The liquid level in the atmospheric stripping tower fluctuates greatly when measured using buoys
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In our company’s atmospheric steam stripping towers, the liquid levels in lines No. 1, No. 2, and No. 3 were originally measured using double-flange differential pressure transmitters, which provided stable and accurate readings at temperatures around 350 degrees. However, due to the corrosive effects of sulfur and chloride ions present in the diesel medium, the diaphragms of these double-flange transmitters became corroded over time, forcing their replacement with float-type level gauges. Yet, these float gauges also gave unstable readings; the liquid level would fluctuate periodically, with significant variations that made it impossible to implement automatic control. Could you help analyze the reasons for this? Alternatively, if there are alternatives to double-flange transmitters, please suggest a cost-effective level gauge. Thank you.
1. The scanning time for this level variable can be increased on the DCS; for example, it can be changed from 1 second to 3–5 seconds before observing again. 2. If software filtering is available, add software filtering for this variable. 3. If this transmitter has a damping time adjustment, try increasing the damping time.
Is it due to excessive heating causing vaporization?
In terms of cost-performance, double-flange design is more suitable. When making a selection, it is necessary to consider the corrosion effect of the medium on the metal of the diaphragm box; the material of the diaphragm box must be chosen carefully, otherwise the outer diaphragm will get corroded after a short period of use, and the flanges will also be damaged, leading to equipment failures and safety accidents. Therefore, the choice of material is extremely important. The diaphragm materials for transmitters include ordinary stainless steel, 304 stainless steel, 316L stainless steel, and tantalum diaphragms; there is surely a suitable option available.
I agree with the opinion from the fourth floor. I was wondering what material the diaphragm of the double-flange differential pressure transmitters you were using is made of? Hastelloy or tantalum could be tried.
The question here is why the liquid level fluctuates significantly as measured by the float; the answers from floors 4 and 5 refer to the material of the diaphragm. Does the level fluctuate significantly with a double-flange differential pressure transmitter? When the liquid level fluctuates periodically, check what’s going on with the process
Buoy measurement should be fine; check the instrument installation.
It may be that the liquid level inside the tower is uneven and the liquid fluctuates, causing the float to become unstable. Apply the ultrasonic level gauge
This phenomenon does not occur when using a double-flange differential pressure transmitter; it might be due to the high temperature of the liquid, which causes boiling. The sound at the site suggests this is the case, but there is no water vapor present – diesel alone should not cause boiling. I consulted the process engineers, who were also unable to explain it. It seems that using a double-flange transmitter is the only option. Using a diaphragm made of Hastelloy should be fine. Thank you all for your help!
Guided wave radar can be used; many of our towers employ this technology. If there is no negative pressure, then a dual-flange differential pressure design should work just fine. Ultrasonic waves are not suitable if there is pressure