Powder Coating Q&A: What Should I Watch Out For On An Older Curing Oven?
Every month, we take a question about powder coating and get an answer from our resident coating expert, Bruce Chirrey. If you have a question for Bruce, please send it to firstname.lastname@example.org. This month’s question is about what to look out for on older equipment.
Question: On a powder coating oven that is well over 10 years old, do the wires go bad and does the oven need to be rewired? What other issues do I need to look out for?
Answer: Oven wiring doesn’t automatically go bad but there is wear and tear on an oven that can cause issues if it has been moth-balled for some time. As with all older appliances, a certified electrician should check for potential code issues and make sure it is safe to operate. This is especially important regarding safety devices such as airflow switches and high temperature limit safeties. Cleaning the motors and making sure they have appropriate amp draws is also important.
The next issue that we see in older ovens is the temperature probes could have been damaged or the connections and/or wiring have developed issues. If the oven does not hold a consistent temperature or tends to shut down due to the high limit being reached, probe replacement or wiring repair might be needed. The signal strength is quite low compared to the wires connected to the motors or other controls, so even a slight bit of damage to the wiring or a loose connection can cause problems.
One of the main things we see if an older oven is put back in service, either after having been decommissioned for an extended period of time or sold to a new owner as used equipment, is the deterioration of the insulation, especially if the oven has ever been moved. You can tell if an oven has degraded insulation if the outside walls get too hot to touch, especially at the tops of the wall panels where they meet the roof. During handling, mineral wool insulation (especially if it has gotten wet due to exposure to moisture or from the inside surfaces of the panels “sweating” and having condensation issues) can break down and settle. The most obvious area of concern is at the top of the panels, which may no longer have insulation inside because it has shifted down during settling.
On belt-driven exhaust and supply fans, you should check to make sure the belts are in good shape, properly aligned, and properly tensioned. Avoid over-tightening the belts to help prevent bearing wear!
Older ovens also tend to have issues with the burner section of their heat units. The burner may have been damaged through handling or from extensive operation, especially at higher temperatures. It is important to check the plumbing connections at the burner’s gas train and to visually inspect the area where the flame is discharged into the heat unit’s airstream. It is not uncommon for the orifice, blossom, or combustion area to be degraded or distorted by heat over time.
Once the wiring, belts, gas plumbing, and burner have been checked, I would then have an oven or paint booth technician come in to test the temperature of the oven. By running an oven recorder, such as a DataPaq, the technician can ensure the oven is operating at the correct temperature and is working as intended.
For further reading, please check out our Buying Used versus New Equipment Guide, which covers some of the other issues you may run into when using an older piece of machinery.
Thanks again, Bruce! Mr. Chirrey and our other systems specialists are always happy to answer your questions and direct you to a solution for your coating needs – Contact us today!
If you are looking for more powder coating information – including tips and tricks, troubleshooting guides, and equipment maintenance schedules – check out our Resources page.