Portable Engines : Engines mounted on skids, wheels, or otherwise arranged so that they can be moved from place to place as the required service indicates
NFPA 37 Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines, 2002 ed. http://pozhproekt.ru/nsis/nfpa/NFPA37-2002.pdf, (Std: Install and Use of Stnry Combustion Engines and Gas Turbines - Amer) {201 NFC}