Installation direction of molecular sieve switching valve
Thread Content
A beginner has a question for the experts: in the air separation process, molecular sieves are always configured in pairs, with one in use and the other in regeneration mode； There are eight molecular sieve switching valves corresponding to them; previously they were butterfly valves, but now they are mostly three-bar valves. I see that the flow diagram requires the four valves behind the molecular sieve to be installed in reverse (that is, the flow direction indicated on the valve bodies is opposite to that shown in the flow diagram). I don’t quite understand why this is required; those who know could please explain it to me patiently.
Forward and reverse orientation is relative to the flow direction; that is, the pressure direction indicated on the valve body is opposite to the flow direction. Regarding why the air outlet valve is installed in reverse order after the molecular sieve, it is mainly because during the regeneration of one path (when pressure is reduced), the other path is in adsorption mode (at normal pressure), and these two paths converge into one. If the valve were installed in the correct orientation, the pressure behind the valve would be higher than that in front of it; therefore, to protect the molecular sieve, it is necessary to install the valve in reverse order. Furthermore, why is the inlet valve for dirty nitrogen installed in reverse? This valve should close during molecular sieve adsorption; according to the flow diagram, the pressure before the valve is low due to the presence of dirty nitrogen, while the pressure behind the valve is high as it is the main air pressure
Simply put, it’s being pressed shut; when we first started testing the system, the outlet valve of the molecular sieve couldn’t be opened due to being pressed