VFTU series generated hot gas heated water bath vaporizers are generally used for the higher capacity requirements. They range from 250,000 SCFH to in excess of 3,000,000 SCFH (6,600 to 80,000 Nm3/hr). They are most commonly used in pipeline back-up service or other high volume systems such as steel mills, or LNG peak-shaving and LNG send-out station duty. 

Tube bundles are available in standard incremental sizes, as are the tanks. Bundles and tanks can be used in a variety of combinations to achieve most customer requirements of steady state capacity and ballast time. Several different process and pressure building bundles can be installed in a single tank. These systems are essentially self contained requiring only on site connection of services and gases prior to being operational.

These units are more expensive for a given capacity than a direct steam vaporizer, but hot water bath vaporizers offer several advantages. The biggest advantage is that the water ballast in the tank can store energy and thereby allow process gas vaporization to continue even after loss of the hot gas heating supply. The ballast time is variable and is often specified by the customer, particularly for back-up systems. If no ballast time is specified, 3 to 5 minutes is typical of the design. Ballast times up to 30 minutes have been specified and achieved for some high volume plant back-up systems.