What Is Pipe Beveling? Weld Preparation

Pipe beveling is the process of machining or grinding an angled edge (bevel) on the end of a pipe to create a groove for butt welding. The bevel geometry determines the weld joint configuration, root penetration, and volume of weld metal required. ASME B16.25 (Buttwelding Ends) defines the standard bevel dimensions for pipe and fittings used in ASME B31.1 and B31.3 piping systems.

A proper bevel allows full penetration of the root pass, adequate fusion between pipe ends, and access for NDT of the completed weld.

Standard Bevel Geometry (ASME B16.25)

Parameter	Standard Requirement
Bevel angle	37.5° +5°/-0° (measured from perpendicular)
Included angle	75° (between two beveled pipe ends)
Root face (land)	1.6 mm +/- 0.8 mm (1/16” +/- 1/32”)
Root gap	Per WPS, typically 1.6-3.2 mm
Bevel type	Single V (standard for pipe)
Surface finish	Smooth, free of notches and laminations

Bevel Types

Bevel Type	Geometry	Application
Single V	37.5° each side	Standard for pipe WT up to ~22 mm
Compound bevel	37.5° + 10° (two angles)	Thick-wall pipe (>22 mm) to reduce weld volume
J-bevel	J-shaped groove	Heavy-wall, automated welding
U-groove	U-shaped groove	Very thick walls, reduces weld metal vs. V-groove
Square end	No bevel, square cut	Thin-wall pipe (<4 mm) for autogenous GTAW

For most process piping per ASME B31.3, the standard single-V bevel per ASME B16.25 is used for wall thicknesses up to approximately 22 mm. Above this, compound or J-bevels are specified to reduce the volume of weld metal (and therefore welding time, distortion, and cost).

Beveling Methods

Method	Equipment	Application
Portable beveling machine	Clamshell-type cutter	Field and shop, NPS 2 to NPS 60+
Lathe	Standard pipe lathe	Shop fabrication, precision bevels
Plasma/oxy-fuel cutting + grinding	CNC or manual torch	Large diameter, field cutting
Grinding	Angle grinder	Small bore, repairs, touch-up
Cold cutting machine	Split-frame cutter	In-service pipeline cold cuts

Pro Tip

After torch cutting, always remove at least 1.5 mm of heat-affected material from the bevel face by grinding or machining. Torch-cut surfaces contain a hardened layer that can cause hydrogen cracking in the root pass, especially in alloy steels (P11, P22) and sour service materials. ASME B16.25 requires the bevel surface to be free of oxide and heat-affected zones.

Wall Thickness Transition

When joining pipe of different wall thicknesses (or different schedules), the thicker pipe must be tapered to match the thinner pipe at the weld joint. ASME B16.25 and ASME B31.3 specify:

Condition	Requirement
Internal misalignment > 1.5 mm	Taper required at 30° max angle
External misalignment	Taper at 30° or weld buildup on thinner pipe
Taper length	Minimum 3x the offset distance
Max internal misalignment (without taper)	1.5 mm

This is common when connecting standard Schedule 40 pipe to a heavier schedule at branch connections or equipment nozzles.

Quality Requirements

• Bevel surfaces must be visually inspected for laminations, cracks, and imperfections
• Root face dimension verified with a bevel gauge
• Bevel angle checked with a protractor or bevel gauge
• Out-of-roundness checked per ASTM pipe specification tolerance
• Cleanliness: free of oil, grease, paint, and rust within 25 mm of the bevel

Beveling is an integral part of pipe spool fabrication and directly affects the quality of butt weld joints in piping systems.

Read the full guide to pipe types