Piston Check Valves
Some types of lift check valves may be installed horizontally. In this design the ball is suspended by a system of guide ribs.
When the medium flow to lift check valves, it must always enter under the seat. When the flow enters, the ball or the disk is raised within guides from the seat by the pressure of the back flow. After that when the flow stops or reverses, the disk or ball is forced onto the seat of the valve when the backflow and gravity.
The seats of metallic body lift check valves are either integral with the body or contain renewable seat rings. Metal disk and seat valves can be reground using the same techniques as is used for globe valves. Disk construction is similar to the disk construction of globe valves with either metal or composition disks.
Detail of this type valve.
The piston check valve, actually said is a type of lift check valve. It has a dashpot consisting of a piston and cylinder that supports a cushioning effect when operation the operator. Considered of the similarity in design to lift check valves, it is better; the flow capacities through a piston check valve are the same as through a lift check valve. When it installation, the actor is the same as for installation a lift check in that the flow must enter from blew the seat. Construction of the seat and disk of a piston check valve is the same as for lift check valves.
The primarily used of piston check valves are in conjunction with globe and angle valves in piping systems especially very frequent changes in flow direction. When the liquid flew frequently, this type of valves should be used, the media usually are steam, water , and air systems or some other special flew media.