The zero point of the Yokogawa mass flow meter is unstable
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Recently, the company purchased a Yokogawa mass flow meter, model: RCCT38-AH108A1SL/KF1/1E1. It was found that the zero point is not very stable when in use. Sometimes it can return to zero, but other times the flow rate fluctuates by a few kilograms per minute; in some cases, this fluctuation can range from ten to over thirty kilograms per minute. Our process is used for measuring the cumulative flow of materials in batches; an unstable zero point can result in either too much or too little material being delivered, which is a serious problem. After performing the zero-point calibration according to the instructions, the situation remained the same; the pipeline supporting the flow meter is separate as well, and there are no significant vibration sources in the vicinity. After sampling each batch, the pneumatic ball valves before and after the pump and flow meter are closed, which helps to rule out process-related issues. The operating conditions of the material are as follows: Medium: slightly viscous liquid; Temperature: room temperature; Inlet pressure: 2 kilograms; Outlet pressure: atmospheric pressure. After checking it, the sales representative from Yokogawa also said that there was no problem with the installation, but due to his limited expertise, he was unable to identify the specific issue. It’s been over a month and a half since they said they would send technicians over, but there’s still no news. Low-flow cutoff for the flow meter: 10 kg/minute, with a typical operating flow rate of 300 kg/minute. There are also three E+H 80I series mass flow meters in the same section; the cut-off value for low flow rates is 5 kg/minute, and no issues with zero-point instability have been encountered. I would appreciate it if fellow sailors could help analyze what the problem is. Furthermore, if the low-flow cut-off value is increased to 30 kg/minute, what impact will it have on the cumulative flow error?
Since your normal flow rate is 300 kg/minute, setting the signal cut-off at 30 Kg/minute shouldn’t present too much of a problem. However, this won’t solve the issue fundamentally; it’s necessary to check whether there are problems with the meter installation or fluctuations in the process medium, such as bubbles, incomplete filling of the pipe, or vibrations at the site. Because sometimes it can return to zero, the gauge is basically fine; and any fluctuations in the gauge’s readings on site are not due to signal interference (grounding issues of the gauge casing are not considered as such)
The instrument is installed vertically, the medium is fixed, and the pipeline remains full at all times. It seems that the likelihood of zero drift is higher after the instrument has been out of use for some time, and once the first sampling is completed. E+H’s 80I is a single straight tube, while Yokogawa’s model has an Ω structure.
Personally, I think a flow rate of 3–15 KG per minute is reasonable for partial resection; if it is used again after a period of time, could this be caused by the formation of bubbles?
Was the salesperson who came from Yokogawa itself or from Yokogawa in Shanghai? Overall, however, there aren’t many people in Yokogawa’s sales team who understand quality, as it isn’t the main focus of their business. I feel like you might have chosen a size that’s too large? 300 kg/m equals only 18 tons per hour; therefore, a size of 38 was chosen.
This post was last edited by zxg.wylton on 2011-7-25 08:17. Straight pipes have good seismic resistance, but low precision. In terms of structure, bent pipes have high precision. The flow meter isn’t very heavy, so it’s easy to remove it in order to check for any dirt; it’s best to rinse it with steam or something similar. It can only be said qualitatively that neither the installation stress nor the operating stress of the pipeline should be too high.
I’ve been on a business trip these past few days; once I return, I’ll disassemble the flow meter and reattach the pipes at both the upstream and downstream ends to give it a try. It works well sometimes and poorly at other times, which is puzzling. After installation, when no low-flow cutoff was applied, the pipeline was filled with stationary material. After remaining unused for over a day, the flow meter’s reading kept changing by a few kilograms per minute; however, after pumping material through it once, the flow meter’s reading returned to zero.
The current flow rate is indeed a bit low; when the process requires it, we plan to increase the flow rate to 600 kg/min