A method of cleaning a heat transfer element within a boiler furnace is provided. and nitridizing the passivation layer. The storage units can be rotated on swivel axes that are oriented essentially at a right angle to the transport conveyor. The luminance color component of the pixel data may be determined by left shifting the green color component of the pixel data by one bit, adding the result to the red color component of the pixel data and the blue color component of the pixel data, and right shifting the sum by two bits.