Custom Heating Element for Scientific Instrument

A laboratory instrument manufacturer was fabricating a heater assembly in house, that was difficult and time-consuming to make, fragile, and yielded inconsistent results. Tutco Farnam was approached for an alternative assembly and provided a redesigned assembly with superior performance at a lower cost.

Project and Challenges

The heater needed to seal against the bore (.182" ID) of a quartz dewar to contain 30 psi of gas stream pressure.

In order to be backward compatible with existing circuitry, a high limit circuit needed to sense the proper resistance at the specified high limit temperature.

Shielded power and sensor lead wires needed to be fed from the pressurized side out to ambient conditions without leakage.

Customer requested 100% of the assemblies be energized and tested for full functionality

Solutions and Their Impact

A miniature heater was packaged into a custom drawn tube to protect the assembly until it was installed.

A double O-ring seal was provided to seal the 30 psi gas stream.

A custom RTD was obtained to fit the small package and provide the correct resistance at the specified temperature. No modification of the high limit circuit was required.

Units were tested 100% on a custom-built tester. After several years of testing, the failure rate of these parts was so low, that it was decided testing was no longer required