![]() One actuator positions the fuel control valves, while a second actuator positions the air control damper. Parallel positioning systems offer key design benefits over the other control schemes for this size of boiler operation. The boiler control system design was selected to be a parallel positioning control with oxygen trim because it was determined to be the best control scheme for the boilers. The combination of the boiler and a burner design allowing for 10:1 turndown with the addition of the latest control technology provided the perfect combination for this specific application. Watertube boilers provide better compensation for expansion and contraction thus providing a longer operational life expectancy. The watertube boiler presented a much smaller footprint and ease of accessing the boiler internals maintenance. Insulating the firetube back wall presented several operational issues such as having to remove the insulation for annual boiler inspections. Safety concerns for plant personnel with high surface temperatures and OSHA requirements for plant personnel protection for areas of greater than 140☏. The firetube boiler back wall would have high elevated temperatures of more than 300☏ thus an energy loss in excess of $25,000 a year. The other negative consideration is the thermal losses off the exterior casing of the firetube boiler, specifically, the back wall area. First is the installation consideration for a firetube boiler that requires additional space for boiler tube replacement if required after years of operation. The firetube boiler design was eliminated due to several considerations. The Inveno Engineering steam team and BASF reviewed all aspects of operation including their loads and run conditions and decided to proceed with a watertube design boiler. All boilers have their positive and negative features. Firetube design and watertube design were the two boiler designs considered. One of the first steps in deciding on new boilers is to determine the operational design of the boiler. The following codes were adhered to during the entire project, Boiler ASME, B31.9, B31.1 ASME pressure vessels, B16.1, etc. ![]()
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