Thermal fluid heaters are offered in 0.5 to 75 million BTU/hr in horizontal or vertical, two-pass or three-pass models, and up-fired or down-fired configuration. Used in closed-loop thermal fluid heat transfer systems, the heaters are designed around a helical coil. Thermal fluid flows through the helical coil, gaining radiant and convective heat from hot burner gases. The heated thermal fluid transfers heat to end users such as tanks, presses, dryers, reactors, chillers, extruders, steam generators or other equipment. Heater features include factory-preassembled design, optional on-site setup and startup, and factory service options. All are customized to meet customer specifications.