Design and Construction
We take special care to design our heaters for optimum geometry of the combustion chamber and the flux density of the helical coil. Thus, our coil has a large heat transfer surface area to provide much lower heat flux rates than those commonly used by others. And the coil diameter and length are sized to virtually eliminate flame impingement and provide optimum flame pattern. The diameter of the pipe used for the coil is sized to provide an ideal fluid velocity of 7 to 11 feet per second. The coil is built to ASME code.

The heater has a steel cylindrical shell that houses a helical coil. Oversized stainless pads inside the shell support the coil, leaving an annular space between the coil and the shell. The inner surface of the shell is covered with ceramic blanket insulation that has low thermal conductivity and low heat storage.

A burner mounts on one end of the shell and fires through the center axis of the coil. Its flame produces radiant energy that heats the inner side of the coil without impinging on its surfaces. Hot combustion gases turn outwards at the end of the coil. They double back into the annular space between the insulation and the exterior side of the coil, heating its outer surfaces by convection. The gases travel back the full length of the coil and then pass through the exhaust stack.

The hot helical coil heats the thermal fluid as it circulates through the coil. In turn, the hot fluid heats various plant equipment as it circulates. Stack heat exchangers for preheating thermal fluid and combustion air further increase burner efficiency.

Maintenance
The heaters are easy to maintain. Components are easy to reach. Electrical controls, motors and pumps are readily available from our large stock of parts. We can usually provide one-day shipment.

We use centrifugal pumps to circulate the thermal fluid. One of three types is used. One type has mechanical seals. One has lip seals. One is sealless.

Pumps that operate at temperatures below 600 degrees F are air-cooled, eliminating the need for water cooling. Pumps that operate at higher temperatures require water cooling.