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The Av-Tek® DEX butterfly valves have a double offset disc design that allows the disc to move off the seat reducing running torque and seat wear. Operation of the DEX may be done with a gearbox and handwheel or with electric, pneumatic or hydraulic actuator. NSF 61/372 Certified. Tested to BOTH AWWA and EN 12266-1 Standards. This ensures the highest quality available.


Technical Specification

The butterfly valve shall be designed expressly for waterworks applications and shall be of the double offset design. Zero and single offset butterfly valve designs are not acceptable. Valves shall exceed the requirements of AWWA C504-15. Valves shall be of the size and class indicated in the Valve Schedule. All valves shall be bubble tight and sized for bi-directional water service, full rated pressure, and a line velocity of 16 feet per second at maximum pressure and up to 50 ft/sec if a line break happens.

Pressure Class: Butterfly valves shall conform to ANSI Class 150B, Class 275B or Class 500B.

Flanges: Flanges shall be in conformance with ASME B16.1 Class 125.Flange faces shall be coated in accordance with Section 2.A.(18) Paint and Coatings.

Valve Lay Length: Flanged valve lay lengths shall be in accordance with AWWA C504-15 AWWA C519-18 , Table 1 short bodied valves or AWWA C519-18-500-B


Body: Valve bodies shall be ductile iron, ASTM A536 65-45-12.

  1. The entire valve body, excluding shaft bores, shall be coated for corrosion protection as detailed in Section 2.A.(18) Paint and Coatings.


Valve Tags: Valves shall be equipped with mechanically fastened stainless steel stamped or engraved tags as detailed in Section 2.A.(19) Marking.Painted lettering on tags will not be accepted.


Disc: The disc shall be ductile iron ASTM A536 65-45-12 or ASTM A536 60-40-18. The disc shall be pinned using 2205 Duplex Stainless Steel pin and O-Ring seals shall be used to prevent the media from entering the disc hub.

Shaft: Valve shafts shall be dual stub shafts of stainless steel ASTM A240 Type 2205 Duplex.


Elastomeric Seat: Valve seats shall be field replaceable and shall be secured to the valve disc by a 316 stainless steel seat retainer ring and secured by 316 stainless steel fasteners. Elastomeric valve seats shall be field replaceable in-line without having to remove the valves from service. The elastomeric seat material shall be EPDM. The valve shall be bi- directionally leak free at the full pressure rating and hydrostatically tested on both sides of the disc. The field replaceable seat shall not require special skills or tools to replace the seal.


Metallic Seating Surface: The metallic seating surface shall be located in the valve body. Seating surfaces shall be a highly wear resistant 316L Stainless Steel. The seat shall be applied through a high alloy weld double overlay process and shall have a final surface minimum thickness of no less than 5mm.


Shaft Seals: Shaft seals shall be appropriate for service specified. Shaft seals shall be composed of multi-O-ring seals protecting both the OD and ID of the shaft bearings. A minimum of 8 O-Rings shall be used on each side of the disc. Elastomer material shall be peroxide cured EPDM.

Shaft Bearings: Valve thrust bearings shall be designed and manufactured to support the valve shaft and transmit disc forces to the valve body while minimizing friction and wear, thrust bearings shall be manufactured from lead free bronze and must have NSF/ANSI approvals. Rubber, PTFE or other plastic materials will not be accepted as shaft bearings.


Paint and Coatings:

  1. All coatings shall be NSF/ANSI 61/372 certified, shall comply with the requirements of AWWA C550 and ANSI A21.16, be holiday free and have a minimum total dry film thickness no less than 12 mils. Heat fusion bonded epoxy shall be used on all standard size butterfly valves.

  2. All sharp edges to be coated shall have the necessary beveling or long radius to assure consistent coating thickness.



  1. All parts subject to disassembly prior to shipment shall be marked for identification and match marked. Match marking information shall be submitted inthe O&M manual.

  2. Casting markings shall conform to the appropriate section of MSS-SP-25 each valve shall be marked with the Valve Manufacturer’s name, valve size, body material, and pressure rating cast into the body of the valve. Lettering shall be a minimum of ½ inch tall and project a minimum of 1/10 inch from the body.

  3. Each individual piece of equipment shall bear a stainless steel nameplate attached with stainless steel screws or rivets, upon which there shall be engraved or stamped the following minimal information. Painted lettering on tags shall not be accepted.

  4. Valve Manufacturer's name or trademark

  5. Valve Manufacturer's serial number

  6. Valve Size

  7. Valve Pressure Rating


Approved Valve Manufacturers

  1. Av-Tek Inc. – DEX 2504 / DEX-HP500

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