Bulkhead Fabrication and Installation

What a Bulkhead Does

A transverse bulkhead is a vertical plate structure that runs across the beam of a vessel, dividing the hull into watertight compartments. Its two primary jobs are structural and safety-related. Structurally, bulkheads resist the hydrostatic pressure of water pushing inward on the hull sides and support the decks above. From a safety standpoint, watertight bulkheads limit flooding: if one compartment is breached, the bulkhead prevents water from spreading through the entire vessel. The US Coast Guard (USCG) and the American Bureau of Shipping (ABS) both set minimum requirements for the number, placement, and watertight integrity of bulkheads based on vessel type and service. Failing to meet these requirements can result in the vessel failing classification or being denied a certificate of inspection.

Stiffeners and Why They Matter

A bare plate, even heavy steel, will buckle under hydrostatic load if it is large enough. Vertical stiffeners — flat bar, T-bar, or bulb flat welded to the plate — divide the panel into shorter, stiffer spans and transfer load to the deck and shell. Your drawing specifies stiffener size, spacing, and weld size. Never substitute a smaller section or increase the spacing without an engineer's approval. During layout, snap chalk lines on the plate face at the spacing shown, then square each line with a combination square before tacking. Stiffeners must be held tight to the plate during tacking — gaps between the stiffener foot and the plate are a direct code violation and a source of leak paths.

Laying Out and Fitting Stiffeners

Start by reading the entire drawing before touching metal. Confirm the plate dimensions, stiffener schedule, and any penetration or bracket locations. Place the bulkhead plate flat on the layout table and mark the stiffener centerlines in both directions. Cut stiffeners to length — they typically stop short of the plate edge by the fillet weld leg size to allow the perimeter weld to be made without interference. Fit each stiffener plumb to the plate surface, clamp it, and tack at both ends before adding intermediate tacks. Tack spacing and minimum tack size are specified in the Welding Procedure Specification (WPS); follow them exactly. After all stiffeners are tacked, verify spacing with a tape measure at top, middle, and bottom of each stiffener run.

Crane Safety and Panel Lifting

Before the overhead crane is used, all students must stand clear of the lift zone. Only the instructor or a designated qualified rigger operates the crane controls during this exercise. Inspect slings and hooks before attaching them — look for cuts, kinking, corrosion, or missing safety latches. The lift points must be marked on the drawing or approved by the instructor; lifting from a single stiffener is not permitted. Wear hard hat, safety-toe boots, and gloves during the lift. Never walk under a suspended load. Guide the panel with tag lines, not your hands.

Plumbing the Bulkhead

Once the panel is set in the hull mock-up, plumb it in both planes: athwartship (across the beam) and fore-and-aft. Use a digital level on each face of the panel. The acceptance criterion for this lab is plumb within 1/8 inch per 4 feet — approximately 0.03 inches per foot, or roughly 3/16-degree tilt. Shim the base as needed and use strongbacks or dogs welded to the adjacent structure to hold position while you recheck. Recheck after every dog or tack is added, because the heat from tacking can pull the panel slightly. Never assume the first reading is final.

Joint Preparation and the Pre-Weld Inspection

All perimeter joints must be prepared to the joint detail shown on the drawing and called out in the WPS. Common requirements include a specific root opening (gap), bevel angle if required, and a clean, mill-scale-free surface in the weld zone. Use a wire brush or grinder to clean at least one inch back from the joint on both sides. Measure the root gap at multiple points — minimum every 12 inches along the joint — and record each measurement on the pre-weld inspection form. If the gap exceeds the WPS tolerance at any point, correct it before proceeding. ABS and AWS both require that joint fit-up be verified and documented before welding begins. The instructor must sign the inspection form before the MIG machine is energized.

PPE and Hazard Awareness

Wear appropriate PPE throughout: safety glasses at all times in the shop, a welding helmet with the correct shade lens during any arc welding, leather welding gloves, and flame-resistant clothing. When grinding, add a face shield over safety glasses and hearing protection. MIG welding produces ultraviolet radiation, spatter, and fumes — ensure ventilation is running and position yourself so fumes rise away from your breathing zone. Grinders and cutting tools have pinch and abrasion hazards; keep guards in place. Follow your shop's lockout/tagout (LOTO) procedures any time you adjust or clear a jam in the MIG wire feeder with the machine off.

Connection to Certification

Bulkhead fabrication and installation is a core task mapped to NCCER Shipfitting module content. The plumb, fit-up, and inspection steps you practice here directly reflect the knowledge and performance skills assessed in NCCER Shipfitting credentialing. The weld joint preparation standards come from ABS Rules and AWS WPS requirements that underpin the AWS D1.1 Certified Welder and ABS/USCG Weld Test credentials. Doing this work correctly in the lab is practice for doing it correctly on a real vessel under classification survey.