Main Engine Exhaust Overhaul & Valve Renewal, RINA-Classed Motor Yacht
Both main engine exhaust systems on a RINA-classed motor yacht were stripped to the hull flanges during an extended hardstand refit: DN350 and DN400 butterfly valves renewed with European-sourced units carrying EN 10204-3.1 material certificates, high-temperature graphite gaskets and stud bolts custom made, a burn-through catch on the starboard expansion joint, and the rebuilt systems pressure tested in line with class requirements.
The chief engineer of a RINA-classed motor yacht on a Coomera shipyard hardstand brought us in to open up both main engine exhaust systems, port and starboard, as part of an extended refit. The lagging blankets came off first, tagged and set aside, then the auxiliary piping and main exhaust pipes were unbolted and lifted clear. What the strip-down found justified the job: seat seals perished to the point of coming out in fragments, corrosion through the valve castings, material loss in a metal elbow section, and flange fasteners corroded well past reuse. Of the four exhaust valves, inspection condemned more than the brief had assumed, and the vessel's engineer had never sighted a class stamp on any of them.
Replacement was a sourcing and fabrication exercise as much as a fitting one. New DN350 and DN400 butterfly valves rated well above the measured operating temperature were sourced through our European supply channel with EN 10204-3.1 material inspection certificates, the documentation a RINA surveyor can accept, and we offered the vessel our class survey contacts and pressure-testing history with assessors to support certification. Every gasket was custom made in high-temperature graphite with metal reinforcement, checked on arrival, and one batch cut with undersized bolt holes was rejected and remade. The original stud bolts proved too short for the new valves, so replacements were manufactured from fresh threaded bar, and every nut, bolt and washer in both systems was renewed. The removal of the starboard expansion joint turned up the find of the job: burn-through marks on its gasket and flange face, caught before it became something far more serious, with new gaskets and special-order spring washers fitted in response.
Reassembly ran with a curtain and extraction rig keeping contamination out of the engine room while yard trades worked around us. Both systems went back together on the new valves, gaskets and fasteners, the water cooling pipework was reinstated with rubber gaskets we cut on board when no spares could be found, and the insulation was renewed over the lot. Before handover we pressure tested from the sea chest using the fire line, proving the valve-to-flange seals and disc sealing in line with RINA class practice, and specified the final torque procedure: a full heat cycle at operating temperature before fasteners are pulled to final torque after sea trial, the difference between an exhaust system that seals and one that puts fumes in the engine room.
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