Allied Corrosion Industries - Leaders in Cathodic Protection and Corrosion Control
LEADERS in CORROSION CONTROL

Allied Corrosion Industries, Inc.

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Stress Corrosion Cracking Direct Assessment (SCCDA)

What is Stress Corrosion Cracking?

Stress Corrosion Cracking Direct Assessment (SSCDA): As defined in the NACE Standard RP0204-2004, Stress Corrosion Cracking (SCC) is the cracking of material produced by the combined action of corrosion and tensile stress (residual or applied). SCCDA Methodology is a procedure that can identify areas where either near-neutral-pH SCC or high-pH SCC can occur on external pipe surfaces. The SCCDA process consists of four steps:

Causes

Stress Corrosion Cracking can be caused by combined corrosion and tensile stress, which can include cold deformation and forming, welding, heat treatment, machining and grinding.

The SCCDA Process

1. Pre-Assessment

In the pre-assessment step, Allied Corrosion or the owner/operator's personnel will collect historical and current data for the purposes of analyzing and prioritizing the threat of Stress Corrosion Cracking. Prioritization of SCC susceptible pipeline segments is performed utilizing the following factors:

High-pH Stress Corrosion Cracking

  • Operating stress exceeds 60% of SMYS
  • Operating temperature exceeds 100°F (38°C)
  • Within 20 miles of a compressor station
  • Age greater than or equal to 10 years
  • Coating type other than Fusion Bonded Epoxy

Near Neutral-pH Stress Corrosion Cracking

  • Operating stress exceeds 60% of SMYS
  • Within 20 miles of a compressor station
  • Age greater than or equal to 10 years
  • Coating type other than Fusion Bonded Epoxy

2. Indirect Inspection

The purpose of the indirect inspection step is to collect additional information that was not available in the owner/operator's historical records. Some of the data that Allied could collect in this step would include data from Close Interval Surveys (CIS), Direct Current Voltage Gradient (DCVG) surveys, and terrain conditions (soil type, topography, and drainage) along the right-of-way (ROW) in which the pipeline is located. Once all of this information is assembled, the direct examination site list is finalized and prioritized.

Mapping and Survey Solutions



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3. Direct Examination

The purpose of the Direct Examination step is twofold. First, this step will either validate or nullify the decision criteria for SCC direct examination site selection. Second, this step provides for the actual digging of the suspected SCC locations for inspection. When performed, these dig sites will render the severity, extent, and type of SCC (intergranular or transgranular cracking). This information is crucial in the post assessment process in order to develop a predictive model and allow for modifications. A wide range of related physical data is collected, along with Magnetic Particle Inspection (MPI) of the susceptible area. NACE Standard RP0204-2004 outlines four different MPI techniques for inspecting the external surface of pipelines. They are:

 

  • DPMI- Dry Powder MPI: The ultimate sensitivity of this inspection technique is 2 to 5 mm long defects.
  • WFMPI- Wet Fluorescent MPI: The ultimate sensitivity of this inspection technique is 1 mm long defects.
  • WVMPI- Wet Visual MPI: The ultimate sensitivity of this inspection technique is 1 to 2 mm long defects.
  • BWMPI- Black on White MPI: The ultimate sensitivity of this inspection technique is 1 to 2 mm long defects. This technique is preferred over the other due to the ease of photographic documentation and maintaining a high sensitivity.

 

 

 

 

 

4. Post Assessment

In the post assessment step, Allied Corrosion or the owner/operator will analyze the data collected from the previous three SCCDA steps for the following purposes:

  • To determine if stress corrosion cracking mitigation is required and if so, prioritize those actions.
  • To define the time interval to re-assess the pipeline segment.
  • To evaluate and verify the decision model used to find stress corrosion cracking.

Our Integrity Management Team is ready to provide turn-key SCCDA services or we can perform any single or multiple step(s) that you, the owner/operator require.

The Allied Corrosion Difference

Our strong understanding of the potential destruction from a compromised pipeline allows us to deliver detailed Stress Corrosion Cracking Direct Assessment to complement any operator's Integrity Management program. Our comprehensive pipeline integrity and cathodic protection engineering services will keep your pipeline assets protected throughout its life-cycle.

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