PSLCW008001 Hall C Dump LCW Surge Tank H2 Recombiner Heater Well

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PS-LCW-008-001Hall C Dump LCW Surge Tank H2
Recombiner Heater Well
Hydrogen recombiner located in the hall C dump
cooling building (bldg95)
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Introduction

• The hydrogen recombiner located in the hall C
  dump cooling building (bldg95) was found to have
  gas (nitrogen) leaks through a weld in both
  heater wells.
• This weld joined a back plate to a 6in tube
  located internal to the exterior 8in pipe.
• The leaks were found using a soap bubble test on
  the internal surface of the 6 inch tube.
• Prior to the leak, the system had a pressure
  cycle between 17 and 22 psi about every 18 hours.
• As a result of this leak the system cycle time
  decreased to every 2 hours causing constant
  replenishment of the nitrogen source

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Existing Piping Layout
2x Heater Well Cross-Arm (Horizontal)
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Detail Heater Well Cross Arm
Fusion-Weld (FAILURE)
Butt-Weld
Fusion Weld
Soap bubble test found leak
Back Plate
6in O.D. Seam-Welded Tube
8in NPS Seamless Pipe
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Project Approach

• Operations, Installation, MachShop, Meng, RadCon,
  QA, Facilities met to determine whether repair
  would be made now or later and discuss the repair
  approach
• Repair Now -- Radiological conditions were as
  good as they were going to get after the extended
  down
• How?
• Only 1.5 weeks left until lock-up
• Decision was made to cut out existing heater
  wells and replace them (new flange would include
  socket-weld connection to cut made in cross-arm
  8in outer tube)
• Established that this work would be treated as a
  Repair of an existing Pressure System
• Established the DA

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Why Pressure System?

• Operating parameters
• Temperature 70C
• Pressure 17-22psig
• EHS manual 6151 for pressure system requirements
• The H2 Recombiner is classified as a pressure
  system/piping based on system pressure exceeding
  15 psi
• EHS manual 6122 for welding requirements
• The welds for the H2 Recombiner are considered to
  be Class A welds based on the fact that the
  system contains pressure piping exceeding 15 psi

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Fabrication

• The CEBAF heater wells are an exact copy of a
  1960s SLAC design
• The system was designed for 150 psig
• Our heater wells had been in service for gt10yrs
• Failure possibly due to thermal fatigue
  occurred at the intersection of the longitudinal
  weld seam of the 6in tube and circumferential
  weld on the heater well end cap
• Decided to fabricate new wells in accordance
  with the existing design but use seamless tube

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Material Tracking

• Machine shop was aware up-front that this would
  be considered a pressure system and that all
  material would need to be closely tracked
• Material certifications were not available for
  all of the material
• QA went to the shop to determine/verify materials
  using their chemical analyzer
• QA also verified the 8in tube material in bldg
  95 (interface for new heater wells)

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Analysis, QA Requirements Peer Review

• Calculations were prepared by the DA
• Calculations done in accordance with B31.3 and
  BPVC Sect. VIII as applicable and included
  internal and externally pressurized shell
  calculations for the 6 and 8 in. tubes, uniformly
  loaded disc calcs for the end cap, weld joint
  analysis, etc.
• Inspection/Examination plan (weld
  procedure/inspection and final system testing)
  developed by QA, Welder, DA, Facilities hold
  points determined, responsibilities assigned,
  timeline formalized
• Calculations and QA plan were submitted for
  technical and Peer Review
• The drawing(s) include a traveler to capture DA,
  technical and peer reviewer, material
  certification, dimensional inspection, welding
  QA, and system testing

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Documentation - Drawings and Traveler
I.D. s for each weld that requires inspection
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Traveler Sheet
Peer Review and DocuShare
Material Certifications
Weld s corresponding to sht 1 of drawing
Inspection reqts per weld
Inspection results
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Post installation discovery

• After installation of the new heater wells in
  the H2 recombiner the potential for large loads
  on the wells developed by thermal growth was
  identified.
• Prior to bringing the system back online, an
  inspection of the as-welded clearances between
  the heater wells and the internals of the H2
  recombiner was performed and showed zero radial
  clearance between the ends of the coped baffle
  and the ID of the 8in tube and zero axial
  clearance between coped baffle and the 6in
  vertical tube.
• In-place grinding or similar method of removing
  material from the baffle to unconstrain the wells
  was not possible because of the risk of
  contamination of the LCW.
• A plan was developed to cut the new wells out of
  the H2 recombiner by parting the 8in tube.
  Material could then be removed from the baffles
  and the wells reinstalled ensuring an
  unconstrained condition.

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Post installation discovery

• This work would be considered as a separate
  repair and follow the same guidelines as the
  original repair
• Layout of 2nd repair
• The hydrogen recombiner assembly drawing has been
  revised to include notes and view showing minimum
  as-welded clearances to ensure the wells can grow
  unconstrained

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DocuShare Folder for H2 Recombiner
After initial log in to DocuShare, navigate to
Facilities\Engineering\Pressure Systems\Pressure
Systems Directory and you will see the
following. Note we are currently looking at page
2
Select the Recombiner Repair link to enter the
project folder for the heater wells
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DocuShare Folder for H2 Recombiner (cont.)
The project folder contains the 7 sub-folders
shown. These are suggested folders from 6151-T1.
This project was a repair so we will now enter
the Repair Sub-folder.
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DocuShare Folder for H2 Recombiner (cont.)
You will see that there are 2 Repairs identified
in the Repair Folder . The first repair was a
redesign of the flange and the inner 6 can.
During installation a potential problem was
identified in regards to the design of the baffle
and the interface between a vertical pipe. The
second repair documents modifications to the
baffle to eliminate potential thermal stresses.
Each repair folder contains the same basic
folders as the main project folder, Project
Status, Engineering, Manufacturing, and Testing.
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DocuShare Folder for H2 Recombiner (cont.)
The following shows a breakdown of the documents
within the Repair 1 folder.
The Engineering folder contains Atlis entry,
drawings, calculations, and photos
The Manufacturing folder contains work permits,
matl certs, inspection results, and the traveler
The Testing folder contains TOSP used to conduct
the tightness test
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Suggestions for the Committee

• Create standard traveler templates for drawings
  
• These templates should generic enough to be used
  for Class A, B, C systems but detailed enough
  to capture all of the requirements for a Class A
  system.
• These can be stored in Ideas along with JLAB
  generic title blocks, or in the form of word
  templates, etc.
• Revise 6151 and 6122 to place the responsibility
  for quality inspection in the hands of the
  Quality Assurance group not the Design Authority.
  The DA does not have adequate training to
  inspect and certify that a part is defective.
• Develop an electronic tracking system based on a
  barcode system that can track the progress of a
  given job and the person completing each stage of
  the job. This will reduce the amount of
  information that needs to be captured on the
  traveler document. The software would record
  material part numbers, fabricator and welder
  information, quality inspector information, test
  and inspection results, and time spent on each
  portion of the job.
• Develop a system to electronically document
  discrepancy reports on received material,
  inspected material, etc. that can be tracked
  based on vendor or process. Develop a means of
  resolving certain non-technical issues on site
  while notifying the correct engineering
  department for deviations that require a more
  detailed investigation.

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Review of Project Flow
Step 1) Who is the DA?
Mtg, phone calls, emails, etc
Step 2) Define the System
Pressure, Temp, Cycles, etc.
Step 3) Classify the System e.g. Pressure
System?
Pressure System? Class A, B, C?
Step 4) Time Line
Design, Matl procurement, fabrication,
installtion, etc.
Step 5) Design, Analysis, Peer Review
Drawings, Calcs, DocuShare, TOSPs
Step 6) Fabrication, Installation, Final System
Testing
NDE, Leak Test, Safety Walk-Through
Step 7) Lessons Learned
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Time Line of Events
Repair 1
Fri, 10/10
Tues, 10/14
Wed, 10/15
Mon, 10/20-23
Tues, 10/14
Wed, 10/15-16
Thurs, 10/16-20
Mon, 10/13
Thurs, 10/23
Repair 2
Sat 2pm, 10/25
Thurs, 10/23
Fri, 10/24