Sour Experiences and HICCUPS of HIC: A Presentation

What is a Sour Environment?

NACE defines a Sour environment is one which contains enough H2S either in the gaseous or aqueous media.

Properties of Hydrogen Sulphide

  • Chemical Formula: H2S
  • Odour: Rotten Egg
  • Boiling point: 60OC
  • Specific Gravity: 1.19
  • Odour level: 0.13 mg/kg

Fatality of Hydrogen Sulphide ( mg/kg)

  • Respiratory breakdown: 100
  • Nerve paralysis: 150
  • Nausea, Dizziness: 200
  • Unconsciousness: 500
  • Asphyxiant, Fatal: 700

What is Sour Service?

Sour Service is defined as a fluid service containing water as liquid & H2S exceeding the limits defined below:

Sour Gas-

Sour Gas Service is defined as the gas service

IF            Total Pressure of the gas being handled is > = 65 PSIA

AND       Partial Pressure of H2S in the gas is > 0.05 PSIA

Then      The Environment is SOUR Gas

Sour Oil and Multi-phase

IF            Fluid handled is Crude or Crude+Water+Gas

AND

  • Gas to Oil Ratio > 5000 (SCF/bbl)
  • H2S content in Gas-phase > 15%
  • Partial Pressure of H2S in Gas Phase > 10 PSIA
  • Surface operating Pressure > 265 PSIA

Then     The Environment is SOUR Oil

Sour Scenario in the oil industry as per NACE MR-01-75

Refer to the below image (Fig. 1) which shows a curve segregating the sour and non-sour region as per NACE MR-01-75. The curve denotes the amount of H2S requirement for qualification of being Sour at a given absolute pressure.

Sour Scenario as per MR-01-75
Fig. 1: Sour Scenario as per MR-01-75

Limitations of NACE MR-01-75

  • Saltwater wells, injection wells
  • Downstream Industries, Petrochemical
  • Refineries and Chemical plants
  • Low-pressure multiphase systems

HIC Scenario – API Nelson Curves

Refer to Fig. 2 which shows the HIC and Non-HIC region.

HIC SCENARIO – API NELSON CURVES
Fig. 2: HIC SCENARIO – API NELSON CURVES

Sour Scenario as per ISO 15156 / EFC 16

Fig. 3 shows the sour service criteria as per ISO 15156/EFC 16.

SOUR SCENARIO – ISO 15156 / EFC 16
Fig. 3: SOUR SCENARIO – ISO 15156 / EFC 16

Sour Service H2S ppm Criteria as per DEP

Shell DEP provides the following H2S criteria for fluid services

  • 0 to 49 PPM: Sweet Service
  • 0 to 499 PPM: Low-Risk Sour Service
  • 500 + PPM: High-Risk Sour Service

Hydrogen Sulphide – What it Can Do!

  • Hydrogen- Hydrogen Induced Cracking (HIC)
  • Sulphide- Sulphide Stress Cracking (SSC)

Dynamics of Sour Environments

Fig. 4 shows the dynamics of sour service environment.

Dynamics of Sour Environment
Fig. 4: Dynamics of Sour Environment

What is Hydrogen Induced Cracking?

HIC    =   Hydrogen Induced   Cracking =Caused due to Hydrogen attack on metal

Also known as

  • Hydrogen Damage
  • Hydrogen Embrittlement
  • Hydrogen Blistering
  • Delayed Cracking
  • Lamellar tearing
  • Underbead cracking
  • Stepwise cracking

Mechanism of Hydrogen Induced Cracking or HIC

Refer to Fig. 5 which shows the mechanism of HIC.

Mechanism of Hydrogen Induced Cracking (HIC)
Fig. 5: Mechanism of Hydrogen Induced Cracking (HIC)

Exhibit – Hydrogen Induced Cracking

Fig. 6 shows an example of a crack by HIC.

Example of Hydrogen Induced Cracking
Fig. 6: Example of Hydrogen Induced Cracking

Requirement of HIC Resistant Materials

Requirements for Carbon and Low Alloy Steels

  • The hardness of Parent Material Less Than 22HRC (237 BHN)
  • The steel shall be fully killed ( SILICON / ALUMINIUM)
  • The material should be Heat Treated by NORMALIZING / ANNEALING / Q AND T
  • Carbon content shall be less than 0.23% and Carbon Equivalent (CE) less than 0.43
  • Sulphur and Phosphorus less than 0.002%
  • Requirements like Calcium Treated, Inclusion Control.

Requirements for Austenitic Stainless Steel

  • Hardness on Parent Materials less than 22HRC (237 BHN).
  • Heat Treated by Solution Annealing.

Requirements for Duplex and Super Duplex Stainless Steel

  • Hardness on parent Material less than 25 HRC.
  • Heat Treated by Solution Annealing.
  • Ferrite shall be 35% to 65%.

Few more Resources for you..

Guide for Coating Selection for External Bolting to Reduce Corrosion
Corrosion Monitoring Techniques & Surveys
Corrosion Protection for Offshore Pipelines
Forms of Corrosion: An Article
Corrosion under insulation: A Presentation
Few job opportunities for you

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Anup Kumar Dey

I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.

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