Investigation on flexible hoses in DFBAs

L. Tavian21 July 2009

With the contribution of B. Vullierme, EN-MME

Today situation

• Detection of news leaks in the vicinity of two DFBAs (L1 & L3) with symptoms identical to the leaks found in the S4-5 in 2007 in flexible hoses.

• The probability of new flexible-hose damages is high.

S4-5 case reminder

Flexible hose LHCDFBA_0114

Line N in DFBAH HCM

CL line

Fixed pointapprox 3.2 m

S4-5 case reminder

TS-MMEanalysis

TS-MMEanalysis

Coloration visible à l’intérieur de l’onduleux

TS-MMEanalysis

2007 investigation conclusion• The defects have been produced after the braid installation.

– Multiple fusion points on the top of the corrugation equally distributed over 360°. (Affected length 10 cm).

– No mixing of materials (braid vs corrugation)– Identification of several leak holes (min 3)– No visible oxidation.– No trace of mechanical wearing– No trace of chemical elements– No damage in between braid layers

• Present most probable cause: Electrical phenomenon– Extremely short (<5ms) or without oxygen or with a cleaning after the defect

creations.– Today this electrical phenomenon is not identifed yet:

• During flexible production (but followed by an efficient cleaning)?• During B183 assembly activity ? (external welding activity with the DFB under vacuum?)• In the tunnel after vacuum evacuation ? (welding/brazing operation?

Ground current return with vibration ? ELQA ?)

Flexible-hose manufacturer recommendations

• 1/Avoid bended flexible hoses.

• 2/ Avoid high velocities in corrugated hoses which could create resonant vibrations resulting in premature fatigue failure. For braided hoses: < 50 m/s in gas if not bended < 25 m/s in gas if bended at 90°

• What is the velocity seen by the DFBA hoses ?

Flow scheme

CV920QV927

SMQ7TT860

TT821Lambda

plate

DFBADS

QRL

C line (PT961, TT961)D line

(L side only)

Flexible hose

Kv max, =%, R

PT821

Flexible hose configuration (straight or bended) not yet known (under investigation).

He velocity in flexible hoses

0

20

40

60

80

100

120

140

160

180

Flex

ible

-hos

e He

vel

ocity

[m/s

]

Vf_R1

Vf_L2

0

20

40

60

80

100

120

140

160

180

Flex

ible

hos

e He

vel

ocity

[m/s

]

Vf_R4

Vf_L5

0

20

40

60

80

100

120

140

160

180

17/2/08 7:02

27/2/08 7:02

8/3/08 7:02

11/4/08 5:02

21/4/08 5:02

1/5/08 5:02

11/5/08 5:02

21/5/08 5:02

31/5/08 5:02

Flex

ible

-hos

e He

vel

ocity

[m/s

] Vf_R3

Vf_L4

S1-2 S2-3

S3-4 S4-5

He velocity in flexible hoses

0

20

40

60

80

100

120

140

160

180

19/11/07 7:02 6/12/07 5:02 27/6/09 3:02 7/7/09 3:02

Flex

ible

-hos

e He

vel

ocity

[m/s

]

Vf_R5

Vf_L6

0

20

40

60

80

100

120

140

160

180

29/3/08 7:02

8/4/08 7:02

18/4/08 7:02

28/4/08 7:02

8/5/08 7:02

18/5/08 7:02

13/2/09 5:02

23/2/09 5:02

Flex

ible

-hos

e He

vel

ocity

[m/s

]

Vf_R6

Vf_R7

0

20

40

60

80

100

120

140

160

180

Flex

ible

-hos

e He

vel

ocity

[m/s

]

Vf_R7

Vf_L8

0

20

40

60

80

100

120

140

160

180

2/3/08 7:02

12/3/08 7:02

22/3/08 7:00

1/4/08 7:00

18/4/09 5:02

26/5/09 3:02

8/7/09 1:02

Flex

ible

-hos

e He

vel

ocity

[m/s

]

Vf_R8

Vf_L1

S5-6

S7-8

S6-7

S8-1

DFBA comparison

00.10.20.30.40.50.60.70.80.9

1

R1 L2 R2 L3 R3 L4 R4 L5 R5 L6 R6 L7 R7 L8 R8 L1

S1-2 S2-3 S3-4 S4-5 S5-6 S6-7 S7-8 S8-1

Arbi

trar

y sc

ale

At least 4 DFBA more critical !

Ultra-sonic vibrations• Is the flow able to produce ultra-sonic vibrations?

– Velocity V= 25 to 100 m/s– Corrugation wave length: l= 0.005 m– Frequency: V/l= 5 to 20 kHz

• If yes, what about ultrasonic welding?– Could explain the multiple fusion points

• If yes, what about the status of the other flexible-hoses?– Braid and corrugations stuck together waiting a thermal or pressure

transient (cool-down and quenches) to develop leaks?• If yes, DFBA in L5, L7, R7 & L8 are critical.

– Braid and corrugations affected but still free of relative displacement?• If yes, stopping the flow will stop the degradation process.

Proposal for consolidation of DFBAs in L1 and L3

• Replace the flexible hoses by smooth piping with lyres and/or pigtails (enough “free” space in the DFB vacuum vessel). – Integration study under way (collaboration with EN-MME) but as the

“as built” configuration is not known, it will need in-situ adjustment.– Proposed internal diameter:10 mm– As for the S4-5, repair intervention by EN-MME.

• Limit the velocity (i.e. the valve opening) in the 16 DFBA circuits. Could have impact on:– The cool-down time of the Q7L.– The PIMs recooling process (time, autonomy)– The temperature uniformity for SCS test.

Leak localization

On DFBA

On CLhose

N

Y

Y

NNew problem tobe investigated

Replace hoses by smooth pipesin DFB L1 & L3

Damageinspection

Multi-fusionpoints

N

Y

Caused byhigh flow

YN

Braid stuckto corrugationN Y

Prepare aconsolidation ofthe other DFBAduring the next

shutdown

Stop or reducethe flow in all DFBA

Hoses very vunerable to

transients(Natural cooldown

or quench):Consolidation ofthe most affected

DFBA:(L5, L7, R7 & L8)

Most probable path

Consolidation road map

(Already done aspreventive measure)

Simultaneous development of

several leaks

No mixing of materials