Ultrasonic Corrosion Surveys

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Ultrasonic Corrosion Surveys

• Presented by
• Harold Hadley
• Inspection Consultant and Contract Chief
  Inspector for Provident Energy

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Where to Look

• Where to look is the first question when planning
  a UT corrosion survey. You must have an
  understanding of
• The corrosion potential of the location.
• Corrosion mechanisms.
• Where the corrosion will occur.
• To understand where the corrosion will occur some
  understanding of the process is required.

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How to look

• How is the data collected?
• Collect as data points?
• Collected as scan information?
• Are the data points to be repeated in the future?
  

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How to look

• How is the data reported?
• Has information already been collected from this
  site?
• Are there previous reports to refer to?
• Did the previous inspection take into account the
  above comments?

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Consider a Typical Inlet System
To inlet separator
To test separator
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Typical Inlet System
Where would the corrosion be?
Ground level
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How to Collect the Data

• Operation of the Ultrasonic instrument is
  straightforward, however challenges emerge in
  obtaining answers to the following
• Where do we put the probe?
• Should we scan the area? Use single point?
• How can we make it repeatable?
• Could we find an anomaly again if we looked in 6
  months? 2 years?
• Could someone else find the anomaly?

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Consider the Data Collection
We need reference points.
350
Insulation Kit
2
3
1
352
351
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Base Line Location Elbows
For elbows start at the first weld and follow the
direction of the flow taking a data point every
1.5 inches or 4 cm.
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A Second Look at the Inlet
350
351
352

• For data points that are on the bottom of the
  line use the same considerations (352).
• Start the data from a reference point and collect
  data in the direction or flow.

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Base Line Information Elbows
Critical .087
4 .298 5 .307
How is Critical Determined?
Where exactly are these points?
How is life expectancy calculated?
Life Expectancy (Years)
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The Next Surveys
Dec May Apr 2002 2004 2006
Total Avg. Period Loss Loss Loss (Mils)
MPY MPY
Look at the data calculations.
Are we comparing the base line data to current
data?
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Consider a 2-Phase Separator
Gas
PSV to Flare or Tank
Mist Pad
Typical Liquid Level
Float Column
Liquid
Inlet Separator (Two Phase)

• Where would the corrosion be?
• Where would damage be?
• What type of corrosion or damage can be expected?

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Where to Look on a Vertical Vessel
410
415
Mist Pad
Typical Liquid Level
Inlet Separator (Two Phase)
420
Float Column
Liquid
425
430
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Location Explanations

• Why did we look at those locations?
• Because it is the most likely place that
  corrosion damage will occur in a vertical vessel.
• Top head
• Condensation corrosion and under-deposit
  corrosion.
• Shell
• Across the mist pad,
• Interface between the gas and liquid,
• Liquid phase,
• There should be at least one band on each
  segment.

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Location Explanations

• Bottom Head
• Liquid phase corrosion,
• Under-deposit corrosion.
• Bottom Elbow
• Stagnant liquid corrosion potential,
• Flow induced corrosion.

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Tall Columns
Mist Pad
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Consider a 3-Phase Separator
Gas
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PSV to flare or tank
Inlet Deflector
Mist Eliminator
Weir or Baffle
4
3
Water Level
Liquid Off Points
Liquid Hydrocarbon
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Where would the corrosion be?
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Three Phase Locations

• There is little difference when choosing
  locations for inspection on horizontal or
  vertical vessels.
• (Lay vessel on its side, remove some hardware,
  and alter internal configurations).

Mist Pad
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Inlet Reciprocal Compressor
Where would the corrosion be?
Is corrosion the only damage that could occur?
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The Locations

• Look at all the locations and consider the
  numerous areas where damage can occur.
• Rotating Equipment introduces damage due to the
  Vibration Factor.
• The corrosion survey on compressors must include
  an inspection for cracking.

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• The following are examples of
• interesting failures and damage.

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Pipeline Failure
Pipeline Failure
A line failed at a Y junction. Junction is under
a road. Junction had been worked on. Line PSVs
were being tested prior to Start-up.
Line failed at a Y junction under a road during
PSV testing prior to start-up.
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Remember the Following Rules

• RUST NEVER SLEEPS

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Remember the Following Rules

• CORROSION OCCURS IN LOCATIONS THAT ARE THE
• COLDEST
• WETTEST
• MOST INCONVENIENT

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Remember the Following Rules

• Your job
• (should you choose to accept it)
• is to find that location!
• (This is not Mission Impossible).