Questions regarding valve installation

The lower layer of the molecular sieve is alumina, which primarily absorbs free water. If it’s blowing in the right direction, don’t you carry the water into the purifier? But back-blowing doesn’t do that, right!

Could you explain your logic? How did I get so confused? Is it related to that? ? ?

The main reason is that when these valves are closed, the pressure behind the valve is higher than the pressure in front of it; installing the valves in reverse orientation serves to achieve a better sealing effect

The problem of backward installation of butterfly valves in air separation systems arises because, 1. the butterfly valve operates by rotating 90 degrees, and 2. when the valve is closed, different forces act on its two sides: one side is subjected to about 5 kilograms of air pressure while the other side is subjected to about 0.2 kilograms of polluted nitrogen pressure. If the valve is not installed in the backward orientation, this pressure difference will cause it to remain slightly open over time, leading to internal leakage.

The purpose of installing the valve in reverse orientation is, firstly, to achieve better sealing when using a butterfly valve in this manner; secondly, it is to prevent pressure air from leaking to the low-pressure side due to the pressures on either side of the valve, thereby avoiding interference with the regeneration of the molecular sieve； Another issue is that the leaked air does not enter the tower, resulting in increased energy consumption for air separation ；

Friend, this seems to have nothing to do with those valves being installed in the wrong direction, right?

I agree with the opinions from floors 6 and 7; this valve is installed in reverse mainly to ensure good sealing performance, and specifically good one-way sealing

Imported triple-eccentric metal-sealed butterfly valves are non-directional, but an installation direction is generally recommended; they should not be installed in the reverse orientation； Domestic versions have a defined orientation; generally, the leakage level is one grade worse, or the pressure rating is one to two grades lower, when used in the reverse direction, and they must not be installed backwards. When welding on horizontal pipes, the valve should be closed to protect the seal ring ； When welding on a vertical pipe, the valve should be closed, and water should be poured onto the valve plate at the welding site to extinguish the slag. When installed in horizontal pipes, it is recommended that the valve stem be horizontal or at a certain angle to the vertical direction. To ensure cleanliness at the bottom bearings.

The people upstairs said it very well – there’s also the reverse connection of the air separation unit, as well as the outlets of the expansion machine and the liquid oxygen pump. For the valve of the molecular sieve, check the markings on it; there is an indication of the medium flow direction and the pressure application direction.

Reasons for the valve being installed in reverse: 1. It is related to the three-bar valve structure used with the molecular sieve; when installed in reverse, the high pressure behind the valve presses it tighter, serving as a measure to prevent leaks. 2. It is related to the design and operation mechanism of the three-bar valve. This valve is not a traditional butterfly valve; the valve disc is not rotated to open or close against a valve seat. The operation mechanism of the three-bar valve involves controlling the action of a solenoid valve: air enters one end of the cylinder while air is expelled from the other end to relieve pressure, thereby driving the valve disc to move. The sequence of movement is as follows for opening: 1. The valve disc moves away from the valve seat; 2. It moves horizontally backward; 3. Once in place, it rotates until it is fully open. For closing: 1. The valve disc first rotates to close at its maximum displacement position; 2. Then it moves back toward the valve seat until it fits perfectly against it. (In some cylinders, if the dampers are not properly adjusted, a loud knocking sound can be heard when the valve is closed; this is due to the valve disc moving toward the valve seat too quickly.) 3. Reverse installation is also one of the measures taken to prevent the valve from opening when the pressure difference exceeds 0.01 MPa.