A Complete Guide to Welding Positions
Every plate and pipe welding position explained — with angles, standards equivalency, SVG diagrams, and real-world applications in pressure vessel, piping, and pipeline fabrication.
Introduction to Welding Positions
Welding positions are fundamental to every qualified weld procedure. Whether you are fabricating a pressure vessel, routing a gas pipeline, or constructing an offshore structure, understanding the correct position — and its governing standard — is non-negotiable.
A welding position describes the spatial orientation of the workpiece and the weld joint relative to the welder at the time of welding. Because gravity acts differently on the molten weld pool depending on the orientation, each position demands different technique, parameter settings, and welder skill. Two major international standards codify these positions:
- ASME Section IX — used predominantly in the Americas for pressure vessels, boilers, and piping (see our article on Welder Performance Qualification per Section IX)
- EN ISO 6947 — the European and internationally harmonised standard, using alphanumeric codes such as PA, PB, PC, PF, and PH
Welding position is classified as an essential variable for welder qualification. A change in position beyond what a welder’s qualification covers requires re-qualification. This makes it critical for welding inspectors, engineers, and instructors to understand position definitions thoroughly.
Angle of Inclination & Face Rotation (ASME Section IX)
ASME Section IX defines welding positions with precision using two geometric parameters applied to an imaginary flat weld plate:
- Angle of Inclination — the angle at which one end of the plate is lifted relative to the horizontal plane (0° = fully horizontal, 90° = fully vertical).
- Rotation of the Weld Face — measured clockwise from the position where the weld face points directly downward (0°/360° = face down / overhead; 180° = face up / flat).
Think of it this way: imagine holding a flat plate at arm’s length. You can tilt it (inclination) or twist it (face rotation). The combination of both angles determines which position applies.
The following ranges apply for each position under ASME Section IX:
- Flat: Inclination 0°–15°; Face rotation 150°–210°
- Horizontal: Inclination 0°–15°; Face rotation 80°–150° or 210°–280°
- Vertical: Inclination 15°–80° (any face rotation 80°–280°); or inclination 80°–90° (any face rotation 0°–360°)
- Overhead: Inclination 0°–80°; Face rotation 0°–80° or 280°–360°
ISO 6947 vs. ASME Section IX — Equivalency Chart
Different industries and regions use different naming conventions. The table below maps every EN ISO 6947 position code to its equivalent ASME Section IX designation, so you can work confidently across international projects. Understanding this mapping is also important for thickness qualification ranges in PQR and WPQ.
| ISO 6947 Code | ASME Section IX Code | Description |
|---|---|---|
| PA | 1G / 1F | Flat position — groove or fillet |
| PB | 2F | Horizontal fillet |
| PC | 2G | Horizontal groove |
| PD | 4F | Overhead fillet |
| PE | 4G | Overhead groove |
| PF | 3G Uphill | Vertical groove — upward progression |
| PG | 3G Downhill | Vertical groove — downward progression |
| PH | 5G Uphill | Pipe — horizontal fixed axis, uphill |
| PJ | 5G Downhill | Pipe — horizontal fixed axis, downhill |
| H-L045 | 6G Uphill | Pipe — 45° inclined axis, uphill |
| J-L045 | 6G Downhill | Pipe — 45° inclined axis, downhill |
Groove Welding Positions — Plate
For plate groove welds, four fundamental positions are defined. The suffix “G” denotes a groove type joint, while “F” denotes a fillet joint.
Flat Position — 1G / PA
In the flat position, the plate lies in a horizontal plane and the weld metal is deposited from above. This is the most comfortable and productive welding position. The welder’s torch angle and travel direction remain largely constant, and gravity assists in consolidating the weld pool into the joint.
Flat position welding permits a wide range of heat input settings because the welder can freely adjust travel speed. Larger electrode diameters and higher currents are practical, making deposition rates significantly higher than in any other position.
Horizontal Position — 2G / PC
In the horizontal position, the plate stands vertically and the weld axis runs horizontally. The weld pool tends to sag toward the lower edge of the groove wall due to gravity. This requires a larger groove angle than other positions to allow the welder to direct the arc to the root and sidewalls effectively.
Horizontal position welding generally calls for a lower heat input to counteract the sagging pool. Faster travel speeds and reduced weaving are preferred. The welder or welding operator must hold a slight upward torch angle to compensate for pool drop.
Vertical Position — 3G / PF & PG
In the vertical position, the plate is held vertically and the weld axis runs vertically. Gravity acts perpendicularly to the weld axis and pushes the molten pool away from the fusion face. The pool tends to pile up and form irregular lumps if not managed carefully.
Two progressions exist:
- Uphill (PF / 3G↑): The welder progresses upward. Travel speed is slow because the welder must weave the electrode to achieve acceptable bead profile. This results in the highest heat input of all four positions, which increases the risk of distortion. Larger diameter electrodes are not recommended for this reason.
- Downhill (PG / 3G↓): The welder progresses downward with gravity, resulting in significantly faster travel speed and lower heat input. However, there is an increased risk of slag entrapment if the arc is not properly managed.
Overhead Position — 4G / PE
The overhead position is the most physically demanding plate welding position. The plate is horizontal but the weld is deposited onto its underside — the welder works with the weld face pointing downward. Gravity actively pulls the molten pool away from the joint, requiring the welder to use a very short arc to maintain metal transfer into the groove.
Low current, faster travel speed, and smaller electrode diameters are essential. This results in a lower heat input. Safety is also a major concern: spatter and slag fall downward onto the welder, so full body and head protection is mandatory. The welder’s position and reach restrictions should be carefully evaluated before beginning an overhead weld.
Identifying Position in Cone Welding
One practical scenario that often confuses engineers and inspectors involves determining the correct welding position for a pressure vessel cone long seam. The answer depends on which side of the cone the welder is working from:
- Outside of the cone: The weld is deposited on a vertical-ish surface running diagonally — this classifies as 3G (Vertical Position).
- Inside of the cone: The weld is deposited facing downward on the inner curved surface — this classifies as 4G (Overhead Position).
Groove Welding Positions — Pipe
Pipe welding positions introduce additional complexity because the joint is curved and, in most cases, the pipe cannot be rotated during welding. This means the welder must physically change body position and torch angle to deposit each section of the weld. Pipe welding positions are essential knowledge for anyone working in oil and gas, chemical plant, or power generation piping — see how they relate to mechanical testing requirements per ASME Section IX.
1G / PA — Rotated Flat (Pipe)
The pipe axis is horizontal, and the pipe is continuously rotated during welding so that the weld is always deposited at the top (12 o’clock position). This brings all segments of the joint into the comfortable flat position. The result is a high-quality, high-productivity weld accessible to welders qualified at the basic flat position level.
2G / PC — Horizontal Fixed (Pipe)
The pipe stands with its axis vertical. The weld joint runs in a horizontal plane around the circumference of the pipe. The pipe must not be rotated during welding. The welder walks around the pipe, maintaining the torch in the horizontal position throughout. This is equivalent to 2G horizontal groove position, and the molten pool sagging is a constant challenge.
5G / PH — Multiple Position Fixed (Horizontal Axis)
In 5G, the pipe axis is horizontal and the pipe is not rotated. This means the welder must deposit weld metal in all four basic positions (flat at the top, horizontal at the sides, overhead at the bottom) in a single pass around the circumference. It is a highly demanding position that requires the welder to smoothly transition technique as they progress.
For 5G uphill (PH), the recommended welding sequence is:
6G / H-L045 — Inclined Fixed (45°)
The 6G position is widely regarded as the most challenging and comprehensive pipe welding test. The pipe axis is inclined at 45° to the horizontal and is fixed — the welder must adapt to continuously changing joint orientations as they travel around the entire circumference without any rotation of the pipe.
A welder who successfully qualifies in the 6G position is deemed competent to weld in all pipe positions. This single qualification covers all positions (1G, 2G, 5G), making 6G the gold standard for pipe welder certification in oil and gas, power, and chemical industries.
6GR — 45° Inclined with Restriction Ring
The 6GR test is a variant of the 6G qualification. Conditions are identical to 6G, with one critical addition: a steel restriction ring is placed approximately 25 mm (1 inch) below the weld joint. This ring simulates real-world access restrictions, such as structural brackets, gussets, or supports that are attached close to the weld area.
Passing the 6GR test demonstrates that the welder can execute high-quality welds even with physical obstructions nearby — a scenario common in offshore structures with T, Y, and K (TKY) connections, as defined in AWS D1.1 Structural Welding Code. It is the most comprehensive pipe welder qualification available.
Fillet Welding Positions — Plate
Fillet welds join two surfaces that meet at an angle, typically a T-joint or lap joint. The suffix “F” identifies fillet weld positions. The same four basic positions apply. Understanding fillet weld positions matters for joint design and weld type selection.
1F — Flat
2F — Horizontal
3F — Vertical
4F — Overhead
1F — Flat Fillet
Both plates are positioned so that the weld axis is horizontal and the weld throat is vertical. The fillet metal is deposited from above into the junction. This is the most straightforward fillet position.
2F — Horizontal Fillet (PB)
A T-joint where the horizontal plate lies flat and the vertical plate stands upright. The weld is deposited on the upper side of the horizontal surface, against the vertical surface. The pool tends to droop onto the horizontal leg, requiring precise torch angle control. This is the ISO PB position.
3F — Vertical Fillet
The weld axis is vertical, and the welder progresses either upward or downward along the joint. Like groove 3G, vertical fillet welding requires significant skill to maintain consistent leg lengths and avoid pool sagging. It is commonly encountered in structural and fabrication work.
4F — Overhead Fillet (PD)
The weld is deposited on the underside of the horizontal surface, against the vertical surface. Full PPE is essential. This is the ISO PD position and mirrors the challenges of 4G groove welding.
Fillet Welding Positions — Pipe
Pipe fillet positions apply to socket welds, set-on branch connections, and slip-on flanges. They share the same numbering system but with distinct geometric requirements for the curved pipe surface.
1F — Flat Fillet (Pipe Rotated)
The pipe axis is inclined at 45° to horizontal and the pipe is rotated during welding. The combination of inclination and rotation ensures the weld is always deposited from above with a horizontal weld axis and vertical throat — equivalent to the flat fillet position.
2F and 2FR — Horizontal Fillet (Pipe)
Position 2F: The pipe axis is vertical. The fillet weld is deposited on the upper side of the horizontal surface (the flat plate or flange face), against the vertical cylindrical surface of the pipe. The pipe is not rotated.
Position 2FR: The pipe axis is horizontal, and the deposited weld lies in the vertical plane. The pipe is rotated during welding. The “R” suffix denotes rotation.
4F — Overhead Fillet (Pipe)
The pipe axis is vertical. The fillet weld is deposited on the underside of the horizontal surface, against the vertical pipe surface. The pipe is not rotated. This is the ISO PD equivalent for pipe and is particularly challenging due to spatter falling on the welder.
5F — Multiple Position Fillet (Pipe)
The pipe axis is horizontal and the deposited weld lies in the vertical plane. The pipe is not rotated. The welder must transition through all four positional orientations while travelling around the pipe circumference — directly analogous to 5G for groove welds.
2F — Pipe
2FR — Rotated
4F — Pipe Overhead
5F — Multiple
Industrial Applications by Welding Position
Understanding which welding positions apply to which industry segments allows engineers to specify the correct welder qualifications and design efficient fabrication sequences. This is directly tied to P-Number and F-Number classification and the qualification thickness ranges for PQR and WPQ.
Pressure Vessels & Reactors
Shell longitudinal and circumferential seams are typically welded in 1G (rotated flat) where possible. Nozzle to shell connections and internal attachments often require 2G, 3G, and 4G capability.
Key positions: 1G, 2G, 3G, 4G
Fixed Piping & Pipelines
Above-ground process piping is typically welded in 5G (fixed horizontal). Long-distance cross-country pipelines may use mechanized welding but manual welds at tie-ins require 5G or 6G qualification.
Key positions: 1G, 2G, 5G, 6G
Offshore Structures
Jacket and topside construction involves complex tubular joints (TKY connections) where access is severely restricted. 6GR qualification is the industry standard for these joints.
Key positions: 6G, 6GR (per AWS D1.1)
Storage Tanks
Tank shell plate butt welds are predominantly in the 2G (horizontal) position for vertical shell seams, and 1G (flat) for bottom annular plate seams welded in the rotated position.
Key positions: 1G, 2G, 1F, 2F
Related Resources
- Thickness Qualification Range for PQR and WPQ (ASME Section IX)
- P-Number, Group No., F-Number and A-Number in Welding
- Mechanical Testing Requirements per ASME BPVC Section IX
- Importance and Calculation of Heat Input and Arc Energy
- Welding Joint Types — A Complete Guide
- Weld Consumable Calculation for Single V-Groove