Duplex Steel Flanges Manufacturer, Supplier & Stockist
Kalpaturu Piping Solutions is an ISO-certified manufacturer of Duplex Steel Flanges with 12+ years of export experience across oil & gas, chemical, and power generation sectors. We specialise in ANSI B16.5 and ASME SA182-compliant duplex flanges (S31803 & S32205 grades) in all pressure classes (150–2500 LBS). Our production range includes slip-on, socket weld, blind, weld neck, and reducing flange variants, tailored to individual customer specifications.
Kalpaturu Piping Solutions is a well-known manufacturer, supplier and exporter of Duplex Steel S31803 & S32205 Flanges in India. We also offer a full-scale variety of flanges, such as slip-on, socket weld, blind, lapped, screwed, weld neck and reducing flanges, to suit a wide variety of industrial needs. Our ANSI B16.5 Duplex Blind Flanges have superior toughness and ductility over the standard ferritic stainless steels in that they are suitable for the highly demanding applications.
We have various sizes, thicknesses, shapes and specifications of our ASME SA182 Duplex Steel Flanges in order to suit the individual requirements of the clients. The flanges have found extensive application in the chemical, oil and gas, fertiliser and heavy engineering industries. Duplex stainless steel flanges, especially S31803 and S32205, are characterised by high stress corrosion cracking (SCC) capabilities, which are passed on through their ferritic stainless steel characteristics.
The chromium, molybdenum, and nitrogen content of duplex steel is better than the austenitic grades in terms of resistance to chloride pitting and crevice corrosion, and the reduced nickel and molybdenum content makes duplex steel cost-effective in terms of corrosion resistance without significantly reducing corrosion-protecting durability.
Being a reputable manufacturer, supplier, and stockist, Kalpaturu Piping Solutions provides these ASTM A182 duplex steel flanges with very competitive prices guaranteed by quality assurance and timely delivery, and hence is a good solution to the industrial piping needs.
Table of content
- What are Duplex steel flanges?
- Specification of Duplex Steel Flanges
- Duplex Steel Flanges Equivalent Grades
- Chemical Composition of Duplex Steel Pipe Flanges (%)
- Mechanical Properties of ASTM A182 Duplex Steel Plate Flanges
- Class 300 SDSS / Duplex Steel Flanges – Dimensional Chart
- Duplex Stainless Steel Flanges – Size Conversion Chart
- Gasket Sizes of Duplex Stainless Steel Flanges
- Duplex SS Flange Pressure Rating Chart
- FAQs About Duplex Steel Flanges
What are Duplex steel flanges?
Duplex steel flanges are tough pipe-joining components that are made of duplex stainless steel consisting of a matching austenite and ferrite microstructure of a material with approximately equal quantities of both phases. This special design offers high mechanical strength and high corrosion resistance. Duplex flanges have good resistance to pitting, crevice corrosion, and stress corrosion cracking S31803 duplex flanges have a PREN of 30–35, while S32205 grades reach 35+, making them superior to 300-series austenitic stainless steel in chloride-rich environments.
Specification of Duplex Steel Flanges
The following table outlines the specification of Duplex Steel Flanges, including size range, standards, grades, pressure classes, and flange face types to meet diverse industrial piping requirements.
| Parameter | Details |
| Size | 1/8″ NB to 24″ NB |
| Standards | ANSI Flanges, ASME Flanges, BS Flanges, DIN Flanges, EN Flanges |
| Designations | ANSI B16.5, BS 1560, BS 10, IS 6392, B2.1 NPT, API, DIN, JIS, MSS SP-44 |
| Grades | ASTM A182 / ASME SA182 F51, F52, F53, F54, F55, F57, F59, F60, F61, UNS S31803, UNS S32205 |
| Pressure Class | 150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS |
| Flange Face Types | Flat Face (FF), Raised Face (RF), Ring Type Joint (RTJ) |
Duplex Steel Flanges Equivalent Grades
The following table shows the equivalent grades of Duplex Steel Flanges, including international standards, Werkstoff numbers, and UNS designations used for Duplex 2205 materials.
| Standard | Werkstoff Nr. | UNS |
| Duplex 2205 | 1.4462 | S31803 / S32205 |
Chemical Composition of Duplex Steel Pipe Flanges (%)
The following table shows the chemical composition of Duplex Steel Pipe Flanges, including key alloying elements such as chromium, molybdenum, nickel, and nitrogen for grades UNS S31803 and S32205.
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | Fe |
| S31803 | 0.030 max | 2.00 max | 1.00 max | 0.030 max | 0.020 max | 22.0 – 23.0 | 3.0 – 3.5 | 4.50 – 6.50 | 0.14 – 0.20 | 63.72 min |
| S32205 | 0.030 max | 2.00 max | 1.00 max | 0.030 max | 0.020 max | 21.0 – 23.0 | 2.50 – 3.50 | 4.50 – 6.50 | 0.08 – 0.20 | 63.54 min |
Mechanical Properties of ASTM A182 Duplex Steel Plate Flanges
The mechanical properties of ASTM A182 Duplex Steel Plate Flanges include density and melting point values for Duplex S31803 and S32205, ensuring high strength and corrosion resistance.
| Grade | Density (g/cm³) | Density (lb/in³) | Melting Point (°C) | Melting Point (°F) |
| S31803 / S32205 | 7.805 | 0.285 | 1420 – 1465 | 2588 – 2669 |
Class 300 SDSS / Duplex Steel Flanges – Dimensional Chart
Below is the Class 300 Duplex Steel Flanges dimensional chart, providing size and weight details for weld neck, slip-on, blind, threaded, and socket weld flanges as per international standards.
| Class | NPS | Weld Neck Flange | Slip-On Flange | Blind Flange | Loose Flange | NPT Flange | Socket Weld (SW) Flange |
| 300# | ½ | 2 | 2 | 2 | 2 | 2 | 3 |
| 300# | ¾ | 3 | 3 | 3 | 3 | 3 | 3 |
| 300# | 1 | 4 | 3 | 4 | 3 | 3 | 3 |
| 300# | 1¼ | 5 | 4.5 | 6 | 4.5 | 4.5 | 4 |
| 300# | 1½ | 7 | 6.5 | 7 | 6.5 | 6.5 | 6 |
| 300# | 2 | 9 | 7 | 8 | 7 | 7 | 7 |
| 300# | 2½ | 12 | 10 | 12 | 10 | 10 | 10 |
| 300# | 3 | 18 | 13 | 16 | 14.5 | 14 | 13 |
| 300# | 3½ | 20 | 17 | 21 | 17 | 17 | 17 |
| 300# | 4 | 26.5 | 23.5 | 28 | 24 | 24 | 22 |
| 300# | 5 | 36 | 29 | 37 | 28 | 31 | 28 |
| 300# | 6 | 45 | 39 | 50 | 39 | 39 | 39 |
| 300# | 8 | 69 | 58 | 81 | 58 | 58 | 58 |
| 300# | 10 | 100 | 81 | 124 | 91 | 81 | 81 |
| 300# | 12 | 142 | 115 | 185 | 140 | 115 | 115 |
| 300# | 14 | 206 | 165 | 250 | 190 | 165 | 165 |
| 300# | 16 | 250 | 210 | 315 | 234 | 220 | 190 |
| 300# | 18 | 320 | 253 | 414 | 305 | 280 | 250 |
| 300# | 20 | 400 | 315 | 515 | 375 | 325 | 315 |
| 300# | 22 | 465 | 370 | 640 | 435 | 370 | 370 |
| 300# | 24 | 580 | 490 | 800 | 550 | 490 | 475 |
Duplex Stainless Steel Flanges – Size Conversion Chart
This Duplex Stainless Steel Flanges size conversion chart helps convert NPS sizes to DN measurements, commonly used in international piping systems.
| NPS | DN |
| 1/2 | 15 |
| 3/4 | 20 |
| 1 | 25 |
| 1¼ | 32 |
| 1½ | 40 |
| 2 | 50 |
| 2½ | 65 |
| 3 | 80 |
| 4 | 100 |
The following table shows the equivalent grades of Duplex Steel Flanges, including international standards, Werkstoff numbers, and UNS designations used for Duplex 2205 materials.
Gasket Sizes of Duplex Stainless Steel Flanges
The following table outlines the gasket sizes of Duplex Stainless Steel Flanges, including inner diameter and outer diameter dimensions for different pressure classes.
| NPS | Gasket ID | 900 LBS OD | 600 LBS OD | 400 LBS OD | 300 LBS OD | 150 LBS OD |
| 1/2 | 0.084 | 2.050 | 2.0125 | 2.0125 | 2.0125 | 1.0875 |
| 3/4 | 1.006 | 2.075 | 2.0625 | 2.0625 | 2.0625 | 2.025 |
| 1 | 1.031 | 3.0125 | 2.0875 | 2.0875 | 2.0875 | 2.0625 |
| 1¼ | 1.066 | 3.050 | 3.025 | 3.025 | 3.025 | 3.000 |
| 1½ | 1.091 | 3.0875 | 3.075 | 3.075 | 3.075 | 3.0375 |
| 2 | 2.038 | 5.0625 | 4.0375 | 4.0375 | 4.0375 | 4.0125 |
| 2½ | 2.088 | 6.050 | 5.0125 | 5.0125 | 5.0125 | 4.0875 |
| 3 | 3.050 | 6.0625 | 5.0875 | 5.0875 | 5.0875 | 5.0375 |
| 4 | 4.050 | 8.0125 | 7.0625 | 7.000 | 7.0125 | 6.0875 |
| 5 | 5.056 | 9.075 | 9.050 | 8.0375 | 8.050 | 7.075 |
| 6 | 6.062 | 11.0375 | 10.050 | 9.075 | 9.0875 | 8.075 |
| 8 | 8.062 | 14.0125 | 12.0625 | 12.000 | 12.0125 | 11.000 |
| 10 | 10.075 | 17.0125 | 15.075 | 14.0125 | 14.025 | 13.0375 |
| 12 | 12.075 | 19.0625 | 18.000 | 16.050 | 16.0625 | 16.0125 |
Duplex SS Flange Pressure Rating Chart
The Duplex SS Flange pressure rating chart shows the allowable pressure limits for various flange classes at different temperature ranges.
| Temperature (°F) | 2500 LBS | 1500 LBS | 900 LBS | 600 LBS | 400 LBS | 300 LBS | 150 LBS |
| -20 to 100 | 6000 | 3600 | 2160 | 1440 | 960 | 720 | 275 |
| 200 | 5000 | 3000 | 1800 | 1200 | 800 | 600 | 230 |
| 300 | 4500 | 2700 | 1620 | 1080 | 720 | 540 | 205 |
| 400 | 4140 | 2485 | 1490 | 995 | 660 | 495 | 190 |
| 500 | 3880 | 2330 | 1395 | 930 | 620 | 465 | 170 |
| 600 | 3640 | 2185 | 1310 | 875 | 580 | 435 | 140 |
| 650 | 3580 | 2150 | 1290 | 860 | 575 | 430 | 125 |
| 700 | 3540 | 2125 | 1275 | 850 | 565 | 425 | 110 |
| 750 | 3460 | 2075 | 1245 | 830 | 555 | 415 | 95 |
| 800 | 3360 | 2015 | 1210 | 805 | 540 | 405 | 80 |
| 850 | 3300 | 1980 | 1190 | 790 | 530 | 395 | 65 |
| 900 | 3240 | 1945 | 1165 | 780 | 520 | 390 | 50 |
| 950 | 3180 | 1910 | 1145 | 765 | 510 | 380 | 35 |
| 1000 | 2675 | 1605 | 965 | 640 | 430 | 320 | 20 |
| 1050 | 2570 | 1545 | 925 | 615 | 410 | 310 | 20 |
| 1100 | 2145 | 1285 | 770 | 515 | 345 | 255 | 20 |
| 1150 | 1655 | 995 | 595 | 400 | 265 | 200 | 20 |
| 1200 | 1285 | 770 | 465 | 310 | 205 | 155 | 20 |
| 1250 | 945 | 565 | 340 | 225 | 150 | 115 | 20 |
| 1300 | 715 | 430 | 255 | 170 | 115 | 85 | 20 |
| 1350 | 515 | 310 | 185 | 125 | 80 | 60 | 20 |
| 1400 | 400 | 240 | 145 | 95 | 65 | 50 | 20 |
| 1450 | 285 | 170 | 105 | 70 | 45 | 35 | 15 |
| 1500 | 230 | 135 | 80 | 55 | 35 | 25 | 10 |
Applications & Uses of Duplex Steel Flanges
- Oil & Gas: Duplex flanges withstand high-pressure subsea applications and resist corrosion from sour gas environments (H₂S). Standard: NACE MR0175.
- Chemical Processing: Superior corrosion resistance to chloride pitting makes duplex flanges ideal for chemical reactors, distillation columns, and heat exchanger manifolds.
- Power Generation: Duplex flanges connect high-temperature steam piping (up to 590°C) in boiler circuits and auxiliary systems with minimal scaling risk.
- Marine & Offshore: Salt-water corrosion resistance (PREN 30–35 for S31803/S32205) ensures long service life in seawater cooling systems and desalination plants.
- Desalination: Duplex flanges join reverse-osmosis membranes and brine heaters, where both pressure and saltwater exposure demand corrosion immunity.
- Pressure Vessels: Duplex construction combines high mechanical strength with corrosion resistance, reducing wall thickness and overall component weight while extending service life.
FAQs About Duplex Steel Flanges
A duplex flange is a piping component manufactured from duplex stainless steel, typically grades UNS S31803 or S32205. It combines the properties of austenitic and ferritic stainless steels, offering high strength, excellent corrosion resistance, and good toughness. Duplex flanges are commonly used to connect pipes, valves, and equipment in high-pressure and corrosive environments.
Duplex stainless steel is widely used in industries that require high strength and superior corrosion resistance. Common applications include oil and gas pipelines, chemical processing plants, offshore platforms, desalination units, heat exchangers, and marine systems, especially where resistance to chloride stress corrosion cracking is essential.
Duplex steel offers several advantages, including higher mechanical strength, excellent resistance to pitting, crevice corrosion, and stress corrosion cracking, and improved durability in harsh environments. It also provides better cost efficiency due to lower nickel content compared to austenitic stainless steels, while maintaining long service life.
The three main types of duplex stainless steel are Lean Duplex, Standard Duplex (such as Duplex 2205), and Super Duplex. Lean duplex provides moderate corrosion resistance with cost efficiency, standard duplex offers balanced strength and corrosion resistance, and super duplex delivers enhanced performance for extreme pressure and highly corrosive applications