Offset butterfly valve

Double and triple offset butterfly valve introduction

Double offset butterfly valve and triple offset butterfly valve can according to the sealing performance into metal seal and soft seal with compact structure、small volume、reliable operation、good sealing、easy maintenance installation convenient and the adoptability is strong advantages. Double offset butterfly valve and triple offset butterfly valve can be widely used in petroleum、chemical industry、light industry、papermaking industrial、pharmaceutical、car automatic control system on a remote concentrated or local control.
 

Double and triple offset butterfly valve technical parameter

● Connection Type: Wafer, Lug, Tri Clamp, Double Flange
● Material: Cast Iron, Ductile iron, Carbon steel. Stainless Steel and others
● Actuator Type: Manual, Electric (on-off or regulating), Pneumatic (spring return or double acting)
● Operating Pressure: 10-100 bar,150LB-900LB
● Medium Temperature: -10 to 180 ℃ for rubber seat, -40 to 450℃ for metal seat.
● Size Range: 2″ to 100″
● Suitable Medium: Water, Oil, Air, Gas, etc.
 

Double and triple offset butterfly valve classification

Based on the connection there are different types of offset butterfly valve.
Wafer Type double and triple offset butterfly valve: The wafer type triple offset butterfly valves was built to keep a tight sealing, protecting against bi-directional pressure differentials, to prevent any backflow in devices that were built for uni-directional flow. This is done by the use of a tightly fitted cap, such as an O-ring, gasket, precisely machined, along with a smooth valve face on the downstream and upstream parts of the valve.
Lug Type double and triple offset butterfly valve: The lug type triple offset butterfly valve configuration is similar to the 3-piece ball valve in which one end of the pipeline can be replaced 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. It is also important to remember that you do not need to shut down the whole device to inspect, clean, repair, or replace the lug butterfly valve.
Flanged End Type double and triple offset butterfly valve: The flanged type double and triple butterfly valve has a flange at both ends of the valve to be attached with pipe flanges. This type of end connection is used for the very large size of butterfly valve.
Welded End Type double and triple offset butterfly valve: The welded end type butterfly valve is used where system is under very high pressure. These types are generally used for small size butterfly valves.
 

Double and triple offset butterfly valve structure introduction

First offset is provided to the central axis of the sealing surface in which the disc rotates 360-degree around the middle axis to provide sealing by deforming the soft seal which results in full friction.

Second offset refers to the position of the shaft with respect to the centerline of the bore. At the time of operation, it produces a cam action to lift the seat away from the seal, results in friction during the first 10 degrees of opening and the last 10 degrees of closure.

Third offset is the geometry of the closing elements. Each sealing element is machined into a conical offset profile, which results in a right-angled cone. Throughout its working cycle, this guarantees friction-free stroking. Contact is only made with the 90° angle functioning as a mechanical stop at the final point of closure; this results in no over-travel of the disc seat.

When these three offset structure is provided together the valve offers a continuous sealing surface, shows minimal wear between sealing surfaces, and provides durable sealing throughout the valve’s life. In addition, sticking and binding of the disk is lowered and less operating torque is required as it has an optimized seating angle.