Shipbuilding sub-verticals, getting the 3G/6G welder mix right by campaign type

A Croatian shipyard's welder pool is never homogeneous. The 3G plate welder runs hull blocks; the 6G pipe welder runs process piping. The ratio between the two shifts by sub-vertical: a new-build hull is heavy on 3G, a refit is heavy on 6G, a yacht-finish leans on TIG specialists, an offshore-support build runs the highest 6G ratio of any campaign. Getting the mix wrong on day one costs the yard months at the back of the campaign.

The four sub-verticals and their welder shapes

Croatian shipbuilding runs four common campaign archetypes and the welder mix is archetype-dependent.

New-build hull, block-assembly hall plus outfitting quay, 18-30 month campaign, 200-400 trade workers at peak. The welder pool runs 75-85% 3G plate (MAG-dominant, vertical-up on hull blocks) and 15-25% 6G pipe (TIG-root with MAG-fill on systems piping). The 6G load builds across months 6-18 as the systems package fits up. Painters and blasters come in heavy in the back third.

Refit and conversion, dry-dock arrival, strip-out, hot work, re-fit, sea trial, 4-9 month campaign, 60-120 trade workers at peak. The welder pool reverses to 35-45% 3G plate, 55-65% 6G pipe. The systems work dominates because the structural work is mostly local repairs rather than full block fabrication. Hot-work permits and confined-space competency run higher than on a new-build.

Yacht finish or specialist build, 6-12 month campaign, 30-80 trade workers at peak. The welder pool runs 40-50% 3G (often aluminium or stainless MIG), 30-40% 6G (high-quality TIG on stainless piping and engine-room systems), and 15-20% specialist TIG joiners on aluminium superstructure. Pay band rises across all trades. The buyer is more sensitive to skill than to volume.

Offshore-support and conversion, FPSO conversions, offshore-wind component fabrication, support-vessel new-builds, 12-24 month campaign, 100-300 trade workers at peak. The welder pool runs 25-35% 3G, 60-70% 6G, with a heavier proportion of 6GR (restriction-ring) qualifications and ASME-IX rather than EN-ISO-9606-1 standard. NDT volume is the highest of any sub-vertical.

The shipbuilding workforce master guide covers the corridor economics across these archetypes; this article focuses on the welder-mix detail.

Why getting the ratio wrong is expensive

A new-build hull that loads the welder pool at a 60/40 3G/6G ratio runs heavy 6G inventory in months 1-4 when the structural work dominates. The 6G welders sit on standing time or get assigned to non-pipe work below their pay grade. Cost per worker-day rises 20-30% on the misallocated 6G. The project sees a margin hit that does not show until month 6.

A refit that loads the welder pool at an 80/20 ratio runs heavy 3G inventory in months 2-6 when the systems work dominates. The 3G welders cover scaffolding, hot-work watch, gas-test attendance: useful work but not what they were sourced for. The 6G crew runs short. Pipe spools queue. The campaign slides 2-3 days per week of shortage.

Both errors are common because the production manager builds the welder request against the headcount target, not the trade ratio. We re-build the request against the campaign archetype at the corridor-fit conversation.

The corridor strengths by welder type

Each corridor carries different strengths on the 3G/6G split, and the corridor mix should reflect this.

Nepal, strongest on 3G plate volume. The Kathmandu screening centre carries 200-400 ready-pipeline 3G welders across MAG and MIG processes. 6G volume is lighter. The Nepali corridor delivers 6G in smaller panels.

India, strongest on 6G pipe volume. The Mumbai, Punjab and Kerala corridors carry Gulf-trained 6G welders with ASME IX qualifications and X-ray-ready pipe-coupon experience. Volume on 3G is also strong but the 6G strength is the corridor differentiator.

Philippines, balanced across 3G and 6G, with strength on aluminium TIG and yacht-finish stainless work. The Filipino TESDA programme produces welders against AWS D1.1 primarily, with ASME IX as a secondary qualification. Filipino welders trained in Subic Bay carry the strongest yacht-finish background.

Bosnia, strongest on 6G pipe and TIG specialism, partly because the local automotive Tier-2 cohort produces precision welders. Volume on 3G is moderate.

Serbia, strong on industrial welding (CNC-integrated, mechatronics-adjacent) but less depth on shipyard-specific welding than Bosnia.

For a 200-welder new-build hull campaign with a 75/25 3G/6G split, the typical corridor mix lands at: 80-100 Nepali 3G welders, 30-40 Indian 6G welders, 20-30 Bosnian 6G welders, 30-40 Filipino welders across both bands. The exact split moves with the yard's systems package and the campaign duration.

The certification standard overlay

The 3G vs 6G distinction is a position code. The standard against which the welder qualifies is a separate decision. The welder certification article covers the standard stack in detail. For sub-vertical planning, the standard pairs run:

New-build hull for European owners: EN ISO 9606-1 primary, AWS D1.1 secondary on the structural blocks.

New-build for cross-Atlantic owners: ASME IX primary on process piping, AWS D1.1 on hull blocks.

Refit work under classification societies: the standard depends on the original build. A vessel built to ABS or DNV under ASME IX runs the refit welds against ASME IX. A vessel built to RINA or Lloyd's under EN ISO runs the refit against EN ISO.

Yacht finish: typically EN ISO 9606-1 for aluminium and stainless, with the joiner trade running its own certification stack.

Offshore-support: ASME IX dominant on process piping, OPITO BOSIET on safety. The 6GR (restriction-ring) qualification appears more often on offshore-support than on any other sub-vertical.

The corridor screening runs against the yard's specific WPS pack, regardless of the underlying standard. We coupon-test in origin against the yard's actual welding procedure specifications. The standard becomes visible at the documentation stage but the practical test is the WPS.

The trade-test compression on 6G panels

A 6G panel is slower to source than a 3G panel for two reasons. The trade test itself is harder (X-ray reading on the coupon, two-week turnaround on the radiography). The available pool is smaller per corridor. The Nepali ready-pipeline of 6G welders runs at 60-80 candidates. The 3G ready-pipeline runs at 200-400.

We compress the 6G timeline by running parallel screening at multiple training centres in the same corridor. A 30-welder 6G panel from India draws from Mumbai, Punjab and Kerala simultaneously rather than sequentially. The mobilisation timeline runs 8-10 weeks ready-pipeline, 12-14 weeks fresh-source. The yard's NDT lead reviews the coupon photographs and X-ray plates by email before the visa appointment.

The pipe fitter article covers the adjacent trade that hands the 6G welder the tacked joint. The fitter and the 6G welder are paired trades on the systems package. Sourcing one without the other creates the same standing-time problem in reverse.

The retention math by sub-vertical

Across Werklist's shipyard placements, retention at month 12 runs:

New-build hull, 80-85% across South Asia corridors, 85-90% across Balkans. Refit, 75-80% across South Asia (shorter contracts make this number less indicative), 80-85% across Balkans. Yacht finish, 85-90% across all corridors (higher pay, more skilled work, longer cycles). Offshore-support, 78-83% across South Asia, 82-88% across Balkans.

What we plan on the scoping call

At the corridor-fit conversation, we ask: what is the campaign archetype, what is the welder headcount by 3G/6G split, what is the certification standard, what is the campaign duration, what is the systems-package load. The answers shape the corridor mix and the mobilisation calendar.

If you are scoping a shipbuilding campaign (sub-vertical, welder mix, corridor), the corridor-fit conversation runs 20 minutes. The number sits on the Zagreb branch page.