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

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Mlp conference 2013

MLP Conference 2013

Spark Spectrometry for Determination of Carbon Equivalent

Presented by:

Ian Cleary, Acuren

Minneapolis, MN

April 24-25, 2013


Abstract
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


Some history
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


Cold cracking
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.


Cold cracking1
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)


Carbon equivalent ce
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


Carbon equivalent
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


Carbon equivalent1
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


Testing carbon equivalent
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.



Testing carbon equivalent2
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


Testing carbon equivalent3
TESTING CARBON EQUIVALENT

  • Acuren intends to introduce a new method for quickly determining carbon equivalent in the field.


Portable testing
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


Portable testing1
PORTABLE TESTING

  • Our solution: Spark Optical Emission Spectrometry (Spark OES)

  • Acuren plans to mobilize spark OES to eliminate the testing bottleneck


Spark oes
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.


Spark oes1
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


Site preparation
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


Site preparation1
SITE PREPARATION

  • Acuren’s operators trained in proper surface prep procedures:1) Surface buffed down with grinding wheel2) Grinding wheel replace with fresh one3) Surface polished to ensure no contaminants remain

  • Aluminum oxide or zirconium oxide disks must be used instead of silicon carbide to prevent carbon contamination.


Testing
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


Testing1
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


Testing2
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



Analysis calibration
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


Analysis calibration1
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.


Analysis calibration2
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


Pipeline testing
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




Expected compositions1
EXPECTED COMPOSITIONS

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




On site testing
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


On site testing1
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


On site testing2
ON SITE TESTING

  • Each spark test crew consists of an operator and experienced non-destructive examination (NDE) technician who know the client’s 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


On site testing3
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



On site testing5
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


Environmental variables
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

    • Acuren’s spark testing machines will be contained within insulated boxes with electric heating pads


Environmental variables1
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.


Conclusions
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.


Conclusions1
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


Mlp conference 20131

SPARK SPECTROMETRY FOR DETERMINATION OF CARBON

EQUIVALENTS

Presented by Ian Cleary, Acuren

MLP Conference 2013


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