Control valves and accessories include: pneumatic control valves, electric control valves, self‑operated control valves, manual control valves, pneumatic diaphragm actuators, electric actuators, electric valve positioners, electric valve regulating modules, etc.
General‑purpose valves include: gate valves, globe valves, ball valves, butterfly valves, check valves, hydraulic control valves, plunger valves, plug valves, diaphragm valves, safety valves, pressure reducing valves, steam traps, air vent valves, balancing valves, needle valves and various lined valves.
Temperature‑reducing and pressure‑reducing devices are available in four specifications: low‑pressure, medium‑pressure, secondary high‑pressure and high‑pressure.
Automatic circulation control valves are supplied in three specifications: low‑pressure, medium‑pressure and high‑pressure.
Solenoid valves cover water‑service solenoid valves, steam solenoid valves, gas solenoid valves, air solenoid valves, vacuum solenoid valves, high‑temperature solenoid valves and others. API 6A valves consist of gate valves, choke valves and so on. Meanwhile, the company can design, manufacture and process non‑standard products according to customer requirements.
The opening‑closing component of a globe valve is a plug‑type disc with flat or conical surfaces, and the disc moves linearly along the centerline of the fluid flow. There are two movement modes for the valve stem: rising‑stem type (the stem moves up and down while the handwheel remains stationary), and rising‑rotating‑stem type (the handwheel rotates together with the stem for lifting and lowering; the nut is fixed on the valve body). Globe valves are only suitable for full‑open and full‑close operation; regulation and throttling are not permitted.
A globe valve is a forced‑sealing valve. Therefore, when the valve is closed, pressure must be applied to the disc to force the sealing surfaces into tight contact and prevent leakage. When the medium enters from below the disc, the operating force needs to overcome friction between the stem and packing as well as the thrust generated by medium pressure. The force required to close the valve is greater than that for opening it. For large‑diameter valves, insufficient force‑bearing capacity may cause stem bending.
In recent years, with the emergence of self‑sealing valves, the medium flow direction of globe valves has been changed to enter from above the disc into the valve chamber. Under medium‑pressure conditions, the closing force becomes small while the opening force increases, so the stem diameter can be reduced accordingly. In addition, this type of valve achieves tight sealing under the action of the medium itself.
According to Chinese valve industry specifications, the flow direction of globe valves shall be from top to bottom. When a globe valve opens, the flow reaches its maximum value at a disc lift of 25 %‑30 % of the nominal diameter, which indicates the fully‑open position. Hence, the fully‑open position of a globe valve shall be determined by the disc stroke.
Advantages of Globe Valves
Simple structure, convenient manufacture and maintenance.
Short stroke, fast opening‑closing action.
Good sealing performance, low friction between sealing surfaces and long service life.
Disadvantages of Globe Valves
High fluid resistance; large force is required for opening and closing.
Not applicable for media containing solid particles, high‑viscosity media or coking‑prone media.
Poor regulating performance.
Classified by stem thread position, globe valves are divided into outside‑screw type and inside‑screw type. According to medium flow direction, they are categorized into straight‑way, Y‑pattern and angle‑pattern types.
In terms of sealing form, globe valves include packing‑sealed globe valves and bellows‑sealed globe valves.
Notes on Globe Valve Installation and Maintenance
Globe valves operated by handwheel or handle may be installed at any position on the pipeline.
Handwheels, handles and pneumatic actuators shall not be used for hoisting purposes.
The medium flow direction shall comply with the arrow marked on the valve body.