Condensate Removal Problem
Example 2 illustrates the use of line-scanned Precision Infrared Imaging (PIR) to visualize the thermal distribution on a high-speed tissue machine Yankee dryer. In this case, the paper machine was making light-weight tissue at a Yankee speed in excess of 5000 feet/minute with steam pressure over 100 psig. The observed reel moisture profile was ragged, with wet front and back edges and a dry streak at the back/center. The mill also experienced occasional sheet blistering at the back/center section of the dryer.

The PIR image shown below includes the entire papermaking surface of this 15-foot diameter Yankee dryer. Front and back edges are indicated. Triggering from a spot on the Yankee head, PROdry Technology engineers captured exactly one revolution of the Yankee dryer and produced the view shown using PROdry's proprietary analysis software. The thermal pattern on the dryer clearly indicates wet edges and four distinct hot spots in the machine direction.

Since PIR images are positively referenced to a known position on the Yankee head, it is possible to relate the temperature distribution in the figure to the dryer internal condensate removal system geometry. The four hot spots in this case occur directly under the condensate header riser pipes, and are the result of blow-thru steam scouring out the condensate layer there. This geometric agreement accounts for the dry area of the reel moisture profile and the occasional blistering at the hot spots. Changes to the Yankee internals produced a more uniform temperature profile and greatly reduced the tendency for the sheet to blister.

The 3-D representation of the Yankee temperature distribution is often helpful in interpreting the large amount of data provided by PROdry Technology's Precision Infrared Imaging system.

	Example 2: PIR line scan and 3-D image of Yankee dryer temperature showing hot spots under riser pipes. ("Rainbow" palette).
Click each to enlarge

© 2007 PROdry Technology, Inc. Site last updated 3/7/07