Presentation on

Sour Service & Hydrogen Induced Cracking

JINDAL SAW LIMITED

Introduction What is HIC, SOHIC, Blistering and SSCC? List of Equipments in NACE Lab

Typical Hydrogen Induced Cracking Test Method Sample preparation ? Cleaning and storing. Solution preparation. Orientation of sample in test vessel Purging and introduction of H₂S. Evaluation of test specimen. Measuring Crack Reporting Safety precaution

Contents

Sour ServiceDefinition : As per ISO 15156

Exposure to oilfield environments that contain H2S and can cause cracking of materials by the mechanisms addressed by ISO 15156-1

Mechanisms in ISO 15156 − SSC, HIC, SOHIC, SZC etc.

Introduction

The hydrogen driven cracking is observed in several modes/mechanism. The modes or mechanisms are sulfide-stress corrosion cracking (SSC), hydrogen blistering, hydrogen-induced (stepwise) cracking (HIC), and stress oriented hydrogen-induced (stepwise) cracking (SOHIC).

The wet H2S /Hydrogen cracking mechanisms require the presence of an aqueous phase, temperatures from ambient to 150°C, and the evolution of hydrogen by a corrosion reaction at the environment/steel interface.

Introduction……Continue

The presence of hydrogen ions does not strongly promote it’s absorption into the steel at the interface. Presence of the bi-sulfide (HS-) promote hydrogen absorption into the steel, poisoning the recombination of hydrogen into a gas in the corrosion reaction. HS- promote the transport of hydrogen across the environment-metal interface and promote blistering, HIC, and SOHIC.

The cracking mechanism for SSC requires extremely low concentrations of hydrogen in the metal (5 ppm). Low quantity of HS- can produce this level of hydrogen in the steel.

Introduction……Continue

Typical Reactions Following two reaction takes place in

corrosionFe = Fe+2 + 2e --- Anodic Reaction2H+ + 2e =2 Ho --- Cathodic ReactionHydrogen produced at cathode either enters

into the steel (in the presence of H2S/HS-) or converts into H2 gas and (in the absence of H2S/HS-) escapes.

HS- Ion produced by following reactionH2O+H2S= H3O+ + HS-

Introduction……Continue

This type of cracking occurs in an aqueous environment with H₂S. when there is no external stress. Crack are generated parallel to the plate surface, starting from nonmetallic inclusion present in the steel and progress linearly or step like from with the passage of time(see figure 1)

What is HIC

HIC Cracking (Figure 1)

SOHIC is a hydrogen-damage mechanism like HIC. The damage mechanism, however, is driven not only by the high pressures that are generated by the hydrogen at the inclusion to steel interface, but also by the external applied stress. These stresses cause the crack path between inclusions to move more directly through the plate. The cracking morphology is more similar to a ladder than a stair step. The inclusions link not as stair steps, but more in a vertical direction like the rungs on a ladder . Another common term that is used to describe this phenomenon is ladder cracking.

What is SOHIC

SOHIC (Figure 2)

Blistering occurs from molecular hydrogen that collects at internal planar nonmetallic inclusions or laminations. Under the internal hydrogen pressure the inclusion (lamination) disbonds from the steel matrix and forms a blister. This type of defect is generated immediately under the surface are called blistering and is generally not considered as a critical. An example of Blistering is shown in Figure 3

What is Blistering

Blistering (Figure 3)

This type of cracking occurs in the presence of stress in an aqueous environment with H2S.

Many crack are generated at sites with defect on the surface or inside where stress is concentrated, and extend in the direction perpendicular to the stress axis. These cracks tend to occur easily in hard welded zones, heat affected zones (HAZ) and other hard places. An example of SSC is shown in below figure.

What is SSCC

SSCC (Figure-4)

List of EquipmentsSR. NO.

INSTRUMENT NAME Nos

1Test Vessel and accessories

(for HIC & Four point bend test)

5

2 Auto Titration Unit 13 Automatic Polishing unit 14 Four point bend test fixture 305 Proof Rings (SSCC tensile test) 5

6pH Meter (for measurement of pH of

test solution) 2

7 Weighing Balance (0-200 gm ) 18 Weighing Balance (0-200 gm & 0-2 Kg) 19 H2S Detector (with 5 sensor) 1

10 H2S Detector (Hand held type) 1

11Water Distillation unit (Capacity 5

Liter/Hr) 1

12 Microscope with image analyzer 1

Automatic Polishing Machine Microscope

Digital pH meter Automatic Titrator

Typical Hydrogen Induced Cracking Test Method

Sample cutting From Plate

Sample preparation

Sample cutting From LSAW pipe.

Test specimen shall be taken from the weld ,90 degree from weld and 180 degree from weld

Three sample per pipe shall be taken1) parallel to the longitudinal axis of pipe

from 90 degree and 180 degree from weld

2) Perpendicular to the weld for weld area

Dimension :- Length : 100 ± 1 mm Width : 20 ± 1 mm

Thickness : Actual thk-1 mm Maximum from each side.

Test specimen shall be full thickness of pipe upto max. 30 mm WT.

Test specimen blank shall not be flattened

Degrease with suitable solution and rinse with an appropriate solvent, such as acetone.

Test specimen may be stored in desiccators after degreasing.

Cleaning and storing

Calculate the surface area of test specimenRatio of test solution to the surface area of

test specimen shall be minimum 3 mL/cm²Solution type A is used for HIC test.

Solution shall consist of 5.0 wt% NaCl and 0.5 wt% Acetic Acid(CH₃COOH) in distilled water.

All reagent added to the test solution shall be ±1.0% of specified quantities.

Initial pH shall be 2.7 ± 0.1 pH and should be checked by digital pH meter.

Solution Preparation

Orientation of sample in test vessel

Typical Test Assembly

Test specimen shall be placed with wide face vertical and separated from test vessel and other test specimen by glass or other nonmetallic rods with minimum diameter of 6 mm

Purging and introduction of H₂STest solution shall prepare in separate sealed

vessel that is purged with nitrogen for at least one hour at a rate of 100 cm³/min per liter of test solution.

Then transfer the test solution to the Test vessel and purged it with nitrogen for atleast one hour at a rate of 100 cm³/min/liter of test vessel volume.

Purging shall start immediately after the test vessel filled up with test solution.

After purging, H₂S gas shall be bubbled through the test solution. The rate of bubbling shall be at least 200 cm³/min/ liter of test solution for the first one Hour.

Then positive pressure of H₂S gas shall be maintained at constant gas flow rate to ensure that the test solution remains saturated with H₂S.

After 1 hour of H2S bubbling, Check the pH & concentration of H₂S. pH immediate after H₂S saturation shall be within the range of 2.7 to 3.3 Concentration of H₂S in test vessel shall be minimum 2300 ppm. Concentration should be checked by automatic titration machine or iodometric titration.

Test Duration & Test Temperature

The test duration shall be 96 Hours. Test time begins immediately after completion of H₂S saturation. Temperature of test solution during the test shall be 25 ± 3 °C.

pH shall not exceed 4.0 for the valid test.

After testing, Exposed test specimen may be cleaned with detergent, but shall not be cleaned with acid or any other means that might promote hydrogen absorption.

Each test specimen shall be sectioned for Evaluation as per the below figure. For longitudinal base sample & Plate sample

Evaluation of Test specimen

For transverse to the weld Sample

Crack shall be evaluated as defined in the following section

Crack shall be check on 100X magnification. All visible cracks shall be measured ,except those which lie entirely within 1.0 mm of the internal or external surface.

Following equations are used for the calculation of CSR, CLR and CTR.

For crack Sensitivity Ratio(CSR)

CSR=[Σ(a X b)/(W X T)] X 100%

For Crack Length Ratio(CLR)

CLR =[Σa / W ] X 100%

For Crack Thickness Ratio(CTR)

CLR =[Σb / T ] X 100%

Report shall consist of the followings as per NACE TM 0284:2003

1. Method of testing adequacy of test specimen degreasing

2. Type of Test Solution3. pH of test solution before H₂S introduction4. pH of test solution after H₂S saturation(start

of test)5. pH of test solution at the end of test6. Temperature of test etc.

Reporting

Following the safety precautions implemented in NACE Lab

Restricted entry.Smoking is prohibited.Use of Mobile phone is not allowed.Mandatory use of Face shield, Surgical hand

gloves and other PPE in NACE lab area.Five numbers of H2S gas detectors are

installed in NACE lab area, audio-visual alarm system is integrated with gas detectors.

One hand held type H2S gas detector.Three numbers of breathing apparatus

available for any emergency.

Safety precaution

Safety precaution ……Continue

First aid box available, CO2 type fire extinguisher are available in NACE lab area.

Exhaust system to drive out H2S gas from the test and gas storage area.

Emergency Preparedness Plan implemented. Emergency control room & ambulance phone no displayed in NACE Lab.

H2S gas Detector

First Aid kit

Breathing Apparatus

Fire Extinguisher

THANK YOU for your time and patience

JINDAL SAW LIMITED