Circular Flap Non-Return Outfall Gates (DN200–DN1500 | HDPE / Stainless Steel Construction)
📄 Executive Technical Summary
Indus Industrial Group supplies corrosion-proof Circular Flap Non-Return Outfall Gates (Tidal Flap Valves) manufactured in nominal diameters from DN200 (8") to DN1500 (60"). Engineered from lightweight, high-density polyethylene (HDPE) with marine-grade AISI 316 stainless steel hinge linkages and EPDM lip seals, or heavy ductile iron, these gravity-operated check gates prevent backflow of river floodwaters, tidal surges, and canal overflows into municipal stormwater networks, culvert outfalls, and wastewater treatment discharge headers across Iraq.
⚡ Key Engineering Features & Performance
📋 Technical Datasheet Parameters
RFQ Pricing Model| Pricing Verification | Commercial Quote on Demand (RFQ) |
| Nominal Diameters | DN200 to DN1500 (8" to 60") Circular Outfall Diameters |
| Door Flap Material | High-Density Polyethylene (HDPE 100) / Stainless Steel AISI 316 |
| Frame Construction | AISI 316L Stainless Steel / Cast Ductile Iron EN-GJS-500-7 |
| Hinge & Hardware | Marine Grade AISI 316 Stainless Steel with POM / Bronze Bushings |
| Sealing Gasket | UV-Resistant EPDM / NBR Lip Seal (tested drop-tight) |
| Backpressure Head | 5 meters to 10 meters Maximum Reverse Backwater Head |
| Cracking Pressure | ≤ 15mm to 20mm water head (ultra-low opening resistance) |
| Hinge Incline Angle | 5° to 10° Forward Tilt for Positive Gravity Closure |
| Mounting Types | Flat Wall Mount with Chemical Anchors / Pipe Flange Mounted (PN10/PN16) |
| Governing Standards | BS 7775 / DIN 19569 / ISO 5208 |
| Sector & Division | Water & Wastewater (Div 01) |
| Parent Category | Penstocks & Channel Sluice Gates |
🏗 Infrastructure Applications & Project Deployments
Municipal stormwater outfalls into Tigris and Euphrates rivers, Shatt al-Arab tidal flood protection, WWTP treated effluent outfalls, and agricultural drainage culverts in Basra, Baghdad, Amarah, Nasiriyah, and Wasit.
🔬 Authoritative Engineering Analysis
Seasonal flooding along the Tigris, Euphrates, and Shatt al-Arab rivers creates dangerous backpressure on municipal stormwater outfalls and wastewater discharge pipes. If outfalls lack reliable non-return protection, rising river floodwaters reverse flow back into municipal sewer networks, causing catastrophic street flooding in low-lying urban areas of Baghdad, Basra, and Amarah. Indus Circular Flap Outfall Gates provide an automatic, gravity-operated non-return barrier that opens freely with minimal internal head while closing drop-tight against reverse river heads up to 5 to 10 meters.
Manufactured with a high-density polyethylene (HDPE) flap door hung on an inclined angle (typically 5° to 10° forward tilt), the valve requires an ultra-low cracking head (less than 10–20mm of water) to open, ensuring stormwater discharges freely under gravity. The lightweight HDPE flap requires 80% less opening force than heavy cast iron flaps, eliminating upstream pooling and water stagnation.
The hinge mechanism is fabricated from heavy AISI 316 stainless steel with self-lubricating POM/bronze bushings that will not seize from silt deposition or algae growth. The seating perimeter features a resilient EPDM or neoprene lip seal vulcanized to the frame, ensuring an airtight, watertight seal against reverse river backflow. Available in wall-mounted or flanged styles at our Basra and Erbil depots.
Technical & Procurement FAQs
Why are HDPE flap valves superior to traditional cast iron flap valves in southern Iraq?
Cast iron flap valves are extremely heavy, requiring high upstream water head just to push them open, which causes local flooding. They also rust and seize shut in Basra's saline water. HDPE flap valves are lightweight, open under 15mm of water, and never rust.
How does the flap valve seal against high reverse flood levels in rivers?
The door is hung at a 5-degree forward angle so gravity holds it naturally closed. When river levels rise outside, the external hydrostatic water pressure pushes the HDPE door tightly against the resilient EPDM perimeter gasket, preventing backflow.
Can flap gates be mounted directly onto existing concrete culvert walls?
Yes. Our wall-mounted flap gates feature pre-drilled stainless steel perimeter mounting flanges that anchor directly to flat concrete outfall headwalls using stainless steel chemical anchor studs.