4. WHAT IS INTERNAL CORROSION ?
Internal corrosion can damage whole internal metallic
structure of tanks and pipes. in oil and gas field 48 %
pipelines failure are caused by internal corrosion and
maximum rate of it occurs at 6 o’clock position
6. CUASES
• Natural phenomenon
• Fluid Corrosivity
• Flow Velocity
• Deposit Accumulation
• Water Accumulation
• Salt water
• H2S (acid gas with iron sulfide the by-product)
• CO2 (Major cause of produced gas corrosion)
• O2
• Bacteria (by products, acid produced)
• Other Impurities In Product
7. Internal Corrosion Control Techniques
Internal corrosion can be controlled by
1) Using corrosion inhibitors
2) Proper monitoring techniques
8. Internal corrosion can be controlled by corrosion inhibitors.
It is chemical Compound that when added to liquid or gas ,
decreases the corrosion rate.
The Effectiveness of a corrosion inhibitor depends on
• Fluid composition
• Quantity of water
• Flow regime
Corrosion Inhibitors
9. Classification Of Corrosion Inhibitors
Corrosion inhibitor is classified into two major types
1) Oil soluble corrosion inhibitor ( for HSD)
2) Water soluble corrosion inhibitor ( for crude)
10. Oil soluble corrosion inhibitor (for HSD)
Oil soluble inhibitor are used in many oil and gas fields. It
has high solubility with oil and mostly added with high
speed diesel products. DCL-6A corrosion inhibitor is
achieving zero leak status in the pipeline. it is approved by
US military specification
11. Water Soluble Corrosion Inhibitor (For Crude)
This type of corrosion inhibitor is used with crude product to
protect the Internal metallic structure from corrosive crude.
Crude oil has many harmful impurities that causes very fast
rate of corrosion.
12. Mechanism Of Corrosion Inhibitor
A common mechanism for inhibiting corrosion
involves formation of a coating often a passivation
layer , which prevent access of the corrosive substance
to the metal.
The nature of corrosive agent depends on
1) The material being protected.
2) On the corrosive agents to be neutralized.
16. Residual Analysis
To make sure the effectiveness of corrosion inhibitors
residual analysis are common method, in which water
sample re collected from all the crude storage tanks at
pumping station .
Corrosion inhibitor residual analysis for any system are
established based on corrosion rate achieved.
Residual analysis tested once in 5 year, or it depends on
previous result.
If previous result was not as such aspect then it is
tested within 2 or 3 years.
17. Corrosion Coupons
Corrosion coupons are a simple yet effective tool for providing a
quantitative estimation of corrosion rates occurring in an
operating system. They also provide a visual indication of the
type of corrosion which may be occurring in the monitored
system.
Corrosion Coupons
18. •Corrosion coupon is a piece of metal of predetermined
shape, size and surface area.
•It is a metal of similar chemical composition to the process
equipment.
•It has a uniform reproducible surface finish.
•It has a distinguishing serial number.
•It is exposed to the same corrosive medium as the process
facilities.
•It is exposed for a fixed period of time.
•It gives visual indication of the type of corrosion.
•It indicates the rate of corrosion
19. 1)The coupons have been cleaned and accurately weighed prior
to shipping .
2)The coupons must be used in vertical direction at 6’o clock
position
Corrosion Coupon Installation Points
3) Be sure the numbered corrosion coupons are recorded
according to position and system for proper correlation. The
dates of installation and removal from the system are critical.
20. 4) Test periods are generally 90 days. Coupons may be observed
at 30 days intervals for reference and signs of corrosive
conditions. In observing the coupons, do not disturb the
surface by scraping or removing material.
5) The corrosion products should be scraped off with a dry
plastic utensil into a bio-sample bottle containing system water.
the coupon can then be dried and returned to the lab for analysis
along with the bio-sample bottle.
21. Electrical Probes
Electrical corrosion probes include devices that can detect
the rate of corrosion in a variety of environments.
Corrosion probes are used in deep core oil and gas drilling.
This corrosion-detecting devices are used to monitor the
amount of internal corrosion in oil tanks, platform pipes,
and deep core or subsea pipes.
23. NACE Standard SPO775
• Coupon size, metal composition, surface condition, and
coupon holders may vary according to the test system design
or the user’s requirements.
• Coupons are often installed in pairs for simultaneous
removal and average mass-loss determination.
• This standard outlines procedures for preparing, installing,
and analyzing metallic corrosion coupons.
24. Coupons may be used alone but they should be used in
conjunction with other monitoring methods such as test
nipples, hydrogen probes, galvanic probes, polarization
instruments, resistance-type corrosion monitors, chemical
analysis of process streams and nondestructive metal
thickness measurements, caliper surveys, and corrosion
failure records.
25. Processing of Corrosion Coupons As
NACE SPO775
• Choose a method of coupon preparation that does not alter
the metallurgical properties of the metal. Grinding operations
must be controlled to avoid high surface temperatures that
could change the microstructure of the coupon.
• Exposure to an environment capable of cracking the alloy used
for the coupon or holder.
• Etch or stamp a permanent serial number on the coupon. It is
possible for a coupon or holder to undergo SCC.
26. Non Destructive Techniques
NDT testing plays most important role for internal metallic
structure through this techniques even we can detect very small
defects and flaws.
Non Destructive testing consist of different testing methods
1) Radiography Testing (R.T)
2) Ultrasonic's Testing (U.T)
3) Fluorescent Penetration Inspection (F.P.I)
4) Magnetic Particle Inspection (M.P.I)
27. Radiography Testing (R.T)
The radiography is the most commonly used non destructive
testing method for pipeline inspection .its principle is that a
source of radiation is directed toward the inspected object. A
sheet of radiography is placed behind the object. the setup
usually takes a few minutes the exposure 1-10 minutes and film
processing about 10 minutes.
28. Ultrasonic’s Testing (U.T)
Ultrasonic is used as an NDT-method to evaluate the integrity
of the automatic welded pipelines girth weld. The principle is to
employ high frequency acoustic waves to probe the inspected
sample. As the acoustic wave penetrates the sample , the wave is
attenuated and/or reflected by any change in the density in the
material. By observing the returned signal many of the
characteristic of the material can be determined.
This setup takes less than an hour or depending on the size of
the sample.
29. Fluorescent Penetration Inspection (F.P.I)
This method is suitable for the detection of cracking and
porosity in welded joints. the principle is that the surface of
the sample is coated a penetrant in which a fluorescent dye
is dissolved or suspended. the penetrant pulled into surface
defects by capillary action.
Less than one hour is usually required as an inspection time
This method is cheaper than R.T and U.T but can only detect
external defects.
30. FPI Testing Procedure
Preclean partPreclean part
Apply penetrant
Prerins Spray
Apply developer
powder
Inspect under U.v
light
31. Magnetic Particle Inspection (M.P.I)
Magnetic particle method can be used for identification of
surface or near –surface defects. The principle is that the
sample is magnetized by dusting magnetic particle over it. A
surface defect will form a magnetic anomly , attracting and
holding magnetic particles and thus giving a visual
indication of the defect.
The sample must be ferromagnetic and the evaluation time
is typically few minutes.
33. In-Line Inspection
Today pipeline inspection through the use of in-line inspection
tool is a standard procedure. These inspection tools collect
highly precise data regarding the geometry of flaws and
defects in the pipe wall. The final goal of the operator being an
understanding of the state of integrity for a given pipeline.
34. In-Line Inspection Methods
The main in-line inspection methods at present include:
•Magnetic Inspection
•Transverse Field Inspection
•Ultrrasonic Inspection
•Ultrasonic crack Detection
•Magnetic Flux Leakage
•Geometric Inspection Tools
•Pigging
35. Pig
Pig is used for the integrity of pipelines. Pipeline pigs are
the device that are inserted into and travel throughout the
length of a Pipeline driven by a product flow.
Today pigs are used during all phases in the life of a
pipeline for many different reasons.
36. Types Of Pigs
•Foam Pig
•Gauge Pig
•Cleaning Pig With Disc
•Cleaning Pig With Magnet
•Caliper Pig (For Geometry of Pipeline)
•Intelligent Pig
39. Function Of Pigging
•Cleaning out the deposits and debris
•Gauging the internal bore
•Location of obstruction
•Liquids removal
•Gas removal
•Pipe geometry measurement
•Internal inspection
•Improving flow efficiency
40. Geometry/Caliper Pig
Geometry/caliper pig is a configuration pig designed to record
conditions, such as dent, wrinkles, ovality, bend radius and
angle and occasionally indication of significant internal by
making measurements of the inside surface of the pipe.
41. Crack Detection Pig
Crack detection tools are specially designed to detect feature such
as ultrasonic inspection tools stress corrosion cracking or fatigue
cracks instead of transmitting sound waves perpendicular to the
pipe wall pulses are transmitted at45 degree circumferentially
through the pipe wall, which enable fine cracks to be defected.
Crack Detection Pig
42. Intelligent Tool With Ultrasonic Technology
On entering the pipe wall, there is an echo and another as the
pulse reflects off the back wall. The taken for these echoes to
return provide a virtually-direct reading of the wall thickness.
Intelligent Tool With Ultrasonic Technology
43. Magnetic Flux Leakage (MFL)
The MFL tools use magnets to induce a flux into the pipe wall.
Sensor are mounted between the “poles” to detect any leakage
which may occur due to thinning, or “metal loss”.
Magnetic Flux Leakage
44. Purpose Of In-Line Inspection
•Asses the health of pipeline.
•Develop the data base of pipeline features.
•Monitoring defects.
•Asses corrosion growth rate.
•Develop strategy for rehabilitation work.
•Develop fitness for purpose assessment of defects.
•Future inspection needs.
•Safety assessment of the puipeline for current operation.
