Rental Boilers | Mobile Boiler Rooms Our Mobile Boiler Systems | Watertube Boilers | Skid Mounted Systems WATERTUBE BOILERS These trailer mounted boilers range in size from 30,000 to 70,000 pounds of steam per hour with operating pressures of up to 350 psi. Boilers with capacities of up to 250,000 pounds of steam per hour are also available through Allied General Services. These units are normally shipped via rail. Watertube boilers can be shipped as "stand alone" units or a mobile feedwater system can be shipped to operate in conjunction with the boiler. These systems are trailer mounted, pre-piped, pre-wired and totally enclosed. Components include deaerator, feed pump set, water softener, chemical mixing and feed system and control air compressor.