Valves such as globe valve, check valve, gate valve, throttle valve and reducing valve all have directivity. If installed in the opposite direction, throttle valves' operation performance may be weakened and service life may be shortened; reducing valves may have no effect; check valves may even cause dangers.

Generally, there are direction marks on the valve bodies. If there is no direction mark, we should correctly distinguish the installation direction according to the working principles of valve.
 
There is left-right asymmetry of globe valves' cavities, thus we should let the fluid flow from the bottom to the top of the valve port to reduce the resistance of the fluid (decided by the shape), to save the efforts (due to the upward media pressure), to make the media not press the packing after closing the valves, and to make the globe valves easily repaired. This is why the globe valves can not be installed in the opposite direction. Other valves also can not be installed in the opposite direction due to their own characteristics.

The location of the valve installation must be easy to operate. Even if the installation is temporarily difficult, we should consider for the operators' long-term work.
 
Make the valve handwheel even with the operators' chest (generally, 1.2 meters above the operating floor) in order to save efforts for operators when they open and close valves. The hand wheels of valves on the ground should be installed upwards and not tilt so as to avoid awkward operation. When install the valves of equipment relying on the wall, we should also leave some room for the operators to stand. Operations which require the operators to raise their heads and to look up should be avoided, especially when valves contain acid, toxic media, etc., otherwise it may cause dangers.
 
Do not install the gate valves in the opposite direction (making the hand wheels downward), otherwise it will keep the media in the bonnet for a long time and the valve stems easily corroded. It also brings inconvenient for replacing the packing. Reducing valves should be installed uprightly in the horizontal pipes and not tilt in any directions. When install piston(lift) check valve, ensure that the valve clack is vertical for flexible lift. When install swing check valve, ensure that the axis pin is level for flexible swing.