A globe valve was reputedly called a globe valve because the central part where all the action is resembled a globe
. I have not found an authoritative source
on this but it sounds somewhat specious to me. The central part of the valve is quite bulbous having to contain a seat
, a plug
, a stem
and often a cage
. And while I can see an analogy to a snake having swallowed a pig, the word globe does not come to my mind.
Nonetheless, there are 3 styles of globe valves: straight pattern, angle pattern and Y-pattern. These are determined by the geometry of the end connection and the stem. In a straight pattern globe, the end connections for a straight line with the stem pointing vertically from this line. A Y-pattern is similar but the stem is angled by 45 degrees from the inlet-outlet path. An angle valve has the inlet and outlet oriented 90 degrees from each other with the stem perpendicular from one and in line with the other.
The opening and closing action follows a straight line, or is linear which differentiates these valves from rotary valves like ball valves and butterfly valves. The plug descends onto the seat which is in the form of a ring and closes off the flow path. Different tapers of plugs will give different characteristics such as an equal percentage or linear characteristic. The size of the seat is made independently of the size of the inlet and outlet connections which allows one to control extremely small flows with a globe valve as long as you can make the seat sufficiently small.
Globe valves are also suited for controlling in situations where there are high pressure differences between the inlet and outlet. The winding path that the media has to follow does not let it speed up too much and reduces the impact of the Bernoulli effect that often damages ball valves.
Globe valves are usually operated by spring-diaphragm actuators although piston actuators, electric actuators and hydraulic actuators have all been used to operate these valves. Prior to much use of electronics in processing plants, all the control signals were 3-15 psi air signals. These signals were fed directly to the actuators. In modern plants, the signals are 4-20 mA electronic ones that are fed to microprocessor controlled positioners that will make predictions about maintenance requirements. But that's the subject of a different write up.