For decades, traditional inspection methods for corrosion or wear on piping under expansion bellows were destructive in nature, usually utilizing basic technology such as pressure (hydrostatic) testing or direct assessments that required removing the bellows.
The latest advances in technology and case studies reveal that higher order mode cluster (HOMC) short-range guided waves can inspect the areas that traditionally could not be accessed without costly destructive testing. Once generated, these guided waves (circumferential or axial modes) identify corrosion and other defects in the piping. The actual data is collected from the accessible piping or wall, which makes it less intrusive, timely and more economical. Additionally, the HOMC technology allows the user to inspect normally difficult assets using conventional guided waves that deploy single modes.
The equipment is a portable, battery-operated instrument similar to ultrasonic testing scopes. The actual probes are 2 or 3 inch squares using a standard coupling. This method has a very short (1/2 inch) nearfield, enabling its use on applications such as soil-to-air interfaces and penetrations that don't have enough room to use other guided wave methods. This system can detect, image, determine amplitude sizing and record location on an X and Y axis.
Common applications of HOMC guided wave include inspecting wall penetration interfaces; soil-to-air interfaces; concrete interfaces; pipe, horizontal tank and vessel supports; and short- to medium-range imaging (maximum of 36 inches).
HOMC technology allows the user to inspect normally difficult assets using conventional guided waves.
HOMC is the best alternative when:
- Limited clearances are present (6 inches or less).
- Close proximity when the area of concern is 2-3 inches from the probe.
- Multiple size ranges of up to 1.5 inches in diameter, pipe to flat plate.
- Can detect through coating (probe placement must be on 1/8 inch or less coating).
Pro-Surve Technical Services recently performed HOMC scanning of units related to piping connected to boilers and heaters, which penetrate through the outside fire box. The piping had a doughnut guide located on the inside of the fire box and expansion bellows on the outside. The client had failures which caused the heaters to shut down. As a result, the client wanted to inspect the other heaters during the shutdown to prevent unexpected failures and shutdowns. The main concern during the inspection was to focus on guide ring wear and corrosion under the expansion bellows.
During the inspection, the suspect location in one of the boilers was cut out and visually verified. Based on the data collected and the R&D utilization of the HOMC system for the expansion bellows inspections, the conclusion is that this is a viable and effective tool for screening and classifying suspect areas. The technology, equipment and training is innovative, but requires extensively trained personnel for success.
For more information, visit www.pro-surve.com, call (281) 922-0200 or visit Pro-Surve's new location in League City, Texas, for a demonstration.
