Installation and flow directions Gate valves flow in both directions with the same effect. Inlet or outlet direction is not required in the installation and the medium can flow from both directions. Globe valves should be installed strictly based on the arrow on the valve body. There is a clear regulation about the inlet and outlet of globe valves, that is, the flow direction of the globe valve should be from up to down.
The fluid of the globe valve flows from the low part and then comes out from the high part. The globe valve's two channels are not on the same level from the appearance, while the gate valve's channels are on the same level. The stroke of the gate valve is greater than that of globe valve.
The gate valve's flow resistance is small when the gate valve is fully opened from the view of the flow resistance. The flow resistance coefficient of ordinary gate valve is about 0.08~0.12. The opening and closing force are small and the medium can flow in both directions. The flow resistance of ordinary globe valves is 3-5 times bigger than that of gate valves. Globe valves can only be sealed fully by forced closing when they are opened or closed. The valve spool of the globe valve can only be contact with the sealing surface when the globe valve is fully closed, resulting in small wear of the sealing surface. Attention should be paid to the adjustment of torque control mechanism for globe valves which require actuators due to great flow resistance.
There are two installation ways for globe valves. One way is that the medium can flow from the bottom of the globe vlave's spool. Its advantage is that the service life of the disc' root can be extended when the globe valve is closed. Also, the disc root can be changed when the pipeline in front of the valve is under pressure. Its disadvantage is that the drive torque is great, which is one time bigger than the upper flow. The globe valve bears great axial force, making the valve stem easily bend. Therefore, this method is only applicable to globe valves whose diameters are below DN50, and the medium should flow from upper parts for globe valves whose diameters are above DN200. Electric globe valves generally adopt the way of the medium flowing from the upper part. The disadvantage of the way the medium enters from above is the opposite of the way when it enters from below.
Sealing
The sealing surface of the globe valve is the side of the trapezoid of valve spools based on the shape of the valve spool. Once the valve spool falls, that means the valve is closed. If the pressure difference is great, of course, the valve can't be closed well. The gate valve is sealed by the side of the valve spool disc. Its sealing effect is not as good as the globe valve's. The gate vale will not be closed like the globe valve when its valve spool falls.
