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What is Cage Guided Control Valve?

A more modern version of the globe valve design uses a piston-shaped plug inside a surrounding cage with ports cast or machined into it.

These cage-guided globe valves throttle flow by uncovering more or less of the port area in the surrounding cage as the plug moves up and down. The cage also serves to guide the plug so the stem need not be subjected to lateral forces as in a stem-guided valve design.

The Cage guided control valve is a balanced valve that can be used as a dump valve, pressure regulator, suction controller, recirculation valve, and plunger lift applications. Compared to the stem-guided series, cage guided control valves feature larger trim sizes (available in 2″ to 10″ end connections) for higher valve coefficients (Cv). Cage guided control valves can be equipped with an optional electric drive or operated with compressed air to meet zero-emission requirements.

Structure of Cage Guided Globe Valve

Cage-guided globe valves are available with both balanced and unbalanced plugs. A balanced plug has one or more ports drilled from top to bottom, allowing fluid pressure to equalize on both sides of the plug. This helps minimize the forces acting on the plug which must be overcome by the actuator:

Unbalanced plugs generate a force equal to the product of the differential pressure across the plug and the plug’s area (F = PA), which may be quite substantial in some applications.

Balanced plugs do not generate this same force because they equalize the pressure on both sides of the plug, however, they exhibit the disadvantage of one more leak path when the valve is in the fully closed position (through the balancing ports, past the piston ring, and out the cage ports):

Thus, balanced and unbalanced cage-guided globe valves exhibit similar characteristics to double ported and single-ported stem- or port-guided globe valves, and for similar reasons.

Balanced cage guided valves are easy to position, just like double-ported stem-guided and port-guided globe valves.

However, balanced cage-guided valves tend to leak more when in the shut position due to a greater number of leak paths, much the same as with double-ported stem-guided and port-guided globe valves.

Components of Cage Guide Globe Valve

1. Valve Trims

According to the needs of the working conditions, different materials and surface hardening treatments can easily be chosen to meet the requirements of each function module of trim to improve its performance of the corrosion, cavitation, and erosion resistance, and lengthen service life.

2. Valve body

The body of LN8 series control valves consists of two passages from upper and lower, forming a shape like a letter “S”. The design of an elliptical section reduces the flow resistance and turbulent flow to keep the flow fluent. The flap in the middle of the upper passage can reduce the eddy flow and increase the flow capacity.

3. Actuator

The standard mate is a Multi-spring pneumatic diaphragm actuator, which can be used in many conditions with the features of strong output force, high reliability, long lifespan, and extensive application. The output force changes with the number of springs. The high-stress-resistant diaphragm, bearing maximum pressure of 0.5 MPa air supply, gives the control valve a reliable shutoff. This type of actuator has a long life cycle of more than 1 million times.

Features of Cage Guided Control Valve

• Modular design concept, combining the American and Japanese schools of high-precision control and the German school of the modular concept.
• The cage valve inner cavity of the valve body is S-shaped distribution, smooth and without dead ends; there are guide wings inside the valve body, which can reduce the mutual force of the medium inside the valve body and reduce the occurrence of cavitation.
• The use of sleeve guidance, large guide diameter, smooth guidance, with good dynamic stability.
• The cage valve seat adopts a floating design, while the sealing surface adopts a tapered form to ensure good alignment of the sealing sub.
• Sleeve window control flow characteristics, flow characteristics control accurately.
• The structure of the inner part is balanced, allowing a large differential pressure, small operating force, and large flow capacity.
• Equipment, linear and quick-open flow characteristics are available.
• Good use in the temperature range of -80 to 593℃.
• And pipeline connection with RF, RJ, FM, and other flange types and SW, and BW welding types.
• The flange distance conforms to GB/T 17213.3-2005 / IEC 60534-3-1:2000; or ISA S75.03-1992 standard.