46 CFR 56.50-80: Lubricating-oil system design requirements
Last reviewed: October 14, 2026
This section sets design and arrangement requirements for lubricating-oil systems. The system must work at a permanent 15° list and a permanent 5° trim, and an independent auxiliary lubricating pump must be provided when pressure or gravity-forced lubrication is used for the main propelling machinery. It also covers coolers, filters, piping, sight-flow glasses and steam machinery.
What it says
The lubricating oil system must be designed to function satisfactorily when the vessel has a permanent 15° list and a permanent 5° trim.
46 CFR 56.50-80(a)“The lubricating oil system must be designed to function satisfactorily when the vessel has a permanent 15° list and a permanent 5° trim.”
When pressure or gravity-forced lubrication is employed for the main propelling machinery, an independent auxiliary lubricating pump must be provided.
46 CFR 56.50-80(b)“When pressure or gravity-forced lubrication is employed for the main propelling machinery, an independent auxiliary lubricating pump must be provided.”
Oil coolers must be provided with two separate means of circulating water through the coolers.
46 CFR 56.50-80(c)“Oil coolers must be provided with two separate means of circulating water through the coolers.”
For internal combustion engine installations, paragraphs (b) and (c) of this section do not apply to vessels in river and harbor service, nor to any vessel below 300 gross tons.
46 CFR 56.50-80(d)“For internal combustion engine installations, the requirements of paragraphs (b) and (c) of this section do not apply to vessels in river and harbor service, nor to any vessel below 300 gross tons.”
The lubricating oil piping must be independent of other piping systems.
46 CFR 56.50-80(e)“The lubricating oil piping must be independent of other piping systems and must be provided with necessary coolers, heaters, filters, etc., for proper operation.”
Steam turbine driven propulsion and auxiliary generating machinery depending on forced lubrication must be arranged to shut down automatically upon failure of the lubricating system.
46 CFR 56.50-80(g)“Steam turbine driven propulsion and auxiliary generating machinery depending on forced lubrication must be arranged to shut down automatically upon failure of the lubricating system.”
Sight-flow glasses may be used in lubricating-oil systems if they can withstand exposure to a flame at a temperature of 927 °C (1,700 °F) for one hour, without appreciable leakage.
46 CFR 56.50-80(h)“Sight-flow glasses may be used in lubricating-oil systems provided they can withstand exposure to a flame at a temperature of 927 °C (1,700 °F) for one hour, without appreciable leakage.”
Steam driven propulsion machinery must be provided with an emergency supply of lubricating oil that must operate automatically upon failure of the lubricating oil system.
46 CFR 56.50-80(i)“Steam driven propulsion machinery must be provided with an emergency supply of lubricating oil that must operate automatically upon failure of the lubricating oil system.”
Common questions
Do paragraphs (b) and (c) apply to internal combustion engine installations on vessels in river and harbor service?
No. For internal combustion engine installations, the requirements of paragraphs (b) and (c) do not apply to vessels in river and harbor service, nor to any vessel below 300 gross tons.
“For internal combustion engine installations, the requirements of paragraphs (b) and (c) of this section do not apply to vessels in river and harbor service, nor to any vessel below 300 gross tons.”
What list and trim must a lubricating oil system handle?
The system must be designed to function satisfactorily at a permanent 15° list and a permanent 5° trim. The text refers the reader to § 58.01-40 of this subchapter for operational requirements at angles of inclination.
“See § 58.01-40 of this subchapter for operational requirements for propulsion and vital machinery at vessel angles of inclination.”
Can sight-flow glasses be used in lubricating-oil systems?
Yes, they may be used if they can withstand exposure to a flame at 927 °C (1,700 °F) for one hour without appreciable leakage.
“Sight-flow glasses may be used in lubricating-oil systems provided they can withstand exposure to a flame at a temperature of 927 °C (1,700 °F) for one hour, without appreciable leakage.”
The text of 46 CFR 56.50-80
Electronic Code of Federal Regulations (eCFR), current as of March 31, 2026 · Read it on eCFR
Lubricating-oil systems
(a) The lubricating oil system must be designed to function satisfactorily when the vessel has a permanent 15° list and a permanent 5° trim. See § 58.01-40 of this subchapter for operational requirements for propulsion and vital machinery at vessel angles of inclination.
(b) When pressure or gravity-forced lubrication is employed for the main propelling machinery, an independent auxiliary lubricating pump must be provided.
(c) Oil coolers must be provided with two separate means of circulating water through the coolers.
(d) For internal combustion engine installations, the requirements of paragraphs (b) and (c) of this section do not apply to vessels in river and harbor service, nor to any vessel below 300 gross tons. For internal combustion engines, two separate means are to be provided for circulating coolant. One of those means must be independently driven and may consist of a connection from a pump of adequate size normally used for other purposes utilizing the required coolant. Oil filters must be provided on all internal combustion engine installations. On main propulsion engines fitted with full-flow type filters, the arrangement must be such that the filters may be cleaned without interrupting the oil supply except that such an arrangement is not required on vessels having more than one main propulsion engine.
(e) The lubricating oil piping must be independent of other piping systems and must be provided with necessary coolers, heaters, filters, etc., for proper operation. Oil heaters must be fitted with bypasses.
(f) Diesel engine lubrication systems must be so arranged that vapors from the sump tank may not be discharged back into the engine crank case of engines of the dry sump type.
(g) Steam turbine driven propulsion and auxiliary generating machinery depending on forced lubrication must be arranged to shut down automatically upon failure of the lubricating system.
(h) Sight-flow glasses may be used in lubricating-oil systems provided they can withstand exposure to a flame at a temperature of 927 °C (1,700 °F) for one hour, without appreciable leakage.
(i) Steam driven propulsion machinery must be provided with an emergency supply of lubricating oil that must operate automatically upon failure of the lubricating oil system. The emergency oil supply must be adequate to provide lubrication until the equipment comes to rest during automatic shutdown.
Sections it refers to
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of March 31, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.