In the event that pressure within a system exceeds its normal level, check valves serve to regulate the flow of fluids. These valves are also utilized in auxiliary systems which necessitate additional pressure control. There are two primary types of check valves: swing check valves and lift check valves. Swing check valves rotate in accordance with the center of gravity, while lift check valves move along the axis. By categorizing check valves in this manner, their functionality and operation can be better understood.
The main objective of employing this particular valve type is to permit the passage of the medium in a singular direction while obstructing the flow in the opposite direction. Typically, this valve operates automatically. When fluid pressure propels it in one direction, the valve flap disengages, allowing the fluid to pass through. Conversely, when the fluid moves in the opposing direction, the valve flap, along with the fluid pressure, presses against the valve seat, effectively impeding the flow.
There are various types of valves, among them the check valve is a common variety. This type of valve is further divided into swing check valve and lift check valve. In the swing check valve, the valve disc, shaped like a door, is mounted on a hinge mechanism that allows it to swing back and forth. This design prevents the valve disc from jamming and ensures it contacts the valve seat surface each time. The disc can be manufactured from metal or lined with rubber, leather, or synthetic materials based on its usage requirements. When fully open, the fluid pressure passes through the swing check valve with minimal constraint, resulting in a low-pressure drop.
In comparison, the lift check valve comprises a valve disc located on the valve seat's sealing surface. The valve disc is free to rise and fall, but the rest of the valve appears similar to a globe valve. The fluid pressure lifts the valve disc from the valve seat's sealing surface, and when the medium backflows, the valve disc falls, blocks the flow, and seals the valve seat. The valve disc can be constructed purely from metal or feature a rubber pad or ring embedded on the disc holder depending on the usage conditions. Since the fluid passage through the lift check valve is narrow, similar to the globe valve, the pressure drop is greater than the swing check valve and the flow is limited.