Canned motor pump for use at high temperatures

Claim 1

A canned motor pump for use with high temperature process fluids having temperatures above 200° C., comprising a canned motor having a rotor assembly including a rotor shaft to which an impeller is secured, said impeller extending into a chamber of the pump having a suction side and a discharge side, spaced apart rotor chambers at opposite ends of said rotor assembly, said rotor chambers comprising a front rotor chamber and a rear rotor chamber, and means forming part of the pump defining a fluid circulating path for circulating a portion of the fluid in the pump into and through the rotor chambers forming part of said fluid circulating path, one of said rotor chambers communicating with said suction side of the pump and another of said rotor chambers communicating with the discharge side of the pump whereby said portion of the fluid flowing into and through the rotor chambers effectively cools the canned motor, and to resist breakdown of the canned motor when subjected to operating current and high temperature fluids, said canned motor has field windings impregnated with a ceramic-like insulating material which is the reaction product of an impregnant comprising a suspension of a silicone resin and a synthetic fluoro-mica in an organic solvent, said reaction product being derived on subjecting the impregnant, after curing, to temperatures above 300° C. to thermally decompose the silicone resin, evidenced by loss of organic radicals from the silicone resin with resulting conversion of the resin to polysiloxane which is exposed to a fluoro-compound vaporized from said synthetic fluoro-mica at the same temperature as that at which decomposition of the silicone resin occurs.