Tandem trim is a high performance specialty trim that is cage guided. The standard design is a uniquely balanced port throttling trim designed to solve difficult high temperature, high-pressure differential applications that would require oversized, heavier actuators if other standard trims were utilized.
Tandem trim provides excellent control, rangeability, and tight shutoff to Class V or MSS-SD-61 in high temperature applications.
This trim is designed with the main and pilot plugs working in tandem. The Tandem trim may be customized to use Raven, Hush, or any standard cage can be used with this trim design.
Typical Applications:
Steam and water pressure reduction
Steam throttling to atmosphere or to a condenser
Isolation
Boiler startup
PRINCIPLES OF OPERATION:
The Tandem Trim consists of a cage and balancing cylinder which is gasketed and trapped between the valve bonnet and body web. The large plug is the control device. Inside the main plug, is an inner plug which is connected to the valve stem.
Valve Closed
When the valve is closed, the balancing chamber above the main plug is at the inlet pressure due to flow past the piston rings. Full inlet pressure acts on top of the main plug which generates a high contact load on the seat and provides positive shutoff.
Valve Opening
When the valve stem lifts, the inner plug is opened and the pressure in the balancing chamber is vented to the downstream side of the valve through a port in the main plug. The equalization of pressure reduces the unbalanced forces on the main plug. As the inner plug continues to lift, the inner plug shoulder contacts the main plug to open it. The main plug is opened without excess force since it is essentially pressure balanced.
Valve Modulating
As the stem positions the main plug to modulate the flow, the unbalanced force remains constant (with a constant differential) allowing smooth control and ensuring that the inner plug remains open.
Valve Closing
When the valve is closing, the main plug first contacts its seat. Further downward movement of the stem then closes the inner plug. Flow past the piston rings then pressurizes the balancing chamber to the upstream pressure, holding the main plug tight against the seat.
Top Guided
The Copes-Vulcan top guided trim is designed for use with a wide variety of process applications involving corrosive, abrasive and viscous fluids.
This style of trim is ideal for control applications where a maximum of free flow area is preferred. It is commonly used in steam and water applications.
RAVEN™
Copes-Vulcan RAVEN™ trims are used in severe service applications where true velocity control is needed by limiting the fluid velocities at the exit of the trim. RAVEN™ trim precludes the problems typically associated with high velocity: erosion, vibration, poor control and cavitation.
Every RAVEN™ trim is custom designed to meet the needs of the toughest liquid, steam and gas services in the power and process industries.
Copes-Vulcan has over 100 years of experience selecting the most suitable materials for the operating conditions and the application. Our expertise has been developed through laboratory research and field experience, resulting in valves that offer superior control, actuation and long-term performance.
Features
Tight Shutoff: Equipped with various plugs (unbalanced, balanced, tandem, etc.) RAVEN™ can provide shutoff classes ranging from ANSI/FCI Class IV to VI and MSS-SP-61.
Resists Plugging and Galling: An internal pressure balancing groove on each disk ensures equal pressure distribution eliminating the potential for side loading and galling of the plug. Bypasses in the flow paths allow entrained debris to clear the main fluid path.
Easily serviced: Quick-change design with no threaded or welded parts. Seat ring is a separate replaceable item.
Characterization: Able to provide application specific performance response for optimum system performance.
Quieter: Size for size RAVEN™ trim has been proven quieter than the stacked disc trims of our competitors in extensive laboratory testing.
Adaptable Flow Direction: Flow can be either over or under the seat depending on the fluid, the service and in some instances, the piping configuration.
Retrofits/Upgrades: Readily tailored to fit valves previously supplied without RAVEN™ trim Copes-Vulcan or other brands.
This trim is a general-purpose cage guided trim for on/off or modulating control. It is designed for low to moderate pressure drop applications. The solid plug has a contour on its lower end that provides varying flow area with lift, thus regulating the flow.
It can be used with a wide variety of non abrasive/non-adhesive compressible and non-compressible fluids. The trim is single seated, metal to metal.
It is the standard trim for valve sizes 1" (38 mm) and smaller.
Soft Seated HUSH
Soft Seated HUSH Trim (double plug) is a high performance specialty trim that is designed to provide and maintain extremely tight shutoff for high pressure differential liquid applications.
This trim is often applied to operating conditions that exhibit pressure drops in excess of 1800 psig where the valves are to remain closed more than 25% of the time.
Typical Applications:
Boiler feed pump recirculation valves
Start-up feedwater control valves
Spray control valves
Heater drain valves
Features
The soft seat provides zero leakage (ANSI/FCI 70-2 Class VI) throughout the service life of the trim preventing lost pump/generating capacity and reducing maintenance costs due to wire drawing and cavitation.
Suitable for use with any liquid application with temperatures up to 500°F (260°C) or pressure drops exceeding 5000 psi (344 bars).
Surface hardened main plug eliminates galling
Balanced design minimizes actuator sizing
The double plug design uses the metal seat for throttling, protecting the soft seat. This assures a long lasting seal.
Trim design includes a strainer to protect the soft seat from entrained solids
Quick change design for ease of maintenance
Lo-Flow
Lo-Flow trim is a general-purpose cage guided plug throttling style trim designed to handle very low Cv applications. It is intended for use with either compressible or non-compressible fluids where there is a moderate or low-pressure drop requirement.
The trim consists of a tapered plug that fits into a cage and seat with a matching taper in the bore of the seat ring. The angles of these tapers are small so that the flow area throughout the trim is essentially constant from inlet to outlet. This results in small changes in flow area with respect to plug travel, providing good turndown for a general-purpose valve.
Numbered Cascade
Copes-Vulcans Numbered Cascade Trim assembly is used in control valves where low flow rates and high turndown requirements prevail such as in desuperheater cooling water control, fuel oil control, blowdown and chemical feed.
A series of labyrinth grooves along the throttling surface of the plug provide a cascading effect so that the pressure drop is equally divided among the grooves, thereby reducing the seat wear that would normally be experienced if the entire pressure drop is taken across the seat. The cage guided tapered plug, in conjunction with the tapered cage bore, provides for maximum trim rangeability.
One Stage HUSH
One Stage HUSH Trim is a specialty trim designed to reduce noise associated with compressible fluids and the undesirable effects of flashing and cavitation that would occur with most single pressure drop trims.
The trim does not prevent flashing or cavitation, however the damaging effects are reduced to acceptable levels through the use of many small ports. The HUSH cage consists of a single cylinder with a large number of radially drilled orifices. The fluid exits the numerous orifices as low energy jets resulting in significant reductions in noise or erosion.
Although many standard designs are available, One Stage HUSH is often custom engineered to provide various flow characteristics for optimal performance under specific operating conditions.
TYPICAL APPLICATIONS:
Drains
Steam pressure reduction
Steam dump
Feedwater regulation
Deaerator level control
Condensate recirculation
CAV-B9
The CAV B9 trim can be applied in liquid service where low-level cavitation is evident.
The stepped radially drilled cage design reduces the effects of cavitation, along with the associated problems of noise and erosion, by forcing the cavitation to occur in the center of the cage, away from the metal surfaces. In both flow under and flow over configurations of CAV B9 trim the fluid is divided into many lower energy jets.
By varying the hole diameter and placement, custom flow characteristics can be provided.
CAV B9 can be used as an effective trim for flashing operations in the flow under the seat configuration.
GAD
The Copes-Vulcan Port Throttling GAD trim was developed to meet the rigorous requirements of feedwater and feedwater start-up control. GAD trim is an excellent solution for all applications where plug instability or vibration exists due to turbulence or high velocity.
The GAD trim is suitable for use with steam and many other fluids. It has been successfully used on high-pressure water applications involving pressure up to 5075 psi (350 Bar) and pressure differential of up to 3625 psi (250 Bar).
FEATURES:
The control mechanism is situated in a zone of low turbulence that avoids flow-induced instability or standing pressure waves.
Custom engineering of the flow control areas optimizes the valve characteristic to system requirements.
The flow streams through the stationary cage result in energy dissipating jet impingement within the bore of the cage.
Designed to give optimum flexibility in power operated control valves, the trim is available in double seat, balanced single seat and tandem versions.
Quick-change design with no threaded or welded parts. Seat ring is a separate replaceable item.
HUSH®
The HUSH® trim is an innovative concept in control valve trim designed by Copes-Vulcan for high pressure drop liquid, gas, and steam applications.
HUSH® is a cage guided trim that provides excellent control by directing the flow through a series of staged pressure drops. Cavitation, excessive leakage, hazardous noise, vibration and mechanical failures can be eliminated with HUSH trim reducing down time and expensive maintenance costs.
Features
HUSH® trim provides a cost effective option for severe duty applications where stacked disc trim is not required.
Resolves existing problems for both compressible and noncompressible fluid flow applications.
Pressure breakdown occurs in stages within the cage away from the plug surface, extending seat and trim life.
Generally limits noise to 85dBa or less
Multiple pressure drops prevent sonic velocity from occurring within valve
Prevents aerated liquids from eroding trim and valve parts
Cascade and Super Cascade
Features
Copes-Vulcan Cascade trim solves the problems of short life and high replacement costs for valve trim in high-pressure drop service. It is a cage-guided plug throttling trim designed primarily for high-pressure drop water applications where cavitation, vibration and excess wear would occur with conventional trims.
Cascade trim features a series of labyrinth grooves, machined into the plug along its throttling surface. This series of grooves provides a cascading effect, so that the pressure drop is divided equally among the grooves. This reduces the amount of inner valve pressure recovery and subsequent vapor formation. Cascade trim is ideally suited for applications where cavitation can exist at low flow conditions, when the plug is just off the seat. By holding the clearance between the plug and the cage in the labyrinth groove section to close tolerances, the proper cascading effect is achieved.
Typical Applications:
Pump recirculation or bypass
High-pressure desuperheater cooling water control
Supercritical boiler start-up reheat
Superheat spray control
Balanced Single Seat Port Throttling
The Balanced Single Seat Port Throttling trim is a general-purpose cage guided trim for both on/off and modulating control. It is suitable for use in most non-abrasive/non-adhesive, compressible and non-compressible fluid services.
The balanced plug design reduces actuator force requirements thus permitting the use of smaller, lighter and easier to maintain actuators while providing tight shutoff capability.
Balanced Single Seat Port Throttling trim is designed for valves 2” (50 mm) and larger and is suitable for applications where the service temperature does not exceed 500°F (260°C).
High-Temperature Balanced Single Seat Port Throttling
The High Temperature Balanced Single Seat Port Throttling trim is virtually identical in all respects to the Low Temperature Balanced Single Seat Port Throttling trim, except that piston rings are used in lieu of the elastomeric seal on the trims plug.
While the use of piston rings does limit the leakage rate to ANSI Class IV, this trim is a viable option when a balanced plug is desirable and when temperatures of the fluid exceeds 500°F (260°F).
The trims are available for valve sizes 2” (50 mm) and larger.
Where to Buy
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