Reference electrode for use at high temperatures and pressures

Claim 1

A reference electrode adapted for immersion in an aqueous liquid at high-temperature and high-pressure comprising: (a) a heat-expandable plastic tube body sealed at one end with a heat-expandable, heat-resistant plastic bridge mounting plug and sealed at the opposite end with an electrode mounting plug enclosing a silver wire, a portion of said silver wire having a fused silver chloride bead, said silver wire fixably disposed within said tube body and immersed within a soluble chloride electrolyte solution contained within said tube body; (b) a corrosion-resistant bridge restraining means circumjacent said tube body opposite the junction of said tube body and said bridge mounting plug, said restraining means selected to have a coefficient of expansion lower than the coefficient of expansion of said bridge mounting plug; (c) a pre-shrunk bridge sleeve surrounding bridge fibers mounted within said bridge mounting plug, whereby heat expansion of said bridge mounting plug against said bridge restraining means directs lateral forces to seal said bridge mounting plug to said tube body while compressing said bridge fibers, and (d) a heat sealing vent means in the wall of said tube body positioned above said electrolyte solution to substantially inhibit bubble formation through internal and external pressure equalization during pressurization and heating of said reference electrode, said heat sealing vent means adapted to close during heating to a temperature above about 300° C.