtering effect without increasing oil resistance, the coarse filter is generally connected in series with the main oil channel, and the fine filter is connected in parallel with the main oil channel.
1. Float type oil filter, in order to make the oil pump work well, the large particles and impurities in the lubricating oil must be removed before entering the oil pump. This task is undertaken by the filter. It is connected to the oil inlet of the oil pump. When the oil pump works, the oil is sucked from the narrow gap between the cover and the float. After filtering through the filter screen to remove the coarse impurities, the oil pipe welded on the float enters the oil pump. When the filter is silted up, the suction of the inlet pipe increases, overcoming the strong force of the filter and making the bad mouth leave the cover, the oil will enter the suction pipe directly from the ring without the filter.
2. The coarse filter is connected in series between the oil pump and the main oil channel, so it is also called the full flow filter to remove the larger impurities in the oil. It is mainly composed of upper cover, shell, paper filter element and bypass valve. When the engine is working, the lubricating oil with pressure is sent into the cavity around the filter core. The larger impurities in the oil are blocked by the paper filter core, and the clean lubricating oil enters the inner cavity of the filter core, and then enters the main oil channel of the cylinder block through the oil outlet.
3. Fine filter: its function is to filter out smaller impurities in lubricating oil, usually in parallel with the main oil channel, there are two kinds of centrifugal and paper plate.
4, the structure of centrifugal fine filter: the hollow shaft is fixed on the shell, the rotor body and the end sleeve are connected into one, located on the thrust bearing, can rotate freely around the rotor shaft. The rotor cover is fastened to the rotor body by a pinch nut, which is pressed with a spring to limit the axial movement of the rotor. Two opposing nozzles are installed below the rotor. When the engine is running, a small part of the oil is pumped out from the oil pump and enters the filter through the oil port. When the oil pressure is lower than 9s kpa, the intake pressure limiting valve closes and the fine filter does not work. When the oil pressure exceeds 98 kpa, the pressure limiting valve gradually opens, the oil through the central hole of the rotor shaft, from the oil outlet hole. Then through the oil hole into the rotor, and from the two nozzles ejected, then the jet reaction force is to push the hand rotation. When the oil pressure rises to 294 kpa, the rotor speed can reach more than 5000r/min, the proportion of impurities in the lubricating oil in the rotor cavity is larger than that of the lubricating oil, under the action of rotating centrifugal force, is thrown to the rotor wall, and attached to the wall cover. The center of the clean lubricating oil, from the center into the two nozzles, constantly to the outside of the jet, the jet of lubricating oil flow back to the lower crankcase. [1]
Commercial Vehicle Filter Assembly,Vehicle Filter Assembly,Car Filter Assembly,Filter Assembly
Ruian Guangzhong Auto Parts Co.,Ltd , https://www.greatfil.com