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Since 1991, the regulations for vapor control during marine loading operations have been determined by the Coast Guard and laid out in 33 CFR 154.800 (Subpart E). From 1991 to 2013, many requests for clarification A revised set of regulations, 33 CFR 154.2000 (Subpart P), was finalized and went into effect August 15, 2013. Any facility built after August of 2013 must reference the revised regulations, Subpart P, for their initial design and certification. Existing facilities were required to comply with the new Subpart P regulations and be recertified, if necessary, by August 15, 2016. The revised regulations include several significant changes that affect many facilities involved in marine loading operations; one requirement will affect all facilities. The most impactful of these changes is the new requirement for an operational review each 5 years for every marine vapor control system.

Operational Review

Subpart P requires that every facility with a Marine Vapor Control System (MVCS) complete an Operational Review (OR) every five years. For facilities initially certified after August 15, 2011, the first operational review must be completed within five years of the initial certification. For all other facilities, the first operational review should have been completed by August 15, 2016. These operational reviews must be conducted by a United States Coast Guard Approved “Certifying Entity.” The Certifying Entity must review all the MVCS documentation, training procedures, and recordkeeping. The Certifying Entity must also observe a loading operation and confirm that the maximum certified loading rate. The OR is completed when any required corrections are made for Subpart P compliance and the Certifying Entity issues a review letter to the Coast Guard. Due to the limited number of USCG Certifying Entities and the vast number of storage facilities, it is recommended that facilities plan for and schedule these reviews as soon as possible.

Mechanical Changes

In addition to the operational review requirement, there are several changes to the regulations that may require piping changes. These changes include a lower pressure relief valve set point, fire-safe valves being required at the inlet of the combustion unit, and a defined distance after a detonation arrester before a pipe expansion can occur.

Previously, Subpart E required a pressure relief valve to fully relieve no higher than 2.0 psig; the new regulations require the pressure relief valve to reach full flow at 1.5 psig. Many pressure relief valves can be adjusted to accommodate this change. However, in some cases this will require a larger pressure relief valve. In some cases, if a facility does not load vessels with a relief valve set point lower than the facility MVCS pressure relief valve, a waiver may be obtained from the USCG engineering office, ENG-5, in Washington, DC.

Many facilities use a flare or vapor combustor to destroy vapors generated during loading. These facilities were previously required to have two automated shutdown valves at the inlet but there was no requirement for the type of valve or valve materials; in subpart P, these two valves are now required to be fire-safe and have at least one located on the dock side of the flare detonation arrester.

Subpart P has also introduced a new requirement regarding the installation of detonation arresters: piping cannot be expanded to a larger size within 120 pipe diameters of a detonation arrestor.

Fortunately, not all of the changes to the regulations are more stringent—several have relaxed the old design requirements. For example, the maximum allowable distance between the facility vapor connection and the required detonation arrester has been increased from 6 meters (19.1 ft.) to 18 meters (59.1 ft.).

Vapor Balancing

If a facility vapor balances to storage tanks during marine loading rather than using a vapor abatement device, there are three changes to be aware of. These facilities will now need a means to detect and prevent backflow in the vapor line from the tank to the vessel and a means to monitor temperature in the tank vapor space. Both of these requirements may be achievable with small instrumentation changes, but still need to be completed and recertified to comply with Subpart P.


Many marine vapor control systems will not be in compliance with the newly published regulations. However, if the system utilizes alternative equipment that is equally safe, it is possible to request an exemption from a regulatory requirement. Exemption requests are reviewed and approved by USCG Headquarters in Washington DC on a case by case basis. A granted exemption gives the certifying entity the ability to approve a system that does not fully comply with the regulations without modifications to the system as specifically stated in the exemption letter.

Aura Engineering has been a USCG approved certifying entity since being founded in 1996. For more information regarding the changes to the USCG regulations, including specifics on the 5-year operational review, please contact Chris Lawrence with Aura Engineering, LLC at