MST ( METALLURGICAL STRESS TECHNOLOGY)

Find out about the condition of the pipe from above ground. A complementary technique for the tools used to inspect pipelines in NACE SP 0502-2008
What test conditions and information can be obtained using MST?

• Detect metal deformation defects in buried or above ground pipelines.
• Identifies defects irrespective of their orientation.
• Estimate the level of Stress in the pipe defect location.
• No interruption or changes to the pipeline operation.
• No limits to the operating pressure and temperature during inspection.
• No special preparation or additional equipment is needed for MST.
• No limit on size, bend, slope etc. of the pipeline.

ADVANTAGES

Easy to operate with single surveyor plus laborer/driver, lower cost than Inline Inspection Tools, Survey Speed of 5 Km per day achievable.  fast reporting.  Accurate location as data correlated with sub-meter DGPS (15 to 20cm accuracy) with other survey tools.

One major advantage lies in the fact that other metal/stress corrosion cracking inline inspection methods the accent is on measuring the geometry of defects and use standard codes to evaluate the defect significance and MAOP with emphasis on the defect developing to become a leak particularly if corrosion is uncontrolled.  Conventional surveys fail to highlight dangerously stressed areas of the pipe or conversely classify a defect as one requiring urgent attention when in reality, the stress level may be low and the defect presents no immediate threat to the operation of the pipe.

HOW DOES IT WORK

The MST technique maps the self magnetic properties and characteristics of ferromagnetic structures.  MST can directly identify the level of stress (a main cause of pipe failure) instead of the geometrical properties of defects.  The existence of metal loss defects or pipe movement / restrictions cause different  levels of stress through the body of the pipe and accordingly cause local changes in the magnetic properties of the pipe. Recording and analyzing data gathered by MST is a guideline to locate metal loss defects and other anomalies in buried pipelines.

SURVEY PROCEDURE

The best methodology is to run the MST at the same time as a DCVG Coating Survey. The DCVG Survey accurately locates the pipeline (if there are Faults) and also identifies the position of faults. If there are no faults for long distances then a pipe locator must be used. The MST is run 50 to 100 meters behind the DCVG, logging any coating fault sites, features etc as the survey progresses. This allows identification of any problems at faults (99+% of all coating faults have no metal Loss but 85% of ILI metal loss indications occur at coating faults)  and also assists in the interpretation and correlation of MST and DCVG data.  The DCVG Ltd Quantum CIPS equipment can also be run at the same time with DCVG electrical measurements logged into the Quantum so all three surveys are accurately correlated. Data from the MST and other techniques can be downloaded and viewed in an Excel Spreadsheet prior to detailed analysis and the preparation of Tables and Graphical presentation

MST TOOL SPECIFICATION

Speed of Operator …Up to 3 m/second
Probability of Detection …….Greater than 85%    (similar to ILI Tools).
Depth of Detection……..more than 5% of wall thickness.
Distance from Pipe         15 pipe diameter (maximum depending on operating pressure)
Working Temperature…..-15 to +60 degrees centigrade.
Diameter of pipe……..Greater than 6 inches  (15 cm).
Thickness of pipe wall…. >1mm.