Sliding-Stem Control Valve Terminology (3)

Seal Bushing :
Top and bottom bushings that provide a means of sealing the yoke,to adjust the spring compression.

Spring Seat :
A plate to hold the spring in position and to provide a flat surface for the spring adjustor to contact.

Static Unbalance :
The ned produced on the valve stem by the fluid pressure acting on the closure member and stem with the fluid at rest and with stated pressure condition.

Stem Connector :
The device that connects the actuator stem to the valve stem.

Trim :
The internal components of a valve that modulate the flow of the controlled fluid. In a globe valve body,trim would typically ionclude closure member,seat ring,cage,stem,and stem pin.

Trim Soft-Seated :
Valve trim with an elastromeric,plastic or other readily deformable material used either in the closure component or seat ring to provide tight shutoff with minimal actuator force.

Upper Valve Body :
A half housing for internal valve parts and having one flow connection. It usually includes a means for sealing agains leakage along the stem and provides a means for mounting the actuator on yhe split valve body.

Valve Body :
The main pressure boundary of the valve that also provides the pipe connecting ends,the fluid flow passageway,and supports the seating surface and valve closure member. Among the most common valve body construction are :
a) Single-ported valve bodies having one port and one valve plug.
b) Double-ported valve body having two port and one valve plug.
c) Two way valve bodies having two flow connections,one inlet and one outlet.
d) three-way valve bodies having three flow connections,two of which can be inlet with one outlet (for converging or mixing flows),or one inlet and two outlet (for diverging or diverting flows). The term valve body,or even just body,frequently is used in refering to the valve body together with its bonnet assembly and included trim parts. More properly,this goup of components should be called the valve body assembly.

Valve body assembly (commonly valve body or valve,more properly valve body assembly):
An assembly of a valve,bonnet assembly,bottom flange (if used),and trim elements. The trim includes the closure member,which opens,closes,or partially obstructsone or more ports.

Valve plug :
A term frequently interchanged with plug in reference to the closure member.

Valve stem :
In a linear motion valve,the part that connects the actuator stem with the closure member.

Yoke :
The structure that rigidly connects the actuator power unit to the valve.