Issues regarding the gasification black water flow meter
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I work at a gasification unit (a space furnace), and there are several black water flow meters in that section that frequently malfunction (the flow control elements include Venturi types and orifice plates; the transmitters used are Yokogawa double-flange type ones). This is a real headache, as these black water flow meters are equipped with flushing water systems. The diameter of the pressure tapping hole is approximately 8 MM. Common issues with these flow meters include fluctuations in readings, which may be too high or too low. Sometimes, turning on the flushing water for a short time and then turning it off resolves the problem; however, the flushing water should not be kept on continuously, as its pressure is relatively high. Given the small diameter of the pressure tapping hole in the flow meter, turning on the flushing water results in infinite positive or negative readings. The failure rate is also quite high; it needs to be rinsed almost daily, and repairs are very troublesome. Does anyone here work in gasification? How are your black water flowmeters cleaned? What is the diameter of the pressure tapping holes, and how is the flushing water controlled? Please help
Since a flushing ring is provided, it needs to be flushed regularly. When selecting a flow meter, it is possible to take into account the characteristics of the medium and opt for types such as vortex flow meters, electromagnetic flow meters, and ultrasonic flow meters, which require less maintenance. The owner’s situation can be used as a basis for technical upgrades; start by modifying one unit, and once the results are satisfactory, gradually roll out the changes to other units.
This post was last edited by Hasty Passer on June 9, 2018, at 18:31. The stable operation of the gasification black water flow meter depends on the flushing water. Firstly, the flushing water must be supplied continuously, but in small quantities; this is because once the flushing water is added, the direction of liquid flow becomes toward the flow meter； The second suggestion is to change the location where the flushing water is introduced: it is usually added from the flushing ring, and prolonged flushing can cause damage to the transmitter diaphragm or reduce its lifespan. A standard differential pressure transmitter is used, and flushing water is introduced near the three-valve manifold of the transmitter. The pressure guide pipe and the flushing pipe should not be connected at a 90-degree angle; instead, the flow direction of the flushing water should be toward the flow meter. After such modification, normal operation will not be affected, but the cycle time will be significantly extended.
The medium in coal chemical industry wastewater is very dirty, and it tends to form scale due to high temperatures and pressures. For applications with high pressure, custom large-diameter wedge flow meters are used, while electromagnetic flow meters are employed in those with lower pressure; the pressure of the washing water is also a concern
Rinsing ring – a scourge of mankind; rinsing water – a disaster for humanity. “The diameter of the pressure tapping is approximately 8 mm”? Oh no, it’s that idiot – why go to such lengths? . . . SB’s ass is also way bigger than 8mm, damn! Go away, go and use the big drill right away – drill away, so that the idiot can pass big stools. Last time, a member mentioned that the lower part of the Venturi flushing ring was blocked; after making modifications by cutting away that lower part, the blockage was resolved. That area is the least likely to get clogged; drilling there to take samples of pressure is the best approach. . .
1. The pressure tapping pipe diameter is too small; it should be DN18 or larger； 2. The flushing water should enter from the horizontal direction of the diaphragm ； 3. To prevent blockages, the pressure tap for the black water flow meter should be positioned at an upward angle; although this does not comply with standards, it is necessary in the coal chemical industry. After making this adjustment,ほとんど maintenance is no longer required! 4. The diaphragm gauges related to the gasification furnace generally become unusable after four to five years due to abrasion, erosion, hydrogen penetration, and changes in pressure during startup and shutdown.
Our pressure tapping pipe is DN50
First, you take port 8, which has a flushing ring – how do you install the flushing ring? There’s an issue with the expression! The design should be fine. I have two options for you: one is that if the pressure measurement is 14 for a non-transmitted differential flow measurement, adjust the rotameter located before the flushing device; keeping it on should not affect the measurements. Another option is to use a flow meter with a remote differential pressure transmitter, one whose pressure tapping size is 50; flushing it should not have any impact
There is a relatively straightforward solution: by changing the flushing water system to a timed flushing control system (with the timing adjustable), the problem can be resolved. Our unit has used this timed flushing control technology, and the results have been good. Since it is a low-flow flushing process, the pressure tapping port should not be large; a smaller diameter actually yields a better flushing effect. In fact, this transmitter can operate for a long time. I generally use ordinary differential pressure transmitters instead of double-flange transmitters, and there are mainly three reasons for this: 1) Ordinary differential pressure transmitters are cheaper than double-flange transmitters ； 2. Installation, maintenance, and replacement should be simple ； 3. Higher reliability (including lifespan).
Keeping the flushing water flowing will inevitably affect the accuracy of the measurement values; no one can guarantee that the pressure exerted by the flushing water on the two diaphragms will be exactly equal, or that the difference between them will remain constant.
Perform timed flushing or modify it to a wedge shape~~