The U31 operates with TSC's QFM suite of software thus providing a common operating environment with other ACFM products. This avoids the need for operator retraining.

The QFM Software contains the following features:

• Operates in Windows 95, 98 or NT environment. Supporting simultaneous running of word processor/spreadsheet package etc, and interface to all common printers. Graphics display of processed data for crack detection.
• Automated clock markings to indicate position on scan.
• Variable speed time base to suit application.
• Multiple screen facility for comparing consecutive scans.
• Screen marker to identify special features.
• Replay facility to review data.
• Real time adjustment of trace position on screen.
• Moveable cursors for use during data review.
• ACFM crack depth calculation and crack size data shown on screen.
• Free format text input associated with each file.
• Multiple page facility in a single file.
• Automated back up of data onto diskette and hard disk.
• Full system status reports for checking hardware.
• Graphical print out of data screens.
• Data transfer into standard spreadsheets.
• Automated set-up of probe-dependent instrument settings.
• Allows off-line review and analysis of data as originally collected.
• Crack depth sizing over a wide range of coating thickness'.
• Operating procedures and software user manuals available in on-line Windows help files.

Background to ACFM:

Alternating Current Field Measurement (ACFM) is an electromagnetic inspection technique and relies on the fact that an alternating current flowing in a component will be disturbed by the presence of a crack. The ACFM probe introduces an electric current locally into the structure and measures the associated electromagnetic fields close to the surface. The presence of a defect disturbs the associated fields and the information is graphically presented to the system operator. The ends of a defect are easily identified to provide information on defect location and length. The significance of a defect, in terms of structural integrity, generally depends on the depth of the defect. Using mathematical models, the system also provides the depth of the defect, thus allowing an immediate evaluation of the significance of the indication.

This is a major advantage compared to other techniques that only give detection or at best, length information. ACFM systems have been used for a range of applications where rugged inspection systems are needed. The speed of scan provides a rapid and cost effective means of inspecting welded connections with reduced cleaning requirements compared to conventional techniques.

The probes have been developed to minimise signals from features that are not cracks, e.g. corrosion, undercut, HAZ, material property changes, etc, thus overcoming the problems often associated with other electromagnetic systems and minimising false calls.

The ACFM technique has been approved for weld inspection by major authorities around the world, including Lloyds, ABS, Bureau Veritas, DNV and OCB Germanischer Lloyd.

Technical Specification:

Subsea Unit Weight: 7.6kg in air 4.3kg in water

• Subsea Unit Size: 142mm diameter x 260mm
• Probe Cable: Length 5 metres standard, up to 50m by special request
• Serial Communications Cable: 5 metres as standard up to 30 metres if required.
• Operating Temperature: -20º + 40ºC
• Maximum Operating Depth: 300m as standard, can be extended to 2000m for ROV deployment
• Power Requirements: 110v AC. 200mA
• Optional Array Support: 16 channels (i.e. 8 sensor pairs) plus position encoder