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High temperature and pressure POX probes

Problem

A major chemical manufacturer following repeated product failure from a competitor approached Peak Sensors.

The key problems here were high pressure and a very high temperature of the vessel containing the reaction of partial oxidisation of natural gas to carbon monoxide (POX). Temperature had to be measured in the highly reactive gaseous atmosphere to control the process and maintain plant safety. The probes had to last for a two-year plant rebuild cycle. The possibility of probe breakage due to furnace insulation movement had to be considered. The customer needed to be supplied full material, process control, testing and safety documentation.

Our Solution

A type B thermocouple was designed through collaboration with the client to contain pressure even with ceramic component failure.

The design consisted of a thick wall Recrystalised Alumina primary sheath with an Inconel alloy 600 support welded to a forged flange. Quality approved (ASME IX) welders were used. The B type conductors were routed through a multibore conax pressure gland, which provides containment at temperature. Each probe was double pressure tested. The first pressure test was on the metal work assembly with hydraulic oil at 106 bar and the second test was on the final assembly at 40 bar with blended air. We supplied a full set of documentation for each probe delivery.

A set of seven probes was installed which allow the plant to run for a two year campaign at which time the full set is always replaced.

Challenges

The challenges faced included addressing the pressure, temperature and reactive gas, as well as the possibility that a probe gets damaged or broken through furnace insulation movement. Adherence to delivery dates was crucial to meet planned shutdown timetables.

Outcome

We were able to meet these challenges and the customer was satisfied. This contract has been repeated many times over the years, again adding to our history of success and ability to delight customers.