Triple offset butterfly valves (TOVs), are also known as triple eccentric butterfly valves, these valves have continued to advance since they are introduced around 50 years back, these valves are now used across many industries. Initially, Triple offset butterfly valves are used for water shut-off purposes but the enhancement in design over the past few years made this valve to be used in critical processes also.
TRIPLE OFFSET BUTTERFLY VALVE
Today, Triple offset butterfly valve offers a variety of advantages to the industry and most recently, they have gained recognition because of their ability to control pollution. In order to tackle this global challenge of emissions, the industry started to look for more innovative ways, and triple eccentric butterfly valve recently looked upon by valve manufacturers for this problem. By introducing new and updated features, Triple offset butterfly valves are used in ways that have never been used before, although they are still used more cost-effectively.
What is Triple Offset Butterfly Valve?
There are three different offsets in the Triple offset butterfly valve (TOV). Two offsets are at the center and the third offset is on the sealing surface creating a cone-like shape of the disk and the seat. Triple offset valves are used where a bubble-tight seal is required, the system is under high temperature and hard sealing with zero leakage is needed.
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.
The 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 offsets are 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.
Classification by Connection Type
Based on the connection there are different types of Triple offset butterfly valves.
- Wafer type ends.
- Lug type ends.
- Both flanged ends.
- Butt-welded types end.
Wafer Type: 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: 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: The flanged type eccentric 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: 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.
How Does Triple Offset Butterfly Valve Work?
The triple offset butterfly valve does not operate like a traditional butterfly valve, which while turning of the lever, turns sideways to allow the media to pass, like handwaving. The triple offset type works like a globe valve, where the disk moves a bit like a cone, going up and down.
A strong seal occurs as the cone moves to become a circle. There is no drag when the seat comes into contact with the disk due to the angled positioning of the disk in relation to the surface.
Application & Benefit of Triple Offset Butterfly Valve
Triple Offset Butterfly Valves are important for applications where bubble-tight sealing is needed. In some applications, bubble-tight sealing cannot be accomplished by using double offset butterfly valves.
Some processes do not adapt themselves well to conventional butterfly valves, such as applications containing harsh chemicals or mediums with small particles susceptible to clogging valves and pipes. In such systems, Triple Offset Technology gives superior advantages where cam action and right-angled conical sealing ensures that the metal seal elements will never come in contact until its final degree of closing.
Here metal to metal sealing provides bubble-tight shutoff which results in no leakage performance.
Friction-free stroking is available throughout the cycle which allows the operation with low torque and extends the valve life.
Valve has no cavities between the sealing elements due to which clogging is eliminated which results in low maintenance and in turn extends the valve life.
Should you have any question, please feel free to contact us. NTGD valve is an experienced triple offset butterfly valve manufacturer.