The Challenge
On tanks intended for outdoor installations, the original equipment manufacturer is often requested to install heating equipment. End user customers require heated fiberglass storage tanks to prevent solidification of stored chemicals due to freezing end/or to limit temperature related viscosity to facilitate pumping. They need an inexpensive I sine means of evenly heating a tank to 60° F, for example, on a continuous basis.
The problem lies in the fact that at temperatures above 190° F, the fiberglass tank experiences damage. This is most likely to occur at the point of contact where the heater is mounted to tank wall.
The Solution
One of the sales engineers at the nearby Chromalox sales office recommended the use of self-regulating heating cable as ideal for this application. The fact that it can be wrapped around the tank for even heating and is available in a variety of wattage ratings makes heating cable ‘an excellent selection. In addition, with Chromalox self-regulating heating cable, there is a definite limit as to how high the cable surface temperature can rise even under worst case conditions’, This limit is dependent on how the cable is applied.
For one particular application, the sales engineer recommended 100 ft. of 10 watt/ft. 240 volt self-regulating cable as adequate to maintain losses with 2″ of foam insulation around the tank. The cable was applied to the tank wall with Chromalox AT-1 aluminum tape. He explained that even on loss of control the self-regulating heating cable inherently limits its own temperature.This application was therefore, inherently fail sale, since there was no way for the cable surface temperature to exceed the 190° F necessary to damage the fiberglass. Also recommended was a Chromalox 3912 series digital indicating 1/4 DIN temperature controller for on/off control. The controller was mounted remotely in a central control location.
The 3912 series temperature controller was used but is not longer produced. The modern replacement would be a HTLS single loop control panel.
Benefits
- Fail safe: With Chromalox’s exclusive self-regulating feature, the cable cannot exceed the temperature required to damage
fiberglass tanks (when installed as described). - Even heating: The cable can be mounted to provide any heating pattern desired for uniform heating around the tanks.
- Inexpensive: Total installed cost of the heating system was less than 10% of the selling price of the tank.
- Attractive: The customer stated that the appearance of the 3912 controller alone would enhance the sale of future heated tank systems.
- Single source: It is almost always more convenient and often less expensive (taking paperwork and customer’s time into account) to purchase a complete system from a single source.
