# Presentation: 438308

## OPS - SCC Workshop R&D Past and Present 

**December 2, 2003**

**Jerry  Rau  -  Panhandle Energy**

## Outline

** ****Review of past R&D accomplishments**
** ****Recent and current SCC R&D efforts**

## The History

**1965**
- Identified SCC as a possible cause of pipeline failures
**1965 - 1970**
- SCC identified as an industry-wide concern, not an isolated incident

## Early Research

**1966 - 1968**
- Carbonate/bicarbonate environments existed at locations of high-pH SCC
- A carbonate/bicarbonate environment could cause SCC of a carbon steel
** ****1966 - 1970 **
- Reproduced high-pH SCC in the laboratory

## Research on the Stress Component

**1975 - 1983**
- Thorough cleaning of the pipe surface to remove mill scale prior to coating should significantly reduce the probability of high-pH SCC
**1980 - 1984 **
- Developed a method to determine the threshold stress for SCC in a single test with a single (tapered) specimen
**1973 - 1983 **
- Discovered that low-frequency, low-amplitude stress fluctuations could reduce the threshold stress considerably

**Notes:**
Thorough cleaning of the pipe surface to remove mill scale prior to coating should significantly reduce the probability of high-pH SCC because the potential would not remain in the critical range for cracking 

## Material Issues

**1970 - 1980**
- Showed that there is no direct correlation between the grade of pipe (for X46 through X80) and its susceptibility to high-pH SCC (1970-1980)
**1973 - 1981**
- Shot peening and grit blasting can significantly increase the resistance of a pipe to SCC** **

**Notes:**
At the committee meeting in January we also adopted five emphasis area and chairmen to direct the research activities.

## Temperature Issues

**1968 - 1975**
- Demonstrated that lower discharge temperatures can have a substantial beneficial effect on reducing the probability of a failure due to high-pH SCC.
- Results in much lower crack growth rates
- Results in narrower range of environmental conditions that will support SCC
- Slower deterioration of coatings

## Mitigation Issues

**1975 - 1995 **
- Periodic hydrostatic retesting is an effective way to assure the integrity of a pipeline that may have stress-corrosion cracks** **
**1972 - 2002 **
- Developed a life-prediction model for high-pH SCC that enables a pipeline operator to evaluate the significance of cracks that are discovered and adequately sized.

**Notes:**
Developed a life-prediction model for high-pH SCC that enables a pipeline operator to evaluate the significance (in terms of pipeline integrity and scheduling remedial measures) of cracks that are discovered and adequately sized. 

## Environmental Issues

**1977 **
- Discovered that relatively dilute groundwater containing CO2 could cause transgranular (near-neutral-pH) SCC
**1977 - 1987 **
- Determined that near-neutral-pH SCC occurs only in areas where little, if any, cathodic-protection current reaches the steel
**1980-2000**
- Determined that stress fluctuations are critical with near-neutral-pH SCC as well as with high-pH SCC

**Notes:**
At the committee meeting in January we also adopted five emphasis area and chairmen to direct the research activities.

## Prioritizing Areas to Inspect for SCC

**1977 - 2002**** **
- Guidelines  developed for improving the cost effectiveness of hydrostatic retesting, in-line inspections, and bellhole inspections.
- Based upon proximity to other SCC locations, coating type, geology, soil type, temperature history, and pressure history

**Notes:**
which are based upon proximity to other SCC locations, coating type, geology, soil type, temperature history, and pressure history,

## Managing SCC

**1965 - 2000**
- A practical way to manage the SCC problem (both high-pH and near neutral-pH) for future pipelines
- The coating and
- The condition of the pipe surface
- Eg. The use of fusion-bonded epoxy coatings on mechanically cleaned surface preparation

## R&D Projects in PRCI Materials Committee

**SCC Susceptibility**
**	**SCC Initiation Susceptibility Ranking/Screening
- 	Review of Stress Corrosion Cracking of Pipelines in Contact with 	Near-Neutral (Low) pH Solutions
**SCC Crack Growth / Re-inspection Intervals**
- 	Growth Model for Assessment after SCC Detection
- 	SCC Crack Growth - Effects of Operating Practices
- 	Effects of Pressure Fluctuations on Near-Neutral SCC Propagation
- 	SCC Crack Extension and Coalescence Modeling
- 	Hydrostatic Testing Frequencies for SCC Control
- 	Field Studies to Support SCC Life Prediction Model

## R&D Projects in PRCI Materials Committee

**SCC Direct Examination **
**	**Application of Phased Array UT Characterization in the Field
- 	Reliable Diagnosis of SCC During Field Inspection
**SCC Engineering Critical Assessment**
**	**SCC Acceptance Criteria
- 	Model for Assessing Remaining Strength of Line Pipe with Co-	existent Corrosion and SCC
**SCC Mitigation & Repair**
- Permanent Field Repair of SCC
- Cyclic Stress/Strain Behavior of Steels for SCC Service

## R&D Projects in PRCI C&I Committee

- Transforming Shallow Cracks to Significant Cracks
- SCC Sample management
- Disbonded Tape - EMAT on MFL
- Prediction of SCC from Field Measurements
- Maps Technology for Stress Measurement
- SCCDA Development Support
- NLH/Barkhausen

## Summary

- Research Continuous From 1965
- Much has Been Learned
- More Still to be Learned