Answer
The Inchmaree Clause (also known as the Additional Perils Clause) is a standard clause in Hull & Machinery (H&M) marine insurance policies.
The clause gets its name from the steamship SS Inchmaree.
While at anchor, a crew member left a valve closed on an auxiliary donkey pump while pumping water into the main boilers. Pressure built up, splitting the air chamber and destroying the pump.
The House of Lords ruled that the loss was not covered under traditional marine policies because a pump explosion in port was not a "peril of the sea" (it was not caused by sea action, storms, or navigation hazards). To address this critical coverage gap for steam-powered ships, underwriters introduced the "Inchmaree Clause."
Key Risks Covered:Latent Defects: Hidden manufacturing, metallurgical, or casting defects in the machinery, hull, or shafts that could not have been discovered through reasonable diligence or standard survey inspection.
Negligence of Crew/Officers: Operational errors or oversight by Master, Officers, Crew, or Pilots (e.g., dry-running a lube oil pump, incorrect valve line-ups, or improper boiler water treatment leading to thermal damage).
Machinery Breakdown & Explosion: Explosions of boilers, breakage of shafts, or burst air receivers.
Contact & Falling Objects: Accidental contact with aircraft, land transport, dock equipment, or heavy machinery drops during maintenance.
Repairer Negligence: Errors committed by shore-side repairers or charterers, provided they are not an Assured under the policy.
Coverage under the Inchmaree Clause is strictly subject to the Due Diligence of the Assured (the Shipowner, Manager, or Superintendent):