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32 APRIL 2016 — PFonline.com THE VOICE OF FINISHING 80 YEARS burner should be sized to handle the load capacity for a bulk load or the pounds per hour of the line speed. Compare BTU and kWh in the oven specifications. Heat and fuel source. There are multiple ways to heat an oven, the most common of which are natural gas and electric heat. Other options include infrared, propane and steam. Look at the cost and accessibility of the fuel sources. In some countries, propane is more common. Steam can be an excel- lent source if the company is already generating steam of sufficient pressure and capacity. Infrared is less common for batch ovens, but has been used in continuous conveyor ovens for many years because it can offer faster line speed, less gap between color changes and increased productivity. Temperature range. Many customers ask for tempera- ture range tolerance (uniformity) without understanding the requirements and process to test this. Before deter- mining a tolerance, ask these questions: What standard are you quoting from for this uniformity? How many thermal couples are going to be inside the oven? Are you looking at air temperature or part temperature? Uniformity is typically established after the oven is installed, and racking or parts positioning is tested to deter- mine the optimum uniformity and temperature ranges required for production needs. Repeat the racking or parts positioning each time to maintain uniformity. If uniformity is critical to the operation, purchase an oven that can achieve this uniformity. Look at the production needs and tempera- ture ranges, as well as how to rack those parts. Insulation. A well-insulated oven is a more efficient oven. Insulation prevents heat loss and ensures exterior surfaces are safe to touch. Although insulation is important, more is not necessarily better. Look at the insulation density and R-values for comparison. Controls. Basic control packages include an on/off switch and temperatures settings, and this may be enough, depending on the application needs. More advanced controls enable oven adjustments based on the product load, the type of part and the different coatings. Exhaust volumes. An oven should remove a sufficient volume of air so the correct volume of combustion air can be supplied. For a dry-off oven, the exhaust volume needs to expel a sufficient volume of air to remove humidity. On lower temperature ovens, exhaust will help keep an oven cool. Some fans, when running for a long period of time, can add 30°F or more to the temperature rise. An oven should not exhaust more than needed because it's throwing away energy—and energy is money. To save energy, heat can be recovered from the exhausted air with a heat recovery system. The recovered heat can be used for other processes or to heat the building. A local utility may also help in paying for a heat recovery system. Best practices, maintenance. Over- or under-cured parts can result in scrap, lost productivity and reduced revenues. A customer recently acknowledged that it is four times more expensive to reproduce a product than if it had been produced correctly the first time. Follow best practices to reduce rework, improve quality and increase efficiency. Air balancing. Make sure the oven is balanced at startup. In a batch oven, rack critical parts the same each time and balance the air to enhance the cure of these parts. For a conveyorized oven, make sure there is an even air supply throughout the oven to eliminate cold spots. Be aware of conveyor openings where cool incoming air may affect the temperature. Compare duct sizes, air volumes, fan quantities and oven layouts. Part positioning. If an operation requires repeat- ability, plan for it and repeat the same steps correctly. Part positioning is critical in industries where absolute uniformity and product runoff is required to commis- sion an oven and system. If this is critical, then the oven supplier will require that the customer place the product in the same spot in the oven every time. Changing part positioning can drastically change airflow and uniformity. Cold spots. A cold spot in the oven will cause a longer cure time for the part, which slows down production and In many batch ovens, heated air is introduced from a supply duct on both sides of the oven. LIQUID/POWDER