- since 1996 -
|NDT.net Issue - 2007-08 - NEWS |
In early January before the snowfall, the melancholy khaki coloured plains surrounding Billings, Montana in the United States of America are swept by bitterly cold winds that dry the skin and make you long for the warmer days of summer or to be in more temperate climes. Surrounded on three sides by mountain ranges and split by the dark freezing waters of the Yellowstone River snaking from west to east, Custer Country as it is locally known, is transformed into an icy wonderland overnight when the snow storms finally arrive from north of the border.
After this years heavy snow and exceptionally cold snap (-23°C) throughout the northern and mid-western regions, this idyllic scene was the backdrop for a busy month for our applications advisor, Mark Nel. Mark spent most of January at a local refinery with our North American associate and distributor, Houston based Mechanical Integrity Inc., observing and working on several automated and manual ultrasonic projects. The work was all in-service on live plant and ranged from automated high temperature corrosion mapping to ToFD on process piping to Phased Array on stainless steel header boxes at elevated tem-perature.
A TD Focus-Scan coupled to Mechanical Integritys automated Twister Scanner with two conventional high temperature probes were employed to gather corrosion data from a 15m section of piping with a sur-face temperature of approximately 250°C. The technicians working at the hot surface needed to be extra vigilant of safety when handling the scanner and working with the hot recycled couplant. The Focus-Scan was configured to show the data from both probes as a C-scan with end views and colour slicing set to represent depth. The data was successfully collected and analysed in 4 days.
The ToFD survey of a piping system ranged from 6mm to 12mm wall thickness and was carried out using the miniature 8-channel TD Pocket-Scan instrument connected to a notebook computer. The data was collected using a MII manual ToFD scanner and encoder.
The stainless steel header box welds, operating at approximately 120°C were manually scanned in a raster pattern using our TD Focus-Scan in Phased Array mode configured for sectorial scanning with a 16 element probe. The purpose of the examination was to detect cracks and corrosion in the weld roots. This simple yet highly effective technique has been used to great effect in numerous examinations worldwide as the demand for quick defect detection & identification without the use of scanners has increased. Using this technique the diffracted crack tip signal is often clearly identifiable in the sector image.
All the work was completed in minimum time and disruption with the analysis and report being completed and delivered to the customers satisfaction prior to vacating the site.
Once again The TD range of advanced ultrasonic equipment has proven effective and reliable in extreme conditions although we understand Mr Nel, originally a native of sunny South Africa is still suffering from thermal shock!