Touch Point Corrosion (TPC)

Many refineries and petrochemical facilities experience leaks and failures in their piping systems due to a phenomenon known as Touch Point Corrosion™. TPC™ occurs when a pipe rests on a metal or wooden object resulting in the potential creation of a corrosion cell. Since the TPC™ areas are inaccessible, manual ultrasonic thickness readings cannot be performed without lifting the pipe. These lifts can lead to other problems such as dislodging environmentally sensitive materials and/or potentially causing additional damage to the piping system.

MISTRAS has developed an inspection methodology that quickly determines the integrity of a piping system by paying special attention to TPC™ concerns. This non-intrusive approach utilizes a combination of visual inspection, semi-automated ultrasonics and manual ultrasonic inspection to identify and evaluate problem areas. This approach offers system owners the benefit of globally inspecting piping systems more rapidly, without further damage being incurred through pipe lifting.

The inspection is performed using a Pocket UT System developed and manufactured by our sister company, NDT Automation. An ultrasonic attenuation study is performed utilizing the Pocket UT System. The ultrasonic data from the inspection is interpreted using a proprietary calculation developed by our in-house engineering staff and programmed into the Pocket UT Instrument. The equation considers a combination of factors including pipe length, amplitude loss, the cross sectional affected area and other factors in order to estimate a percent (%) wall loss. The wall loss then leads to an A-D Grade of the area in question.

- Technique is utilized for typical non welded supports, I-Beam, saddle, etc.
- Can be utilized stand alone to screen suspect support areas or as a secondary to GUL screening
- Damage is characterized into 4 Categories (A, B, C, or D)
- Surface preparation is required on the top ¼ of the pipe
- Diameters ranges from 3” – 20”/Temperature <150°F
- Allows prioritization of supports to focus on the worst, and monitoring program for remainder
- Portable battery operated