nace nuclear symposium buried pipe coatings.ppt

Bob WalcheskiVice President – Technical Services

UESI Nuclear Services - a company

3306 Enterprise Road, Fort Pierce, FL

4TH ANNUAL NACE NUCLEAR POWER PLANT COATINGS SYMPOSIUMJANUARY 16, 2013 Orlando, Florida, USA

4TH ANNUAL NACE NUCLEAR POWER PLANT COATINGS SYMPOSIUMJANUARY 16, 2013 Orlando, Florida, USA

Conducting a Condition Conducting a Condition Assessment of Buried Pipe Assessment of Buried Pipe Coatings Coatings

Presented By:

Conducting a Condition Assessment of Buried Pipe Coatings

General Background:

Most nuclear power plants have extensive underground piping systems, some which transport water containing radioactive isotopes (e.g. tritium).

The buried piping systems have utilized preventative measures for corrosion protection (Coatings, Linings, CP, etc.)

Buried pipe is normally reliable, however damage to corrosion resistant coatings can compromise piping leading to leaks.

As nuclear power plants age, underground piping has greater potential to corrode. Since these systems are normally inaccessible, the condition of many nuclear plant piping systems is largely unknown.

NACE NUCLEAR POWER PLANT NACE NUCLEAR POWER PLANT COATINGS SYMPOSIUMCOATINGS SYMPOSIUM


General Background:

It has been discovered that small leaks have occurred, however have not caused plant safety hazards or jeopardized public health and safety.

As pipes continue to age and further corrosion occurs, the likelihood and severity of leaks could increase without mitigating actions.

The nuclear power industry is re-examining the current approach to design, maintenance & inspection of buried pipe.




U.S. Operating Commercial Nuclear Power Reactors


Nuclear Industry Initiatives – EPRI’s Initiative & Strategic Activities

Nuclear Strategic Issues Advisory Committee (NSIAC) Buried Pipe Initiative:

Encompasses all buried and underground piping Requires procedures and oversight Requires prioritization through risk ranking Requires inspections Requires each plant to have an asset management plan

Risk Ranking Software (BPWORKS)

Correlates the likelihood of failure against the consequences of failure.

Risk = Likelihood x Consequences




EPRI Documents:

1016276, “An Assessment of Industry Needs for Control of Degradation in Buried Pipe” (Gap Analysis identified needs)

1016456, “Recommendations for an Effective Program to Control the Degradation of Buried Pipe”

EPRI Coating Field Guide - “Protective Coatings for Power Plants”




EPRI Buried Pipe Integrity Group (BPIG)

- Forum for nuclear plant owner to discuss buried pipe issues and exchange information & experiences (OE Sharing)

- Forum to obtain a consensus on industry issues

- Technical support on buried pipe issues, as well as support for related products

- Interface with support Vendors

- Provides R&D sponsor opportunities



Nuclear Industry Initiatives – NACE

Technical Guidance Report on Nuclear Buried Piping (TG 404)

Establishment of “daughter committees” for:

- Information exchange for topics which are not being currently handled by existing committees

- Establish/write standard – Nondestructive Evaluation (NDE) Technologies to Evaluate Buried Pipe on Nuclear Sites

- Establish/write standards specific to nuclear – Cathodic Protection, Coatings

- Address entire Power Industry, not just nuclear power



Industry Consensus Approach

“Reasonable Assurance” – Inspection Planning Guidance is a Graded Process that involves:

- Inventory and Risk Ranking

- Creating Line Groupings

- Indirect Inspection

- Direct Inspection, Examination, Assessment

- Feedback to overall program



Direct and Indirect Inspections and Examinations

Indirect Inspection - Survey techniques used to assess the likelihood of degradation without having direct access to the section of the component (pipe/pipe system) being examined. Results are typically qualitative and less accurate than direct inspection/examination.

Direct Inspection & Examination - An Inspection, Assessment or Nondestructive Evaluation (NDE) examination that is made in immediate contact with, or in close proximity to the section of the component being examined/assessed. Provides better degree of quantitative measurement (coating thickness, wall thickness, degradation or discontinuity size, specific degradation type, etc.) and assessment of condition.



Condition Assessment of Pipe Protective Coatings/Linings

Visual Inspection Coatings Assessment:

Intent is to perform as-found inspection of the as-found coating/ lining in accessible areas (excavations) on designated piping to identify indication and causes of degradation, determine the apparent degradation mechanism, identify/assess the severity of

degradation, and quantify its extent.

Accomplished through an effective use of resources by an established graded process involving focused and quality inspections.

Involves Planning, Procedures, Performance, Documentation, and Evaluation.




Buried Pipe coatings/linings Visual Inspection attributes:

Use standard ASTM practices to characterize coating cracking, blistering, checking, peeling, delamination, chalking, flaking, rust & degree, or other noted degraded condition(s)

For tape wraps identify gaps and/or disbondment that may be occuring at overlap edges. Identify if tape wrap appears to be installed with adequate overlap. Inspect for tears, holes, gaps, etc. which appear to be detrimental to protective function (e.g. moisture intrusion)

For shop of field applied linings (FBE, HDPE-bituminous composites, etc.), inspect for evidence of potential disbondment (bubbled or raised areas, sags)




Buried Pipe coatings/linings qualitative Visual Inspection attributes:

Visually assess adhesion of as found coating by observing for evidence of peeling/delamination, tape wrap edges curling, bubbles and sags

Sound coating/lining with non-destructive tapping tool (e.g. plastic or wood hammer) for hollow, non-intact sound to identify hidden voids, cracks, etc. (especially at areas of bulges, bubbling, sags or suspect areas)

Use an inspection magnification viewer to assess micro-cracking, disintegration and to inspect found degradation to provide best characterization.




Buried Pipe quantitative measurements:

Dry film thickness (correlate with coating system and/or installation documentation if possible)

For coatings/linings damaged to substrate, characterize substrate surface degradation and inspect for evidence of pitting or general metal loss (rusting/rust degree, pitting & pit measurement)

For coatings/linings damaged to substrate, measure pipe wall thickness via UT.




Reporting:

Photographic documentation of representative conditions

Use piping layout drawing, sketch, photograph and label piping general arrangement in each excavation (use for reference identification of specific and general assessment/inspection finding & remarks)

Identify pipe/piping by unique line number, facility system and note as-found environment conditions (watered/wet, sand, clay, rocky, etc.) especially if noted/witnessed during excavation activities




Reporting – Photographic Documentation is invaluable:





Cracking, disintegration/flaking Soil embedment into wrap overlap




Failed, delaminated to substrate Inter-coat delamination failure/breakdown




Cracking of Somastic Coating Somastic Coating with tape wrap failing




Sagging & lifting of wrap edges @ bottom invert

Brittle, cracking hot applied coal tar




Coating failure to pipe substrate – pitting evident




Multiple pipe runs (failing poly-liner on left), (good conditions noted on right)

Importance of use of line no., and reference by photo, layout to reference conditions




Area of coating to be removed for NDE - removed coating prior to install of UT-GW collars



Reporting:

Identify areas that require repair prior to backfilling

As applicable, work with Assessment team to suggest repair methods and materials


Tape wrap repair



Reporting:

Correlate to past assessments

Include information on in-service conditions (as possible/achievable):

- Operating History- Maintenance History- Ground water chemistry- Soil chemical and physical characteristics- Soil stress and backfill- Cathodic Protection




Reporting:

Correlate to past assessments

NDE Evaluation and Indirect Assessment data (as applicable):

- Other visual inspections/exams- UT thickness, guided wave- Other NDE surface and volumetric examinations- Holiday Testing- Above ground or internal soil potential/stray current

surveys/findings- Chemical and Metallurgical analysis (as applicable)




Reporting – Summary and Recommendations:

Summarize Assessment Findings with detailed focus on degradation severity, OE,

For those coating/lining systems assessed to be in good and/or minimally acceptable degraded condition and satisfactory continuing to perform protective function, qualify remaining service life by reference to manufacturer data, known site stresses, piping system and operating parameters, maintenance history




Document comprehensive Assessment Data and Formal Reports




Thank you for your attention!

Questions, discussion …


nace nuclear symposium buried pipe coatings.ppt

Documents

pipe coatingsgeneral background

pipe protective coatings liningsreporting

pipe protective coatings linings

pipe coatingscondition assessment

buried pipe

coatings linings damaged

somastic coating

assessment