Double Offset Butterfly Valve

Types of Double Offset Butterfly Valves based on Connection

Wafer Double Offset Butterfly Valve

The wafer type of the double offset butterfly valves is constructed to provide a strong sealing, safeguard against bi-directional pressure differentials, and to prevent any backflow in devices that were built for unidirectional flow. This is done by the use of a tightly fitted seal material, such as an O-ring, or gasket, precisely machined, along with a smooth valve face on the downstream and upstream parts of the valve.

Lug Type Double Offset Butterfly Valve

In the lug body type of the double offset butterfly valve configuration, one end of the pipeline can be removed without impacting the other side of the valve. This can be achieved with threaded inserts, flanges, and two sets of lugs (bolts) that do not use nuts so each flange has its bolts. In a Lug type connection, you do not have to shut down the whole device to inspect, clean, repair, or replace the lug butterfly valve.

Flanged Double Offset Butterfly Valve

The flanged double offset butterfly valve uses a flange at both ends of the valve to be attached to pipe flanges. This type of end connection is used for the very large size of the butterfly valve.

Welded End Double Offset Butterfly Valve

The welded end double offset butterfly valve is used where the system is under very high pressure. These types are generally used for small-size butterfly valves.

Features of Double Eccentric Butterfly Valve:

• The shaft and disc arrangement of ZECO double eccentric butterfly valve provides camming action to the disc which disengages from the seat at minimal rotation. This design minimizes war points at the top and bottom of the seat typical with conventional butterfly valves;
• ZECO double offset butterfly valve has two offsets. The first offset is that the shaft is positioned downstream of the center line of the seat. The second offset is that shaft is off the center of the vertical axis of the seat;
• ZECO double offset butterfly valve can have a rubber seat, PTFE seat, and fire-safe PTFE seat.;
• The fire-safe seat of ZECO double eccentric butterfly valve with dual seal including primary PTFE seat insert and metal seat. In the event that the PTFE insert is destroyed, the secondary metal seat provides an effective shut-off.

The Parameter of Double Offset Butterfly Valve

1. Valve Type: Double Offset Butterfly Valve.
2. Pressure Rating: ANSI 150, ANSI 300, etc., suitable for different pressure levels.
3. Temperature Range: Standard operating temperature from -20°C to 200°C (-4°F to 392°F).
4. Body Material: Typically stainless steel, carbon steel, or ductile iron.
5. Disc Material: Made of corrosion-resistant materials such as stainless steel or ductile iron.
6. Seat Material: Utilizes resilient materials like EPDM or PTFE for reliable sealing.
7. Actuation Type: Can be operated manually, pneumatically, or electrically.
8. End Connection: Available with wafer, lug, or flanged end connections.
9. Leakage Rate: Engineered to meet industry standards for minimal leakage.
10. Fire Safety: May feature fireproof seat design and metal-to-metal seals.
11. Compliance: Complies with industry standards such as API, ANSI, and ISO.
12. Maintenance: Designed for easy maintenance with replaceable seats and seals.
13. Accessories: Compatible with various accessories like positioners, limit switches, and actuators.

The Operation Theory of Double Offset Butterfly Valve

The operation theory of a Double Offset Butterfly Valve involves precise control over fluid flow. Similar to Victaulic Butterfly Valve 705, it utilizes a double offset design for optimal performance. Whether it’s a 1/2 inch butterfly valve or 2 1/2 butterfly valve, the principle remains consistent: the disc offsets from the centerline of the valve seat to minimize friction and wear, enabling smooth operation and tight shut-off.

The Parameters Table of Double Offset Butterfly Valve

Parameter	Description
Valve Type	Double Offset Butterfly Valve
Pressure Rating	ANSI 150, ANSI 300, etc.
Temperature Range	-20°C to 200°C (-4°F to 392°F)
Body Material	Stainless steel, carbon steel, ductile iron
Disc Material	Stainless steel, ductile iron, aluminum
Seat Material	EPDM, PTFE, metal-to-metal
Actuation Type	Manual, pneumatic, electric
End Connection	Wafer, lug, flanged
Leakage Rate	Meets or exceeds industry standards
Fire Safety	Fireproof seat design, metal-to-metal seals
Compliance	API, ANSI, ISO
Maintenance	Replaceable seats and seals for easy upkeep
Accessories	Compatible with various actuators, limit switches

Relevant Information about Double Offset Butterfly Valve

1. Rotor: The rotor is the part of the valve that rotates to control the flow of fluid. In a Double Offset Butterfly Valve, it’s the disc that pivots.
2. Stator: The stator is the stationary part of the valve, typically consisting of the valve body and seat. It provides support and creates a sealing surface for the rotor.
3. Universal Joint: The universal joint connects the actuator to the valve shaft, allowing for rotational movement. It ensures that the motion from the actuator is accurately transmitted to the valve.
4. Shaft Seal: The shaft seal prevents leakage along the valve shaft where it passes through the valve body. It’s crucial for maintaining the integrity of the valve and preventing fluid loss.
5. Driving System: The driving system includes the actuator and associated mechanisms that provide the force to operate the valve. It ensures smooth and precise control of the valve’s movement.