wbs 6.2.5 stave assembly · wbs dictionary definition: wbs 6.2.5 refers to the loading of assembled...

WBS 6.2.5Stave Assembly

Gabriella Sciolla

L3 Subsystem Manager

Brandeis

U.S. ATLAS HL-LHC UpgradeDOE Independent Project / CD-3a Review

Brookhaven National LaboratoryUpton, New York July 9-11, 2019

Outline

• Deliverable Overview

• Technical Progress and Plans Progress since CD-1

Remaining work for CD-2

ES&H

Quality Assurance and Control

• Cost and Schedule CD-3a Needs

• Risk Main Deliverable Risks

External Dependencies

• Closing Remarks

G. Sciolla, ITK Stave Assembly US ATLAS HL-LHC DOE IPR/CD-3a, July 9-11, 2019, BNL 2

Deliverable Overview

Stave Assembly Deliverables

Stave assembly is the last step in the production of the ITk Strip staves before the detectors are shipped to CERN

In production, 196/206 staves will be assembled at BNL FY21-24 50% of the ATLAS barrel strip detector

Receive and re-test components Stave cores from Yale

Modules from BNL/LBNL/SCIPP

End of Stave card from DESY

Stave assembly Positioning and gluing of modules on cores with 50 μm precision

Wire bonding

Staves testing Both mechanical and electrical testing

Shipping to CERN Staves received + tested before releasing them to international ATLAS


From the WBS dictionary

WBS number: 6.2.5 WBS Title: Strips Tracker Stave Assembly

WBS Dictionary Definition:

WBS 6.2.5 refers to the loading of assembled modules (6.2.4) onto the stave cores (6.2.1) for the barrel part of the ITk silicon strip tracker as well as to the final mechanical measurement and electrical testing of the loaded staves.

The ITk barrel detector consists of 392 staves configured in 4 readout layers. Each stave carries a total of 28 modules, 14 modules on each side. The US will deliver 196 working staves to the ATLAS tracker. All the assembled and tested modules built in the U.S., which correspond to 50% of all barrel modules, will be shipped to BNL where they will be mounted on stave cores. Also affixed to the stave will be an End-of-Stave (EOS) card supplied by a non-US institution. The module mounting process will use a custom-programmed XYZ stage to place and survey each module on the stave core. Once all modules are placed and glued, they will be wire bonded and put through an electrical test and final burn-in process. Quality assurance and testing will be provided at all stages.

Brookhaven has the primary responsibility to provide technical resources, space, and supplies.Brandeis University manages the stave assembly and provides most of the labor associated with programming the XYZ stage and testing the loaded staves. Harvard University and University of Pennsylvania participate in various tasks related to the stave assembly, in particular DAQ and testing.

6

US Organization at L4


6.02 ITk StripsL2M: C. Haber (LBNL)

Deputy: G. Sciolla (Brandeis)

6.02.01 Stave CoreL3M: J. Ashenfelter (Yale)

6.02.04 ModulesL3M: G. van Nieuwenhuizen

(BNL)

6.02.01.01 Cores LBNL

IC: C. Haber (LBNL)

6.02.03 HybridsL3M: A. Ciocio (LBNL)

6.02.02 Readout Electronics

L3M: E.Thomson (Penn)

6.02.05 Stave Assembly

L3M: G. Sciolla (Brandeis)

6.02.01.05 Cores YaleIC: J. Ashenfelter (Yale)

6.02.01.06 Cores Iowa

IC: S. Prell (Iowa St)

6.02.02.01 DCS/LV/HV

IC: D. Lynn (BNL)

6.02.02.02 Power BrdIC: J. Joseph (LBNL)

6.02.02.03 ABC*,HCC*,AMAC

IC: J. Kroll (Penn)

6.02.03.01 Hbrd BNLIC: A. Tricoli (BNL)

6.02.03.02 Hbrd LBNLIC: A. Ciocio (LBNL)

6.02.03.04 HbrdUCSC

IC: A. Affolder (UCSC)

6.02.04.01 Mdls BNLIC: G. van Nieuwenhuizen

(BNL)

6.02.04.02 Mdls LBNLIC: A. Ciocio (LBNL)

6.02.04.04 MdlsUCSC

IC: A. Affolder (UCSC)

6.02.05.01 Stave BNLIC: D. Lynn (BNL)

6.02.05.03 Stave Penn

IC: M. Newcomer (Penn)

6.02.05.08 Stave Harvard

IC: M. Morii (Harvard)

6.02.05.09 Stave Brandeis

IC: G. Sciolla (Brandeis)

6.02.02.04 ABC*,HCC*

IC: A. Grillo (UCSC)

6.02.02.05 DC-DCIC: J. Ashenfelter (Yale)

6.02.01.10 Cores Mass

IC: C. DallaPiccola(U.Mass)

6.02.04.07 Test Duke IC: M. Kruse (Duke)

6.02.04.10 Test Mass IC: C. DallaPiccola

(U.Mass)

Many in this community have collaborated since mid-1990’s. The 11 institutions are now tightly linked since formalizing these specific roles and responsibilities beginning in 2015.

6.02.04.11 Test IowaIC: U.Mallik

(U.Iowa)

CQ.3

Experience of the Team

Institute Members Past Experience Relevant to this Deliverable

BNL D. Lynn ITk strips since 2008; Former local support activity coordinator; HV Mux leader; General strips R&D

Gerrit van Nieuwenhuizen

WA98 Silicon Drift Detectors, PHOBOS Silicon Detector, STAR Intermediate Silicon Tracker, ATLAS ITk since 2015

P. Kuczewki, Senior Electronics Tech, STAR Silicon Vertex Tracker, ITk Strips, HV-Mux

R. Burns Senior Mechanical Tech, ITk strips since 2010, stave core R&D

C. Musso Electronics tech, wirebonding, 3D detector wirebonding and testing

Brandeis G. Sciolla BaBar Drift Chamber; Directional Dark Matter Detectors R&D; ATLAS Muon System; ATLAS ITk since 2017

A. Duskin Mechanical engineer with >20 years of experience in ATLAS; Designed alignment for ATLAS Forward MDTs; LZ; ATLAS ITk since 2018

Harvard M. Morii Electronics for Kaon experiment at KEK; OPAL calorimeter; BaBar Drift Chamber; LUX; ATLAS Muon; ITk since 2017

S. Sansone Manager of Harvard Physics Dep. machine shop; ATLAS MDT; LSST

Penn Engineering team

Designed ITk chips!


Stave Assembly Overview

XYZ stage used for mounting,

gluing, and surveying modules

Stave mounted in assembly frame fixed to granite table.

System of computers/monitors

for real time feedback

Mounting bridge

Automated glue dispenser

Camera


Stave Testing Overview (2)


Temporary testing station

Example of testing code

Pelican case used for shipping

Technical Progress & Plans

Stave Assembly Project at a glance

• TM prototype: 1 full stave (FY17-2018)

• Electrical prototype: 1 stave with 3 electrical modules (FY18)

• Pre-production 1 (FY18-19) 2 x SS 13-modules electrical staves

ABC130 chipset, 13-module bus tape design

• Pre-production 2 (FY19) 2 x LS 28-modules electrical staves

New: *chipset and 14-module bus tape design

• Pre-production 3 (FY20) 9 x 28-module electrical staves, LS+SS

o Final electronics and stave cores

o Opportunity to finalize system and ramp up for production

• Production (Apr 2021-Jul 2024) Starting in April 2021


2018 Director's Review

CD1

2019 Director's Review

Huge amount of progress since CD1!

We are on track to meet Project’s goals

CQ.1

2019 CD3a

Technical progress since CD1:

Electrical Prototype -- “Stavelet”


• Spring 2018: Completed assembly of first electrical prototype 3 electrical modules on a 13-module core

First read out using ITSDAQ

First measurements of noise, gain, etc.

Technical progress since CD1:

PP1-Stave1

• Assembly completed in Sep 2018 Loaded with 12/13 electrical modules

ABC-130 chips, first EoS card from DESY

• Deployed new volumetric glue dispenser ≈ 2 min, down from ≈ 8min

• Read out and electrically tested Results of noise, gain, etc. measurements according to specs

• Metrology results according to specs

• Shipped to RAL for first system testG. Sciolla, ITK Stave Assembly US ATLAS HL-LHC DOE IPR/CD-3a, July 9-11, 2019, BNL 15

New glue dispenser

PP1-Stave1

Technical progress since 2018 DR:

PP1-stave2


• PP1-stave 2 completed in May 2018

Loaded with 13/13 electrical modules (130 chipset)

• Deployed new Brandeis bridge to mount modules

Successfully tested parallel module mounting and glue dispending 2 modules/syringe

• First modules successfully read out and tested

• Will be used at BNL to perfect testing procedures

PP1-Stave2New Brandeis bridges

Remaining Work for CD-2

• Pre-production 2 2 x LS 28-modules electrical staves

o New: *chipset and 14-module bus tape design

Stave 1 – IMPORTANT as it is the basis for Local Support FDR o June-July : prep work for new stave core, assembly frame, LS sensors, bridges, EoS

o Aug: assemble and test side A

o Sep-Oct: assemble and test side B

– NB: first time slave EoS will be used!

o Nov: prepare for FDR

o Dec 2019: Local Support FDR

Stave 2 – Goal: improve assembly and testing procedures o Nov: assemble and test side A

o Dec: assemble and test side B

• Pre-production 3 (FY20) Preparation for PP3 will start early 2020 and by CD2 PP3 will be in full

swing… RAMP UP ETC.


Demonstration of assembly methods and

completion of fully functional detector

component with ~ final components

ATLAS Reviews for Stave Assembly

Technical reviews at CERN include

Preliminary Design Reviewo Passed in Oct 2018

o Topics reviewed: stave/petal cores, the mounting of modules/EOS, and the electrical/thermal/mechanical evaluations of the loaded staves/petals

Final Design Reviewo Schedules in ~ December 2019

o Review will be based on assembly and testing of PP2-Stave 1 (US deliverable)

Production Readiness Reviewo Expected date: Late 2020

o Once passed, production can start!


CQ.7

ES&H for Stave Assembly

• Safety is of the highest priority within the Project Work at each institute adheres strictly to its ES&H policies

The BNL ES&H Liaison (L. Stiegler) provides oversight and advice

Institute contacts act as interfaces between their institute and BNL

• Hazards in Stave Assembly are pretty low risk Robotic machinery (XYZ stage); mitigation: interlocks, barrier, ES&H training

Glues; mitigation: gloves and eye protection, ES&H training


CQ.6

Institute Institute ES&H Contact

BNL Achim Franz ([email protected])

Brandeis Andrew Finn ([email protected])

Harvard Tiffany Lee ([email protected])

Penn Kimi Bush ([email protected])

Cost and Schedule

RLS Changes Since CD-1

• The RLS has been quite stable since CD1 With the exception of some shifting of tasks due mainly to availability of

parts (mainly ASICS)o In sync with the international ATLAS Schedule

Overall impact on schedule is minor o Recovered later start in production by decreasing the duration of batches

o Last stave delivered at CERN: Aug 2024 (CD1) July 2024

Overall change in budget is contained o +200k$ (after 2017 actuals are correctly taken into account)

• Budget changes described and approved in BCP-005 Total impact on this L3 system was +3% of the total L3 cost

• Main reasons for cost increase Need for additional cleanroom space at BNL during production

o ~50k$/year * 4 years + overhead


CQ.2

Cost Profile


FY17 FY18 FY19 FY20 FY21 FY22 FY23 FY24

BCWS

ENG 21,141 236,299 169,050 136,349 144,421 100,006 112,830 79,430

EQUIP 180,927 419,977 269,601 158,207 162,958 167,849 172,882

MAT 2,124 49,038 64,427 352,828 396,957 210,566

STU 2,128 356

TECH 189,723 153,357 132,302 145,646 358,272 550,009 562,614 402,945

TRAVD 8,050 12,212 9,448 11,566 7,119

TRAVF 5,783

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000Total Cost by Resource Category

FTE by resource category


In Stave Assy: Labor is 50% On-Project and 50% Scientific Labor

• Scientific labor mainly students/postdocs/faculty from Universities

• In principle vulnerable to funding of University Research Grants

• We are hopeful that DOE will continue and reward the University’s

substantial contribution to the success of the project

FY17 FY18 FY19 FY20 FY21 FY22 FY23 FY24 FY25

Y-FTE

ENG 0.23 2.44 1.22 0.90 1.47 1.27 1.49 1.00

SCI 1.32 2.49 1.54 1.66 2.61 3.11 3.50 2.55 0.20

STU 0.06 0.01

TECH 0.93 0.81 0.67 0.71 1.68 2.54 2.52 1.75

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

Axi

s Ti

tle

FTE by Resource Category

Strips Schedule – Stave Assembly


We are here

Critical Path? No Stave Assembly is not on the Critical Path until the very end of the project

In production, schedule driven by hybrids/modules production

Milestones


CERN key dates:

Due at CERN: Oct 1, 2024

Float: 62 days (3 calendar months): gained ~ 2 months of float

Aligned with International ATLAS Schedule

Lowering in the pit starts on 4/1/2025

Milestone Date in P6

End of pre-production 2 1/23/20

End of pre-production 3 3/29/21

10% of staves delivered at CERN 1/4/22



Long Lead Procurements


WBS Activity ID Activity Name Date Trigger By Review Date Days After

Material

(AYk$)

6.02.01 Stave Core

LBNL SC200510M Material Payment for Co-Cure Batch 1 of 12 Facings (Remainder are Shipped to UK)9/8/2020 PRR 6/18/2020 82 48

SC200720M Material Payment for Co-Cure Batch 4 of 25 Facings (Remainder are Shipped to UK)12/21/2020 PRR 6/18/2020 186 51

Yale

SC200474M Material Payment for Ordering Production Bus Tapes (FY19) 8/19/2020 PRR 6/18/2020 62 33

SC200475M PMT: Material Payment for Ordering Production Bus Tapes (FY20) 8/20/2020 PRR 6/18/2020 63 445

SC500890M Material Payment for Assembly Line & Tooling Procurement and Fabrication-Second Assembly Line11/11/2019 FDR 10/18/2019 24 76

SC501204M PMT: Material Payment for Order, Receive, Inspect Batch of Honeycomb (Ultracor)2/6/2020 FDR 10/18/2019 111 163

SC501210M Material Payment for Order, Receive, Inspect Batch of Foam Blocks-Single Source (ALLCOMB)2/21/2020 FDR 10/18/2019 126 54

6.02.02 Readout Electronics

BNL RE140420M Material for QC Testing Setup 1/17/2020 FDR 9/13/2019 126 61

RE140450M Material for QC Testing 5/11/2020 FDR 9/13/2019 241 5

RE140470M Material for Packaging Devices for Irradiation 6/9/2020 FDR 9/13/2019 270 5

RE140530M Material for Post-Irradiation Testing 10/13/2020 FDR 9/13/2019 396 3

LBNL

RE261330M Material for Production PCB Order Part 1 1000 8/28/2020 PRR 8/27/2020 1 13


RE261350M Material for Production Passive Components Order 8/28/2020 PRR 8/27/2020 1 68

RE261370M Material for Production Shield Box Order 8/28/2020 PRR 8/27/2020 1 128



RE261380M Material for Passive and Active Test Board Order 9/30/2020 PRR 8/27/2020 34 77

RE261420M PMT: Material Payment for Load Boards Production 2/19/2021 PRR 8/27/2020 176 800

RE261425M Material for Load Production Active and Passive Test Boards 11/16/2020 PRR 8/27/2020 81 10

RE261430M PMT: Material for Production Test System 12/31/2020 PRR 8/27/2020 126 196

Yale 0

RE530450M Material Payment for Coils 11/29/2019 FDR 9/13/2019 77 109

6.02.03 Hybrid Assembly

LBNL HA24200M PMT: Common Items (Wire, Jigs, Fixtures) Plus Some Lab Equipment (Vacuum Pumps, Chiller)9/11/2019 FDR 9/13/2019 -2 172

HA260038M Material Payment for Hybrid Panels 11/7/2019 FDR 9/13/2019 55 47

HA260298M Material Payment for Hybrid Panels 11/5/2020 PRR 8/27/2020 70 98

6.02.04 Module Assembly

BNL MA162420M Material Payment in Preparation for Production 3/15/2021 PRR 8/27/2020 200 17

LBNL MA25350M Material Payment in Preparation for Production 3/15/2021 PRR 8/27/2020 200 16

UCSC MA45350M Material Payment in Preparation for Production 3/15/2021 PRR 8/27/2020 200 23

6.02.05 Stave Assembly

BNL SA190004M PMT: Payment for Glue Dispenser Consumables for Production Year Periods 1 - 46/30/2020 FDR 10/22/2019 252 149

6.02.07 US Contributions to CERN Procurements-BNL

BNL RE140400M PMT: Material Payment for Fabrication Order of All HV MUX Devices 1/17/2020 FDR 9/13/2019 126 895

RE261405M PMT: Material Payment for Production BPOL12V from CERN 6/2/2020 FDR 9/13/2019 263 210

RE310390M PMT: Material Payment for Production by CERN 6/18/2020 PRR 6/18/2020 0 853

RE321030M PMT: Material Payment for Chip Production Order 7/8/2020 PRR 6/18/2020 20 473

Grand Total 5,360

Long Lead Procurements Drill Down

• One long lead procurement for SA: glue dispenser disposable parts

• From BoE:


NB: direct cost

Why is it needed?

• We have been using this glue dispenser for about 1 year It took some work to optimize, but eventually obtained very

satisfactory performanceo Gluing time went from ~ 10 min/module to ~ 2 minutes per module

• Our only worry is that over the years the manufacturer may stop producing the disposable parts Getting a new glue dispenser and re-optimizing gluing procedure

would generate substantial delays (and unnecessary costs)

• Simple solution Buy all disposable parts before production starts instead of diluting

the purchase over the years

Not a huge item: 122k$ (direct)

• Local support FDR will review the assembly procedure: December 2019


CQ.5

Risk Management

Risk Overview for Stave Assembly


Risk Description: Risk 6.2.5.2

US ATLAS HL-LHC DOE IPR/CD-3a, July 9-11, 2019, BNL 35

WBS 6.2.5 Type Threat Risk ID RD-06-02-05-002

Status Active

Expires 3/18/2024

Title Underestimation of yield of staves

SummaryThe assumption on the yield for loaded staves (95%) may be too optimistic. Additional loaded staves may be lost due to mechanical failure (e.g.: the cooling pipes break) or electrical failure (e.g.: staves are unreliable, noisy, or have bad data transmission performance).

Owner Carl Haber

Probability Pre 10% Post 3%

Cost Lo $200K Hi $2,000K

Schedule Lo 0.5 Hi 2.0

Tech Impact 0(N)

Post Mitg Prob 1(VL)

Impact Score Cost 3(H) Sched 1(L) Rank=70

MitigationRe-test all components (modules and cores) before starting the assembly; carefully follow the procedure and apply a stringent Q&A during the stave assembly. Thorough testing of the staves needs to be performed as soon as production is completed or at completion of each side.

ResponseIf a problem is discovered after the stave is fully loaded, the stave will be tested thoroughly to understand the

origin of the failure. If the problem is found to be in the stave core, the entire stave may be lost. In this case, the cost will be substantial

CommentsAveraged over the entire project cost ($40M) for 200 staves, the cost/stave is $0.2M. The high side cost is assuming

10 lost staves in addition to the assumed yield

Phase Effected Pre-production/Production

G. Sciolla, ITK Stave Assembly

External Dependencies

• Stave Assembly schedule is tightly linked to:

Availability of parts

o Mainly modules and stave cores (internal dependencies) Main constraint

o EoS cards from DESY (external dependencies)

International ATLAS schedule (external dependencies)

o Minor constraint

• External dependencies are contained

Availability of EoS cards

o Slow start in preproduction

o Production: we expect all EoS to be delivered within the first 2 months

Review dates (PDR, FDR, PRR)

o More complex dependencies than you’d think because these are joined

reviews with stave cores and petals (both cores and assembly)

G. Sciolla , ITK Strips – Stave Assembly Director's Review, May 14-16, 2019, BNL 36

CQ.4

Closing Remarks


1. Stave Assembly has made substantial progress since CD1 Completed electrical stave and PP1 (2 half staves)

Starting PP2 now; will start PP3 in 2020

On target to start production in 2021: will build 50% of Strips Barrel staves (196) in FY21-24

2. RLS is in good shape and the risk register is up-to-date

Float is 3 calendar months

3. Strong team with good complementarity between BNL and Universities

BNL provides mostly technical manpower and infrastructure

Universities provide mainly physicists for s/w development and stave testing

4. Dependencies mainly internal (modules, cores)

External dependency on EoS resolved at the very beginning of production

5. One long lead procurement (glue dispenser disposable parts) will eliminate risks

6. ES&H: no major danger in Stave Assembly, but all procedures are in place

7. Before CD2: successful completion of PP2-stave 1 28-module LS stave with star chipset

BACKUP

Bio Sketch of L3 Manager

Gabriella Sciolla, Professor of Physics, Brandeis University

• Member of ATLAS since 2011

• ITK responsibilities

US ATLAS Level-2 Strips Tracker Upgrade Construction deputy manager

L3 manager for stave electrical assembly (5.2.5)

Group heavily involved on stave assembly at BNL

• Other ATLAS roles

Muon Combined Performance Convener (2014-2016)

US Physics Advisor (2013-present)

• Selected committee activity:

HEPAP, Fermilab PAC, SNOLab Board of Directors, SNOLab Science and Technical Review Committee, CPAD

• Previous experiments: DELPHI, BaBar, DMTPC

G. Sciolla , ITK Strips – Stave Assembly CD1 Review, July 10-12, 2018, BNL 39

Risk Register (Stave Assembly)


CQ.2

From DocDB 196-v21

Risk Register (2)


Risk Register (3)





Status Active

Expires 3/18/2024

Title Problem with adhesive used to glue modules to stave.

SummaryModules are attached with SE4445, a removable thermal silicone. This has been used extensively in the past. We could run into a problem with the use of this adhesive in large-scale production.

Owner Carl Haber


Cost Lo $48k Hi $192K

Schedule Lo 1 Hi 4

Tech Impact 0(N)

Post Mitg Prob 3(L)

Impact Score Cost 2(M) Sched 2(M) Rank=60

MitigationCareful QA on each batch of glue measuring the pull, peel, and shear strength to ensure that the specifications are met.

Response Get a new batch of glue and test again before using

CommentsIt takes a substantial amount of time to get a new batch. Max cost impact is due to 2 months of delay in the stave assembly schedule.






Status Active

Expires 3/18/2024Title Stave does not meet electrical specification due to bad modules

SummaryModules are tested before being mounted on the stave. None-the-less some staves may be found to be electrically unreliable or noisy due to defective modules or modules not properly wirebonded.

Owner Carl Haber



Schedule Lo 1 Hi 2

Tech Impact 0(N)


Impact Score Cost 1(L) Sched 1(L) Rank=20

Mitigation

Re-test modules before mounting them on the staves; carefully follow the procedure and apply a stringent Q&A during the stave assembly. Thorough testing of the staves needs to be performed as soon as production is completed or at completion of each side.

Response

If a problem is discovered, the stave will be tested thoroughly to understand the origin of the failure. If the problem is in a single module or electronics component, the stave will be set aside and the component(s) will be replaced at the end of Production.

CommentsThe cost impact calculation takes into account the cost of the additional electronics components and of the manpower necessary to diagnose and fix the problem






Status Active

Expires 1/7/2021Title End of Stave (EOS) card is delayed Summary The EOS is a German deliverable. It could be delayed

Owner Carl Haber



Schedule Lo 0 Hi 0

Tech Impact 2(M)


Impact Score Cost 1(L) Sched 1(L) Rank=20

MitigationWe will prepare a dummy version of the EOS which will allow us to test the stave electrically and then be replaced with the EOS when it arrives- extra PP3 version

Response The dummy versions will be installed and staves will be tested this way.

Comments

IT will take between $10k and $20k to build the dummy EoS. The impact to the schedule is negligible because the EoS cards will be all produced at the beginning of production. Even if they were late by a few months, we will be able to reabsorb the delay in the schedule.

Phase Effected Pre-production/Very beginning of Production


Schedule for one Batch in Production

From BoE:


How long does it take to make a batch, what it takes too

Cost Estimate Type


27%

27%

46%

0%

6.02.05 Stave AssemblyESTIMATION TYPE

Existing PO, Work Complete

Extrapolating from Actuals

Analogy

Expert Opinion

• Labor estimates are from recent experience in ITk Strip prototype construction as well as past experience building the SCT ATLAS detector (mainly Analogy)

• Estimates for equipment and material comes from quotes, recent purchases, and past experience (mainly quotes Extrapolating from Actuals)

Equipment and materials: quotes

Labor: past experience

wbs 6.2.5 stave assembly · wbs dictionary definition: wbs 6.2.5 refers to the loading of assembled...

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