Heaters for Double Boiler Tanks
The heater types used in double boilers are the Screw Plug or Flanged Immersion Heater.
Understanding the workings of a double boiler tank is best before designing one.
A double boiler is a tank in a tank. The reason being that direct contact with the heating source may have an adverse reaction to the chemical, like perhaps breaking the chemistry down prior to affecting the part.
Double boiler tanks are used in Electroless Nickel Plating. Usually an outer tank filled with water or glycol (inhibited) and an inner tank made of stainless with a PVC lining. This system provides the lowest Btu’s per Square inch than any other.
Standard immersion heaters are 35 to 40 Watts per square inch. For this application, De-Rated immersion heaters are 15 -20 Watts per Square inch, which are typically used along with an electro polished sheath material surface. The 15-20 WSI on the sheath material results in an effective conducted 3 WSI in the double boiler tank because all the surface area of the tank is used to heat the chemistry.