Issues regarding the on-site level gauge in the negative pressure tower
Thread Content
There is currently an alkylation unit in use, with a negative pressure tower operating at around 90 kPa. The level gauge used on site is of the magnetic flap type. It often happens that the liquid level at the bottom of the tower disappears, yet the float of the level gauge fails to descend. Upon cleaning, no dirt is found; the float is quite clean. Could it be that the float is stuck somewhere?
The liquid density in the bottom of the tower is 0.95. The level gauge and float are manufactured by small factories; there is no problem with them rising normally, but it is easy for them to stop rising when there is no liquid left in the bottom of the tower. Some liquid can still be drained from the level gauge during emptying.
No pictures, no truth – the float is too thick and it’s stuck
It’s hard to take pictures; the float is too thick and can’t rise up. This can be ignored
It’s quite difficult to analyze just by looking at the description. But saying that the material in the bottom of the tower is very clean – I’m not sure about that. Additionally, the bottom of the tower should not only have a magnetic flap level indicator on-site, but also a level indication that is transmitted to the DCS; it is necessary to check whether the display on the DCS is normal. It’s very likely that the float is still stuck.
The design institute originally designed a dual-flange remote transmission system, but this was changed during construction to a reed switch system; since things are set up this way on site, there’s nothing more to say about the remote transmission option
Do you mean it can’t be lowered? Does it stay there even when cleaning is carried out?
This does occur inside the vacuum tank. I still haven’t fully understood it to this day. But according to theoretical speculation, it should be that the gap between the float and the tube is small, and there are issues with the pipes that connect the upper and lower ends of the magnetic float to the tank. It’s different, or there is dirt inside.
Take a look to see if there’s something like iron somewhere on the magnetic flap that is attracting the floating magnet. I’ve encountered situations where the welded part of the magnetic flap could be attracted by a magnet, as stainless steel welding rods were not used.
It is recommended that the top opening of the magnetic flap be connected to the gas in the tower, which means that the magnetic flap level gauge has two gas connection ports to the tower. This method works quite well under high vacuum conditions.