NOVEMBER 2--Westar Energy found a better way to see through flames in monitoring for slag problems in three boilers that drive three 800-MW generators at its St. Marys, KS, electric-generating plant. Traditionally, operators would wear protective visors to check through inspection ports, attempting to look through flames for signs of slag buildup on the boiler tubes. "That's typical practice in the utility industry, and we make multiple inspections per day," says Carl Schultz, senior PdM analyst for thermography at Westar. "We thought there should be a better way and began exploring the use of an infrared (IR) camera to capture what was happening with slag inside the boiler."
Westar started by researching cameras specifically developed for through-the-flame capability in the 3.9-μm band. It learned about an innovative new development, an 8--14-μm band bolometer camera that utilizes proprietary filtering to also operate in through-the-flame mode. Westar selected the portable, dual-range MikroScan 7400 camera, which offers three selectable temperature ranges, including a high-temperature (400°C--1600°C) range needed for IR imaging inside the boilers where combustion temperatures can exceed 1100°C.
Patented IR filtering on the MikroScan 7400 allows dual-spectral-band operation--8- to 14-μm long-wavelength mode or mid-wavelength with 3.9-μm microfilter for through-the-flame imaging. "This lets us use the camera for a wider range of applications, such as predictive maintenance monitoring in the long-wavelength band on motors, bearings, and electrical cabinets in the ambient to 400°F range," says Schultz. "Then we can switch to the 3.9-μm band and high-temperature range to image the boiler tubes for slag condition," notes Schultz.
Mikron Infrared (Hancock, MI; www.mikroninst.com) perfected proprietary technology to enable a bolometer camera to image other very narrow spectral bands at high temperatures, says Jon Chynoweth, Mikron Infrared marketing director. "In this case, we can deliver 3.9-μm through-flame capability along with general-purpose 8-14-μm utility," he says.
The MikroScan 7400 is battery-operated and self-contained in a rugged, IP54-rated metal case for simple, point-and-shoot versatility. It includes on-board digital voice recording and can simultaneously record high-definition 14-bit thermal images with digital visual images. It comes standard with extensive onboard image processing software and stores images and data to PCMCIA cards. Images can also be viewed in real time via video output or optional built-in IEEE 1394 (FireWire) interface.
