#1 Flanges Manufacturer

Kalpataru Piping is one of India’s most trusted flanges manufacturers and exporters, delivering precision-forged flanges across 50+ material grades to industries worldwide. With decades of hands-on expertise in the piping and metallurgical space, we manufacture every style of industrial flange from weld neck and slip-on to blind, socket weld, lap joint, threaded, and spectacle blind types — in full compliance with ASME B16.5, ANSI, DIN, API, and BS standards. Our flanges serve critical applications in oil and gas, petrochemical, power generation, pharmaceuticals, food processing, and marine industries.

Every flange that leaves our facility undergoes rigorous third-party inspection, hydrostatic testing, and dimensional verification. We stock and supply stainless steel flanges, carbon steel flanges, alloy steel flanges, nickel alloy flanges, duplex steel flanges, super duplex flanges, Monel flanges, Hastelloy flanges, and Inconel flanges — all available in custom sizes from ½” NB to 48″ NB. When your project demands reliability and traceability, Kalpataru Piping is your partner of choice.

Table of Contents

• What Are Flanges?
• Our Complete Forged Fittings Range
• Flanges Material & Grade Availability
• Technical Data
• Types of Flanges We Manufacture
• Flanges Applications
• Certifications, Standards & Quality Assurance
• How We Manufacture Flanges
• Frequently Asked Questions

What Are Flanges?

A flange is a forged or cast ring of metal that mechanically joins two sections of pipe, a pipe to a valve, a pump, or any other piece of process equipment. Flanges create a bolted, sealed joint that permits easy disassembly for maintenance, inspection, or modification — making them the second-most-common joining method in industrial piping after welding.

A standard flanged connection consists of three elements:

1. The pipe flange – forged, machined, and faced to a specific standard
2. The gasket – compressible material seated between the two mating faces
3. The bolting – studs and nuts that compress the gasket to form a pressure-tight seal

Flanges are classified by pressure class (150#, 300#, 600#, 900#, 1500#, 2500# per ASME; PN6 to PN400 per DIN), facing type (raised face, flat face, ring-type joint, tongue-and-groove), size (½” NB to 48″ NB), and material grade. Choosing the right combination for your operating temperature, pressure, and fluid chemistry is critical to plant safety and uptime.

At Kalpataru Piping, we manufacture flanges in all pressure classes, all facing types, and sizes from ½” NB to 48″ NB across more than 50 material grades. Our pipes and tubes division allows us to supply complete piping solutions under one roof.

Flanges Material & Grade Availability

Flanges Technical Specifications

Types of Flanges We Manufacture

Kalpataru Piping manufactures the complete spectrum of industrial flange types. Each style is engineered for specific pressure ratings, installation methods, and operating conditions.

1. Weld Neck Flanges

Weld neck (WN) flanges feature a long tapered hub that is butt-welded to the pipe. The gradual bore transition reduces stress concentration, making this the preferred choice for high-pressure, high-temperature, and cyclic-load applications in oil refineries and power plants. Available across all pressure classes up to 2500#.

2. Slip-On Flanges

Slip-on (SO) flanges slide over the pipe and are fillet-welded on both the bore and the face. They are easier to align and significantly more economical than weld neck flanges. Best suited for low-pressure, non-critical services. Size range: ½” to 24″ NB.

3. Blind Flanges

Blind flanges are solid discs used to seal the open end of a pipe, vessel, or valve — either permanently or for temporary isolation during pressure testing. They experience the highest bending stress of any flange type and are available in all pressure classes and materials.

4. Socket Weld Flanges

Socket weld (SW) flanges have a socket bore into which the pipe is inserted and secured with a single fillet weld. Ideal for small-bore piping (½” to 2″ NB) in high-pressure, non-corrosive services where internal crevices are acceptable.

5. Lap Joint Flanges

Lap joint flanges are used with a stub end and can rotate around the pipe, making bolt-hole alignment simple. They are economical where frequent dismantling is needed and where the flange material need not match the pipe alloy. Often used with copper nickel pipes and tubes.

6. Threaded Flanges

Also called screwed flanges, these are connected to the pipe by threading — no welding required. Used in hazardous environments where welding is prohibited, or in low-pressure compressed air and water services.

7. Orifice Flanges

Orifice flanges are used with orifice meters to measure flow rates. They are furnished with pressure tappings and are manufactured in pairs to ASME B16.36.

8. Spectacle Blind Flanges

Spectacle blinds consist of a solid disc (blind) and an open ring (spacer) joined by a web, used in pairs to isolate or connect pipeline sections. Manufactured per ASME B16.48.

9. Long Weld Neck Flanges

An extended weld neck that acts as a nozzle, used in pressure vessels and heat exchangers where the flange is welded directly to the shell.

10. Ring Type Joint (RTJ) Flanges

RTJ flanges have a machined groove that seats a metal ring gasket, forming an extremely high-pressure seal. Used in subsea, wellhead, and refinery services requiring pressures above 600#.

11. API 6A Flanges (Type 6B / 6BX)

Manufactured to API Spec 6A for wellhead and Christmas tree equipment. Available in 2,000 / 3,000 / 5,000 / 10,000 / 15,000 / 20,000 PSI ratings. See our API 6A type 6BX flanges range.

Flanges by Material Grade Guide

Selecting the right flange material is as important as selecting the right type. Below is Kalpataru Piping’s complete material portfolio with key application notes and internal product links.

Flanges Applications

Kalpataru Piping’s flanges are engineered to perform in the most demanding process environments across the globe. Our products are qualified and currently in service across the following industries:

Oil, Gas & Petrochemical

High-pressure weld neck and RTJ flanges in carbon steel, alloy steel, and super duplex grades are critical to upstream wellheads, midstream transmission, and downstream refinery piping. Our alloy steel products and super duplex steel flanges are particularly suited here.

Power Generation

Boiler feed water, main steam, and turbine bypass lines demand flanges with verified creep strength at elevated temperatures. We supply F91, F22, and F11 alloy steel flanges tested to ASME PTC and IBR standards.

Chemical & Pharmaceutical

Corrosion is the primary failure mode in chemical reactors, absorption columns, and solvent recovery systems. Hastelloy C276, Monel 400, Incoloy 825, and SMO 254 flanges provide the chemical resistance these services require.

Marine & Offshore

Seawater piping, fire-fighting systems, ballast systems, and HVAC aboard ships and offshore platforms rely on copper nickel 90/10 and 70/30 flanges for their inherent biofouling resistance.

Desalination & Water Treatment

Super duplex (S32750/S32760) flanges handle chloride-laden brine streams in SWRO, multi-effect distillation (MED), and multi-stage flash (MSF) desalination plants without stress corrosion cracking.

Food, Beverage & Dairy

Hygienic stainless steel 316L flanges with smooth, crevice-free finishes meet 3-A sanitary standards for CIP lines, storage tanks, and pasteurisation units.

Pulp, Paper & Fertilisers

Aggressive bleaching chemicals (chlorine dioxide, sodium hypochlorite) and fertiliser plant acids (phosphoric, sulphuric, nitric) demand Hastelloy or titanium flanges to resist uniform and localised corrosion.

Cryogenic & LNG

Low-temperature carbon steel (ASTM A350 LF2) and stainless steel 304L/316L flanges rated down to -196°C serve LNG storage, regasification, and air separation units.

Certifications, Standards & Quality Assurance

Kalpataru Piping is committed to delivering flanges that meet or exceed international quality benchmarks. Every order is backed by full material traceability and documented quality records.

Standards We Manufacture To

• Dimensional Standards: ASME B16.5, ASME B16.47 (Series A & B), ASME B16.36, EN 1092-1, BS 4504, DIN 2527–2638, JIS B2220, GOST 12820, API 6A
• Material Standards: ASTM A105, A182, A350, A694, A516; ASME SA-182, SA-336; ASTM B564 (nickel alloys); ASTM B160/B162/B166/B168 (Inconel/Incoloy)
• Inspection Standards: ASME Section V (NDE), ASME Section IX (welder qualification), NACE MR0175/ISO 15156 (sour service)

Quality Tests Performed

Certifications Held

• ISO 9001:2015 Quality Management System
• PED 2014/68/EU (Pressure Equipment Directive) for export to Europe
• IBR (Indian Boiler Regulations) approval for boiler-grade materials
• NABL-accredited laboratory test reports available

How We Manufacture Flanges

Our flanges undergo a tightly controlled, 8-step manufacturing process that combines traditional forging expertise with modern CNC machining and non-destructive evaluation.

1. Raw Material Procurement & Incoming Inspection — We source forging-grade billets and bars only from approved mills, accompanied by mill test certificates (MTC) per EN 10204 Type 3.1. Each incoming lot is PMI-verified before it enters our store.
2. Heating & Open/Close Die Forging — Billets are heated to the correct forging temperature range and pressed or drop-forged using open-die or closed-die tooling. Forging refines the grain structure, eliminates voids, and imparts superior mechanical properties compared to plate-cut flanges.
3. Heat Treatment — Solution annealing, normalising, or quench-and-temper cycles are applied depending on material and specification. This relieves forging stresses and achieves the target microstructure for mechanical property compliance.
4. Rough Machining (Turning & Boring) — Forgings are rough-turned on CNC lathes to near-net shape, reducing the amount of material removed in the finishing stage.
5. Precision CNC Finish Machining — High-speed CNC vertical turning centres machine the bore, outer diameter, flange face, and hub dimensions to ASME/DIN tolerances. Surface finish (Ra) is verified by profilometer.
6. Bolt Hole Drilling (CNC Drilling) — High-speed CNC drilling centres, often with four-axis indexing, drill all bolt holes to ASME B16.5 bolt-circle and hole-diameter tolerances in a single setup to ensure concentricity.
7. Marking — Flanges are marked with heat number, material grade, pressure class, flange size, ASTM/ASME standard, and manufacturer’s logo per MSS SP-25, using low-stress die stamps or electrochemical etching.
8. Final Inspection & Non-Destructive Evaluation — Dimensional checks (go/no-go gauges, CMM), visual inspection, hardness testing, and any specified NDE (RT, UT, MT, PT) are completed by our QA team and, where required, a third-party inspector before packing and dispatch.

FAQs – Flanges