Double Offset Butterfly Valve

Material:

Body and Disc: Ductile Iron, ASTM A536 Grade 65-45-12
Retaining Ring: Stainless Steel, Type 304
Resilient Seat: EPDM
Shaft: Stainless Steel, Type 304 or 316
Bushings: Lead-free bronze
O-Ring: EPDM or Buna-N (optional)

Corrosion protection:

Fusion bonded epoxy coating, AWWA C550

Understanding the Benefits of Double Offset Butterfly Valves:
This is an overview on the AWWA C504/C516 double offset butterfly valve and a its key features and characteristics.
With growing interest in Double Offset Butterfly Valves this session will highlight the benefits and the differences of this valve. The very first leak tight butterfly valve was designed in the 1940’s as a concentric style valve. This valve was used until the single offset (eccentric) butterfly valve as introduced in the 1950’s (pre-computer) and it is still the most utilized butterfly valve in the United States today. The Double Offset Butterfly Valve design corrects the unavoidable design flaws of the AWWA C504/C516 single offset commodity butterfly valve. The Double Offset Butterfly Valve offers a modern design and is intended to solve all the issues found in typical commodity butterfly valves.

Double Offset Butterfly Valves are designed and made for functional longevity in water systems. They are designed with a double offset whereby the disc is asymmetrical (allowing for a higher Cv) and the valve shaft is attached at the back of the disc and a few degrees from centerline. This allows for a camming effect, whereby the elastomeric seal is not compressed until the disc is rotated into the body. This prevents the possibility of a “compression set’” on the elastomeric seal and consequently the seal will not leak if the valve is held in the open position for extended periods of time.

Manufacturing Double Offset Butterfly Valves requires tighter machining tolerances and better casting then commodity zero offset or single offset (eccentric) waterworks butterfly valves. Double Offset Butterfly Valves are a true zero leakage bi-directional resilient seated butterfly valve due to the prevention of compressed seats. Additionally, the valve vacuum seals. This is especially important in a line break whereby outside soils and waters can enter the negative pressure of the butterfly valve.

Double Offset Butterfly Valves require high quality castings and machining to produce tight tolerances between disc and body. This allows for a very small about of exposed elastomer used at sealing which in turn allows for the highest industry localized velocities. Double Offset Butterfly Valves exceed the AWWA pressure classes of 150 and 250 psi. They can be used to over 42 feet per second (fps). This design allows for the highest published flow rates for any AWWA butterfly valve.

Double Offset Butterfly Valve body seats are a nickel alloy welded overlay to the ductile iron body. There is a natural metallurgical bond between the ductile iron and the nickel ensuring there is no chance for corrosion to form between the body and the seat. This design ensures the valve will always seal. Furthermore, Double Offset Butterfly Valves utilize five (5) O-rings to maintain a dry shaft and seal. This dry shaft design prevents corrosion from forming in the shaft bore and removes the need for manually servicing/ maintaining packing.

Double Offset Butterfly Valves are fusion bonded epoxy coated and adhere to a rigorous established QA/QC program. This system tests for, thickness, coating adhesion (pull test), cathodic disbanding, holiday free, and impact resistance (ding) testing.

In conclusion, Double Offset Butterfly Valves are a very high quality and longevity isolation valves. Providing owners and end-users peace of mind knowing they can isolate their transmission lines without the expense of specialty line services.

Features:
Double Offset Butterfly Valves are built to exceed each respective international standard including AWWA C504/C516.

Longest leak free seal in industry. Double Offset Butterfly Valve design provides an additional offset over industrial and commodity butterfly valves. This additional offset prevents the valves elastomeric seal from being compressed in the open position and prevents the elastomeric seal from taking a “compression set” which becomes a leak pathway when the valve is closed. This design greatly increases the longevity of zero leak sealing.

Double Offset Butterfly Valves are manufactured and received as a true zero leak bi-directional isolation valve.

Double Offset Butterfly Valve pressure classes exceeds the AWWA Standard of 150 and 250 psi limits by simply using a 17-4 shaft at a very low-cost adder. These are routinely design and build true longevity waterworks valves to the highest flow velocities, 580 psi and higher and to world scale large sizes.

The Double Offset Butterfly Valve exceeds the AWWA Standard maximum 16 feet per second (fps) design.

All sizes have a very quickly field replaceable seat (if ever needed). The seat replacement can be accomplished in less than five hours for a 96” butterfly valve. Compare this timeline to the several days needed to replace the seat for most AWWA valves. Double Offset Butterfly Valve seat replacements are very easy, nothing complex and factory skillsets are not needed.

Baked on fusion bonded epoxy coating is applied on valves up to 96-inch.

Tight tolerances in casting and machining provide for a high spec valve tested to tens of thousands of cycles with documented no leaks.

A corrosion free zone of both a dry shaft and disc hub versus a wetted valve shaft. This allows the actuator to be removed without needing to dewater the pipeline.

A Few Key Items:

Most modern designed valve in the utility market by at least 20-30 years and specifically designed for the “municipal” market.
Double offset will provide leak free sealing over its life versus antiquated single offset or concentric design valves.
75-90 year expected service life.
Fastest and least costly seat replacement of all valves. No factory assistance is needed.
The valve is the only AWWA C504/C516 butterfly which utilized modern design of CAD and FEA in its development.
Low maintenance and virtually service free.
True zero leakage bi-directional.
NSF-61 Certified.

The AWWA Double Offset Butterfly Valve is a rugged and dependable resilient seated, double offset valve designed for high performance in water treatment facilities, pipelines, pump stations, and industrial settings. This high specification valve is built to last with a weld overlaid body seat, innovative dry shaft, and fusion bonded epoxy coating and NSF/ANSI 61 certified.

Product Features and Benefits:

Double offset design with 360 degree sealing
Rugged and corrosion resistant
Nickel chromium weld overlaid body seat
O-ring sealed dry shaft
Long-term sealing at extreme velocities
AWWA C504 compliant and NSF/ANSI 61 certified
Field replaceable rubber seat with common tools
Sizes 6"-160" ANSI Class 150, 250 or 350 flanged
Manual, electric, or hydraulic actuation

6 - 166" Double Offset Butterfly Valve