Double Offset Butterfly Valves
Double offset high performance butterfly valves. The valve has two stems offset from the centre. It is capable of providing accurate, stable, throttle flow control.
High-performance butterfly valves are a lower-cost valve option with benefits including high-quality to API 609, firesafe and they will seal against flow from either direction. The valves can be supplied in various materials of construction suitable for different service. Materials of construction to include exotic materials Aluminium Bronze (AB2), Super Duplex (SSDS), 6 Moly (6Mo), Hastelloy (C276) and Titanium (Ti). This valve type is suitable for the harshest offshore environment such as FPSO, fixed rigs or LNG carriers.
The double offset butterfly valve is generally used in:
- Oil & Gas (O&G)
- Power Generation
- Process & Chemicals
- Water & Wastewater Treatment
Non-firesafe high performance Double Offset Butterfly Valve
Firesafe high performance Double Offset Butterfly Valve
Metal seated firesafe high performance Double Offset Butterfly Valve
|Description||BUTTERFLY VALVE |
High Performance Double Offset Fire Safe
|Design Code||API 609 / EN593|
|Size Range||NPS 2” – 50” / DN 50- 1250|
|Maximum Pressure/Rating||20 bar – 150#/ 50bar – 300#|
|Design Temperature||-50°C to +500°C (MOC Dependant)|
|End Connections||Wafer / Lug|
|Body Seat||PTFE / RPTFE / Metal|
Materials of Construction
|Body||Carbon Steels inc. Low Temp|
|Austenitic/ Super Austenitic Stainless steels|
|Duplex/ Super Duplex alloys (1A-6A)|
|Hastelloy® B, C, Inconel|
|Monel®, Alloy 20|
|Others upon request|
|Shaft||AISI 410, AISI316, 17-4Ph, Monel® K500, UNS32760, Titanium|
|Seat||PTFE, RPTFE, Inconel 625, SS316|
Frequently Asked Questions
A Butterfly valve is a quarter-turn rotary motion valve with advantage of low pressure drop and high-pressure recovery.
Butterfly valves are used to stop, start, and regulate fluid flow.
Concentric butterfly valves also known as ‘resilient seated’ butterfly valves are suitable for a wide range of applications such as cooling water, chemicals, brine,oil mud, hydrocarbons, wastewater, firewater, seawater, natural gas and flare gas amongst many others. The stem is centred in the middle of the disc and the disc centred in the valve body. The disc is constantly in contact with valve seat. Seats can include EPDM, NBR, Viton, Silicon, Teflon, Hypalon and neoprene.
A high performance butterfly valve. This valve has three offsets from the centre. The third offset is the elliptical seat geometry. This along with the two eccentric shaft offsets, allows the disc to seal against the seat with no friction. This seat design allows for uniform sealing, and thus bi-directional tightness at maximum differential pressure.
The triple offset design is used where bubble tight shut-off, zero leakage is required in common applications such as steam, chemical, refining, and offshore oil and gas. They offer a lower cost, lower torque option, than alternative style metal seated valves. It is low maintenance and offers an extended valve life.
A double offset butterfly valve is a high performance butterfly valve. This valve has two stems offset from the centre. It is capable of providing accurate, stable, throttle flow control.
Butterfly valves can be bi-directional but often have a preferred flow direction. It’s strongly recommended to install the valves in the preferred flow direction, as it will extend the valve’s life span and will also lower the operating torque. High-performance butterfly valves for hydrocarbon service generally do not have a preferred flow direction and are bi-directional.
Yes, Triple Offset Butterfly valves can be used for isolation. Triple Offset is a great alternative to the block valve incumbents like gate. If gate was not applicable to process conditions ball valves were utilized.
Triple Offset Butterfly valves have the following but not limited to advantages in this application;
Ease of operation
More readily available than other valve offering
Motor Operated Valve (MOV) are often called On-Off valves as the motors act to fully open or fully close valves in pipelines. With regards Butterfly valves they fully open or fully close the disc with tight shut off as per plant requirement.
The lugged wafer design, butterfly valve is held in place between two pipe flanges by bolts that join the two flanges and pass through threaded holes (or lugs) in the valve’s body. This design type can be used for dead-end service.
The wafer type butterfly valve, also known as non-lugged is sandwiched between two pipeline flanges. It may sometimes have unthreaded guiding holes for ease of installation.
Flange type or Double Flanged Butterfly valves have two flanges – one either end as opposed to lug type which has one flange in the centre. Flange type have a larger face to face than wafer or lugged. These can be used for dead end service.
This can depend on butterfly valve type installing – contact Frenstar for assistance with installation or to request Installation, Operation and maintenance manuals.
Butterfly valves can be used in throttling / flow control, or on-off control. High performance butterfly valves are widely used for throttling control.