Standards: ANSI/ASME B16.5 (½"-24") · ASME B16.47 Series A/B (26"-60") · Classes: 150-2500 · Types: WN · Blind · SO · SW · Lap Joint · Threaded
Kalpataru Piping Solution supplies pipe flanges across the standard, class and type range, forged in stainless, duplex and super duplex. The volume types are weld neck flanges for the strongest butt-welded joints and blind flanges for closing off a line, alongside slip-on, socket weld, lap joint and threaded patterns. We forge them in stainless steel flanges and duplex steel flanges, and flanges are organised first by dimensional standard, which is set by pipe size, so the tables below take you to the right one.
Because a flange must match the pipe and the mating flange exactly, ordering by the correct standard, class, facing and bore matters here more than on almost any other component. The flanges match the grade of the pipe fittings and pipe, so a flanged joint stays one material. Every flange ships with a mill test certificate and is dimensionally checked before dispatch.
B16.5 or B16.47? The Size Decision
The first flange decision is the dimensional standard, and it is decided purely by pipe size.
Standard | Size range | Notes |
ANSI / ASME B16.5 | NPS ½ inch to 24 inch | Small and medium bore; classes 150 to 2500 |
ASME B16.47 Series A | NPS 26 inch to 60 inch | Large-diameter, the heavier MSS SP-44 lineage |
ASME B16.47 Series B | NPS 26 inch to 60 inch | Large-diameter, lighter and more compact bolting |
This is why the B16.5 and B16.47 pages are separate and are not duplicates: they cover different size ranges. A 12 inch flange is B16.5 and a 36 inch flange is B16.47, and Series A and Series B B16.47 flanges of the same size and class are not interchangeable because their bolting differs. Give us the pipe size and we will confirm the standard.
Flange Types
|
Type |
What it is |
Best for |
|
Weld neck (WNRF) |
A tapered hub butt-welded to the pipe |
High-pressure, high-temperature and cyclic service; the strongest joint |
|
Blind |
A solid disc with no bore |
Closing off the end of a line or a vessel opening |
|
Slip-on (SORF) |
Slides over the pipe and is fillet welded |
Lower-pressure lines, easier fit-up and lower cost |
|
Socket weld |
Pipe seats in a socket and is fillet welded |
Small-bore high-pressure lines |
|
Lap joint |
Used with a stub end so the flange can rotate |
Lines needing frequent dismantling |
|
Threaded |
Screwed onto threaded pipe, no welding |
Where welding is not permitted |
Pressure Classes & Facings
Each flange is rated to a pressure class, 150, 300, 600, 900, 1500 or 2500, which sets its pressure-temperature limit and its thickness and bolting; a higher class means a heavier flange. The facing is the sealing surface: raised face (RF) is the general-purpose default, flat face (FF) is used against cast-iron equipment, and ring-type joint (RTJ) with a metal ring gasket is used for high-pressure and high-temperature service, typically Class 600 and above. Both the class and the facing are set by the piping specification and must match across the flange, gasket and bolting.
Flange Grades
Flanges are forged, and the grade follows the pipe. We supply stainless steel flanges in A182 F304 and F316 for general and corrosion service, duplex steel flanges in F51 and super duplex steel flanges in F53 and F55 for high-chloride and seawater duty, plus carbon, alloy and nickel-alloy grades to order. Keeping the flange, the pipe fittings and the bolting to matching grades is what makes a joint code-compliant.
Quality, Certification & Testing
Every flange ships with an EN 10204 mill test certificate, heat-number traceable to the forging grade, and is dimensionally checked to the governing standard for bore, bolt circle and facing before dispatch. Positive material identification confirms the grade, NACE MR0175 documentation for sour service and third-party witness through BV, SGS or TUV are arranged at order stage. Common classes, types and grades ship quickly; large-diameter B16.47 and high classes are confirmed on enquiry. Send the standard, class, type, size, facing and grade and the quote comes back with the certification built in.
Our Steel Flanges Products
Flanges: Frequently Asked Questions
Weld neck, blind, slip-on, socket weld, lap joint and threaded flanges to ANSI/ASME B16.5 in half an inch to 24 inch and ASME B16.47 in 26 inch to 60 inch, classes 150 to 2500, forged in stainless, duplex and super duplex. If a standard, class or grade is not listed, ask, because we hold more than the site shows and can source to specification.
Pipe size. ANSI/ASME B16.5 covers flanges from half an inch to 24 inch, and ASME B16.47 covers large-diameter flanges from 26 inch to 60 inch. They are not duplicates and not interchangeable: a 12 inch flange is B16.5 and a 36 inch flange is B16.47. B16.47 also has two series, A and B, whose bolting differs, so those are not interchangeable with each other either.
Strength and fit-up. A weld neck flange has a tapered hub butt-welded to the pipe, giving the strongest joint for high-pressure, high-temperature and cyclic service. A slip-on flange slides over the pipe and is fillet welded, which is easier to align and lower in cost but suited to lower-pressure service. The piping specification usually names which to use.
A flange class, 150 to 2500, is its pressure-temperature rating. A higher class means a thicker, heavier flange with more or larger bolts that holds a higher pressure at a given temperature. The class is set by the piping specification and must match across the flange, gasket and bolting for the joint to seal and be rated correctly.
Yes. Every flange ships with an EN 10204 mill test certificate, heat-number traceable to the forging grade, and is dimensionally checked before dispatch, with positive material identification, NACE documentation for sour service and third-party witness inspection available at order stage.