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ANSI B16.11 · Small Bore High Pressure
Socket Weld Flanges
M.S. Socket Weld Flanges Manufacturer & Supplier – Mumbai, India · Since 1999
ANSI B16.11 CertifiedClass 3000 / 6000Small Bore High PressureDirect ManufacturerPAN India Supply
M.S. Socket Weld Flanges (SW Flanges) are designed for small bore, high-pressure piping systems. The pipe is inserted into a socket (counterbore) in the flange body and externally fillet-welded — creating a strong, compact joint without the need for butt welding. Ideal for hydraulic systems, steam lines, pneumatic piping and chemical service where space is limited. Manufactured from IS:2062 mild steel at our Darukhana, Mumbai factory to ANSI B16.11 standard. Available in ½″ to 3″ NB (15mm to 80mm) in Class 3000 and Class 6000.
Quick Specifications
StandardANSI B16.11
Size Range½" (15mm NB) to 3" (80mm NB)
Pressure ClassClass 3000 / Class 6000
End TypeSocket Bore + External Fillet Weld
Face TypeRaised Face (RF)
Material GradeIS:2062 Mild Steel (MS)
Lead Time3–7 Days (Standard)
SupplyPAN India | Darukhana, Mumbai
Class 6000Max Rating
80mmMax NB Size
25+Years Mfg.
What Are Socket Weld Flanges?
Socket Weld Flanges (SW Flanges) have a socket (counterbore) machined into the flange bore. The pipe end is inserted into this socket and a gap of approximately 1.6mm is maintained between the pipe end and the socket bottom (to allow for thermal expansion during welding). A fillet weld is then applied externally around the pipe-socket junction to complete the joint.
Key advantages of Socket Weld Flanges: No butt welding required — easier to install; Self-aligning — the socket centres the pipe automatically; Compact — suitable where space is limited. Key limitation: Not suitable for slurry, highly viscous fluids or services requiring pigging because the socket-pipe annular space can trap material and cause crevice corrosion or blockage.
Socket Weld vs Welding Neck — When to Use Which?
Use Socket Weld Flanges for: small bore (≤80mm NB), high-pressure, non-corrosive clean service where butt welding is difficult or space is limited. Use Welding Neck Flanges for: all sizes, critical service, cyclic loading, slurry/corrosive service where the annular crevice of SW flanges is unacceptable.
Why Choose I.S. Engineering Co.?
25+ Years Experience
Manufacturing Socket Weld Flanges in Mumbai since 1999. Trusted by 500+ clients across India.
Factory-Direct Pricing
No middlemen. Buy direct from the manufacturer at the most competitive prices in Mumbai.
100% Quality Inspected
Every Socket Weld Flanges undergoes dimensional and material inspection before dispatch from our Mumbai factory.
PAN India Delivery
Supplying to Mumbai, Pune, Delhi, Bangalore, Chennai, Hyderabad, Ahmedabad and all major cities across India.
Socket Weld Flanges – Dimensional Specifications
| NB Size | Class | Approx. Max Pressure (bar) | Socket Depth (mm) | Fillet Weld Size |
|---|---|---|---|---|
| 15mm (½") | 3000 | ~210 bar | 14mm | 6mm |
| 20mm (¾") | 3000 | ~210 bar | 16mm | 6mm |
| 25mm (1") | 3000 | ~210 bar | 18mm | 8mm |
| 40mm (1½") | 3000 | ~210 bar | 22mm | 8mm |
| 50mm (2") | 3000 | ~210 bar | 25mm | 10mm |
| 65mm (2½") | 3000 | ~210 bar | 28mm | 10mm |
| 80mm (3") | 3000 | ~210 bar | 30mm | 12mm |
| 15mm (½") | 6000 | ~420 bar | 16mm | 8mm |
| 25mm (1") | 6000 | ~420 bar | 20mm | 10mm |
| 50mm (2") | 6000 | ~420 bar | 28mm | 12mm |
| 80mm (3") | 6000 | ~420 bar | 32mm | 14mm |
* Dimensions are indicative. Custom sizes available on request. Contact I.S. Engineering Co. at +91 83558 15350 for specific sizes, tolerances and full specification sheets.
Socket Weld Flanges – Industries & Applications
Hydraulic Systems
Used in hydraulic power packs and high-pressure hydraulic pipework where space is limited and pipe sizes are small. Class 6000 SW flanges suitable for very high hydraulic pressures.
Steam Lines
Used in steam distribution lines, steam tracing systems and process steam piping where small bore pipe is used. SW flanges provide a compact, high-integrity joint for steam service.
Instrument & Pneumatic Lines
Used in instrument air headers, pneumatic control lines and process sampling connections. Compact size ideal for instrumentation and control systems.
Chemical Service
Used in small bore chemical process lines where strong, leak-proof joints are required. Note: Not recommended for services where crevice corrosion in the socket annulus is a concern.
Oil & Gas Small Bore
Used in small bore oil and gas instrument lines, sample connections and utility piping on offshore platforms and onshore process plants.
Fabrication Shops
Widely used in fabrication workshops for high-pressure pipe spool fabrication because socket weld installation requires less welder skill than butt welding — easier to achieve weld quality.
Socket Weld Flanges – Frequently Asked Questions
What are Socket Weld Flanges?
+Socket Weld Flanges (SW Flanges) have a counterbored socket into which the pipe is inserted before being externally fillet-welded. They are used for small bore piping (up to 3" NB) in high-pressure service. The socket self-centres the pipe and the external fillet weld creates a strong, compact joint without requiring butt welding.
What is the difference between Socket Weld and Welding Neck Flanges?
+Socket Weld Flanges: pipe inserts into socket, fillet welded externally, suitable for small bore (≤80mm NB) high-pressure clean service. Welding Neck Flanges: butt welded to pipe end, suitable for all bore sizes including large, critical and cyclic service, slurry and corrosive fluids. SW flanges are easier to install; WN flanges are more versatile and better for demanding service conditions.
What sizes are available for Socket Weld Flanges?
+I.S. Engineering Co. manufactures Socket Weld Flanges in sizes from ½" (15mm NB) to 3" (80mm NB) as per ANSI B16.11 standard. Available in Class 3000 and Class 6000 pressure ratings.
What is the 1.6mm gap rule for Socket Weld installation?
+When installing a Socket Weld Flange, the pipe should be inserted fully into the socket and then pulled back 1.6mm (1/16 inch) from the socket bottom before welding. This gap allows for thermal expansion of the pipe during welding — preventing distortion and cracking at the socket bottom. This is a mandatory installation requirement per ANSI B31.3.
Can Socket Weld Flanges be used for slurry or viscous fluid service?
+Socket Weld Flanges are not recommended for slurry, highly viscous fluids or services requiring pigging because the annular space between the pipe and socket can trap material, causing crevice corrosion or flow obstruction. For slurry and corrosive service, use Welding Neck Flanges with butt weld ends which provide a smooth bore with no crevice.
What is the maximum pressure for Socket Weld Flanges?
+I.S. Engineering Co. supplies Socket Weld Flanges in Class 3000 (approximately 210 bar at ambient temperature) and Class 6000 (approximately 420 bar at ambient temperature). Actual maximum allowable working pressure depends on the operating temperature — consult ANSI B16.11 pressure-temperature tables for your specific service conditions.
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