GLOBE VALVES
All globe valves utilize the “port closure” concept of valves. By this it meant that fluid passes through a specific opening (rather than a general passageway, as in the case of gate valves), and the fluid is controlled by means of a stem-mounted disc or inserted plug in that area.
Despite of lacking the straight through, unobstructed passageway of the gate valve, these globe types are superior in two key aspects - throttling and service- ability under frequent use. They are better at the throttling function because they permit fluid to exit uniformly around the circumference of a seat, rather than “slicing” down to limit passage through a nar- rowly restricted area.
Stem
The stems of JC globe valves are forged from one piece and ACME threaded, then mechanized and finally provided with a smooth finishing in order to minimize friction.
Body and Bonnet Gasket
The design of the body-bonnet gasket varies depending on the class of the valve.
Class 150 to 600 globe valves consist of a circular male-female connection with a graphite or spiral wound gasket.
Class 900 and above globe valves consist of a ring type joint.
In pressure seal designs the sealing is achieved through a gasket that takes advantage of the internal pressure of the line. The material most commonly used is high-purity graphite being located between the body and the body retainer ring.
Body and Bonnet
Bodies and bonnets are high quality cast and afterwards precisely machined, directing the attention to prevent stress concentration.
Bonnets are made either of one piece only –the yoke then being an integral part of it – or have two pieces, depending on the size of the valve. This ensures the perfect alignment with the body what leads to an accurate opening and closing.
Bodies of globe valves are designed considering the same characteristics as gate valves, which in this case means that the disc is guided in bigger valve sizes or high pressure service in order to avoid vibrations and better seat.
Backseat
All JC gate and globe valves have backseat threaded in the bonnet, or for the pressure seal valves, welded to the bonnet.The hard facing is stellite 6 or equivalent.
