This 34″ diameter shell and tube heat exchanger with a 240″ long graphite tube bundle is a vital component of our customer’s operations. Their process fluid composition is very aggressive and compatible with very few heat transfer media. Our customer investigated other options, but found that the Impervite graphite shell and tube is the most cost effective solution.
The impregnated graphite does have its limitations however. Over time, the process will corrode the graphite. Alpha sintered ceramic tube would be an ideal heat transfer media for this process since it is universally corrosion resistant to most all chemicals up to 400 degF. If the thermal load was less, ceramic would be an obvious choice. However, due to the heat transfer area required for this process load, Impervite graphite was found to have the lowest life cycle cost and was chosen as the heat transfer media of choice.
Field assistance and service
Recognizing the aggressiveness of process fluid, regular unit inspections were scheduled. After 18 months in service, a loose tube is found during shutdown inspection. The process is critical and downtime is costly. A CG Thermal Field Service Technician assisted by onsite service technicians field tested the unit, identified and plugged the failed tubes, and the heat exchanger was brought back on service. Once instructed by our Field Service Technician, spare materials were kept in stock, and onsite personnel plugged tubes when necessary.
Inspection and Recommendations
Arrangements were made for the unit to ship to our facility in Twinsburg, OH for inspection during a scheduled maintenance shutdown period. Normally, a process side test would be conducted, but in this case, a significant number of tubes had been plugged over the years and the face of the tube sheet was significantly eroded. Clearly, the entire tube bundle had provided its service life and needed to be replaced.
All other components were inspected and the domes were tested. The shell and all the steel components that only saw the service fluid or atmosphere, were all in good operational condition. We submitted our work order summary and recommendations to the customer.
Refurbishment to OEM standards
The customer agreed with the recommendations explained in the work order summary. The graphite components were replaced and all steel components were sandblasted and painted, and new hardware was installed. Our customer had a refurbished unit to OEM standards for a fraction of the cost to replace with new.