Some Like It Hot Page 2
In the hands of an expert, an IR camera is a valuable tool for a wide range of applications. Locating heat or air-conditioning losses in a building are examples, or inspecting high-voltage electrical equipment: Poor connections increase resistance and create more heat than good connections. Thermography can detect roof leaks and identify water-damaged areas, inspect boilers and furnaces, locate low-intensity forest fires before they burst out of control, help find lost hikers and campers by detecting their body heat, and even aid in evaluating and treating injuries and diseases in both humans and animals. The aviation industry uses IR to detect water intrusion and laminate condition of composite parts of airplanes. Thermography is the only way to inspect carbon-fiber laminates—moisture meters won't work on carbon—so it's the favored technique for surveying racing sailboats, which float on hulls and under masts made of that material. In the marine industry thermography is often used to survey a vessel in need of repair due to composite failure or accident.
In thermography, at least as applied in marine applications, "absolute temperature usually isn't important," Ashton explains; it's changes in temperature, and the rate of change, that he observes. The change in temperature of the hull can come from natural means—the sun coming up or going down if the boat's outside—or artificial ones. In fact, Ashton often uses an external heat source to warm the hull so slightly that it's barely noticeably to the touch, then watches it cool over a controlled time on the sensitive IR camera. Sometimes he even warms the boat from the inside, using electric heaters. The method depends on the situation, but the images seen from a direct external heat source are the most dramatic.
As the hull cools, Ashton watches the colors change on the Pro 400's LCD, snapping stills frequently; a typical thermo survey results in hundreds of pop-art-colored digital IR photos captured on removable storage media. Back in his office, he downloads the pictures to his computer and interprets them with the help of sophisticated software. He can change the color palette on any image to make certain features or problems stand out more clearly or even convert it to grayscale. His final survey report will include a selection of photos, each one interpreted in a caption so the client can understand what the colors mean, with a conventional digital image next to it as a reference. Ashton often uses a graphics program to draw on the images and highlight problem areas.
Most of Ashton's clients prefer not to share his findings with other folks, especially writers—heck, they probably want to sell their boats, not tell the world what's wrong with them—but I was cleared to attend a thermographic survey of a 25-foot sportfisherman that's 20 years old but was built to the top standards of the time. The owner liked the boat enough to invest in renovating her but wanted to know what he was getting into before starting. As Ashton heated each section of the hull, I watched the IR image change on the camera's PDA display. The color changes, reflecting the hull's cooling, were obvious, but figuring out what the changes meant took experience.
This article originally appeared in the September 2006 issue of Power & Motoryacht magazine.