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Valves

2950 E. Birch Street
Brea, CA 92821
T: +1.714.528.2301
Email: valves@curtisswright.com

Triple-Offset and Resilient Seated Butterfly Valves

In 1992, Curtiss-Wright Nuclear introduced the first Safety-Related and ASME Code triple offset butterfly valves to the nuclear power industry through its PermaSeat SP product line. Today the triple offset valve design has been installed in almost every U.S. plant and plays a critical role in the safe and efficient operation of a nuclear reactor.

With over 25 years of nuclear operating experience, PermaSeat SP butterfly valves have proven to be effective and reliable in both modulating and isolation applications.

Beyond the triple-offset butterfly design, PermaSeat SP also provides large diameter butterfly valves (80" and higher), as well as both high performance and rubber-lined designs. This extensive portfolio of butterfly valves is one of the largest in the industry that can improve the reliability of plant systems, solve industry obsolescence issues, and support subsequent license renewal.

Models

    Triple Offset

    The PermaSeat SP TOSV butterfly valve is a dedicated triple offset geometry design. This particular feature eliminates the disc-to-seat rubbing condition, normally associated with high performance butterfly valves, which induces wear of varying degrees, even in metal seated versions.

    Key Features and Benefits

    Triple Offset Design Eliminates unnecessary wear and prolongs seat and seal life
    Ease of Maintenance Field replaceable seat and seal ring
    Bi-Directional Shut-Off Provides zero leakage capability
    Non-Galling Design Enables a wide variety of material options
    Additional Features Live loaded packing, double block and bleed design, gate valve replacement design

    Principles of Operation

    The offsetting of the shaft in two axis, when combined with the tilting cone / ellipsoidal segment means that there is complete removal of 'scuffing' and surface pick up during the full 90 degree movement. The seal ring, which is of laminated construction, uses the seat ring as the stopping point, eliminating separate mechanical stops. There is no need for critical settings for disc-to-seat contact to achieve required shut-off. This is beneficial in situations where actuators and controls are fitted.

    When closed, the seat is bi-directionally tight, with a zero leakage rate in either direction. The seat sealing load is torque induced, thus when the disc movement reverses to 'open', the operating torque quickly reduces, due to the on / off contact action of seal to seat and swing clear action via shaft offsets. Since the seal action is 'contact' without any 'rubbing' action, then galling does not occur and so the same material can be used for both seal and seat.

    General Specifications

    Size: 3" to 84"
    Ratings: ANSI Pressure Class 150 to 2500
    Connections: Wafer Flangeless, Wafer Lugged, Double Flanged (short and long patterns), and Butt Weld
    Quality Class: Commercial, Safety-Related ASME Section III

    Plant Design

    PWR, BWR, CANDU

    Typical Plant Applications

    • Service Water
    • Component Cooling Water
    • Containment Purge/Vent Isolation
    • Alt. Decay Heat Removal, RHR System
    • Radiation Waste Control Isolation
    • Air Header System
    • Sump Floor Drain-Containment Isolation
    • Heater Drain
    • Condensate Polishing
    • Condensate/Feedwater Loop
    • Hydrogen Cooler Heat Exchanger System
    • Raw Water Treatment

    Permaseat Triple-Offset Butterfly Valve TOSV Series

    Resilient Seated

    PermaSeat SP Resilient Sealed Valves are suitable for isolation and flow control applications and have a proven record for reliability over the past 30 years for applications in seawater cooling, circulating water systems, and condensate systems.

    The ease and flexibility of material selection enables both simple and arduous applications alike to be within the capability of this valve series.

    Key Features and Benefits

    Single or Double Offset Design Excellent for both isolation and control duties
    Ease of Maintenance Integral body seat, individual seat, or resilient seal ring are field replaceable
    Positive Shut-Off Achieved without excessive interference between seat and seal ensuring maximum seal life and low seating and unseating torques
    Ebonite Liner Enables a wide variety of material options
    Additional Features Effective in high-chlorine environments such as brackish water and seawater, where the natural resistance of Ebonite insulates the wetted portions of the valve body from corrosive attack by such aggressive media

    Principles of Operation

    The valve is a bi-directional tight shut-off device incorporating a resilient seal mechanically retained around the periphery of the valve disc. The seal is available in various types of elastomers, the selection being dependent on the valve duty and working pressure and temperature. The seal seats against a metal face machined into the body of the valve. Positive shut-off is achieved without excessive interference between seat and seal ensuring maximum seal life and low seating and unseating torques.

    The E-Series has an ebonite lining which is a hard, natural rubber, bonded and autoclave cured to achieve maximum strength and adhesion. It has a corner locking overlap feature around the flange and shaft bores to maintain optimum stability. The seat contact area, against which the resilient disc seal ring locates, is fully machined to ensure consistently tight shut-off.

    In operation, there is a key difference when compared with other rubber lined valves. The ebonite is part of the structural rigidity of the body and the resilient seal is disc located. This is the element being compressed during sealing on closure. This eliminates dragging on the liner, which occurs on other valve designs where the disc is solid and the seal is made by compression of the liner. It is particularly effective in high-chlorine environments such as brackish water and seawater, where the natural resistance of Ebonite insulates the wetted portions of the valve body from corrosive attack by such aggressive media. The use of Ebonite in this application allows the use of Carbon Steel valve bodies, and actually makes them more corrosion-resistant than stainless-steel bodies in brackish water applications.

    General Specifications

    Size: 2" to 144"
    Ratings: ANSI Pressure Class 150 to 300
    Connections: Double flanged, wafer lugged and wafer flanged
    Quality Class: Commercial, Safety-Related, ASME Section III

    Plant Design

    PWR, BWR, CANDU

    Typical Plant Applications

    • Ocean Water Discharge
    • Condenser Waterbox
    • Circ Water
    • Various Other Applications
    Permaseat Triple-Offset Butterfly Valve R&E Series
    Permaseat Triple-Offset Butterfly Valve R&E Series

    Available PermaSeat SP Products

    • TOSV Series – Triple Offset Butterfly Valves
    • R&E Series – Large Diameter Butterfly Valves
    • T Series – High Performance Butterfly Valves
    • C Series – Rubber Lined Butterfly Valves