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CERN/Tc/2oo 61/9 18.7.1961

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARC~

TECHNICAL SPECIFICATIONS OF THE SAFETY VENT LINE FOR TBE 2 m

HYDROGEN BUBBLE CHAMBf :d.

The European Organization for Nuclear Research (CERN)

has constructed a 28 thousand million electronvolt Proton­

Synchrotron at Meyrin near Geneva.

For nuclear physics experiments with this machine

a visual detector of the tracks of ionizing particles, balled

a hydrogen bubble chamber, is being built.

The bubble chamber will con~ain about 1000 litres of 9.

liquid hydrogen at a temperature of about -·250 C and a pressure

of 5-7 ata. The extremely low temperature of liquid hydrogen

requires that it be insulated with a high vacuum. Every effort

will be made to make the bubble chamber and surrounding tank as

vacuum tight as possible, however even a small leak would destroy

the vacuum insulation. In this ,,ase the liquid hydrogen would

vaporize very rapidly and upon warming to room temperature would

expand nearly a thousand fold. This quantity of gas, about

1000 normal cubic meters, would P.resent an extreme explosion

hazard if it were allowed to vent to the atmosphere. · . For

safety of personnel and equipment a safety exhaust system con­

sisting of rupture discs and relief valves, a safety vent line

and a 500 cubic meter sphere is required to handle and store the

gaseous hydrogen in the event of such an emergency.

The following specifications are concerned only with

the safety vent line.

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I N D E X

1.. EXTENT OF OFFER, FACILITIES y GUARANTEES, DELIVERY AND

ERECTION DATES

1.1 Extent of Offer

1,2 Facilities

1.3 Guarantee

1.4 Delivery and erection dates

2, GENERAL INFORMATION

2.1 Operation

2.1.1 Normal Conditions

2.1.2 Emergency Conditions

2.1.3 Return to normal conditions

2,2 Construction rules

2.3 Design prescriptions

2.3.1 Material and nominal bore

2.3.2 Temperatures

2.3,3 Pressures

2.3.4 Vacuum requirements

2.4 General Arrangements

3. DE'I'AILED SPECIFICATIONS

3.1 General

3,1,1 Tubes

3 .1. 2 Flanges

3,1,3 Gaskets

3.1,4 Expansion joints

3 .1. 5 Valves

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3. 2 Straight line inside the bub-ble chamber building

3.3 Straight section through the ventilation duct

3.4 Expansion joint between valve adaptor and bubble chamber building

3. 5 Expansion joint between bubble ch_ambelr? and wall­mounted line

3.6 Stop valve

3.7 Section inside the sphere

3.8 Adapting pieces for the valve

4. ERECTION

4.1 Civil engineering work

4.2 Supports

4.3 Erection and lining up

_5. MATERIALS AND EXECUTION OF WORK

5.1 Vent line

5.1~1 Material and work

5,1,2 Welding

5,1.3 Cleaning

5.2 Supports

6. INSPECTION DURING FABRICATION

1. TESTS AND CERTIFICATJ!~S

7.1 General

7.2 Steel plates

7.3 Welding

7.4 Tests at CERN si "':e

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8, GENERAL FORM OJi' 'IHI: TE~LLER

8.1 TechnicQl inforTiation

8,2 Commercial information

B.3 Calendar fo~ benders

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1. EXTENT OF OFFER, FACILITIES, GUAPJi.N'l1EES, DEJ~IVER.Y AND ERECTION DATES

1. 1 J!::::isten t gf _ of:f eT

CERN will have preference for a tcmder of the com­

plete safety vent line including accessories, erection and

tests as specified under par. 3, 4 and 7.

However, as the installation includes items normally

manufactured by specialised firms, CERN will also consider

tenders for one or more parts of the installation.

The offer shall include transport to CERN site at

Meyrin near Geneva. Transport from Geneva railway statim

to the CERN site can be either by normal road truck or the

railway truck can be drawn on trailers for unloading at

CERN. The cost fer the latter way of transportation is

about Fr.Sw. 150.- per truck depending on the size.

CERN vvill provide on site fre(:J of charge g

a) Electrical energy 380 volts, 3 phase, 50 cycles

from fixed points;

b) Welding gases;

c) Compressed air (6 kg/cm2 , moist);

d) Nitrogen gas for testing;

e) Equipment for the pneumatic pressure test and

for the vacuum test;

f) Scaffolding, ladders and light lifting gear for

erection work;

g) A site hut for the contractor's men,

Tenderer should indicate how many electrical

connections, kw., Nm3 of gas etc. will be necessary.

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All other equipment, mateTials, tools cmd instruments 1

necessary for erection and testing must be provided by tho

contractor.

A limited area will be available on the site for the

storage of material at the contractors risk, Due to spac,2

limitation the size and shape of the area to be used must be

discussed between the contractor Bnd CEHN.

1.3 Guarantee

The successful tenderer(s) shall be responsible for the

quality and proper performance of the whole installation

as well as of the component parts supplied by himself or

by his subcontractors J.:.PJ a perL<:?.LS!.! _one ye_q.L.£. starting the

day after succes.sful complE~tion of tests on CERN site and

the taking over b;y CEHH, It must be stated clearly by the

tenderer that he is willing to give th~s guarantee,

l , 4 ~L...§11q~?r(C~£.:hJ2~n De~ Gs_

CER.N should f)e informed at least 10 days in advance

of any delivery of material to CERN site, The complete

safety vent line with all accessories is required to be

erected, tested and ~eady for ope~ation, at the latest

by March 31, 1962. A shorter delivery time would however

be much appreciated,

2. GENERAL INFORl/I.A.rrroN

2.1 0120~.12

2. 1, l .~ro1:n1~L..££.D§i tj~£..rn1

The safety vent lire will as a rule be under a

vacuum of about io-3 torr obtains~ by means of a suita~le vacuum pump, However CERN hes the pcrnsi bili ty to fill

it with purified H2 gas at slight overpressure (1,05 ata)

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instead of always keeping the vent line at a high

vacuum, Ambient temperatures can fluctuate in

extreme cases between-30°c and +40°C.

2,1,2 Emergency conditions

The frequency of this condition is of cours im-

possible to predict, However, in all probability it

will take place very rarely, if at all;

In the case of emergency a mixture of evaporated

hydrogen and liquid hydrogen will stream through the

vent line entering the tube with a temperature which 0

can be as low as -250 C, During the passage the li-

quid will evaporate and at the same time the safety

vent line will be cooled down violently.

The final pressure will be about 3 ata if the

safety sphere was previously filled with hydrogen and

less if it was evacuated. If for some reason the

safety sphere were filled with air there would be the

possibility that an explosion will take place when the

evaporated hydrogen streams intb the sphere. The

maximum pressure from an explosion is calculated to be 2

about 15kg/cm gauge,

2.1.3 Return to normal conditions

When tho equilibrium stage has been reached after

an emergency, the safety vent line will be emptied and

finally brought back to normal operation conditions.

2,2 Construction rules

CERN requires the construction to be approved by

"Schweizerische Verein von Dampfkesselbesitzorn (SVDB)"*,

*Address~ Plattonstrasso 77, Ziirich, Switzerland,

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which means that the tenderer can uso the regulations

governing pressure vessels issued this authority, or

the rules of his own country, whichever are the more

stringent, Special attention must be paid to tho wel-

ding factor and to the impact stress, especially at low

temperatures.

The tenderers attention is also called to the vacuum

specification. This is perhaps stricter than found in

normal industrial practice and only the highest quality

workmanship and material, especially the welding, will

meet this specification,

2. 3 Design prescripti9ns

2.~.l Material and nominal bore

CERN wants a 350 mm nominal llore safety vent

line made of a stai~less steel quali Lcppropria te

for the temperature, pressure and vacuum conditions

pr~scribed below. HoweveT the tenderer should boar

in mind tho very rare occasions of the ultimate low

temperature which in addition will only act during

a short time.

,- ')c Maximum tempcratuer ~·JG-

2 i:::r'oC Ultimats low temperature - )0 ;

Pressures 2

Ultimate highest working pressure = 15 kg/cm gauge

Hydraulic tE:rnt pressure = kg/cm 2 gauge·

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2.3.4 Vacuum reguirements

The design and construction shall be such .that

the safety line can be evacuated to an absolute

pressure of at least 10-3 torr with a vacuum pump

stand having an effective pumping speed of 2000 l/sec,

The total leak rate should not be greater than

1 x 10- 2 .torr-liter per second.

2.4 peneral arrangement

The arrangement is shown on the attached drawing,s

155-68-0C, 155-69-0A and 155-72-0B.

As will be seen from these drawings the .vent line

consists of:

a) About 50 m of flanged tube along the inside

NW wall of the bubble chamber building;

b) a section (with vacuum valve) passing the ven­

tilation duct in a 450 mm tube and throug]1 .the

building wall;

q) a s~cition, allowtng thermal expansion, between

(b) and the valve (e);

d) a section allowing thermal expansion between

the bubble chamber and (a), As the bubble chamber

is movable along the entire length of the building,

it is foreseen by CERN to make adapting pieces for the

connection of (a) and (d),

The nearest section of (a) will then be removed,

e) A 350 mm bore - stop valve;

f) a section with flanges about 4 m in length, in­side the sphere;

g) adapting pieces for the connection at the valve to the line and to the sphere nozzle of 500mm bore.

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h) Hardware, brackets, nuts and bolts, blind

flanges for the testing of the complete assembly

and other miscellaneous items necess~ry to make up

the complete project.

The component parts (a) to (h) are further

specified in the following section.

3. DETAILED SPECIFICATIONS

3.1 Gene rel ~·-·--

3 .1.1 Tubes

The tubes forming the vent line ~ust be manu­

fnctured with only one longitudinal welding seam.

Circumf~rential seams must be limited to the minimum.

possible and 2 longitudinal seams should never meet,

3.1.2 Flo.nges

The tenderer should use DIN or ASA norms for

the flanges in respect of thickness, bolts etc,

Owing to the vacuum requirements the flange

joints must be extremely tightg CERN~ with past ex-

perience of pressure and vacuum vessels, proposes

the use of 11 0 11 -rings to seal the joints. The align-

ment of tho individual pipes must be such that all the

flanges are drawn up metal-to-metal completely· around

the circumfo:rence; this is necessary if the 11 0 11 -ring

is to be confined entirely in the event of a pressure

surge,

In principle CERN has adopted as standard the

11 0 11 -ring groove dimensions given by the compilation

of Angst and Pfister A.G. of Zilrich, Switzerland. If

the tenderer elects to use machined grooves in the

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flanges, then it is suggested that the grooves be

locCtted in the flanges facing the sphere, The coun­

terflanges must then have a polished are·a opposite to

the grooves.

Alternatively the tenderer may elect to polish

both flanges and f:urnish the n0 11 -ring confined between

two concentric retaining rings in a manner similar to

that indicated by Heraeus GmbH of Hanau, Germany, in

their cato.logue on vacuum equipment; 3Td Ed., Section A,

page VIII - 2,

The tenderor's attention is drawn to th8 fact

that for reliable sealing, the surfaces of the flanges

in contact with the 11 0"-rings must be .finished to better

than 64 microinches roughness. No redial grooves or

scratches of any kind can be t'olera ted,.

The tenderer can of course also proposo his own

solution for the sealing of the flange joj.nts. He should

then be prepared to provide samples and tests to de­

monstrate that the method prOpo~ed by him is at leist

as good and as sriitable for the present application as

the 11 0 11 -r_ing seals,

Nuts and bolts for tho flan~e connec.tions shall

be made of stainless steel,

3.1.3 Gaskets

· Standard rubber 0-rings shall be supplied b~

the successful' tenderer. However CEP.2~· reserves tho

right to supply 0-rihgs of another (low temperature)

material which then should be used for the erection,

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3 .1. 4 Ex12ansion section<L

The sections (c) and (d) mentioned in para­

graph 2,4 must nllow thermal expan,sions, CErn~· propose

1.Jellows expansion joint~~ which must be equipped with tie

bars to take the pressure forces. The tenderer is in-

vited to propose another solution taking into account

that forcea in excess of 5 tons should not act on the

bubble chamber or on the building.

3 .1. 5 Valves ~---=·;<;

They should be non-lubricated, pressu~e and

vcccuum tight and of a well tried, reliable type suitable

for the pressure, temperature and vacuum conditions

requested,

3. 2 Strair,;ht line inside. the bubble ch2,mbe:r: buildiJ:l.€i

The section (a) consists of 7 pieces flanged together,

each piece having a length of 6500 mm,

3,3 Straight section through the ventilat_ion duct

Section (b) will consist of one straight tube with

flangos, Inside the building there must be a stud

carrying a flangod-on 100 mm bore valve having particulars

as specified in 3.1.5; furthor a stud of 20 mm bore for

pressure indication and a thormomoter well must be

provicled,

Outside the building the tube will be attached to

the concrste vnll: the contractor must design the proper

cons true tion so the:-c t this ono o.nd only 11 in termodie, te fixed

point" is capnble of tccking the lood of 5 tons mentioned

previously.

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3,4, Expansion joint between valve adaptor and bubble

chamber building

This section (c) ~ill cohtain a sharp bend at about

30° relative to the direction defined by the outer wall of

the bubble chamber building along which the safety line runs,

and a straight part carrying one or two bellows with tie bars

for almost all the length. As far as possible this section

should have flanges only at the ends. The tenderer should

propose a proper design and the contractor in consultation

'with CERN must make the final construction.

3, 5. Expansion ,joint between bubble chamber and wall

mounted line

This part (d) contains one horizontal and one verti.cal

90° bond (which should be kept as short as possible), one

straight tube with bellows J.nd tie bars and one short·aQ,ap­

ting piece in the horizontal part between the, two bends.

The other particulars are as mentioned in 3.4,

3. 6 Stop ve.l ve

One 350 mm full bore stop valve (e) should be delivered

having the following cnQracteristics:

Vacuum conditions: 'The.valve housing, stem seal and seat

must be tight for 10-3 Torr on one side . ' 2

and. 1 kg/cm gauge on tho other side.

Leak rate should be l~ss than 1 x 10-3 Torr

liter por second.

Pressure conditions: The valve body and stem seal must moot

the working and test pressures noted in

paragraph 2, 3. 3 with. the seat open Ein'd

closed. The valve ioat should withstand

13 atmbspheres (gauge) pressure from ~~ther

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direction, and it should bo bubble tight

with ~ pressure difference of 6 atmo­

spheres (gauge) across it,

CERN is fully EHvare that a valve

meeting the full pressure and vacuum

specifications may not 1rn corr:mercially

Dvailable, CERN :Ls prepL1T(0d to work

with tho successful tenderer in the

adaptation of existing commercial equip­

ment.

Flanges should have polished surfaces for tho 0-rings,

One straight tube (f) of about 5 m length complete

with flangos,

Two adapting pieces short as possible must be

supplied for the fitting of the valve

to the 500 mm nozzle of the sphere,

to the vent line and

For seal of the

flanges see remarks of paragraph 3,1,2. Detnils will be

discussod further between CERN o.nd tho contractor, Noto

that the valve may have ASA flanges and the balance of the

work.DIN flanges.

4, ERECTION

4,1 Civil engineering work

CERN will supply and instc.11 b:rackets fitted to the

I-beams of the bubble chambe:r walls and to the I-beams of

the crane bridge, If consido:red necessary by the contrac-

tor a pillar with bracket could be erected close to the big

valve.

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Outside the building there will be no other possibili­

ties for supports other than those mentioned,

The tube of 450 mm bore insicle which the vent lino must

pass th7 ventilation duct will also be supplir:;d D.nd instoILed

by CERN.

The contractor must in due tima supply the necessary

information and drawings indicating his wishes. If further

beams and brackets are wantod along the wall, tho contractor

must supply the ma terLtl yvhile CERN will make the ins talla-

ti on. This also applies to tho intermediate fixed point.

No work affecting buildings, foundations or other in-

stallations will be allowed~ Therefore any modification

affecting such p~rts ~ due to delay of the contract or

insufficient information will be made by CERN at the

contractor's expenses.

4.2 Supl?orts

Tho successful tenderer shall supply all supports,

Bolts and nuts necessary for the erection of the safety

vent line.

The supports which should be bolted to the above-mention­

ed br2ckets must be der>igned to allow 2. froe thermal con­

traction along tho axi~ of tho tubo and should at the samo

time guide it properly.

Supports inside tho bubble chamber building must in

2ddition be designed to ensure an easy dismounting of each

of the 6.5 m long tubes (supports shown on t~e attached

drawings are intended as an indication only).

4,3 Erection and li~

The contractor shall erect, carefully line up and

assemble the complete safety vent line in 2 way that secures

the vacuum tightness and prevents any undue stressing.

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5. MATERIALS AND EXECUTION o:E1 WORK

5.1 Vent line

5.1.1 Materiel and work ~~--~~-~-~--~

It must be new and of approved qu2lity for the

pressure nnd temperature conditions mentioned in para-

gro.ph 2.3. · Further it must meet all requirements for

operation with hydrogen gas, All work shall be exo-

cuted sccording to thl'> highest stcmd,::i.rds of workmanship,

Tho plates shall be handled during all stages of

fabrication and erection in a way that secures the

greatest possible final cleanliness,

5 .1. 2 Vfolding

The welding factor must comply with tho rules

used and shall be indicated in the tender together with

the calculation of the wall thickness. Tho electrodes

and the procedures must be approved by the surveyor.

Only welders having certificate for stainless steel

welding must be used 9 at the contractorls factory ns

well as on the CERN site. CERN requires the success-

ful tenderer to deliver two welding samples of the same

thickness as will be used for the vent line,

The welds shall hnve a quality complying with

tho most recent standards fer completely pressure and

v,?cuw-0:1 tight vrelding sear1s.

The greatest possible cleanliness should be ob­

served and all scale removed after each welding,

After completion of ull welding ea.ch seam muEit be

completely X-rny or rnagnaflux tested and ::my defec;t

repaired by the contractor without expense to CERN•

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The inner surface must be extremely clel'.n in

order to avoid contamination of the highly purified

H2 gas which might be stored in the sphere. When

the final pressure and vacuum tests are finished the

surface must be washed with c~rbon tetrachloride,

trichloroethylene or similar liquids. Any residue

of oil, water, dust e,nd. chemicals mi;cs t be renoved,

5.2 Supports

The choice. of material is left to tho tenderer who

however should consider the dhnger of cooling down any

supporting structure of the building.

Bolts, nuts washers and similar iteus, if made of

steel, shall be cadmium plated while other steel parts

shall have a coating of red lead.

6. INSPECTION DURING FABRICATION

CERN reserves the right to inspect the mnnufacturo of

all items at the factory of the contractor·or his subcom~rac~

tors and at CERN site at any stage of producti:rn 2~nd ::ct any

normal working time,

7, TESTS AND CERTIFICATES

7.1 General

All testing demanded must be su:pervif.rnd by the surveyor

mutually agreed upon by CERN and the successful tenierer.

CERN should be informed by the contractor not lnt0T thRn

seven do.ys in advance of o.ny planned t(rnt ou-Csido CERN site

whereupon CERN will inform him whether or not it will p~r-

ticipo..te, Any test on CERN site will be v;i tnessed by CERN,

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Faulty material or faulty manufacture detected by any test

shall be, as.CERN decides, replaced or repaired without

cost to CERN.

All expenses for tssts and certificates are at the cost

of the contractor who must accordingly make provisions for

thee in his offer, For every test mentioned below under

7,2, 7,3 and 7,4 certificates in duplicate have to bo sup­

plied,

7,2 Steel plates

Material certificates must be submitted covering the

process of steel fabrication and giving chemical composition,

yield point, tensile strength, elongation (in o/o), and

impact strength, at the temperature limits mentioned in

paragraph 2.3.

7.3 ~slding

As previously mentionSd a complete X-ray or magnaflux

testing of all wolding seams shall bo made. Films must be

examined by the surveyor and shall finally become the pro­

perty of CERN.

7J4. Tests at CERN site

After erection the contractor shall test the installation

as follows:

a) A hydraulic pressure test of the completed line

with all apertures firmly closed shall be made at the 2

CERN site, with a test pressure of 24 kg/cm • The

expansion bellows, links etc. must of course be de­

signed to withstand these pressures,

b) By filling slowly the vent line with air up to

15 kg/cm 2 gauge with simultaneous soap solution testing,

The final pressure shall be maintained for at least

2 hours and still no leaks shall be detected by soap

solution tests.

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c) By evacuating the line to 10-3 Torr, closing and

studying the pressure rise during 48 hours. The leak -2 rate shall be lower th2n 10 Torr liter per second.

If (c) proves unsuccessful:

d) By filling the line with helium to 15 kg/cm2 gauge

and using a helium leak detector for finding the leak(s)

(leak detector will be supplied by CERN).

8. GENERAL FORM OF THE TENDER

In order to facilitate the adjudication the tender

shall be divided into the following sections:

a) technical information

b) commerDial information

c) calendar for tenders.

B.l Technidal information

The tenderer must describe the design, the materials

and methods of manufacture, the wolding, erecting, testing

and finish of the complete installation as specified in

s·ections 2,3,4,5 and 7. In particular he should pay atten-

tion to all points where CERN has asked him to make pro-

posals.

All calculations, weight, dimensions and certain. tech­

nical data (e.g. resulting strains) must be mentioned.

Preliminary drawings of the supports and the expansion

joints as well as prospectus describing valves shall ~e

attached to the tend~r, together with a list of the pro­

posed subcontractors.

After settlement of the contract detailed plans of

tubes, supports and fixations and other component parts

have to be supplied at jointly agreed dates. Should the

contractor not deliver the drawings in time all modifications

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or changes due to this delay shall be made at his expense

or by himself,

The tenderer must propose a delivery programme stating

dates of material delivery to CERN, time of erection and

a programme for tho tests on site.

8.2

8,3

This section must unit nna total prices of

the follo

3.6, 3,7, 3,8, The costs for certificates, tests and third com-

pany inspections made at the factory of the contractor

or his subcontractors must be indicated.

The sumnation of these costs must give the total

fixed

B. Total coc3 ts of , transport, insurance,

erection and final test at CERN site should be stated

sep1:;,ra te1y,

C. The summation A+ B should give the total fixed

price of the safety vent line ready for operation,

D. Any price or price difference due to alterations

should be stated separately.

E. The altornativos include:

a) other material than staihless stool (for

instnnce aluminium, co1Jper or other cold re-

0i· "+0r1t ma+e-~i·~1°)· i...J U vC, ... . J "-·--~ ,; ..i.. ..... ~ 0 '

b) other suggestions by the tenders~

'l'lw closing date for receipt of tenders t CERN is

tho 29thof Se ember 1961, at noon, No extension after

this d::ct to c~m be od,