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Application Notes:
Inspecting Steam Systems |
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According to the U. S. Department of Energy (DOE), more than 45 percent of all the fuel burned by U.S. manufacturers is consumed to raise steam. "Steam is used to heat raw materials and treat semi-finished products. It is also a power source for equipment, as well as for building heat and electricity generation. But steam is not free. It costs approximately $18 billion (1997 dollars) annually to feed the boilers generating the steam." |
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Generally speaking, steam is a very efficient way to transport heat energy because the amount of latent heat required to produce steam from water is quite large, and steam is easily moved in pressurized piping systems that can deliver that energy at manageable costs. When steam gets to its point of use and gives up its latent heat to the environment or to a process, it condenses into water, which must be returned to the boiler for re-conversion to steam.
Several condition-monitoring technologies are useful for monitoring steam systems to determine how well they are functioning. Among those technologies is infrared (IR) thermography, in which technicians use thermal imagers to capture two-dimensional images of the surface temperatures of equipment and structures.
What to check?Using a combination of ultrasound and thermal inspections significantly increases the detection rate of problems in steam systems. Check all steam traps and steam transmission lines, including any underground lines. In addition, scan heat exchangers, boilers and steam-using equipment.
What to look for?Steam traps are valves designed to remove condensate as well as air from the system. During inspections, use both thermal and ultrasonic testing to identify failed steam traps and whether they have failed open or closed.
Also use your thermal imager while your steam system is operating to scan: Steam transmission lines for blockages, including closed valves, and underground steam lines for leaks, heat exchangers for blockages, boilers, especially their refractories and insulation, steam-using equipment for any anomalies and recent repairs to confirm their success.
Consider creating a regular inspection route that includes all key steam-system components in your facility, so that all traps are inspected at least annually.
What represents a "red alert?"Steam is very hot and often transmitted at high pressure, so any condition that poses a safety risk should take the highest repair priority. In many situations, the next most important kinds of problems to deal with are those that can affect production capabilities.
What's the potential cost of failure?The cost to an operation that completely loses its steam system varies from industry to industry. Among the industries that use the most steam are chemicals, food and beverage processing and pharmaceuticals.
Follow-up actionsThe DOE program for Steam Trap Performance Assessment recommends "sight, sound and temperature" as the dominant techniques for inspecting steam traps.
Whenever you discover a problem using a thermal imager, use the associated software to document your findings in a report, including a thermal image and a digital image...
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