Coldwell-Wilcox Technologies, LLC

- Flap Gates



Flap gates are the simplest way to prevent water from returning back into pipes and openings. The gate is designed so that whatever the size, a small flow will open the gate with unseating pressure and will remain watertight with seating pressure. Also known as tide gates and floodgates because of their ability to prevent back flow into a discharging system. Normally flap gates are round or rectangular cast iron. If required, both round and rectangular can be ductile, 2% nickel or NiResist cast. Rectangular flap gates can also be fabricated in A36 steel, 304(L) or 316(L) stainless steel.


The cast flap gates where shown in the plans and specifications and listed in the flap gate schedule shall be as manufactured by Coldwell-Wilcox Technologies, LLC of Cincinnati, Ohio. Gates shall be cast iron, ductile, 2% nickel or NiResist, construction with circular, square or rectangular openings as called out by the specifications and site drawings. Flap gates shall be thimble, pipe flange or wall mounted. Concrete wall mounted gates shall be anchor bolted and non-shrink grouted in place.

The equipment provided shall be cast, fabricated, machined, assembled and placed in proper operating condition per the drawings, specifications, engineering data, instructions and recommendations of the gate manufacturer unless otherwise noted by the engineer. Gates shall be supplied with all parts and accessories as specified within the site specifications and drawings and as required for a complete installation.


The flap gates shall be the latest standard product in regular production by a manufacturer whose products have proven reliable in similar service. A single manufacturer shall supply the flap gates.


All materials will comply with applicable provisions and recommendations of the following, except as otherwise shown or specified:


Manufacturer's data and drawings shall be submitted for approval in accordance with site specifications and engineering drawings. Manufacturer's submittal shall include but not limited to gate material specification sheet, gate data summary sheet, site plan drawings and paint/coating data sheets.


Gates shall be designed and shop tested to the applicable CWT standard. Design and operating heads shall be per the site schedule and/or specifications.


The flap shall be one piece cast iron, ductile, 2% nickel or NiResist casting with iron-to-iron, bronze or neoprene seats. The flap shall be designed with integral ribs and hinge bosses to safely withstand the design head with a safety factor of 5.


The frame shall be one piece cast iron, ductile, 2% nickel or NiResist casting with iron-to-iron, bronze or neoprene seats. The integrally designed back flange shall be faced and drilled to match the mating thimble bolt pattern, pipe flange bolt pattern or wall mounted configuration. The seat face of the frame shall be sloped from the vertical a minimum of two (2) degrees. Metal thickness of the frame shall be a nominal 1' with flanges not less than 1 1/2 inches thick.


Bronze: Seat facings shall be malleable extruded bronze of a composition, which will resist dezincification and will increase in working ability with cold working. The extruded seat facings shall be a special shape to fill and permanently lock in the machined dovetail grooves when impacted into place. Attaching pins and screws shall not be allowed. The installed seat facings shall be machined to a 63 micro-inch finish or better.

Neoprene: Seat facings shall be the best grade of neoprene having a tensile strength of 1,500 p.s.i., a minimum elongation of 400 percent and a durometer hardness of 50-60. An exact slot shall be machined in the seat face to accept the neoprene which shall be mechanically retained without the use of fasteners.

Cast Iron: The castings shall be machined to a 125 micro-inch finish or better forming the cast Iron seat facings.


Hinge arms shall be fabricated or cast in one of several materials listed in the materials schedule. The hinge arms shall be UHMW or bronze bushed. The hinge pins shall be bronze or stainless steel as detailed in the materials section. The hinge arm and pin configuration is designed to be in double shear with arm to flap adjusting screws to align the flap seat face to the frame seat face. Pivot lug bosses shall be flap and frame mounted with non-corrosive grease fittings without bushings. Bushing and grease fitting configuration shall be as specified in the job specification.


Wall thimbles will be furnished for all flap gates that are not attached to pipe flanges or concrete wall mounted and as specified in the job specifications. Wall thimbles shall be of the section 'F', 'E' or 'MJ' (mechanical joint) and depth as indicated on the plans and listed in the gate schedule. They will be cast iron, ductile, 2% nickel or NiResist one-piece construction, of adequate section to withstand all operational and reasonable installation stresses. Wall thimbles will be internally braced during concrete placement. A center ring or water stop will be cast around the periphery of the thimble. The front flange will be machined and have tapped holes for the flap gate attaching studs and metal stamped vertical centerlines with the word 'TOP' for correct alignment.

Large wall thimbles will be provided with holes in the invert to allow satisfactory concrete placement beneath the thimble.


Steel and cast iron components shall receive manufacturer's standard TNEMEC epoxy series N140-1255 pota-pox beige and TNEMEC series 69 pond 28BL finish prior to shipment. Total system shall be 12-16 mils DFT.

Tnemec coal tar epoxy series 46H-413 or Tnemec potable epoxy series N140 pota pox are available, as specifications require. Coal tar epoxy total system shall be 20-26 mils DFT. Tnemec potable epoxy total system shall be 12-16 mils DFT.


Each gate shall be fully assembled and shop-inspected in the vertical position for proper seating. The flap shall be fully opened and closed to ensure that it operates freely and seals.


Installation shall be in complete accordance with manufacturer's instructions and recommendations. Anchor bolts will be set in accordance with approved manufacturer's drawings.


Contractor shall make adjustments required to place system in proper operating condition. Contractor shall conduct functional field test of each flap gate in the presence of the Owner's Project Representative to demonstrate that each part and all components together function correctly.

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