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MLP Conference 2013 Spark Spectrometry for Determination of Carbon Equivalent Minneapolis, MN April 24-25, 2013 Presented by: Ian Cleary, Acuren.

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Presentation on theme: "MLP Conference 2013 Spark Spectrometry for Determination of Carbon Equivalent Minneapolis, MN April 24-25, 2013 Presented by: Ian Cleary, Acuren."— Presentation transcript:

1 MLP Conference 2013 Spark Spectrometry for Determination of Carbon Equivalent Minneapolis, MN April 24-25, 2013 Presented by: Ian Cleary, Acuren

2 ABSTRACT As pipeline maintenance and repair activities proceed at a faster and faster pace, the quality control of those repairs must keep pace Laboratory testing of steel chemistry is a major bottleneck in the process of welding to active pipelines Spark optical emission spectroscopy offers a fast and reliable way to get accurate chemistry results in the field 2

3 SOME HISTORY Strome, Alberta (February 19, 1985 – 8:00 pm) Workers caught in the unplanned ignition of leaking LNG from a pipeline they were working on Fireball 40m across 3

4 COLD CRACKING The leak was caused by cold cracking at a weld in the pipe Typically occurs at the toe of the weld, in the HAZ (Heat Affected Zone) Metal in HAZ cools rapidly after welding, which tends to harden the steel and make it more susceptible to hydrogen induced cold cracking. 4

5 COLD CRACKING How hard the steel will become after welding is related to its chemistry Several elements affect hardenability Most important elements: carbon and carbon-equivalent (manganese, silicon, nickel, chromium) 5

6 CARBON EQUIVALENT (CE) Low carbon = less likely to harden excessively High carbon = more likely to harden excessively Calculating carbon equivalent CE) attempts to estimate how much each element is worth in terms of resultant hardenability 6

7 CARBON EQUIVALENT In early days, pipeline industry had few regulations around steel chemistry. Carbon content guidelines were in place, but other elements were often ignored Steel chemistry results not stored for future generations 7

8 CARBON EQUIVALENT Welding on these pipes presents potential for serious hazard, if not handled correctly Regulations now require that carbon equivalent of the existing pipe be known before welding can occur 8

9 TESTING CARBON EQUIVALENT Currently, one way CE can be determined is by testing pipeline shavings in the laboratory. Small amount of metal shavings are collected from a pipe where welding will happen. 9


11 TESTING CARBON EQUIVALENT Shavings sent back to Acuren laboratory where they are analyzed Problem: Process takes time (transport + testing + backlog) With hundreds of samples coming in from hundreds of locations, chemical analysis is a major bottleneck in the pipeline maintenance process 11

12 TESTING CARBON EQUIVALENT Acuren intends to introduce a new method for quickly determining carbon equivalent in the field. 12

13 PORTABLE TESTING A few portable material identification technologies exist, but most have serious limitations. For example: Positive Material Identification (PMI) is unable to detect carbon 13

14 PORTABLE TESTING Our solution: Spark Optical Emission Spectrometry (Spark OES) Acuren plans to mobilize spark OES to eliminate the testing bottleneck 14

15 SPARK OES Each element has a characteristic emission line Spark OES measures chemical composition of metal by igniting a tiny portion of it with a high voltage electric spark Machine detects emission lines with two sensors: a light optic and an ultraviolet (UV) optic. 15

16 SPARK OES Wavelengths mapped to characteristic emission lines of each element Machine compares intensity of each emission to a standard, determining the concentration of each element within the sample 16

17 SITE PREPARATION First step (most important): surface preparation Surface must be clean and flat Spark OES is highly sensitive – any amount of grease, dust, or contamination will cause incorrect results 17

18 SITE PREPARATION Acurens operators trained in proper surface prep procedures: 1) Surface buffed down with grinding wheel 2) Grinding wheel replace with fresh one 3) Surface polished to ensure no contaminants remain Aluminum oxide or zirconium oxide disks must be used instead of silicon carbide to prevent carbon contamination. 18

19 TESTING Head of probe has a detachable adapter that is the working end of the spark machine To take a reading, adapter is held against the surface of the sample Operator presses the trigger Spark is emitted from an electrode within the adapter 19

20 TESTING Spark penetrates a few hundred μm into the surface and ignites the metal Surface must be flat so that plasma is contained within the adapter 20

21 TESTING UV spectrum detected in head of probe Ordinary light spectrum transmitted by fiber optic through probe cable and into main housing of the spark unit Longest fiber optic cable that can be used is eight meters (past that the light signal becomes degraded with loss of results) Intensities of the wavelengths are detected and results analyzed by a proprietary algorithm 21


23 ANALYSIS & CALIBRATION Analysis algorithm relies on an automated calibration procedure: iCalization or iCal iCal works by testing an iCal reference standard – a piece of metal of precisely known composition – at the beginning of a shift, after transportation, or after cleaning 23

24 ANALYSIS & CALIBRATION iCal builds up a library of readings of this standard material that allows machine to compensate for changes in temperature and humidity, vibrating during transport, and minute differences in component placement after cleaning Adapter thoroughly cleaned after 50 uses Argon gas is used to flush the machine of water vapor and oxygen before each test. 24

25 ANALYSIS & CALIBRATION To ensure accuracy of readings, a second metal of known composition (the control standard) is tested every time the machine is set up Unlike iCal the control standard was chosen because composition is very similar to the pipeline that will be analyzed Second calibration allows operator to determine if spark testing unit is reading accurately in range of interest 25

26 PIPELINE TESTING Acuren has dedicated three of its four TXC03 spark testing units to carbon equivalent evaluation of pipelines digs. These three machines have been fine tuned to give the most accurate possible results in the expected composition ranges of existing pipes 26


28 EXPECTED COMPOSITIONS OverallCMnSiCuNiCrMoVNbB Min0.100.600.050.01 0.005 0.001 Max0.301.600.40 0.200.25 0.0500.0700.001 28

29 EXPECTED COMPOSITIONS Therefore the dedicated spark testing units will yield high accuracy results on any existing line, with special attention to the old pipe. 29

30 TX03 ACCURACY (IDEAL CONDITIONS) 30 CC (air)SiMnPS Conc. Level (ppm) Precision 50102010 10010 2010 50020 10 2030 100050 20105020 3000100 4020300 5000120 7060 10000150 120 20000440 150200

31 TC03 ACCURACY (IDEAL CONDITIONS) 31 CrMoNiCuNbVWB Conc. Level (ppm) Precision 50103 2 1002010 20104 5002010 20 50 100020 1020 80 3000302040 3050 500050 4060 5080 100007012040100 180 2000080160250120 200300

32 ON SITE TESTING Size and weight of the spark machines is a limitation –Each machine has dedicated truck and crew –Each unit mounted on hand truck secured to back of crew cab vehicle –Deploying unit is two-person job, rolling the truck down a ramp onto the ground with the help of a winch –Once on ground, machine can be wheeled to edge of excavation ditch 32

33 ON SITE TESTING Eight meter cable often allows main housing of machine to remain outside ditch Once powered up the machine is tested on the control standards to verify proper operation and calibration If test fails the machine is recalibrated with iCal If iCal fails repeatedly, machine is taken back to shop for examination 33

34 ON SITE TESTING Each spark test crew consists of an operator and experienced non-destructive examination (NDE) technician who know the clients procedures and requirements NDE technician performs magnetic particle inspection and ultrasonic testing of proposed test area to ensure polishing is done according to client regulations 34

35 ON SITE TESTING Polishing is performed with 120 grit and will go no deeper than 5-8% of nominal wall thickness When appropriate test area is located, operator prepares surfaces and performs test Single spark test consists of at least three readings in same small area 35


37 ON SITE TESTING Operator checks burn marks left by machine as well as consistency of readings to determine if burns were good Good = black with small white spot at center Bad = grey or white 37

38 ENVIRONMENTAL VARIABLES Optics must have operating temp. of 36°C –Unit has built in heating system –Extreme cold weather can increase time taken for instrument warming –Acurens spark testing machines will be contained within insulated boxes with electric heating pads 38

39 ENVIRONMENTAL VARIABLES Primary screen –Stops working in extreme cold conditions –Machine will need a tent to keep warm and dry while shielding the screen from glare –TX03 comes with app for iPad that allows operator to see results in real time without leaving ditch. 39

40 CONCLUSIONS Spark spectrometry can give fast, accurate results in the field No longer need to send samples back to lab Report is printed in PDF format at site. 40

41 CONCLUSIONS Our lab tests show that spark spectrometry can give very consistent readings from one measurement to the next. With proper calibration and surface preparation, spark spectrometers are a portable way to get results: –Repeatable –Precise –Accurate 41


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