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An overview of marine vapour control system safety requirements

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Author(s): W. N. Tuttle, P.E. & J. W. Young, P.E., Warner Nicholson Engineering Consultants, P.C., USA

The generation of flammable vapours during cargo transfer into marine vessels presents numerous hazards even without the implementation of vapour control systems. Some of these hazards are: cargo tank overfill, cargo spillage, and fire and/or detonation of the cargo or its vapours.

When vapour control is included, additional hazards can be introduced by the very nature of the vapour containment system. These hazards include, in addition to the ones already listed, over or under pressuring the marine vessel, inclusion of sources of ignition such as vapour conveying equipment, vapour destruction or recovery equipment, etc.

The United States Coast Guard (USCG), under the authority of section 183(f) of the United States Clean Air Act, issued regulations in 1990 to ensure the safety of personnel, equipment and operations of a facility Marine Vapour Control Systems (MVCS) which contain and control the emission of vapours emitted from a marine vessel’s cargo tanks during the loading of crude oil, gasoline blends, or benzene.

In subsequent years further cargoes were included and the control of these was added to the original regulations by USCG policy letters. At this moment the United States Coast Guard Regulations coupled with the policy letters are the most comprehensive set of safety requirements for MVCS currently being enforced. Numerous countries have either emulated these regulations with the addition of local requirements or have adopted them in whole with the exception of the requirement for USCG Certification of the MVCS. One of the features of the current USCG regulations within the USCG jurisdiction is a third party Certifying Entity (CE) review of the design, installation and operation of the MVCS.

Some terminal operators, outside of the USCG jurisdiction, have voluntarily chosen to follow the USCG Regulations and have requested a third party Certifying Entity review of their systems to insure compliance with the safety requirements. The pertinent USCG Regulations may be found in the Code of Federal Regulations (CFR), 33 CFR Part 154, Subpart E. (For the complete text of these and other regulations please go to http://www.vaporcontrol.com/links.html at the bottom of the page click on the desired regulation). These regulations contain the requirements for facility based vapour control systems. In these regulations reference is made to earlier  USCG Regulations that deal with the requirements for the marine vessels themselves.

For example, 46 CFR Part 39, Subpart D contains the majority of vessel vapour control regulations and the requirements for the vapour collection equipment installed on marine vessels.

Marine vessel requirements

Important areas addressed by 46 CFR Part 39 include:

• Cargo gauging system (§39.20-3)

• Tank ship liquid overfill protection (§39.20-7)

• Vapour overpressure and vacuum protection (§39.20-11)

• High and low vapour pressure protection for tank ships (§39.20-13)

• Operational requirements (§39.30-1)

• Lightering and topping-off operations with vapour balancing (§39.40)

• Personnel training (§39.10-11)

Other applicable regulations for vessel MVCS and loading operations are contained in 33 CFR section 155.750 (Oil transfer procedures), 33 CFR section 156.120 (Requirements for transfer), 33 CFR section 165.170 (Equipment tests and inspections), and 46 CFR section 35.35-30 (c) (Declaration of inspection).


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