Electric heater cold pin insulation

DETAILED DESCRIPTION It is a general object of this invention to improve the reliability of electric resistance heaters.
It is a more specific object of this invention to provide an electric heater tube that does not require drying to avoid moisture related ground faults.
This invention is an improved resistance heating element for use in heating process streams that has a moisture impervious or water impermeable coating that covers an elongated connector, i.
e.
cold pin, at the tube end.
The moisture impervious coating prevents water adsorption from grounding the cold pin to the tube wall and shorting out the heating element.
The moisture impervious coating covers the length of the elongate connector, except at its ends where it is connected to a resistance wire or other heating element inside the tube and provides a terminal attachment point outside the heater tube.
The coating is in addition to the insulating material in the form of packed powders currently provided in most heater tubes.
The packed powder is still provided to allow the heating element to properly oxidize.
In this manner the coating provides an added layer of electrical insulation in the cold pin region that will not lose insulating capability when the permeable packing material adsorbs moisture.
The coating has the advantage of making the heater element more tolerant to moisture penetration that does occur between the time of manufacture and startup.
The coating prevents the moisture penetration that does occur from lowering insulation resistance to values that would produce a ground fault.
The coating also allows rapid powering of the tubes even in the case of moisture presence.
Any gradient that causes a concentration of moisture as the vapor is driven along the element to the point where the due point is reached will not pose severe problems.
Moisture concentration in the cold pin area will not produce a ground short due to the presence of the coating.
Shorts between the wire heating elements and the tube are less severe because current is limited by the resistance of the wire between the power supply and the point of the short