3.5.4 Other feedthroughs
Thermocouple feedthroughs transmit low thermoelectric voltages and must be tailored to the thermocouple used. The materials of the conductor pair for thermocouples must either be identical to those of the thermocouple or must be at least thermoelectrically comparable, so that a thermoelectric neutral transfer of thermoelectric voltage takes place. Elastomer sealed feedthroughs are also available for mineral insulated thermocouples and seal the sheath vacuum-tight through O-rings.
Feedthroughs for liquids are flanges welded pipes with open ends or with Swagelok® or VCR fittings. Double-walled pipes are used for feedthroughs that carry cold or hot fluids, where the fluid-carrying pipes are thermally insulated from the flange.
Insulators provide galvanic isolation to portions. The ceramics hermetically sealed and soldered to the flange connections can separate, depending on the length of the insulating distance, large potential differences in the high kV range.
Pipe feedthroughs clamp with two in a row elastomer O-rings glass and metal pipes vacuum-tight.