In the world of flow control, butterfly valves play a major role — especially in industries dealing with liquids, gases, and steam. Among the various types, double offset and triple offset butterfly valves stand out as high-performance options. But what’s the real difference between them? And when should you choose one over the other?
A butterfly valve is a quarter-turn valve that controls flow using a rotating disc. When the disc turns parallel to the flow, the valve opens; when perpendicular, it closes.
These valves are compact, quick to operate, and ideal for regulating flow in pipelines. Now, let’s explore the offsets.
In a standard (concentric) butterfly valve, the stem and disc are centered in the valve body. This setup causes the disc to rub against the seat throughout the opening and closing process — leading to wear, friction, and limited durability.
To solve this, engineers introduced offsets, which are intentional misalignments of the shaft and disc to minimize friction during operation.
There are two common offset designs used in industrial settings:
Double Offset (2x offset)
Triple Offset (3x offset)
Let’s look at each in detail.
In a double offset butterfly valve, two key misalignments are built into the design:
First Offset: The shaft is moved behind the centerline of the sealing surface.
Second Offset: The shaft is also offset horizontally from the centerline of the pipe.
These two offsets create a cam-like motion, allowing the disc to lift away from the seat early in the opening stroke. This significantly reduces friction between the disc and seat.
Reduced seat wear compared to concentric valves
Supports higher pressure and temperature
Typically uses a soft seat (like rubber or PTFE)
Suitable for water, HVAC, oil & gas, and general industrial use
A triple offset butterfly valve includes the same two offsets as the double offset valve — but adds a third one:
Third Offset: The sealing surface is angled in a conical shape, and the disc edge matches this profile.
This final offset ensures that the sealing surfaces touch only at the final point of closure — with no rubbing during opening or closing. The seal is achieved through mechanical torque, not interference.
Zero friction during operation
Typically uses a metal-to-metal seal
Can handle extreme pressures and temperatures
Excellent for steam, gas, chemicals, and high-performance applications
| Feature | Double Offset | Triple Offset |
| Number of Offsets | Two (axial and radial) | Three (axial, radial, and angular sealing) |
| Seal Type | Soft seat (rubber, PTFE) | Metal-to-metal seat |
| Friction During Operation | Minimal, some rubbing | Near zero – no rubbing during open/close |
| Pressure & Temperature Range | Medium | High (up to 1500 psi and >500°C in some cases) |
| Leakage Class | Class IV or V | Class VI (bubble-tight, zero leakage) |
| Typical Applications | Water, HVAC, oil & gas, general fluids | Steam, chemicals, refinery, cryogenics, etc. |
| Cost | Moderate | Higher due to complexity and materials |
| Lifespan | Good | Excellent (less wear and longer operational life) |
Choosing between a double and triple offset butterfly valve depends on your specific application:
You’re working with moderate pressure and temperature
A soft seal (like EPDM or PTFE) is sufficient
You want good performance at a lower cost
You need a tight shut-off, but not necessarily zero leakage
You're in industries like water treatment, power plants, or oil refineries
You need high sealing performance (zero leakage)
The fluid is hazardous, corrosive, or high-pressure steam
You require a metal seal for high temperature or abrasive flow
You’re operating in critical service applications (like nuclear, aerospace, or offshore platforms)
Here’s a quick breakdown of common materials used:
Body: Ductile iron, carbon steel
Disc: Stainless steel, aluminum bronze
Seat: EPDM, NBR, PTFE
Body: Stainless steel, duplex steel, Inconel
Disc: Hardened stainless steel, Stellite-coated
Seat: Metal (usually same as or harder than the disc)
These material choices affect the valve’s resistance to corrosion, pressure, temperature, and wear.
So, what’s the bottom line?
Double offset butterfly valves are a great mid-range option — balancing cost, performance, and reliability.
Triple offset butterfly valves are engineered for extremes, offering frictionless operation, metal sealing, and ultra-tight shut-off — perfect for harsh environments.
Choosing the right valve is all about understanding your process conditions, fluid type, and performance expectations.
