CRG-TM 11 February 2019 Page 2 - indico.cern.ch€¦ · VMY536aM QCCV-AERB15 Booster 1065042 QSCB-8-C01 Ball pass inner race frequency clearly visible. (SKF 7222) at female rotor

CRG-TM 11 February 2019 Page 2Page 2

CRG-TM 11 February 2019 Page 3

Outline

• Consolidations of “minor” concerns

• Spare and protection of accelerometer mounting pads (change wrt2013 LS1 Technical Specification)

• Geometrical differences between new spare compressors (# > 1’000’000) and original compressors ( 760’000 < # < 790’000)

• Homogenisation of covers (end flanges) and connections for balancing piston oil injection

• MTBF and major issue with premature bearing failure

• Investigations : maintenance reports & support from Aerzenexperts

• Consolidation proposals and Conclusion


Aerzen at CERN

o LHC accelerator :o 4 (identical) compressor stations of 5 compressorso Two types of compressors: total 20 units in operation

VMY536aM (7459 m3/h @ 2950 rpm): 8 booster units + 1 spareVMY536aH (5699 m3/h @ 2950 rpm): 4 booster units + 8 high stage units + 2 spares

o HIE-Isolde accelerator & CAST Experiment :o 2 (identical) compressor station of 2 compressorso Two types of compressors: total 4 units in operation

VMY436M : 1 booster + 1 shared spareVMY236H : 1 high stage + 1 shared spare

Total : 29 compressors for 6 installations dedicated to full and continuous4-years operation for physics research


Accelerometer mounting padsM1H Motor FS horizontalM1P Motor FS horizontal PVM1V Motor FS verticalM1A Motor FS axial

M2H Motor DS horizontalM2P Motor DS horizontal PVM2V Motor DS vertical

M2A Motor DS axial

E1H Compressor male DS horizontalE1P Compressor male DS horizontal PVE1V Compressor male DS vertical

E1A Compressor male DS axial

E2H Compressor male FS horizontalE2P Compressor male FS horizontal PVE2V Compressor male FS vertical

E2A Compressor male FS axial

E3H Compressor female DS horizontalE3P Compressor female DS horizont.PVE3V Compressor female DS verticalE3A Compressor female DS axial

E4H Compressor female FS horizontalE4P Compressor female FS horizont.PVE4V Compressor female FS verticalE4A Compressor female FS axial

Casings modified in order to allow the fixation of

mounting pads for the vibration measurements


Geometrical issue : connection of the oil injection

pipes for the bearing lubrication

Original

compressors

(760000 < #

< 790000)

New spare

compressors

(# > 1000000)

New spare compressor

QCCV-AERH10

(VMY536aH #1015467)

Difference of 20 mm

=> Will be corrected


End flanges / covers : connection of oil

pipe for balancing piston

1 x G 3/8” (centre) NPT 1/2“ and G 3/8” Blind flange

• Three versions available

for the covers

(Verschlußdeckel)

• Connection for the

balancing piston is not

equivalent for all the

compressors -> will be

standardized


End flanges / covers : connection of oil

pipe for balancing pistonAsset Position Model Serial Number

Flange

(Male screw)

Flange

(Female screw)

QCCV-AERB05 VMY536aM 767678 1 x G 3/8” 1 x G 3/8”

QCCV-AERH11 VMY536aH 1033979 NPT 1/2“ + G 3/8” NPT 1/2“ + G 3/8”QCCV-AERH12 VMY536aH 1046012 NPT 1/2“ + G 3/8” NPT 1/2“ + G 3/8”

QCCV-AERB01 QSCB-18-CO1 VMY536aM 767677 1 x G 3/8” 1 x G 3/8”

QCCV-AERB02 QSCB-18-CO2 VMY536aM 765583 1 x G 3/8” 1 x G 3/8”

QCCV-AERB03 QSCB-18-CO3 VMY536aH BOOSTER 765817 1 x G 3/8” 1 x G 3/8”

QCCV-AERH01 QSCB-18-CO6 VMY536aH 766667 1 x G 3/8” 1 x G 3/8” QCCV-AERH02 QSCB-18-CO7 VMY536aH 766665 1 x G 3/8” 1 x G 3/8”

QCCV-AERB04 QSCB-4-C01 VMY536aM 770804 1 x G 3/8” 1 x G 3/8”

QCCV-AERB15 QSCB-4-C02 VMY536aM 1065042 1 x G 3/8” Blind flange

QCCV-AERB06 QSCB-4-C03 VMY536aH BOOSTER 766668 1 x G 3/8” 1 x G 3/8”

QCCV-AERH07 QSCB-4-C06 VMY536aH 766669 NPT 1/2“ + G 3/8” 1 x G 3/8” QCCV-AERH04 QSCB-4-C07 VMY536aH 766666 1 x G 3/8” 1 x G 3/8”

QCCV-AERB07 QSCB-6-C01 VMY536aM 784310 NPT 1/2“ + G 3/8” NPT 1/2“ + G 3/8”

QCCV-AERB08 QSCB-6-C02 VMY536aM 774982 1 x G 3/8” 1 x G 3/8”

QCCV-AERB09 QSCB-6-C03 VMY536aH BOOSTER 784197 NPT 1/2“ + G 3/8” NPT 1/2“ + G 3/8”

QCCV-AERH08 QSCB-6-C06 VMY536aH 770492 NPT 1/2“ + G 3/8” 1 x G 3/8” QCCV-AERH10 QSCB-6-C07 VMY536aH 1015467 NPT 1/2“ + G 3/8” NPT 1/2“ + G 3/8”

QCCV-AERB10 QSCB-8-C01 VMY536aM 767679 NPT 1/2“ + G 3/8” 1 x G 3/8”

QCCV-AERB11 QSCB-8-C02 VMY536aM 777043 NPT 1/2“ + G 3/8” NPT 1/2“ + G 3/8”

QCCV-AERB12 QSCB-8-C03 VMY536aH BOOSTER 770494 1 x G 3/8” 1 x G 3/8”

QCCV-AERH06 QSCB-8-C06 VMY536aH 783114 1 x G 3/8” NPT 1/2“ + G 3/8”QCCV-AERH05 QSCB-8-C07 VMY536aH 777170 NPT 1/2“ + G 3/8” 1 x G 3/8”


Issues since 2009 (LHC run 1 & 2)

Total of 21 issues

3 types of issues (severity) :

• Major: requires immediate unplanned stop

• Medium: repair/exchange can be planned and wait for next LHC technical stop

• Minor: compressor can continue to operate with increased monitoring

7

2

3

4

0

5

0

1

2

3

4

5

6

7

8

Booster High Stage

VMY 536 issues vs severity

Minor Medium Major

7

2

3

4

2

3

0

1

2

3

4

5

6

7

8

Run 1 Run 2

VMY 536 issues vs LHC run

Minor Medium Major


Analysis of the issues

Issues vs installations

P18 appears to be less affected by the problem;

P8 more.

Issues vs serial number

Almost all compressors affected

Number of issues vs serial number

P18 P4 P6 P8

1 6 5 9

Issues vs installations


Analysis of the issues

Run 1 + 2 :

21 issues out of which 11 before

25’000 h1

2

0

2

0

4

1

2

1

2

0

1

2

3

0

1

2

3

4

5

6

7

0-5000 5001-10000 10001-15000 15001-20000 20001-25000 25001-30000 >30000

Issues vs operation time since overhauling

Booster High Stage

MTBF Run 1 & 2 [h] MinorMedium +

majorMajor

Total 4168 7295 17507

VMY536aM 14280 42840 n.a.

VMY536aH Booster 20285 81142 n.a.

VMY536aH 8418 10288 18519

MTBF Run 2 [h] MinorMedium +

majorMajor

Total 3555 4570 10664

VMY536aM 10692 16039 n.a.

VMY536aH Booster 31188 n.a. n.a.

VMY536aH 6461 6461 10769

Request: min. 40’000 h in between major overhauling


Issues during run 1Model Asset Type Serial number Position Description Severity Date when notedRH when noted Date when stoppedRH when stopped

VMY536aH BOOSTER QCCV-AERB12 Booster 770494 QSCB-8-C03 Bearing failure Medium May-09 15734 Jun-09 15734

VMY536aH QCCV-AERH03 High Stage 770493 QSCB-4-C06Compressor break down

Caused by bearing failureMajor Dec-10 24198 Dec-10 24198

VMY536aH QCCV-AERH08 High Stage 770492 QSCB-8-C07Compressor break down

Caused by bearing failureMajor Jun-11 29896 Jun-11 29896

VMY536aH QCCV-AERH07 High Stage 766669 QSCB-8-C06

Bearing frequency of the inner race on the

driven side male 7222 (8.54xn und Multipeln,

sidebands 1xn and 0.43xn)

Minor Jul-11 41000 Jan-12 44104

VMY536aH BOOSTER QCCV-AERB03 Booster 765817 QSCB-18-C03

Visible is a bearing frequency outer race 7222

on the driven side of the male rotor (6.47xn

und Multipel).

Minor Aug-11 27000 Jan-12 31224


Bearing frequency of the inner race on the

driven side female (8.52xn with multiple

sidebands 1xn and cagefrequency).

Minor Dec-11 17000 Feb-12 18000

VMY536aH QCCV-AERH07 High Stage 766669 QSCB-8-C06 Excessive wear on plain bearings Medium Dec-11 44104 Dec-11 44104

VMY536aH QCCV-AERH04 High Stage 766666 QSCB-4-C07 Damaged rotor Medium Dec-11 33846 Dec-11 33846

VMY536aM QCCV-AERB04 Booster 770804 QSCB-4-C01Evtl. light bearing freqency balls (2.68xn und

MultiplenMinor Sep-12 28000 May-13 42000

VMY536aM QCCV-AERB10 Booster 767679 QSCB-8-C01Light bearing frequency balls 7222 at male

rotor (5.36xn und Multiplen).Minor Sep-12 34000 Apr-13 48000

VMY536aM QCCV-AERB11 Booster 777043 QSCB-8-C02Bearing damage rolls SKF 7222 (2.694xn und

Multiplen, sidebands cage 0.43xn), picture 1Minor Aug-12 28000 Apr-13 42000


Roller bearing frequency outher race SKF 7222

BEGAF (6.46xn und Multiplen, Sidebands cage)

on DS male rotor,

Minor Feb-13 8000 Aug-13 12000Run 1: 12 issues. Majority of bearing issues.

• 2 major issues: breakdown of CP6 QSCB-4 (Dec 10) and of CP7 QSCB-8 (Jun 11)

• Vibration analysis started in July 2011.

• All bearings of the high stages + 2 boosters (detected with the new vibration monitoring

system) were replaced during YETS Dec 2011-Jan 2012

• Increase of pipe diameter for balancing piston (high stages)

• 4 minor issues detected from Sep 12 to Mar 13: repaired during LS1 overhauling.


Issues during run 2Model Asset Type Serial number Position Description Severity Date when notedRH when noted Date when stoppedRH when stopped

VMY536aM QCCV-AERB15 Booster 1065042 QSCB-8-C01

Ball pass inner race frequency clearly visible.

(SKF 7222) at female rotor DS (8.5xn and

Multipel).

Medium Nov-15 2590 Jan-16 13000

VMY536aH QCCV-AERH08 High Stage 770492 QSCB-4-C06Bearing frequency inner race female rortor

7222 (8.488xn and Multiplen). Major Mar-15 4262 Mar-15 4262

VMY536aM QCCV-AERB05 Booster 767678 QSCB-4-C02

Roller bearing frequency (8.52xn und

Multiplen, sidebands cage). The frequency

matches with inner race of bearing 7222BEGAF

Medium May-15 6300 Oct-16 18000


Roller bearing frequency on the female rotor

(8.52xn und Multiplen, sidebands cage).

Picture 1. New. The frequency matches with

inner race of bearing 7222BEGAF

Minor Dec-15 9888

VMY536aH QCCV-AERH05 High Stage 777170 QSCB-6-C06Inner race frequency visible. (SKF 7222) at

female rotor DS (8.51xn and multiple)Medium Nov-15 12684 Feb-17 21000


Bearing damage on the female rotor. The

damage is clearly seen on the inner race of the

bearing 7222

Major Oct-16 14583 Jun-18 27724

VMY536aH QCCV-AERH12 High Stage 1046012 QSCB-6-C07Bearing frequency from the inner race (bearing

7222) on the female rotorMedium Oct-17 26605 Jan-18 31000

VMY536aM QCCV-AERB08 Booster 774982 QSCB-6-C02Bearing frequency from the inner race (bearing

7222) on the female rotorMinor Nov-17 26865

VMY536aH QCCV-AERH10 High Stage 1015467 QSCB-6-C07Bearing frequency from the inner race (bearing

7222) on the female rotorMajor Jun-18 3473 Jun-18 3473

All issues : ball bearing on the

female rotor (driving side)

Run 2: 9 issues

• 3 major (unplanned stop), 4 medium (planned stop), 2 minor

• 2 issues concern VMy536 aM and 7 issues concern VMy536 aH


Check of maintenance reports (Aerzen)

Damaged of (axial) bearing

always confirmed. One or

several ones are found damaged

Heavy scratches are also found on

the radial bearing (shaft seal and

bearing housing)


SKF Expertises

• Three bearings sent for expertise

to SKF :

1. 2012 : QSCB-18-CP3 and

QSCB-8-CP3 (boosters aH)

2. 2016 : QSCB-8-CP1

(booster aM)

• The three reports mentioned :

1. «Contamination by foreign

particles is the primary

cause»

2. «Standstill vibration»

(ring-shaped wear patterns

on ring raceways, caused

by vibration with the bearing

stationary)

Fig. 6: Further photo of the ball path with ring-shaped wear pattern (arrow) in the ball path.


Check of oil cleanliness

• Our installations are not within the required class;

• Samples are taken at the bottom of the PS -> global

condition of the oil ;

• Filtration rating ?

• Why no major bearing issue with Stal, Howden,

Kaeser, Mayekawa installations ?


Check of oil cleanliness : filtration rating

25 μm

25 μm

10 μm

Proposals :

• to change filter for bearing injection to 10 microns• and to install a monitoring (delta p)


Check of oil cleanliness : filtration rating

Check of filtration rating for non QSCB installations in progress :

• STAL QSCA AL P2/P8 : STAL internal pump or IMO with F621 (before pump) and F670

(HP) / F639 (LP) for general oil flow

• STAL QSCA Linde P4/P6 : STAL internal pump or IMO P600 with F621, Desmi P640 / F640

and P670 / F679

• QSCC Mayekawa : 1F610/2F610, then F620, 1F620/2F620 (?)

• Q-WAT Mayekawa : 10 microns filter on the injection

• Howden ATLAS-SR : F1610 (inlet oil pumps), nF1622

• STAL ATLAS-MR : nF0600 (general), nF0601, CP2 : 2F0613/2F0614 and then 2F0621,

6F0611/6F0612 puis 6F0621

• Howden CMS : inlet pompe F638/F639 (40 microns) then F618/F616 (15 microns)


Summary of meetings with Aerzen

• Two meetings CERN-ARZEN at CERN : 19-Sept-2018 and 13-Dec-2018, incl. visit by Aerzen

specialist of customer support

• Aerzen confirmed that the problem is mainly coming from particles in the oil.

In their documentation, Aerzen recommends filters of 10 to 25 μm max.

When Aerzen is in charge of the plant, 10 μm filters are fitted.

Aerzen recommend to change F623 to 10 μm and to add a PDT monitoring

• For the high stage CPs, calculations give a lifetime of 19’000 h and 30’000 h for the axial

bearings on the female rotor and male rotor respectively.

If the axial bearings are upgraded, lifetimes -> 59’000 h and 92’000 h respectively. Aerzen

recommend to change the axial bearing on the female rotor (SKF 7322 instead of 7222).

• Investigation to change also the bearing for the male rotor shows that it is very difficult :

• Missing space : it is necessary to have newly shaped set of rotors

• Housing covers need to be machined;

• Balancing pistons: pressure will need to be reduced with adjusting valves and

probably automatically controlled

Aerzen do not recommend to change the axial bearing on the male rotor.

• For the boosters (aH & aM), calculations give lifetimes of minimum 250’000 h. Aerzen do not

recommend to change the axial bearings on the boosters (VMy536 aM)


Bearings calculations



Check of lubrication circuits and connections for QSCB



• Boosters : no difference found

• High stages :

• HV619 and m2 connection not existing (both AL & Linde)

• Connection to PV627 : AL via «w» port and Linde via «m1» port

QSCB-18-C07 QSCB-8-C07 EV627S & EV628R

• All compressors : EV627R and EV628R are disconnected



PID to be updated

• High stages :

• HV619 and «m2» connection not existing (both for AL & Linde)

• Connection to PV627 : AL via «w» port and Linde via «m1» port

m1

EV627S & EV628R disconnected on all installations


Visit at P18 and P8 with Aerzen


Summary of the visit at P18 and P8 with Aerzen

Compressor lubrication :

• x1, x2, x3 are the preferred connection for the oil

injection in the compressor. They shall be

connected by order of priority, x1 being at a higher

pressure in the stage, than x2 and x3.

x1, x2 and x3 are all connected on all

compressors, x2 via a throttling valve. It is to

mention that x3 was found with a plug (to be

checked if it is the case for all compressors)

• On the boosters (AL & Linde), the m2 port is used

for oil injection in the compressor via a throttling

valve. Aerzen mentioned that m2 is usually used

for measurement but can be used also for

additional oil injection

• On high stages, it is the economizer port v1 that is

used for additional oil injection in the compressor

with a throttle valve. Aerzen mentioned that this

connection is usually to connect the refrigerant

fluid to be compressed and not the oil.


Summary of the visit at P18 and P8 with Aerzen

• High stages Linde : the oil return connection from the phase separator (from coalescers) is

made via “m1” instead of “w”. Aerzen explained that “w” and “w1” are the preferred

connections for the oil return. But Aerzen stated that the “m1” connection is also a point of

low pressure (measurement) in the compressor.

• On all installations the EV627S and EV628R are disconnected. These EVs were to manage a

variable VI via «y3» port that has been abandonned (Udo’s communication).

• Aerzen described also the oil injection system for the lubrication of the bearings : there are

indeed only two injection ports, but the circuits system is such that all bearings are lubricated

with «fresh» new oil. After having passed through each bearing, the oil is diverted into the

compressor. There is no risk of contamination from a bearing to another one.

QSCB-18-C07 QSCB-8-C07 EV627S/628R


Conclusion

• Since the beginning of the LHC operation, 21 issues were recorded giving a MTBF between

10’000 and 20’000 h depending on the issue considered

• After the breakdowns in 2010 and 2011, CERN implemented a vibration monitoring system

and has increased the diameter of oil injection pipes for the balancing piston on high stages

• Nevertheless the MTBF for run 2 is about 10’000 hours. ( Requirement: min. 40’000 h)

• The 9 issues during run 2 concern the ball bearing on the female rotor.

• All reports (Aerzen & SKF) mentioned oil contamination by foreign particles. If we want to

increase the reliability and the MTBF, the priority is to improve the oil cleanliness. (Filter rating,

oil cleaning systems)

• As the lifetime of the axial bearing on the female rotor of high stage compressors is given for

50% of the CERN specification and that a correlation exists between the observed issues and

this first potential failure, it is wise to consolidate the bearing for these compressors


Proposal

• Upgrade QSCB-n-nF623 with a mesh of 10 microns (instead of 25 microns)

• Install a PDT monitoring (same as nPDT621) : QSCB-n-nPDT623

• Upgrade the axial bearing on the female rotor of VMY536 aH compressors (SKF 7222 to SKF

7322)

• Oil cleaning (studies to be made for QSCB, QSCA).

Two possible options :

1. Passive cleaning : fine filter to be installed in parallel of the main flow (cost : ~ 4 kCHF)

2. Active cleaning : external oil pump system equipped with a fine filter and fed from PS(centrifugal PN25 oil pumps available from ATLAS-SR -> build a skid)

Preferred option : active cleaning :

- Build a skid with an (ATLAS-SR) Alweiller pump and a fine filter

- Adapt flanges connection on the PS of the various QSC to connect the skid


Improvement of oil cleanliness : present experience

Filter of 3 μm in

secondary flowAlert !

It is possible to improve the oil cleanliness (active and passive) :

• With an circulator equipped with a fine filter (3 μm) -> Kaeser B163, ATLAS ANRS

• With a fine filter installed in parallel of the main flow -> ATLAS SR, QSCCA-4

ATLAS SR :

3 µm filter PN25 with delta P

installed on the ATLAS SR


Improvement of oil cleanliness : QSCB example

25 μm

PDTF

Passive : 8 filters necessary (32 kCHF)

Active : adapt flanged connections

(Similar for QSCA Linde)

Documents

CRG-TM 11 February 2019 Page 2 - indico.cern.ch€¦ · VMY536aM QCCV-AERB15 Booster 1065042 QSCB-8-C01 Ball pass inner race frequency clearly visible. (SKF 7222) at female rotor