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Some of the country’s largest coal-fired power plants are in the Four Corners area. Consuming thousands of tons per hour these coal-eating behemoths require constant attention and repair, and each of those repairs require inspection. That is in addition to the scheduled outages or “turnarounds” which are typically scheduled for each unit every two to five years. At one time or another every NDE method may be used in these plants.
 NDE Teams are regularly asked to create a grid on in-service pressure piping prior to taking Ultrasonic thickness (U/T) readings. High-pressure steam lines are subject to fast erosion and preventative inspections are done in an effort to prevent dangerous failures. After establishing the grid pattern – normally with literally thousands of locations charted – the teams take the U/T readings, prepare isometric drawings reflecting the readings, take pictures of any marked indications and complete the report.
- When thick-walled piping is welded, usually as a part of a valve replacement, the extreme wall thickness calls for a very detailed welding and inspection procedure. In these cases our Tech's will be called out to make a magnetic particle (M/T) inspection of the thick-walled weld in progress – usually after the root pass, hot pass, half out and then full out. This process routinely takes as much as 12 hours or more. During that time our technician must be on station at all times. When the weld is complete an R/T Team will be called out to shoot the completed weld.
- During turnarounds our R/T crews work within a tightly controlled time window. The welding crews work two ten-hour shifts daily – welding replacement high-pressure tubing in the cavernous boilers. For about 3½ hours a day there are no crews in the boilers – 2:30am to 6:00am – that is our “shot window”. During that time our crews X-Ray a percentage of all welds completed since the previous night. It’s a demanding job requiring the most skilled technicians in order to accomplish the daunting task within the narrow time slot.
- When the three monster turbines on each unit spool down and the turbine deck goes quiet in one of these super-sized coal-fired plants, the specialists step up to the plate. Turbine inspections are handled by technicians who specialize in this type of work. Whereas normal-sized items are magnetic particle inspected for flaws with magnetic yokes running on household current at 30 amps, giant parts like a turbine shell require giant power. This job calls for magnetic field energy of between 1500 and 6000 amps, 480 volts – serious power for serious power plant equipment.
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