GRP Flange

Description

GRP Flange Supplier India | Backing Ring & Fixed Flange | PN4 / PN6 / PN10 / PN16 | DN50–DN1200 | GI / SS304 / SS316 Backing Ring | Municipal Water / Irrigation / Sewage / Cooling Water | KELOR

Supplier: Krishna Industries (KELOR) – Ahmedabad, Gujarat, India
Established: 2017 | GSTIN: 24AKLPP6499B1ZT | IEC: AKLPP6499B
MOQ: 10 Nos | Type: Backing Ring & Fixed/Integral GRP Flange
Pressure: PN4 / PN6 / PN10 / PN16 | Sizes: DN50–DN1200

GRP Flange Supplier in India

Krishna Industries (KELOR), based in Ahmedabad, Gujarat, supplies GRP (Glass Reinforced Plastic) / FRP Flanges — backing ring type (loose flange on GRP stub end) and fixed/integral GRP flange — GI / SS304 / SS316 / MS+FBE backing ring — PN4 / PN6 / PN10 / PN16 — DN50 (2″) to DN1200 (48″) — drilling as per ANSI B16.5 Class 150 / ISO 7005 / DIN 2501 — AWWA C950 / IS 12709 / BS 7159 — GST invoice — MOQ 10 Nos — project BOM supply — Pan India dispatch from Ahmedabad.

GRP flanges are the standard connection method for large diameter GRP pipeline systems — municipal water supply transmission mains, irrigation distribution networks, sewage rising mains, industrial cooling water, and seawater intake pipelines. Furthermore, the backing ring type is the most common configuration on Indian projects because it allows bolt hole alignment without rotating the heavy GRP pipe — critical for large diameter DN400–DN1200 installations where pipe rotation is not practical on site.

Backing Ring Type vs Fixed GRP Flange — Which to Specify

Backing Ring Material Selection

Pressure Rating and Resin Selection

Technical Specifications

Critical Installation Notes — GRP Flange Bolting

GRP flanges require different bolting practice from steel flanges. Incorrect bolting is the most common cause of GRP flange cracking and leakage on Indian project sites.

• Full face gasket mandatory: Always use a full face rubber gasket (EPDM or NBR) that covers the entire GRP flange face including the bolt holes. A ring gasket (like a spiral wound gasket used on steel flanges) concentrates bolt load on the inner ring area and causes the outer GRP flange face to crack under bolt torque. This is the single most common GRP flange installation error on Indian sites.
• Never use raised face (RF) steel flange against GRP: If connecting GRP flange to a steel valve or fitting, use flat face (FF) steel flange — not raised face. RF steel flange bears only on the small raised ring area and creates extreme point loading on the GRP flange face, causing cracking.
Bolt torque sequence: Tighten bolts in a star pattern (opposite bolt pairs) in multiple passes — never tighten one bolt fully before moving to the next. GRP is less forgiving of uneven bolt load than steel.
• Backing ring bolt holes must align before tightening: The advantage of backing ring type is that the ring rotates for hole alignment — always align fully before starting bolt torque sequence.
• Use load spreading washers: Fit large flat washers (backing washers) under nuts to distribute bolt load over larger GRP area — prevents bolt hole elongation under preload.

Applications in Indian Industries

Municipal Water Supply Transmission Mains

Backing ring type — GI or SS304 backing ring — PN6 — DN300–DN1200 — polyester resin GRP. Flanged connections at valve stations, air release valve tees, wash-out points, and thrust blocks on large diameter GRP water transmission mains. Furthermore, JICA and World Bank funded bulk water supply projects across Gujarat, Maharashtra, Tamil Nadu, and Rajasthan are a major source of large diameter GRP flange demand — EPC contractor procurement with project BOM quantities of 200–2000 flanges per contract.

Irrigation Distribution Networks

Backing ring type — GI backing ring — PN6 — DN300–DN800 — polyester resin. PMKSY and state irrigation department funded pipeline irrigation projects — Gujarat SSNNL, Maharashtra WRD, AP Irrigation. Very high volume — irrigation pipeline projects routinely have 500–5000+ GRP flanges in the BOM. Moreover, GRP pipeline is the preferred material for irrigation mains because it resists the corrosive alkaline soils common in Indian agricultural areas where MS pipe rusts rapidly.

Sewage Rising Mains and Gravity Mains

Backing ring type — SS304 backing ring — PN6/PN10 — DN300–DN600 — vinyl ester resin for H2S resistance. Municipal sewage rising mains where H2S corrosion destroys MS pipe within 5–7 years — GRP resists H2S attack providing 40+ year design life. ETP and STP sewage collection networks in Indian industrial clusters — Ankleshwar, Vapi, Dahej GIDC.

Industrial Cooling Water

Backing ring type — SS304 or SS316 backing ring — PN6/PN10 — DN400–DN1200 — vinyl ester resin. Cooling water intake, distribution, and discharge pipelines for power plants, refineries, and coastal industrial — seawater cooling systems where MS pipe and flanges corrode rapidly. Additionally, GRP eliminates the biofouling and corrosion problems that affect MS cooling water systems at coastal Gujarat, Maharashtra, and Tamil Nadu industrial installations.

Related Products — Krishna Industries (KELOR)

• Gear Operated Butterfly Valve — CI/DI body large bore butterfly valve — standard isolation valve at GRP pipeline flanged stations — use flat face (FF) butterfly valve flange against GRP flange
• Double Flanged Butterfly Valve — DN200–DN600 flanged BFV — used at valve stations on large diameter GRP water mains
• Single Plate Wafer Check Valve — pump discharge NRV on GRP rising main pump stations
• Threaded Flanges — MS and SS threaded flanges for small bore connections to GRP main lines
• Stud Bolt — A193 B7 stud bolts for GRP flange bolting — specify with load spreading washers and full face EPDM gasket

Frequently Asked Questions

1. What is the difference between GRP and FRP flanges?

GRP (Glass Reinforced Plastic) and FRP (Fibre Reinforced Plastic) refer to the same product in Indian usage — a composite flange made of glass fibre reinforcement in a resin matrix. GRP specifically implies E-glass fibre reinforcement. FRP is the broader term that can also include carbon fibre or aramid fibre reinforced composites. For standard Indian water supply, irrigation, and sewage applications, GRP (E-glass + polyester or vinyl ester resin) is the correct and most economical specification. Specify FRP with carbon fibre only for very high performance requirements — offshore, aerospace — not for standard pipeline applications.

2. Why must I use a full face gasket with GRP flanges?

A GRP flange face is not as strong as a steel flange face under concentrated bolt load. A ring gasket — which is standard for steel raised face flanges — leaves the outer portion of the GRP flange face unsupported. When bolts are tightened, the unsupported outer GRP flange ring bends backward under bolt load and cracks at the inner edge of the ring gasket. A full face gasket covers the entire flange face including the outer ring area — it distributes the bolt preload evenly across the full flange face and prevents this cracking. Always specify full face EPDM or NBR gasket for every GRP flange connection, regardless of whether the mating flange is GRP or steel flat face.

3. What drilling standard should I specify for the backing ring?

Specify the drilling standard to match the mating flanges in your pipeline system. ANSI B16.5 Class 150 is the most common specification on Indian projects using imported GRP pipe or international project specifications. ISO 7005 / DIN 2501 PN6 or PN10 is common on European-standard GRP pipe systems. IS 12709 drilling is used on CPWD and state PWD projects following Indian standards. Confirm the drilling standard from the GRP pipe manufacturer’s drawing or the project piping specification before ordering. Mixing drilling standards causes bolt hole misalignment on site — specify clearly at order stage.

4. Can GRP flanges be used with steel valves and fittings directly?

Yes — with one critical requirement: the steel flange face must be flat face (FF), not raised face (RF). A raised face steel flange bolted against a flat GRP flange concentrates the bolt load on the raised ring area only — the GRP flange face outside the raised ring is unsupported and cracks under bolt torque. When ordering butterfly valves, gate valves, or other steel flanged equipment to connect to GRP piping, always specify flat face (FF) flanges on the steel equipment. Most Indian valve suppliers supply raised face as default — specifically request FF when ordering for GRP pipeline connections.

5. What is the MOQ and how do I order for a project BOM?

MOQ is 10 Nos for standard sizes. For project BOM supply, share your complete flange schedule — size, pressure rating, backing ring material, drilling standard, resin type, and quantity per size — and we provide a consolidated project quotation within 24 hours. Large diameter GRP flange projects (DN300–DN1200) are supplied with mill certificates, dimensional inspection reports, and pressure test certificates as required by project QA plans. GST invoice with GSTIN 24AKLPP6499B1ZT. Pan India dispatch from Ahmedabad.

Conclusion

Krishna Industries (KELOR) supplies GRP / FRP Flanges for municipal water supply transmission mains, irrigation pipeline networks, sewage rising mains, industrial cooling water, and seawater intake pipelines — backing ring type (GI / SS304 / SS316 / MS+FBE backing ring) and fixed/integral GRP flange — PN4 / PN6 / PN10 / PN16 — DN50 (2″) to DN1200 (48″) — ANSI B16.5 / ISO 7005 / DIN 2501 / IS 12709 drilling — AWWA C950 / IS 12709 / BS 7159 — GST invoice — project BOM supply — Pan India dispatch from Ahmedabad. Share your flange schedule for consolidated project pricing within 24 hours.