Oil and gas projects often use sour service pipe materials in H₂S environments.
Sour service means the system contains hydrogen sulfide, also called H₂S.
H₂S can create serious cracking risks in steel pipes, fittings, flanges, and pressure parts. These cracks may be hard to see at first. But they can lead to leakage, failure, shutdown, or safety risk.
This is why HIC and SSC testing are important.
These tests help engineers check if the material can resist cracking in H₂S service.
This guide explains HIC, SSC, common test standards, buyer checks, and how DLSS can support sour service pipe projects.
What Is Sour Service?
Sour service means the working environment contains H₂S.
H₂S may be found in:
- Sour gas pipelines
- Oil field piping
- Gas gathering lines
- Refinery systems
- Pressure vessels
- Offshore platforms
- Subsea systems
- Chemical process lines
For oil field, refinery, and offshore projects, buyers can also review DLSS oil and gas pipeline solutions before selecting the pipe material.
In sour service, steel may absorb hydrogen. This can create cracks inside the steel or on the surface.
The risk depends on many factors.
Buyers should check:
- H₂S level
- pH value
- Chloride content
- Temperature
- Pressure
- Water phase
- Material grade
- Hardness
- Heat treatment
- Welding condition
- Project standard
Sour service should never be guessed. It should be confirmed before ordering material.
What Is HIC?
HIC means Hydrogen-Induced Cracking.
It happens when hydrogen enters the steel.
The hydrogen can collect inside the material. Over time, this may create internal cracks.
HIC can happen even when the pipe is not under high stress. This makes it dangerous for sour gas pipelines and pressure parts.
HIC is often linked to:
- Carbon steel
- Low alloy steel
- Pipeline steel
- Pressure vessel steel
- Sour gas service
- Wet H₂S service
HIC cracks may form inside the steel thickness. They may not be easy to find by simple visual inspection.
HIC Test Standard
The common test standard for HIC is NACE TM0284.
This test is used to check the resistance of pipeline and pressure vessel steels to hydrogen-induced cracking.
A typical HIC test includes:
- Prepare test samples from the pipe, plate, or material.
- Put the samples into an H₂S test solution.
- Keep the samples in the test solution for a fixed time.
- Cut and polish the samples after testing.
- Check the cracks under a microscope.
- Report the HIC test results.
Common HIC result terms include:
| Term | Meaning |
|---|---|
| CLR | Crack Length Ratio |
| CTR | Crack Thickness Ratio |
| CSR | Crack Sensitivity Ratio |
Typical project acceptance criteria may include:
| Item | Typical Limit |
| CLR | ≤ 15% |
| CTR | ≤ 5% |
| CSR | ≤ 1.5% |
These values are common examples only.
Final acceptance criteria should follow the project specification, end-user requirement, and purchase order.
What Is SSC?
SSC means Sulfide Stress Cracking.
It happens when three things exist together:
- H₂S environment
- Tensile stress
- Sensitive material
SSC often starts from the surface. It can lead to sudden brittle cracking.
SSC is a serious risk for:
- High-strength steel
- Welded areas
- Heat-affected zones
- Hard materials
- Sour service equipment
- Oil and gas pipeline parts
Hardness is an important factor. Higher hardness can increase SSC risk.
This is why sour service projects often have hardness limits and heat treatment requirements.
SSC Test Standard
The common test standard for SSC is NACE TM0177.
This standard is used for testing metals against sulfide stress cracking and stress corrosion cracking in H₂S environments.
A common SSC test method uses a stressed sample.
A typical test may include:
- Prepare the test sample.
- Apply tensile stress to the sample.
- Put the sample into an H₂S test solution.
- Hold the sample under stress for the required time.
- Check if the sample cracks or fails.
For many projects, the test time may be 720 hours, or 30 days.
The final test method, stress level, and acceptance rule must follow the project specification.
HIC vs SSC: Simple Comparison
| Item | HIC | SSC |
| Full Name | Hydrogen-Induced Cracking | Sulfide Stress Cracking |
| Main Cause | Hydrogen enters the steel | H₂S plus tensile stress |
| Stress Needed | May happen at low stress | Needs tensile stress |
| Crack Location | Often inside the steel | Often starts from the surface |
| Common Material | Carbon steel and low alloy steel | Higher-strength steel, welds, HAZ |
| Main Test | NACE TM0284 | NACE TM0177 |
| Common Risk | Internal cracking | Sudden brittle cracking |
| Key Control Point | Clean steel and HIC test | Hardness, stress, and SSC test |
HIC and SSC are different risks.
A material may pass one test but still need the other test.
Buyers should confirm both requirements before ordering.
Common Standards for Sour Service Pipes
Sour service projects may use several standards.
| Standard | Main Use |
| NACE TM0284 | HIC testing for pipeline and pressure vessel steels |
| NACE TM0177 | SSC and stress corrosion cracking testing in H₂S environments |
| NACE MR0175 / ISO 15156 | Materials for H₂S-containing oil and gas production |
| NACE MR0103 / ISO 17945 | Materials for sour petroleum refining environments |
| API 5L | Line pipe for pipeline systems |
| EN 10204 3.1 / 3.2 | Material certificate and inspection document |
| ASTM / ASME standards | Pipe, tube, flange, and fitting material requirements |
For upstream oil and gas production, buyers often review NACE MR0175 / ISO 15156 compliance before confirming sour service materials.
For refinery sour service, NACE MR0103 / ISO 17945 may be more suitable.
The correct standard should follow the project specification.
When Are HIC and SSC Tests Required?
HIC and SSC tests may be required when the pipe will work in sour service.
Common project types include:
- Sour gas pipelines
- Gas gathering systems
- Oil field flowlines
- Refinery hydrotreaters
- Sour water systems
- Pressure vessels
- Offshore platforms
- Subsea pipelines
- Chemical plants with H₂S risk
Tests may also be required when the end user, EPC contractor, or inspection company asks for them.
Do not assume the test is not needed.
If the project mentions sour service, H₂S, NACE, MR0175, MR0103, TM0284, or TM0177, buyers should confirm the test requirement before ordering.
What Buyers Should Confirm Before Ordering
Before buying sour service pipes, buyers should prepare clear information.
Buyer Checklist
- Project standard
- Service medium
- H₂S content
- H₂S partial pressure, if available
- pH value
- Chloride content
- Temperature
- Working pressure
- Material grade
- Pipe size
- Wall thickness
- Seamless or welded requirement
- Heat treatment condition
- Hardness requirement
- HIC test requirement
- SSC test requirement
- Impact test requirement, if required
- MTC requirement
- EN 10204 3.1 or 3.2 certificate
- Third-party inspection requirement
- Required delivery time
- Destination country or port
Clear information helps the supplier check the material faster.
It also helps avoid wrong material selection.
What Should Be Included in the Test Documents?
For sour service projects, documents are very important.
Buyers may request:
- Mill Test Certificate
- Chemical composition report
- Mechanical property report
- Heat treatment record
- Hardness test report
- HIC test report
- SSC test report
- PMI report
- Ultrasonic test report
- Dimensional inspection report
- EN 10204 3.1 certificate
- EN 10204 3.2 certificate, if required
- Third-party inspection report
For critical projects, the documents should match the heat number, batch number, and material marking.
Traceability is important.
Material Selection for Sour Service
Sour service material selection depends on the project.
Common material options may include:
| Material Type | Common Use |
| API 5L line pipe | Sour gas pipelines and gathering lines |
| ASTM A106 carbon steel pipe | Process piping and pressure service |
| Low alloy steel | Higher pressure or special service |
| Stainless steel 316L | Some lower-risk corrosive service |
| Duplex stainless steel | Higher chloride and strength needs |
| Alloy 825 | Acidic and sour environments |
| Alloy 625 | Severe sour and corrosion service |
The final material should be approved by the project engineer or end user.
Do not choose sour service material only by price.
For lower-risk corrosive service, seamless stainless steel tubes may be considered when the project specification allows stainless steel material.
Welding and HAZ Risk
Welding can change the material condition.
The heat-affected zone, also called HAZ, can become more sensitive to cracking.
For sour service projects, buyers should check:
- Welding procedure
- Hardness limit
- PWHT requirement
- Weld inspection
- HAZ testing
- NACE requirement
- Third-party inspection
Even if the pipe body is qualified, the weld area may still need extra control.
DLSS Testing and Documentation Support
DLSS supports pipe, tube, flange, and fitting projects for oil and gas, refinery, offshore, and chemical service.
For sour service projects, the DLSS quality control process can help buyers check material grade, testing, documents, marking, and packing before shipment.
- Material review
- NACE requirement review
- HIC test coordination
- SSC test coordination
- PMI testing
- Hardness testing
- Ultrasonic testing
- Dimensional inspection
- MTC review
- EN 10204 3.1 documents
- EN 10204 3.2 inspection support
- Third-party inspection support
- Packing and marking before shipment
DLSS can work with third-party inspection companies such as BV, SGS, TUV, LR, ABS, or other project-approved inspection companies.
Example Scenario: Sour Gas Gathering Line
A sour gas gathering line may require API 5L pipe with HIC and SSC testing.
In this type of project, the buyer may ask for:
- NACE MR0175 / ISO 15156 compliance
- HIC test according to NACE TM0284
- SSC test according to NACE TM0177
- Hardness control
- MTC
- EN 10204 3.2 certificate
- Third-party inspection before shipment
This kind of requirement should be checked before production.
If the test is requested after production, it may cause delay, extra cost, or material rejection.
FAQ
What does HIC mean?
HIC means Hydrogen-Induced Cracking. It happens when hydrogen enters the steel and creates internal cracks.
What does SSC mean?
SSC means Sulfide Stress Cracking. It happens when material is under tensile stress in an H₂S environment.
What is the main difference between HIC and SSC?
HIC can happen inside the steel and may not need high stress. SSC usually needs tensile stress and often starts from the surface.
Which standard is used for HIC testing?
NACE TM0284 is commonly used for HIC testing of pipeline and pressure vessel steels.
Which standard is used for SSC testing?
NACE TM0177 is commonly used for SSC and stress corrosion cracking testing in H₂S environments.
Is NACE MR0175 the same as NACE MR0103?
No. NACE MR0175 / ISO 15156 is mainly used for H₂S-containing oil and gas production. NACE MR0103 / ISO 17945 is used for sour petroleum refining environments.
Does every sour service project need both HIC and SSC tests?
Not always. The test requirement depends on the project standard, material, service condition, and end-user requirement.
Can DLSS support HIC and SSC testing?
Yes. DLSS can help coordinate HIC and SSC testing, MTC review, EN 10204 3.1 / 3.2 documents, and third-party inspection support.
Conclusion
HIC and SSC testing are important for sour service pipe projects.
They help buyers reduce the risk of cracking, leakage, shutdown, and material rejection.
HIC testing checks the risk of internal hydrogen-induced cracking.
SSC testing checks the risk of sulfide stress cracking under stress in H₂S service.
Before ordering sour service pipes, buyers should confirm the project standard, H₂S condition, material grade, hardness, heat treatment, HIC test, SSC test, and document requirement.
DLSS supports sour service pipe projects with material review, testing coordination, inspection documents, third-party inspection support, and export packing.
If you need pipes, tubes, flanges, or fittings for sour service, send us your material grade, standard, size, quantity, H₂S condition, and inspection requirements. Our team will help review your inquiry before quotation.
