pipe joining techniques for phase 2 upgrades high-pressure ... · pipe joining techniques for phase...

Pipe joining techniques for Phase 2 upgrades high-pressure systems -Summary report from CERN’s 18th of May 2018 workshopJEROME DAGUIN – PAOLO PETAGNA

T H AN KS T O : G E O R G V . , F R ITZ M . , A N TT I O . , K A R OL R . , B A R T V . , P A U L K . R . , P I E R R E D . , A L L E N Z . , P E TER R . , H A N S P . , C H I - MEN G L .

25.06.18 JÉRÔME DAGUIN - CERN 1

Outline

CERN’s 1 day workshop

Context of Ph2 upgrades

Leak tightness and reliability

The joining techniques

◦ Brazing techniques

◦ Welding techniques

◦ Fittings

Conclusion


CERN’s 1 day workshopPIPE JOINING TECHNIQUES FOR PHASE 2 UPGRADES HIGH-PRESSURE SYSTEMS


CERN Workshop – 18th of May 2018


https://indico.cern.ch/event/721360/overview

1 full day

8 talks

≈ 60 participants

Mailing list created (contact me if you want to be added)

“The workshop is intended as an informal and

open discussion on all the aspects of joining

techniques for CO2 cooling system piping,

including fittings, welded joints, brazed joints

and special connections involving electrical

breaking.”

https://indico.cern.ch/event/721360/overview

Context of Ph2 upgrades


The ATLAS iTK Ph2 upgrade


Pixel outer barrel

Pixel inner systemPixel outer endcap

Strip barrel

Strip endcap

392 CLs

158 CLs

384 CLs

108 CLs

? CLs

>1000 cooling

loops

>10000 pipe

connections of all

types

The CMS TK Ph2 upgrade


TBPS Flat/Tilted

109 CLs

TB2S

124 CLs

>600 cooling

loops

>10000 pipe

connections of all

types

TEDD

280 CLs

TBPX/TFPX

104 CLs

TEPX

32 CLs

Ph2 upgrades numbers

CMS TK + EC is around 500kW

ATLAS iTk is around 250 kW

CO2 at -35°C or below

PS= 130 bar

Ptest = 186 bar



No gas vessel (pipe, etc.) is absolutely leak tight

◦ And actually it does not need to be

The leak rate must be low enough that the required operating pressure is maintained and that the lost fluid is not doing any damage to the environment or incurs a large financial loss

All estimates must be seen in the context of the system size (number of joints)

For what we need r<10-4 mbar.l.s-1 (He) is entirely adequate

◦ Which is (relatively) easily achievable…



Reliability is the real challenging requirement we need to achieve in our systems!

◦ This is what:

◦ During installation costs money, time and nerves

◦ During operation costs acceptance

How do we quantify reliability ?

◦ By a failure rate

We need to establish

◦ What failure rate do we need ?

◦ How can we establish this performance for a given design/part ?



A verification for system larger than 10-100 fittings is beyond our means…

◦ Use industry standards connection techniques as much as possible

◦ They have much larger use statistics

◦ The problem is that for the tube dimensions we aim for, there is no industry standard – not even for brazing or welding

◦ In the qualification think carefully about the loads for which the joining technique needs to be qualified and perform control tests using these loads

◦ Include tests at increased stress level to find faults without the need of excessive statistics


Pass/fail test sample size to demonstrate a failure rate of 1 in 10,000

Reminder:

PS=130 bar

Ptest on site = 1.44 x PS = 186 bar

Ptest in lab for qualifications = 2 x PS ? = 260 bar ?

Brazing techniques


Soldering/BrazingJoining of two components with a brazing filler material (BFM), whose liquidus temperature is below the melting point/range of any joined component◦ No melting of the component material

Soldering of stainless steel/copper:◦ Typically used SnAg3.5 (ISO 9453 S-Sn96Ag4; Tliq = 221°C), Rm ≈ 25 MPa

Brazing at high temperature of stainless steel/copper:◦ Typically Ag-based filler metals, i.e. AWS BAg-7 (Tliq = 650°C), Rm ≈ 400 MPa

SolderingTl_FM < 450°C

BrazingTl_FM > 450°C


Brazing techniques

Classified by heating technology:


Brazing techniques – Manual brazingManual Brazing at Atmosphere

•Heat Sources: Flame Torch (Acetylene), Induction, (Plasma, Arc…)

•Working Temperature of common filler metals: 600-800°C• Steel/Stainless Steel, Copper Alloys: I.e. AgCuZnSn

(650°C)

•Application of flux necessary to remove surface oxides

•Brazing of tube fittings:• Lap joints (5-10 mm overlap, rule is min. 3x Wt)

• Gap clearance of joint 0.1-0.2 mm on diameter

• Manual process, individual qualification of personnel necessary


Brazing of CMS Pixel Ph1 tubes in CERN EN/MME workshop

Brazing techniques – Manual brazingManual Brazing at Atmosphere

Preparation of components:• Cleaning/Etching (Surface treatment)

• Application of flux on brazed surfaces

• Assembly and possible inertion for tubes (Ar-flush inside) to avoid oxidation on the inner wall

• Brazing material normally applied as rods/wires

• Brazing with avoiding overheating (can change viscosity of filler, incrusting of flux)

Post treatment:• Cleaning/removal of flux from components. Mechanically and cleaning with detergent/warm water

(surface treatment)

Flux contains components as KF, Borates etc. -> corrosive!

• Visual inspection

Precautions:

• Ventilation of fumes (flux) which can condense on surrounding surfaces


Brazing techniques – Vacuum brazing

General features of vacuum brazing

Assemblies brazed in vacuum chambers (10-2 mbar…10-7 mbar)

Parts have to be clean (outgassing, pollution) and principally oxide-free (wetting properties)

Heating performed by radiation, induction, (laser, microwave, EB..)

◦ Most common technology: vacuum furnaces with resistor heaters

Use of vacuum compatible filler-materials (no volatile components at corresponding brazing temperatures)

◦ Most common BFM for vacuum brazing:

◦ Silver-Copper alloys (780-950°C)

◦ Gold-Copper alloys (950-1050°C)

◦ Nickel-based alloys (1000-1200°C)



Advantages of vacuum brazing◦ No flux used/necessary

No residual fluxing agents have to be removed/cleaned after process, no risk of corrosion induced by remaining flux (mostly acids containing fluorides and/or chlorides)◦ Brazed parts stay clean and no oxidation

occurs during brazing processBesides flux has not to be removed, the surfaces stay clean and metallic (applications for UHV and RF-cavities)

Specifically for furnace brazing:◦ Low distortion of assembled pieces due to

homogeneously heated partsHigh precision assemblies maintain their geometry and alignment

Disadvantages of vacuum brazing◦ General high costs:

◦ Vacuum furnace equipment

◦ Only batch production possible

◦ Preparation of all assembly parts necessary (surface treatment)

◦ Vacuum grade filler materials more expensive

◦ Long brazing cycles (up to few days from cold to cold)

Specifically for furnace brazing:◦ Complete assembly has to be heated

Due to high brazing temperatures material properties will be influenced by the heat treatment (annealing, grain growth, diffusion/precipitation)

◦ Complex preparationFixed placement of filler material, fixed positioning of assembly parts has to be assured




SS-copper transition

for dielectric

SS-SS direct brazing of

VCR-connector to capillary

ss-copper transition for

subsequent orbital welding

Brazing to ceramic

with Cu-sleeves

Assembly sequence:

1. Brazing copper sleeves to capillary/tube

2. Brazing of VCR-connector (with nut) or welding fitting

3. Final assembly with dielectrics

Usage of three different BFM with decreasing melting range

Inlets SS-capillaries (Øo1.6mm and Øo2mm)

Return copper pipes (Øo5mm)

Qualific

atio

n s

am

ple

s fo

r US

-inspectio

n

US-imaging of SS-Cu transition

Assembly of capillaries for CMS PIXEL Ph1 upgrade

Brazing techniques - Soldering

Soft soldering was used for the CMS Tracker Outer Barrel piping connections

◦ Single phase C6F14 cooling with max 6 bar

◦ Copper-Nickel pipes 2.2/2.0 and 2.5/2.3

◦ Joint sleeve in brass

◦ Soft solder from CERN store: Multicore SnPbAg 62/36/2 with core flux (ERSIN 362)

Final soldering was done in situ (≈50%)


Tip of the soldering iron

machined to a concave

shape for increased

thermal contact area to

the pipe and the brass

pieceSoldering iron with fume extraction tip

Developments are on-going for soft-

soldering of SS pipes

Welding techniques


NASA welding methodSelecting the right welding parameters for automatic welding

2325.06.18 JÉRÔME DAGUIN - CERN

The Low-Limit / High limit method is a good method to select the

nominal welding parameters and assure that possible fluctuations do

not bring the series welds out of spec.

Welding power

Not fully penetrated To much penetration Full penetration (all good welds)

Low limit weld High limit weldNominal limit weld

Weld

sa

mp

les

NASA welding methodCertification procedure

Each welding type is pre-qualified with weld samples◦ 5 Low limit welds, 5 nominal welds and 5 high limit welds.

◦ From each weld group the following tests are done to qualify the quality

◦ All visual inspection (in and outside), all should look similar

◦ 1 burst test (>4x design pressure)

◦ 1 longitudinal cut and microscopic analyses

◦ 3 samples for further research if needed

Production of a series of welds◦ 3 high, 3 low and 3 nominal pre welds samples.

◦ All process welds done at nominal settings

◦ 3 high, 3 low and 3 nominal post welds samples.

◦ The pre and post weld samples are send to NASA for inspection

◦ 1 burst, 1 microscopic and 1 spare for each type

◦ All process welds are inspected visually and compared with post and pre weld samples.

◦ Dye penetrant tests on process welds

Due to the automatic welding and the similarity of all welds, no further complex inspection of the welds is needed

2425.06.18 JÉRÔME DAGUIN - CERN

Welding techniques – Orbital welding

Orbital welding on SS or Ti is standard and “easy” down to 1/8” and 200µ/300µm Wt

Massively used in all systems in operation and under development

Requires careful alignment, good pipe preparation and Ar protection


SWAGELOK M200 Orbital welder setup

@ Sheffield

CMS PIXEL Ph1 Supply manifoldLHCb VELO cooling blocks

Welding techniques – Orbital weldingOrbital welding below 200µm Wt is more tricky…◦ CMS Ph2: 2.5OD/150µm Wt Ti tubes

◦ ATLAS Ph2: 2.5OD/180µm Wt Ti tubes

Tube cutting, preparation and alignment extremely difficult for butt welding of thin wall tubes◦ Sleeve welding reduce difficulty

Machine stability at low current is essential for thin wall tubes welding◦ Such machines are not available OFF-the-shelves in industry

◦ Sheffield developed their own machine with VBC company

◦ Can weld down to 125µm Wt Ti tubes

◦ Argonne is proposing to add thickness welding a sleeve together with the tube

◦ Enables better alignment as well !


Cross section through 2.5mm x 0.178mm wall

tube and sleeve fitting at welded joint area

Butt

weld

Sleeve

weld (filet)

vbc IP50

Fittings


Fittings – VCR typesStainless steel fittings with metal seal◦ Can be re-used (almost) indefinitely – gasket need to be changed

◦ Extremely reliable

◦ Leak tight

Available for pipe sizes of 1/8”, 1/4”, 1/2”, 3/4” and 1”

Many suppliers on the market since couple of years◦ Swagelok, Rotarex, Hamlet, Fitok… and even Hikelok on ALIBABA !!!

Female nut silver plated to prevent galling when tightening

Don’t exist for tubes smaller than 1/8”◦ Drilling of blind glands + brazing allows for use with smaller pipes

Connection is quite bulky…


Fittings – Custom design


Laser-welding between

gland and tubing

Identical

glands

¼” hex male nut M5.5 x 0.9

threads

Aluminum gasket being captured

inside the male nut

¼” hex female nut with M5.5 x

0.9 threads

OD 2.2 mm, wall 0.1 mm

304L ss tubing

Enhanced version for Ph2 TBPX/TFPX

CMS PIXEL Ph1 FPIX design Fixed male nut induced torque transfer

to tube during tightening and self

untightening during

pressure/temperature cycles in the

assembly phase

CMS PIXEL Ph1 BPIX design

ATLAS IBL LAPP design

Electron Beam welds

Fittings – Custom design

Material choice and welding parameters are essential when designing such fittings

◦ Hot cracking issues in the development phase of the FPIX Ph1 fittings (See Stephanie T. talk in Bonn in 2016)

https://indico.cern.ch/event/469996/contributions/2148019/attachments/1277061/1895241/FPIX_Laser_Welding_Bonn_Forum_2016.pdf

Design is not as simple as a scale down of SWAGELOK VCR design…

◦ Small size induce new constraints (tightening torque, torque transfer…)

Since our sampling capacity is limited, testing and validation parameters should be much more constraining than operational parameters

◦ PS=130 bar

◦ Ptest on site = 1.44 x PS = 186 bar

◦ Ptest in lab for qualification = 2 x PS ? = 260 bar ?


https://indico.cern.ch/event/469996/contributions/2148019/attachments/1277061/1895241/FPIX_Laser_Welding_Bonn_Forum_2016.pdf

Fittings – Large sizes

Phase 2 plants will need up to 2” pipes◦ Anything above 1” cannot be done with VCR

Standard flanges available in DIN, ANSI or B10 dimensions◦ Outside diameter of flanges 184 – 216 mm for DN50

◦ Generally too big for our installations…

SAE flanges used for high pressure hydraulic up to 400 bar (6000 PSI)◦ O-ring replaced by CF copper gaskets

◦ Testing foreseen at CERN in the coming weeks

Compact flange option to be investigated◦ Described in the NORSOK standard

◦ Used in Oil and Gas industry


Conclusions

We are about to build (very…) large systems with (very…) large number of connections of all types

Wide range of joining techniques available

◦ Make the good choice based on the detector constraints

◦ Take it into consideration in the early phase of the design

This is a bit more than just plumbing…


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