DEX Double Eccentric Butterfly Valves

Certified to NSF/ANSI/CAN 61/372

Tired of Butterfly valves failing?

Find out why Av-Tek will outlast the rest!
We give you what the others can’t or, to be honest, won’t!

Afraid you won’t be able to perform the necessary maintenance on your system due to failed butterfly valves?

With Av-Tek ®, you get a double offset, high-performance butterfly valve, that far exceeds the standard (commodity type) AWWA valves!


O-rings and Shaft Seals

  • 8 O-Rings create a dry shaft so you no longer need to exercise the valve
  • O-Ring shaft seals can be change with out removing the valve shaft
  • The front cover, under the gearbox, keeps you from getting wet, with the valve in the closed position, and you remove the gear from the valve while under pressure.


Double offset Design

  • With the stem on the back of the disc and the seat on the front of the valve body, this is a double offset butterfly valve
  • Double offset BFV’s make it so the resilient seat is not compressed between the body and disc
  • When a compression seat set happens on the EPDM seat, it will cause a leak path, this happens on standard AWWA C504 Butterfly Valves


Welded Body Seat

  • Double overlay 316L SST Body Seat
  • Robot welded and finished
  • No chance of the seat coming loose with high velocities.


Materials of Construction

  • The Av-Tek DEX body and disc are constructed of Ductile Iron as a standard
  • 250 PSI Pressure Rating – Bi-Directional
  • Cast in lifting eyes for easy installation


2205 Duplex SST Shaft

  • 2205 Duplex SST is standard on all DEX valves
  • Duplex is stronger than 316 SST
  • Duplex is more corrosion resistant than 316, 304 and 17-4 PH
  • Shaft pins are used to secure the disc to the shaft


Resilient Seat and Retaining Ring

  • EPDM Resilient Seat on the Disc
  • EPDM Holds up great when chlorine is present
  • 316 SST Retaining ring for ease of maintenance
  • EPDM Seat has a “T” Shape, making it blow out proof


Other Features

  • Stems are drilled and tapped on the end making maintenance easier
  • FA Mounting Flanges for Gears and Actuators
  • Buried Service or Plant service in stock
  • Electric, Pneumatic and Hydraulic actuators can be adapted easily

We keep our products in stock to make sure
we can ship to our clients in a timely manner.

Most water operators and engineers in the USA have never used or seen a double-offset or double eccentric butterfly valve. 

As Av-Tek sales representatives travel the country we find that approximately less than 10% of wastewater or water departments are using this “new” technology in the USA. 

The reason we say it is a “new” technology is that it is still not used in about 90% of the water and wastewater markets in the USA. 

However, this technology has been around for decades in most markets around the world, just not the USA. 

The double offset design is now gaining significant traction in the USA market.  There are a few main questions people want to know about the double eccentric butterfly valves and a few main reasons why they change from a commodity type zero or single offset butterfly valve.

Scheduled and emergency maintenance can be a major cost and problem when an isolation butterfly valve won’t operate. Most failures on butterfly valves can be prevented if the valve is engineered the right way to begin with.

…therefore you eliminate the seat set or deformation due to being in the open position.

Never Again Worry About Exercising your Water Valves. A series of 8 o’ring seals, designed to create a dry shaft. When raw iron is mixed with water, corrosion begins while the dry shaft in the DEX double offset butterfly valve prevents this corrosion without the need to exercise the valve.

Why Should You Change to Double Offset Butterfly Valves?

Leak-Free Water Valves

Av-Tek offers a unique warranty on all double offset butterfly valves: 3-year, leak-free warranty. 

Standard commodity type valves that meet the minimum requirements of AWWA C504 are zero or single offset butterfly valves. The way these valves are designed creates a leak path when the valve is exercised or when the disc stays in the open position. 

This is due to the disc and the body compressing the resilient seat and creating a seat set or deformation of the seat.  That seat set then becomes a leak path.  A true double offset does not touch or rub the resilient seat until the last 10% of closing, therefore the seat does not get a seat set or deform due to being in the open position.

Never Again Worry About Exercise your Water Valves

This is because a series of 8 O-Ring seals are used to create a dry shaft, unlike your standard waterworks butterfly valves, which use packing glands that require them to be wetted in an area of the valve that is uncoated.  

When raw iron is mixed with water corrosion begins.  This is why there is a requirement for the standard type valves to be exercised regularly, while the dry shaft in a double offset butterfly valve prevents this corrosion without the need to exercise the valve.

What many are finding to be true and you will too, is that by using higher quality valves, you get a longer life out of the valve, less maintenance, and drip tight shut off.

Feel free to reach out to us for all your questions you might have in regards to butterfly valves in your system.

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Double Eccentric Butterfly Valve