1

Ultrasonic Corrosion Surveys

Presented by

Harold Hadley

Inspection Consultant and Contract Chief Inspector for Provident Energy

2

3

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.

4

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?

5

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?

How to look

6

Consider a Typical Inlet System

Insulation Kit

Insulation Kit

Insulation Kit

Insulation Kit

Insulation Kit

Insulation Kit

To Inlet separator

To test separator

To inlet separator

To test separator

7

Typical Inlet System

Insulation Kit

1

2

3

Ground level

Where would the corrosion be?

8

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?

9

Consider the Data Collection

350

351352

We need reference points.

Insulation Kit

1

2

3

10

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.

123

4

5

6

7

5

123

4

6

7

• Start the data collection in the same area (be sure you are measuring on the bottom).

• In the case of high velocity all measurements should be on the outside of the elbow.

What about horizontal elbows?

11

Insulation Kit

1

2

3

350

351352

A Second Look at the Inlet

• 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.

12

Base Line Information Elbows

How is Critical Determined?

How is life expectancy calculated?

Where exactly are these points?

Critical : .087

4 .298* 5 .307

Life Expectancy (Years)

13

The Next Surveys

Are we comparing the base line data to current data?

Dec May Apr2002 2004 2006

Look at the data calculations.

Total Avg. PeriodLoss Loss Loss(Mils) MPY MPY

14

Consider a 2-Phase Separator

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

GasPSV to Flare or Tank

Mist Pad

Typical Liquid Level

Float Column

Liquid

Inlet Separator (Two Phase)

15

Where to Look on a Vertical Vessel

Mist Pad

Liquid

410

415

420

425

430

Typical Liquid Level

Float Column

Inlet Separator (Two Phase)

16

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.

17

Location Explanations

Bottom HeadLiquid phase corrosion,Under-deposit corrosion.

Bottom Elbow Stagnant liquid corrosion potential,Flow induced corrosion.

18

Tall Columns

Mist Pad

19

Consider a 3-Phase Separator

Where would the corrosion be?

Liquid Hydrocarbon

Inlet Deflector

PSV to flare or tank

Mist EliminatorWeir or Baffle

Liquid Off Points

3

4

5

6

7

Water Level

Gas

20

Three Phase Locations

There is little difference when choosing locations for inspection on horizontal or vertical vessels.

(Lay vessel on it’s side, remove some hardware, and alter internal configurations).

Mis

t Pad

21

Inlet Reciprocal Compressor

To Plant or Process

1st Stage

Compression

1st Stage Scrubber

1st Stage Cooling

2nd Stage Compression

2nd Stage Cooling

3rd Stage Compression

3rd Stage Cooling

4th Stage Compression

4th Stage Cooling

8

16 17

9

32

24 25

33

1

3

10

12

15

18

20

23

26

31

34

36

4

30

22

6

7

28

2nd Stage Scrubber

3rd Stage Scrubber

4th Stage Scrubber

14

Inlet Scrubber

Suction Bottles Discharge Bottle

39

Compressor Discharge Scrubber

2

5 11

27

37

13

1921

29

35

38

Is corrosion the only damage that could occur?Where would the corrosion be?

22

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.

23

The following are examples of interesting failures and damage.

24

25

26

27

28

29

30

Pipeline Failure

A line failed at a Y junction. Junction is under a road. Junction had been worked on.Line PSV’s were being tested prior to Start-up.

Pipeline Failure

Line failed at a Y junction under a road during PSV testing prior to start-up.

31

Remember the Following Rules

RUST NEVER SLEEPS

32

Remember the Following Rules

CORROSION OCCURS IN LOCATIONS THAT ARE THE:

COLDEST

WETTEST

MOST INCONVENIENT

33

Remember the Following Rules

Your job

(should you choose to accept it)

is to find that location!

(This is not Mission Impossible).