VT-200 Double Offset Butterfly Valve

A double offset high performance butterfly valve for large lines where a gate valve would not fit the available face-to-face.

Double offset disc lifts clear of the seat within the first degrees of travel

Field replaceable seat ring on wafer and lug bodies

One piece blowout proof shaft with no through-hole in the disc face

Short laying length where a gate valve will not fit the available space

Specifications

Design standard: API 609 Category B / ASME B16.34
Nominal size: DN80 – DN600 (NPS 3 – 24)
Pressure class: Class 150 / 300
Body material: ASTM A216 WCB, A351 CF8M, ductile iron to order
Trim material: 316 stainless or ENP disc, reinforced PTFE or metal seat
End connection: Wafer, lug or double flanged to ASME B16.5
Operating temperature: -29 °C to +200 °C with PTFE seat
Face-to-face: API 609 / ASME B16.10 short pattern
Actuation: Gearbox standard, ISO 5211 pad for pneumatic or electric
Test practice: Shell and seat to API 598

Product detail

On a DN500 line a gate valve is long, tall and heavy, and often there is simply no room for it. A butterfly valve does the same isolation job in a fraction of the laying length. The VT-200 is double offset: the shaft sits behind the disc face and off the pipe centreline, so the disc lifts clear of the seat within the first few degrees of travel instead of scrubbing across it.

Why the offset matters

A concentric rubber lined valve wears its liner every time it is operated, because the disc is in contact through the whole stroke. The double offset geometry breaks that contact almost immediately, so the seat lasts through many more cycles and the operating torque drops. It is the difference between a valve you replace and a valve you re-seat.

Seat and shaft

A laminated or reinforced PTFE seat retained by a mechanically fastened ring, replaceable in the field without removing the valve from the line for wafer sizes. The shaft is one piece through the disc, pinned, and blowout proof; there is no through-hole in the disc face that could become a leak path.

Throttling

The valve will throttle usefully between roughly 20 and 70 degrees open. Outside that band the flow characteristic is not worth much and the disc sees high velocity across a small opening. If the duty is genuinely modulating, specify a control valve instead and we will size it.