Published on 07 July 2016
A Japanese Member company has chosen to take the manufacture of a sensor component in-house thanks to a solution provided by TWI.
TLV, an international company specialising in steam engineering products and services, first approached TWI when it experienced a problem with thermocouple sensor assemblies incorporated in the steam traps it manufactures for oil refinery plant applications.
The sensor’s 0.2mm diameter thermocouple wires, used to measure the temperature inside the steam traps, were failing within a year of operation at a rate of around one per cent. The thermocouples were exposed to temperatures ranging from -20°C to 250°C, a high level of humidity, and occasionally H2S or oxidising agents. TLV initially hypothesised that corrosion might be to blame, and commissioned TWI to investigate.
A detailed analysis of four failed thermocouples, along with one that had not been used, revealed that corrosion was not the cause of the failures, and that the problem was more likely to originate from the welding process used in their manufacture and the design of the component. This theory was corroborated by further examination of the joint interfaces of disassembled parts, and two additional thermocouple sensors of a different design.
At this point TLV, which had previously subcontracted the assembly of the sensor bracket, decided to bring its manufacture in-house. The company asked TWI to recommend an appropriate joint design and develop a suitable welding technique for joining the thermocouple wires to the sensor bracket. Taking joint materials and the design of the sensor into consideration, TWI identified that resistance welding was the most appropriate technique, and provided guidance on the process and suppliers of suitable equipment. These recommendations were verified through welding and testing trials conducted at TWI.
TLV has now adopted the process and produces welds using its new in-house sensor bracket design and welding system. TWI continued to assist by verifying the quality of the first products from this new assembly system. This is the latest instalment of a working relationship that has covered multiple related projects and seen TWI provide a range of services spanning failure analysis, welding process selection and weld quality assessment.
For more information, please contact us.