【Weekly Question 20090713】Experience in maintaining mass flow rate

Looking at the questions posed by the original poster, it seems like they were meant only for on-site maintenance staff. The designers don’t even know how to answer your question.

It can also be said that it relates to your design experience – under what circumstances does your design firm recommend the use of mass flow meters!

Emerson Coriolis Oli split-type mass flow meter； F200 series with sensors and core processors, 24VDC1700 series of converters. Fault: When medium flows through the sensor, neither the on-site display nor the DCS display shows “0 Kg”. Check: The current at the output terminal is not 2.9 mA; this is abnormal ； The voltage of the core processor is approximately 14VDC, which is normal ； The output voltage of the core processor is 0 mV, which is abnormal ； Observe the core processor indicator light; its flashing is abnormal ； Upon closer inspection of the sensor junction box, there are signs of water. Based on the above observations and test results, it can be concluded that water entering the junction box caused damage to the core processor. Solution: Replace the core processor with one of the same specifications but from a different batch. New issue: A traffic indicator is available, but it’s only 1/10 of the empirical value. The regular configuration parameters of the converter were checked, and no abnormalities were found. When viewing the device details, it was found that the sensor configuration information did not match the actual device. After reconfiguring the sensor information data, the device returned to normal.

What are the solutions to the frequent malfunctions of the radar level gauge used for monitoring the level of the guide fluid, which is installed near the feed inlet? Solution: Install a protective sleeve on the existing director’s measurement rod; use a white steel tube with dimensions Ø57×3.5 as the protective sleeve, make symmetrical holes every 180° with a distance of 200 millimeters between each hole, and orient the side of the tube without holes in the direction of the feed inlet – this will resolve the problem.

Mass flow meters are chosen for use. Due to their high cost, we are generally cautious when selecting them. There are several situations in which a mass flow meter is chosen: 1. For trading purposes, where the unit price of the goods is high and high measurement accuracy is required. 2. For device evaluation. For example, at the export point of finished products and at the import point of raw materials. 3. Applications requiring high measurement accuracy. For example, in cases where the measurement results have a significant impact on the entire process. 4. The owner specifically requested the use of a mass flow meter. In other cases, other types of flow meters are generally selected based on the operating conditions. What was said upstairs about making holes every 180 degrees actually means that the distance between adjacent holes is 200 mm; a hole is also made on the opposite side of each hole. By \"every 180 degrees,\" it refers to holes being positioned symmetrically. I’m not sure if I understand correctly.

The data storage of Emerson’s Coriolis mass flowmeters is powered by microbatteries; therefore, a long power outage can result in data loss, so prolonged outages should be avoided. If there is a power outage and the device is used again, it is necessary to check the data once more.

We use Emerson’s Coriolis mass flow meters; once they are purchased, they are simply installed and left alone. No zero-point calibration is done before use, and so far they have never broken down, so we don’t have any experience with maintenance at all. Let’s first learn from everyone else’s experience

Type: Coriolis Olli. Brand: Schlumberger. Application area: Metering of propylene raw material. Fault description: The flow rate was significantly high and unstable. Solution description: It was suspected that the flow meter was damaged; after it was taken out of service, it was sent to a calibration facility where it was found to be functional and showing normal readings. Since the special cable that connects the sensor to the flow computer was not taken along when the instrument was removed, it was determined that there was a cable fault. After removing the cable and examining it, it was found that the insulation covering of the cable was damaged, exposing the shielding layer. When this cable was connected to the cable protection tube and then to the conduit and the ground, the shielding layer being already grounded at the flow computer caused a problem of two points of grounding for the shielding. After wrapping the damaged area of the special cable’s insulation with electrical insulating tape, the instrument displayed normal readings.

Application area of the process: feeding and discharging within the unit. Fault description: The flow meter remains constant at a certain value; the historical trend shows a straight line. Solution description: The manufacturer was consulted; the reason for the unchanged values could be vaporization of the medium being measured by the sensor. Since the measuring medium is always in liquid form, vaporization causes abnormal operation of the sensor. Normal operation was achieved after reducing the valve opening of the mass flow meter.

Type: Coriolis; Brand: Rosemount Alfa Laval mass flow meter; Location in the process: Reactor feeding; Description of the fault: During operation, the reading of the mass flow meter sometimes experiences jumps. Solution description: Later, the fluctuations in the indicated value were related to the vibrations caused by the startup of a nearby feed pump; after installing supports for the mass flow meter, the fault disappeared.