(a) Piping. The definitions contained in 100.2 of ASME B31.1 (incorporated by reference; see 46 CFR 56.01-2) apply, as well as the following:
(1) The word piping within the meaning of the regulations in this subchapter refers to fabricated pipes or tubes with flanges and fittings attached, for use in the conveyance of vapors, gases or liquids, regardless of whether the diameter is measured on the inside or the outside.
(b) Nominal diameter. The term nominal diameter or diameter as used in this part, means the commercial diameter of the piping, i.e., pipe size.
(c) Schedule. The word Schedule when used in this part refers to specific values as given in ASME B36.10M and B36.19M (both incorporated by reference; see 46 CFR 56.01-2 ).
(d) Fittings and appurtenances. The word fitting and the phrase fittings and appurtenances within the meaning of the regulations in this subchapter refer to pressure containing piping system components other than valves and pipe. This includes piping system components whose function is to join branches of the system (such as tees, wyes, elbows, unions, bushings, etc.) which are referred to as pipe joining fittings, as well as components which operate on the fluid contained in the system (such as traps, drains, strainers, separators, filters, meters, etc.), which are referred to as “fluid conditioner” fittings. Thermometer wells and other similar fittings which form part of the pressure barrier of any system are included under this heading. Expansion joints, slip joints, rotary joints, quick disconnect couplings, etc., are referred to as special purpose fittings, and may be subject to such special design and testing requirements as prescribed by the Commandant. Refer to subpart for design requirements for fittings.
(e) Nonstandard fittings. “Nonstandard fitting” means a component of a piping system which is not fabricated under an adopted industry standard.
(f) Vital systems.(1) Vital systems are those systems that are vital to a vessel's survivability and safety. For the purpose of this subchapter, the following are vital systems:
(i) Systems for fill, transfer, and service of fuel oil;
(ii) Fire-main systems;
(iii) Fixed gaseous fire-extinguishing systems;
(iv) Bilge systems;
(v) Ballast systems;
(vi) Steering systems and steering-control systems;
(vii) Propulsion systems and their necessary auxiliaries and control systems;
(viii) Ship's service and emergency electrical-generation systems and their auxiliaries vital to the vessel's survivability and safety;
(ix) Any other marine-engineering system identified by the cognizant OCMI as crucial to the survival of the vessel or to the protection of the personnel aboard.
(2) For the purpose of this subchapter, a system not identified by paragraph (1) of this definition is a non-vital system.
(g) Plate flange. The term plate flange, as used in this subchapter, means a flange made from plate material, and may have a raised face and/or a raised hub.