High temperature control for exhaust analysis
05 July 2018
The control of emissions from combustion engines has made several headlines in the past, bringing the subject to the fore on several occasions.
For those involved in designing and manufacturing the analysis equipment it is essential that they reproduce accurate results and that requires precision equipment especially at high temperatures. For one manufacturer the expertise and precision it needed was found at Bürkert Fluid Control Systems.
Exhaust gas analysis is not just required for automotive applications, it is also essential for many industrial processes, such as power generation, oil and gas refining and chemical manufacture. Each industry has its own requirements and as such the equipment used to measure and analyse emissions gases needs to be tailored to each situation.
Manufacturers of gas analysis equipment provide the tools necessary to measure and monitor emissions that enable operators to stay within the levels stated in national regulations. As such it is essential that the sampling and measuring equipment is as accurate as possible to ensure compliance and maximise productivity.
Stack emissions analysis
Protea is a leading manufacturer of FTIR gas analysers and bespoke sampling and analysis systems for process, emission and environmental monitoring. As part of a recent design project the company needed to develop a heated multi-stream selection unit to enable a range of heated sample streams to be fed to a single analyser, for a range of analysis applications.
To keep response times fast, sample gas streams are channelled to a control valve unit. For the majority of the time the sample gas goes to a bypass vent without passing through the analyser. When a sample is required the respective valve directs the gas stream for analysis. In any other application the control task could be easily performed by a standard, 3-way solenoid valve but in this case the whole process, and hence the valves, needs to be maintained at 180°C.
Although the Protea designers had a solenoid control valve that could be used within this design, some questions had been raised in the past about the long term reliability of the valve. In order to deliver an improved product to the end user, a search was launched for a better component.
High temperature solutions
Chris Muten, Design Engineer at Protea, takes up the story: “The real challenge for this control valve is the high operating temperature, not just of the medium but the surrounding environment as well. It is essential that the coil, electrical connections and process connections can all withstand at least 180°C.
“Having already used Bürkert solenoid control valves in other applications, we were aware of the high build quality and long term reliability of their products. This led us to enquire about their high temperature range of solenoid valves to see if there was a product that would fit our design. A conversation with Clive Halliday, North West Account Manager for Bürkert, soon led us to a variant of the Type 355, 3-way solenoid valve, constructed in stainless steel and incorporating PTFE seals. This high temperature variant would prove to be the solution we were looking for.”
Adapting to new applications
Having agreed on the specification of the solenoid valve, the Protea engineers designed a mounting block that would allow four solenoid valves to be positioned together and also help to maintain the temperature within the analysis pipework at 180°C.
Clive Halliday explains: “The speed with which this project has been delivered can be largely attributed to the huge diversity of the Burkert product range. Coupled with the extensive knowledge of our application engineers, we make every effort to deliver the most effective and reliable solution available.”
Chris Muten concludes: “The work to create the prototype of this analysis system has certainly paid off because we have since received two further orders for very similar equipment, albeit for entirely different applications. The analysis and monitoring of exhaust systems is very important for companies to ensure they comply with regulatory standards and so it is essential that the equipment is both accurate and reliable. The fact that Bürkert will guarantee the performance of their solenoid valve up to 250°C is very important to the reliability of our equipment.”
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