Seeking advice on using backflow wind to measure density

It should normally be 0; if it is not, there is a leak in the pipeline or the primary valve.

Yes, if the value must show as 0 after opening a valve once, then the calibration is correct. It is recommended to check whether the backflow pipeline leading to the inside of the reactor is unobstructed, as such pipelines can easily get clogged by ash.

Backblowing is also a rough pressure balance. . . Backblowing can’t measure the density of shit. That dog boy doesn’t believe it, :P. We can use a pool of water to conduct a simple experiment: 1. Keep the liquid level constant and test whether the reading on the pressure gauge remains stable while blowing air; observe this for 1 hour straight. 2. Change the liquid level and test again to see if the pressure gauge’s reading stays stable, observing once more for 1 hour. Hehe. 3. First, determine the actual fluctuation amount of the pressure gauge reading when air is blown in. 4. Then calculate the theoretical change in the pressure gauge reading that results from changes in density. 5. After that, compute the ratio of the actual fluctuation amount to the theoretical change amount, in order to find out how large the uncontrollable errors are when using air blowing to measure density. 6. Well, I guess that’s it; there’s nothing else to say :lol Hehe. Backflow also leads to a rough equilibrium in pressure. . . Backblowing can’t measure the density of shit. Identification completed.

Judging from your reply, it seems you’ve never even seen oil refining equipment, right? Backflow is only implemented to prevent ash from entering the pressure guiding pipe; do you think backflow can be used to measure density?

1. Oh~~~ I really have never seen it before. . . Just as I’ve never seen a fly give birth. . . I’ve seen maggots in septic tanks; they eat feces and can also swim :lol 2. Thank you! . It would be more appropriate if you first understood the original poster’s question before criticizing me. .

Theoretically, it should be zero in reality, as the gas is considered to have no pressure drop. However, in the backflow system used in catalytic cracking, the pressure tap pipes are more or less filled with catalyst, and in some cases the pipes are even completely clogged with catalyst. It is incorrect to assume that the value is zero just because it isn’t zero after closing the primary valve; the proper approach is to close the primary valve and then open the drain valve on the pressure tap pipe near the transmitter and purge it for a while. If there is a large amount of catalyst inside, it is necessary to open the flow control orifice valve to allow high-pressure air to purge the pipe. To prevent damage to the transmitter during this purging process, it is necessary to switch the three-way valve assembly, and it is also advisable to open the drain valve on the transmitter’s diaphragm box to remove as much catalyst as possible. When using backflow ventilation, it is also necessary to blow the pressure tapping with high-pressure air; indeed, these tapping points tend to clog easily. If large amounts of instrument air are used for cleaning without opening the flow-limiting orifice valve, it is very likely that the tapping will become blocked and lose its ability to perform measurements.

The density measurements for the catalytic cracking reaction section were obtained by using values derived from the backflow differential pressure measurement. Over 10 years ago, I was in charge of the instruments used in that reaction section, and almost all of those density measurement devices stopped working. The additional density measurement devices that were installed after major modifications to the catalyst system also stopped functioning shortly after they were put into use; the process engineers tried to fix them, but it was pointless as they stopped working again after a few days. Moreover, many of the pressure measurement tubes for backflow were blocked by catalyst, making it impossible to clear them even with compressed air. In the end, the process engineers gave up on trying to fix them, and that’s how all of those devices stopped working. Besides, density is of no use for control either; it’s basically just a rough reference value – its presence doesn’t make any difference. However, the catalyst reserve, the pressure differences across various control valves, and the top pressure of the tower are still very important; any failure in these aspects can have a significant impact on the process. Process engineers will never agree to proceed without fixing such issues, which poses a problem for instrument technicians. I remember that in the second year after I started working at the factory, I worked together with the shift leader to clear the pressure tapping point for backflow ventilation. The pressure tapping point at the top of the separator was quickly clogged due to carbonization; so we bent a 6-inch copper pipe into an arc, opened the flow control orifice valve and the drain valve on the pressure tapping point, inserted the copper pipe through the drain valve, passed it through the pressure tapping valve, and reached the area where carbonization had occurred. Then we used a wrench to strike the copper pipe, using force to push the coke aside. It’s extremely dangerous for that yellowish, high-temperature oil and gas to escape from the drain valve at the pressure tapping point; it’s all thanks to the high-pressure air from the instruments that prevents too much of that oil and gas from coming out. My heart beats wildly with fear – I’m really worried that a mistake in operation could lead to a fire, ending my life in an instant, without even having time to run away from those towers that are dozens of meters tall.