Complete Knowledge Document: Flanges & Pipe Fittings

Suitable for foreign trade inquiries, product introduction, technical communication (English version ready for website use)

1. Basic Definition

Pipe Fittings: Components used to connect, change direction, change diameter, branch or close pipelines.

Flange: A disc-shaped connecting part with bolt holes, used to assemble pipes, valves, equipment nozzles; enables easy disassembly for maintenance.

All ASME standard carbon/alloy steel flanges & butt-weld fittings are pressure-containing parts for industrial piping systems.

2. Main Applicable Standards

Flanges

ASME B16.5: NPS 1/2 ~ NPS24 Steel Pipe Flanges & Flanged Fittings (most widely used)

ASME B16.47: NPS26 ~ NPS60 Large Diameter Flanges (Series A / Series B)

ASME B16.36: Orifice flanges

ASME B16.48: Spectacle blinds & spacers

Butt-weld Pipe Fittings

ASME B16.9: Factory-made wrought butt-weld fittings (elbow, tee, reducer, cap, stub end)

MSS SP-43: Light weight stub ends for lap joint flanges

ASME B16.28: Wrought butt-weld short radius elbows

Pipe Standard (Matching OD)

ASME B36.10M: Welded & seamless carbon/alloy steel pipe

ASME B36.19M: Stainless steel pipe

3. Common Flange Types (ASME B16.5)

WN Weld Neck Flange

Long tapered hub, butt weld to pipe. Best strength, anti-leakage. Preferred for high pressure, high temperature, critical service (oil & gas, power plant).

SO Slip On Flange

Slides over pipe, fillet weld inside & outside. Lower cost, medium pressure service.

LJ Lap Joint Flange

Used together with Stub End. Flange rotates freely for easy bolt hole alignment; ideal for stainless steel pipelines (save SS cost).

BL Blind Flange

Blank disc without bore, to block pipeline ends or equipment nozzles.

SW Socket Weld Flange

Pipe inserted into socket, fillet weld. Normally ≤ NPS4, small-bore high pressure.

TH Threaded Flange

NPT thread connection, no welding, used for low pressure, fire risk sites.

Flange Face Types

RF Raised Face — Most common

FF Flat Face

RTJ Ring Type Joint — High pressure & high temperature

MF/MFM Male & Female

TG/TG Tongue & Groove

Pressure Class

Class150, 300, 400, 600, 900, 1500, 2500

Higher class = thicker flange, larger bolt size, higher pressure bearing capacity.

4. Main Butt-Weld Pipe Fittings (ASME B16.9)

Elbow: 90° LR / SR, 45°, 180° return bend

Tee: Equal tee, reducing tee

Reducer: Concentric reducer, eccentric reducer

Cap: Pipe end closure

Stub End: Matches lap joint flange

5. Material Common Grades

Carbon Steel

ASTM A105 (forged flanges)

ASTM A234 WPB (butt weld fittings)

Alloy Steel

A182 F11/F22 / A234 WP11 WP22

Stainless Steel

A182 F304/F316 / A403 WP304 WP316

6. Core Matching Rule

Flange NPS = Pipe NPS

Butt-weld fitting NPS = Pipe NPS

All components must follow same standard + same pressure class for assembly

Cannot mix ASME B16.5 NPS24 and ASME B16.47 NPS26; bolt circle dimensions differ.

7. Key Terminology for Inquiry & Order

Schedule: SCH40, SCH80, SCH160, XXS (define wall thickness)

NPS: Nominal Pipe Size

DN: Metric nominal diameter

RTJ / RF: Flange facing

Heat treatment: Normalized, Tempered, Quench & Temper

NDT: Non-destructive test (UT, MT, PT, RT as required)

8. Downstream Application Industries

Oil & gas, refinery, petrochemical, thermal power, chemical plant, water treatment, marine, LNG, new energy hydrogen pipeline, metallurgy.

9. Short English Version (Can be directly used on website/catalog)

Flanges and pipe fittings are essential pressure piping components.

Main standards include ASME B16.5, ASME B16.47 for flanges, ASME B16.9 for butt-weld fittings.

Major products: WN, SO, LJ, BL flanges; elbows, tees, reducers, caps, stub ends.

Materials: A105, A234 WPB, stainless steel, alloy steel.

Widely applied in oil & gas, petrochemical, power generation, water treatment and industrial process piping.