This case study covers the Thermcraft CoilCraft Element System and how it was developed. It then describes how this element type was used to solve a furnace-ased problem.
Challenge Faced in 2006
In the middle of the year 2006, Thermcraft received an order from Perryman to produce a series drying ovens for processing metal scrap as part of a proprietary process developed by Perryman. Based on specifications received, units were supplied that employed its standard PH-C series heavy-duty cast plate heaters mounted under the client supplied process unit. The units showed satisfactory performance for two years.
The customer added process air to aid in removal of volatiles produced as a result of processing. This additional loading factor to the heaters resulted in metals fines contaminating the heater compartment. Hence heater failure occurred at both ends of the chamber where contamination was the highest.
The heaters were replaced but they lasted only around six months. Again heaters were installed and the same problem was encountered. In order to replace heaters, there was a need to remove the furnace top and the rotating drum causing high expense and downtime in addition to the heater cost.
Potential Solutions Suggested for the Problem
In order to solve this problem, Perryman and Thermcraft discussed probable solutions for the problem and developed a list of requirements for a product that would overcome these limitations. The solutions proposed had to meet the folloiwing criteria:
- Design of a new heater system is required to ensure that when the heater fails there is no need to disassemble the entire furnace.
- It was proposed that the existing power supply for the furnace need not be replaced.
- Certain provisions have to be integrated into the system to protect elements from becoming contaminated.
- Conversion to the new version should involve as little production down time as possible
- Above all, the conversion had to be economic.
Solution: Thermcraft ’s CoilCraft Element System (CCE)
On reviewing several alternatives, they came to the conclusion that Thermcraft’s CoilCraft Element System is the most suitable alternative to overcome these limitations.
Fine-tuning adjustments of the CCE System to suit this application are listed below:
- This system is essentially a heavy gauge wire element integrated with a ceramic support structure.
- To suit this application, leads were designed so that both would exit the same side element end, enabling insertion or removal of each individual heater without disassembling the furnace, only requiring the opening of the terminal compartment.
- Thermcraft was also able to provide a design with a slightly lesser watt loading on each element, which typically translates into a longer element life.
- The design would ensure that balanced three phase power is maintained and interlocking shields are provided to protect against contamination of the element because of product dust escaping from the process unit.
- The only wiring changes needed were in the terminal compartment of the furnace, leaving the power supply as originally manufactured.
Conversion Process from Existing System to Thermcraft’s CCE System
Thermcraft and Perryman agreed that Thermcraft would provide the heaters, support system, and engineering and construction drawings along with comprehensive instructions while Perryman would do the actual conversion. On receipt of the materials Perryman began disassembly of the existing system.
Perryman discovered an additional problem. The nature of certain of the heater failures had caused damage to the underlying insulation that had to be replaced.
After replacement of damaged insulation in the furnace base, the actual conversion process began. The steps followed during the exact conversion are listed below:
- Firstly, sections of the steel furnace shell in the terminal compartment were cut away, ensuring that there is no damage to the structural integrity of the furnace enabling passage holes for the new element system to be drilled through the sidewall insulation.
- The exact guidelines of the areas to be cut were provided by Thermcraft to ensure good alignment and strength.
- After drilling of the passage holes the CCE System installation began.
- A support structure was installed at the furnace center to avoid mechanical damage during assembly and electrical shorts and to enable future element replacement operations.
- Elements were then fitted in from the sidewalls into their respective slots.
- Metal pans were installed to ensure that there is no product contamination as work progressed.
Installation of Power Supply
On completion of all the internal work, a new power distribution block was added to one terminal compartment for connecting easily the incoming three phase power lines from the power supply. Then a series of jumpers were installed between the various heaters. The heaters were then connected through additional “bank” wiring to the power block in conjunction with Thermcraft’s supplied drawings and instructions.
On completion of the wiring the system was ready to begin operations.
The Material Process Manager at Perryman Company expressed that it was a rather easy conversion without any major issues. Drawings, supplied instructions, and other information precisely reflected the degree and scope of work required and all the parts fit in place as shown. The area supervisor indicated that the entire conversion only took three days and if they had received the floor insulation sooner, it would have been completed earlier. One must note that Perryman Employees did an excellent job with respect to speed, accuracy and workmanship in performing the conversion with the end-result looking very professional.
The issue faced by Perryman was solved amicably and the end-result was excellent. Temperature uniformity of the rebuilt unit is very good and it also has a rapid heat-up cycle. One reason for rapid heating is the low thermal mass of the CoilCraft Element System (CCES).
The material costs of the CoilCraft Element System (CCES) elements match with the Cast Plate Heaters. Perryman did some test changes before the conversion was actually completed and found the elements were very easy to replace whether one or more need to be replaced.
Since replacement is easy, maintenance costs and production downtime will be greatly reduced when a failed heater has to be replaced. Based on the outcome of this conversion, Perryman plans to retrofit the other units as production requirements allow.
This information has been sourced, reviewed and adapted from materials provided by Thermcraft.
For more information on this source, please visit Thermcraft.