Analysis of the reasons for the fluctuation in the Rosenmont 3051 pressure transmitter? Request for additional information
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Problem description: Recently, the Rosemount 3051 transmitter on the company’s oil pipeline has been experiencing fluctuations. The time between each transition is not fixed and follows no pattern; these transitions can reach high alarm levels, resulting in the interlock shutting down the pump and affecting production. The pressure transmitters on the unit are all installed vertically directly above the pipeline, while the transmitters that detect pressure fluctuations are installed at the pump outlet or the main pipe outlet. But not all pressure transmitters at the pump outlet or main pipe outlet experience a jump. Replacing the faulty pressure transmitter results in stable operation for a while, but the fluctuations still occur. Solutions tried: 1. Interference in the wiring was suspected; after measurement with instruments, no interference was found, the grounding was proper, and the cable resistance from the field site to the control room was within normal limits. (Therefore excluded) Exception: if it’s a interference issue, does the fluctuation occur continuously, rather than happening at intervals before resolving on its own? 2. The system cards and channels were suspected to be the issue; after testing and replacing the channels as well as the cards, the glitches continued to occur. (Therefore excluded) 3. Remove the front and rear covers of the pressure transmitter; after removing the front cover, try pressing or tapping on the LCD screen with your hand – the numbers will appear intermittently or even show garbled characters. Tighten the fixing screws; tightening them too much will result in a reading of zero, and the value within the system will also drop to zero. While tightening the screws, the LCD display will fluctuate, and the system screen will also change. Furthermore, the transmitter was disassembled; the two signal copper wires connecting the front and rear panels were thickened using solder. After reinstallation, no glitches have occurred for now, and the situation is under observation. It is temporarily suspected that oxidation of the signal copper rod inside this transmitter is to blame, and the vibration in the location where it is installed is causing poor contact, which leads to voltage fluctuations. There are a few things I don’t understand right now; I’d like to hear what others think. 1. If poor contact is caused by vibration, this issue has not occurred over the ten-odd years that the entire system has been in use. All the pressure transmitters are installed in the same locations, and only a few of them experience fluctuations. If it’s the pump outlet that experiences significant vibration, and there are several pumps, each equipped with a pressure transmitter, will only some of those transmitters show fluctuations? 2. The books I read before all talked about liquid transfer, and it was stated that instruments should not be installed directly above the pipes. I asked the experienced workers at the factory, and they said that this is the standard way of installation; it has been used for over a decade without any problems. They also said that the pipes are almost always filled with liquid, so this doesn’t cause any issues. 3. Is the Rosenmont 3051 effective at reducing vibration?
Rosemount has a jumper; that is, if the transmitter fails during self-diagnosis, the default setting at manufacture is to use the maximum value, which seems to be 21.6 Ma. You can set this jumper to output a fault value at the minimum level, which seems to be 3.6 Ma. This can rule out the possibility of a header malfunction.
The stability of the 3051 transmitter is good; I think the issue lies in the installation on site – excessive pipeline vibration and high-frequency vibrations can, over time, lead to poor contact between the internal contacts. This is because the transmission module, power supply module, and display module inside the 3051 transmitter all use pins or contact points for connections. Extend the down-taking pressure tube and try fixing the transmitter to a separate pillar.
If the vibration is severe, it can be adjusted by lengthening the pressure transfer tube, which can serve as a damping mechanism; installing the gauge below the pipeline also makes maintenance easier. For materials that crystallize easily, insulation and heating should be provided. It worked fine before, but now there are problems; it’s possible that the vibration generated by the pump itself during discharge is greater than before, so we need to adjust our instruments as well.
Based on the owner’s description, the transmitter that was having problems continued to function for a while after being replaced before experiencing fluctuations again. I believe the issue lies not with the transmitter itself (unless it’s of poor quality, but Rosemount transmitters are of good quality). It’s likely that the problem is related to the installation location – there might be intermittent vibrations at that site, so it would be worth trying to install the transmitter in a different location to see if that resolves the issue.
Based on the description, it should be poor contact caused by vibration. The poster can find a way to add metal hoses to avoid pipeline resonance
Take down the transmitter, use a pressure pump to apply pressure and maintain it for a while – then you’ll know whether it’s a problem with the transmitter or not
It’s to take it down, not to look it up; there was a typo
Well, it was later determined that the issue lay with the transmitter; the exact cause of damage to this transmitter isn’t yet clear. Can excessive vibration cause the transmitter to get damaged? Is the quality still poor? I replaced the transmitter at the same location with a new one; after some time, fluctuations occurred, and then the sensing part of the transmitter was damaged. It didn’t respond when pressurized. Upon removing it, I saw many small pits on the surface of the diaphragm – could this be the cause of the problem? The diaphragms of other position transmitters that experience jumps do not exhibit this phenomenon. I also learned something about the inspection methods you suggested; thank you.
Well, it was later determined that the issue lay with the transmitter; the exact cause of damage to this transmitter isn’t yet clear. Can excessive vibration cause the transmitter to get damaged? Is the quality still poor? I replaced the transmitter at the same location with a new one; after some time, fluctuations occurred, and then the sensing part of the transmitter was damaged. It didn’t respond when pressurized. Upon removing it, I saw many small pits on the surface of the diaphragm – could this be the cause of the problem? The diaphragms of other position transmitters that experience jumps do not exhibit this phenomenon. However, I’ve also learned something new about the inspection method you suggested; thank you.
The solution I’ve proposed to my supervisor is the same as what you mentioned; we’ll wait to see the results of the discussion at the meeting, as this change involves a significant amount of work. Also, the managers always say that this problem doesn’t occur elsewhere; it only shows up here. If there’s an issue with the installation method, then fluctuations will also occur in other places. . . . This leaves me speechless. . . .