46 CFR §56.30-35

1. (a)This section applied to pipe fittings that form a seal by compressing a resilient gasket onto the pipe joint primarily by threaded fasteners and where joint creep is only restricted by such means as machined grooves, centering pins, or welded clips. Fittings to which this section applies must be designed, constructed, tested, and marked in accordance with ASTM F1476 and ASTM F1548 (both incorporated by reference, see § 56.01-2). Previously approved fittings may be retained to the satisfaction of the Officer in Charge, Marine Inspection.
2. (b)Gasketed mechanical couplings may be used within the service limitations of pressure, temperature and vibration recommended by the manufacturer, except that gasketed mechanical couplings must not be used in—
   1. (1)Any location where leakage, undetected flooding, or impingement of liquid on vital equipment may occur; or
   2. (2)In tanks where the liquid conveyed in the piping system is not chemically compatible with the liquid in the tank.
3. (c)Gasketed mechanical couplings must not be used as expansion joints. Positive restraints must be included, where necessary, to prevent the coupling from creeping on the pipe and uncovering the joint. Bite-type devices are generally not accepted for this purpose. Machined grooves, centering pins, and welded clips are considered positive means of protection against creep.