# Presentation: 248957

## SCC Management

***16” Camas to Eugene***
***26” Sumas to Washougal***

**Notes:**
Thanks Ron, I’d like to talk a little bit about an SCC management plan we have developed for NWP. Primarily based on West Coast work near Portland and Seattle.  A hydro/ILI/DA approach.

## Outline

**16” Camas to Eugene **
**Background /Issues**
**Integrity Strategy Execution**
**Current Status**
**26” Sumner to Washougal**
**Background / Issues**
**Segment by Segment Strategy**
**SCC strategy**

**Notes:**
16” near Portland, Oregon, Integrity Strategy implemented for several years and then discuss 26” line along I-5 corridor from Canadian border thru Columbia River Gorge.

## NWP I-5 Corridor 

**16” Camas to Eugene**

**16” Camas - Eugene**

**Notes:**
Oregon City is a suburb of Portland Oregon.  Just a quick visual.  

## 16” Background / Issues

**Oregon City Requalification in 1994**
**22 hydrostatic test failures**
**Most of these 6 miles downstream at 1000 to 1100 psi**
**16” x 0.250” wall; X52; Bitumastic coating; ERW Lonestar steel**
**MAOP 896 psig**
**Cracking is SCC (classical high??; near–neutral pH??)**
**Continued SCC Management (1994-2001)**
**Through excavations**
**SCC coupons**
**Strategy to build & apply ILI  **
**16” UT Crack Detection (Sept. 2001) **
**Liquid slug; no fun in a gas pipeline, max elevation 300+ feet**
**Ensure longer term integrity (where are the subcritical cracks)**

**Notes:**
Hit Point 1 ----  A, B, D.  Requal in ‘94
Point 2 ----  since 1994
Point 3 ----  Tool run

## 16” UT ILI C-Scan

**16” UT ILI C-Scan**

**Notes:**
Brought this slide along as a courtesy for my English unit challenged friends.  It’s the Same area with a metric view...
	GOOD CORRELATION BETWEEN USCD (ILI) DATA AND FINDINGS IN THE FIELD (BOTH SHEARWAVE AND GRINDING) 

## 16” Short term Integrity Strategy

**Identified couple of hundred**
**Depth 25-40%wt: 9 features**
**12.5-25%wt: **
**<12.5%wt: **
**2002 digs validated ILI accuracy**
**Length and Depth range (grinding)**

** ****API 579/BS7910; Level II and III; Well established**
** ****J****IC**** = 257lbs/in; SMYS=52 ksi; SMUTS=66 ksi**
** ****Pressure 1.39 MAOP (1245 psi)**
** ****Crack size = upper bound value from ILI + 10%wt**
** ****Immediate Repairs**
_** **__**Nine**_** of several hundred features un-acceptable **

** ****Elastic-Plastic Fracture Mechanics Type**
** ****Industry Standards: API 579, BS7910:1999**
** ****Level 2 Assessment**
** ****Low bound FAD Equation**
** ****Very conservative**
** ****Level 3 Assessment**
**Based on measured stress-strain curve **** **
**Based on measured R-curve**
**Accurate and less conservative**

**Notes:**
 Numerous features identified in this section of pipeline; more than what was expected. There were nine features that were in 25 to 40% range. The excavations validated the depth range that was predicted and length predictions. The validation in the field was carried out using grinding; since traditional shear wave is inappropriate for SCC (colonies). 
This is a failure assessment diagram; and the methodology is well described and has been utilized extensively in oil and gas industry as stated in API 579 and BS7910.  The diagram shows the y-axis is stress intensity ratio and x-axis is load ratio. The red line depicts the locus of failure in a structure. If a structure with a crack falls within the locus it is acceptable and outside is unacceptable. All the defects found on this pipeline were plotted in a FAD; and all engineering decisions were solely based on this well accepted and tested industry fracture mechanics methodology. As Williams we test the pipeline to its MAOP and 1.39 MAOP. At MAOP all defects were acceptable, but as a prudent operator we made our excavation decisions on 1.39 MAOP.  
We utilize this elastic-plastic methodology; level 2 or level 3 depending on the extent of data. If we have accurate stress-strain data, we utilize level 3, which gives us less conservatism in the calculations. 

## 16” Future Integrity & Current Status

**Based on 2001 ILI and 2003 Field**
**Establish growth rate using linear assumption**
**Excavation data from the field**
**Growth Rate = 0.03 in/year**
**Excavation and Re-inspection driven**
**22.5  to 35% requires action in 4-6 yrs**

**  **_**NO INCIDENT**_
** ****Validates Strategy**
** ****ILI identify sub critical**
** ****Fracture mechanics evaluation **
** ****Continued monitoring & repairs 2004+**

**No Incident since Integrity strategy implemented; Continuous Improvement**

**Notes:**
1 )  Crack growth rate is critical to defining future integrity management. There is literature data, however we decided to validate and build on such information. We utilized 2001 ILI data with 2002/03 excavation data to establish growth rates. There was extensive validation; and required adjustments to field data. The growth rate that was utilized in this program was 0.03 in/year. Excavations have been identified for 2004, and they are driven by the detailed analyses as shown.
2) This is a Failure assessment diagram according to API 579; The growth rates are utilized to depict defects as a function of time in this plot. This is the basic methodology we utilize to define future repairs. 
3) It is critical to note that on the 16” pipeline, since the execution of this strategy there has been no incident. Continued integrity management, leveraging new excavation data, mechanistic data and fracture mechanics analyses are critical to the future of this system. Continuous improvement in all aspects of this integrity strategy is essential to SCC management. 

## 26” Snohomish to Washougal

**Primarily 26” O.D. , 0.281” wt**
**DSAW pipe, X-52**
**Field applied bitumastic asphalt**
**Installed in 1956**
**Regular Corrosion Inspection**
**Only Snohomish to Sumner SCC susceptible**
**One Incident (at MAOP 674 psi – 59% SMYS)**
**SCC in 2003**
**Lake Tapps**

| Segment (north to south) |  |  |
| --- | --- | --- |
| Sumas to Mt Vernon
44 miles |  |  |
| Mt Vernon to Snohomish
46 miles |  |  |
| Snohomish to Sumner
42 miles |  |  |
| Sumner to Ft. Lewis
17 miles |  |  |
| Ft. Lewis to Chehalis
46 miles |  |  |
| Chehalis to Washougal
73 miles
 |  |  |

**Segment specific Integrity Strategy**

**Notes:**
There was an incident at Lake Tapps; a rupture on the 26” due to SCC. Field applied bitumastic asphald, DSAW X 52. 
This has had regular corrosion integrity management over the years. 
It is critical to note, that currently only one segment is considered SCC susceptible. There is excavation data to support this conclusion, and there is ongoing work to validate this conclusion.
It is important to note that segment specific SCC strategy is essential.

## Slide 9

## 26” Critical Size & Crack Growth Rate

**Maximum survived flaw size is a function of  (FAD Level II):**
**length and depth,& Pressure applied (Class Location)**
**Actual yield, tensile, and toughness properties (upper bound value used)**
**Crack growth rates (literature & field)**
**Re-hydro re-inspection was 2 years**
**Re-inspection was 6 – 9 years**

**Sub critical crack size defines integrity strategy**

**Notes:**
The snohomish to sumner, which was SCC susceptible; the integrity strategy for this segment was driven by the analyses shown here. This is a plot of crack length versus depth, and the orange line depicts the defects that would survive the contemplated hydrostatic test.  
The pink line represents the threshold as defined by the ILI methodology.  
Short term and longer term integrity strategies were evaluated using FAD; additionally the reinspection and rehydro calculations were conducted.  It was envisage that hydro would be required every 2 years; potential reinspection was 6-9 years. 
Hydrostatic test issues for Williams NorthWest are three fold: a) an old pipeline with original material and weld defects exposed to 100% SMYS; b) identification of sub critical defects as small as possible provides substantial safety and future integrity; c) actual yield higher than SMYS; so non –conservative unless additional safety factors are applied on top of calculations. 

## 26” Segments of the System

| Segment (north to south) |  |  |
| --- | --- | --- |
| Sumas to Mt Vernon
44 miles |  |  |
| Mt Vernon to Snohomish
46 miles |  |  |
| Snohomish to Sumner
42 miles |  |  |
| Sumner to Ft. Lewis
17 miles |  |  |
| Ft. Lewis to Chehalis
46 miles |  |  |
| Chehalis to Washougal
73 miles
 |  |  |

**2003 SCC failure**
**Crack detection completed**
**DA model being developed **

**No SCC failure**
**3 insignificant SCC identified**
**DA model being applied**

**No SCC ever found**
**DA model being applied**

**No SCC susceptibility**
**DA Model being developed **

**SCC susceptible – ILI driven; No SCC – DA to establish susceptibility**

**Notes:**
26” Sumas to Washougal is approximately 200 miles in total length. There is one segment that exhibits SCC susceptibility, and all other segments have the potential, but to date have no susceptibility to SCC.  The plan is for the SCC susceptible section, Snohomish to Sumner an integrity strategy that includes crack detection is being executed. A DA model will be developed using extensive data from this segment, and will be applied to others to validate non-existence of SCC. 

## SCC Integrity Strategy

**Susceptibility**
**DA driven**
**Extent of susceptibility defines IMP**
**Life Cycle Modeling**
**Fracture mechanics driven**
**Crack growth rate driven**
**Mitigation strategy**** (data and analyses driven)**
**ILI or Hydro**
**Repair, grind out, or replace**

**SYSTEMATIC, DATA & MECHANISM-DRIVEN STRATEGY CRITICAL**

**Life Cycle Modeling**

**Confirmatory Excavations**

**SCC Susceptibility Model**

**Ongoing SCC Monitoring**

- Sampling Model

**Existing Defect Size Distribution**

**Cyclic Pressure History**

**Future Integrity Model**

**Integrity Actions**

**Applicable SCC Rate Studies**

** ****ILI Data**
** ****Soils, Terrain, Topo Model**
** ****Coating Disbondment**
** ****Corrosion Linearity (MFL)**
** ****Pipe Design**
** ****Material Properties**
** ****CP Data**

**Notes:**
Red box, gathering appropriate field data to build up SCC Susceptiblity model and test conclusions for each particular pipeline segment.  Systematic data gathering req’d to understand mechanisms driving risks..