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Vacuum Insulated Pipingfor

Cryogenic ServiceSystem Design and Installation

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Chart IndustriesHistory• World’s largest cryogenic design/manufacture of cryogenic

equipment for over 40 years.Facilities• Worldwide facilities including North America, Czech Republic,

China, GermanyProducts• Storage tanks, pipe, transport/delivery tanks, injectors, test

chambers, controls systems, etcMarkets• Industrial gas, medical, biological, electronics, aerospace,

automotive, restaurant, beverage, etc.Vacuum Insulated Pipe Brand Names• MVE• CVI• Python

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Types of Cryogenic Piping

Static vacuum• Section vacuums are factory sealed• Very high and stable efficiency• Long life expectancy• Simple field installation

Dynamic vacuum• Requires continuous operation of vacuum pump• Less efficient than static vacuum pipe

Foam insulated copper• Medium/low efficiency, degrades with time• Lower initial cost but higher operating cost and shorter life

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VIP Applications

Volume related applications• Nitrogen expands 700X from liquid to gas

Refrigeration related applications• LN2 temperature is –320 degrees Fahrenheit• LN2 heat of vaporization is 92 BTU/#

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VIP Applications

Volume related applications• N2 Purge gas

– Beverage & food packaging• Aerospace• LNG as fuel

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VIP Applications

Refrigeration related applications• Cryo-bio storage• Biological freezing• Food freezing• Electronics testing – HALT/HASS• Entertainment – fog effects• Super conductors• Deflashing of rubber parts• Cryo tempering

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VIP Design and construction

Sizes• Rigid

–½” pipe size thru 10” pipe size• Flex

–¼” ID flex thru 10” ID flex

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Pressure rating• Normally 150 psig for LN2

–Most LN2 applications require pressures of 20-70 psig

• Normally 300 psig for LCO2

• Special pressures on request

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Code• ASME B31.3 Process piping

New Prague manufacturing shop approvals• ASME “U” stamp

–Certificate #8,377• ISO-9001:2000 Quality System

–Certificate #GQC-246

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Double wall – vacuum insulated• Nearly 400 deg F temperature differential from

inner to outer• Vacuum minimizes gas conduction and

convection• Long thin walls minimize metal conduction• Multi layer super-insulation minimizes radiation

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Inner pipe Outer – jacket pipe End closure

Support Internal bellows Gas trap Super-insulation

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Materials• Inner carrier pipe options

– Pipe, welded, schedule 5, type 304 SS– Pipe, welded, schedule 5, Invar– Convoluted flex, type 321 SS– Specials on request

• Vacuum jacket material options– Pipe, welded, schedule 5, type 304 SS– Convoluted flex, type 321 SS– Specials on request

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Materials• Super-insulation

–Multiple layers of cryogenic grade spacer paper and aluminum foil or double aluminized Mylar

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Low conductivity spacers• Multiple leg support of low conductivity

composite materialsLow conductivity end connections• Bayonets are most common• Field joint end transitions

–Require welding together on-site

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VIP Design and constructionWhen filled with LN2, SS inner pipe shrinks in relation to outer (jacket) pipe.• 0.003 inch per inch of length (0.72” / 20’).

Bellows placed on inner line or outer jacket to compensate.• Internal bellows

– Easier for on site installation– Protected from damage

• External bellows– Allows higher pressures– Cleaner flow path

Invar inner pipe has extremely low shrink rate• Bellows not required on lines shorter than 20’

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VIP Design and constructionVacuum• All vacuum surfaces cleaned to remove contaminates• Getters installed to maintain vacuum

– Molecular sieve– Palladium oxide

• Helium mass spectrometer leak testing• Heating during evacuation process• Vacuum retention test prior to shipment

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VIP Design and constructionEvacuation port• Annular space overpressure relief

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VIP Design and constructionOptional Testing/Quality Measures• Radiographic inspection (5% of butt welds)• Pressure test (each section)• Inspection by ASME Authorized Inspector• Dye penetrant testing• Material traceability

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VIP Design considerationsCryogenic liquid• LN2 – most applications• LO2 – requires special components & cleaning• LHE – requires special components & mfg• LCO2 – requires higher pressure & special

components

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VIP Design considerations

Design Pressure – Maximum Allowable Working Pressure (MAWP)• What is the pressure required by the end use application

– What is requirement right at point of use?• What is the pressure drop through the pipe system?• What is the pressure supply capability of the liquid

source?• What is the pressure control capability of the liquid

source?• Are there multiple use points/pressure requirements

within the system?

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Flow requirements are used to size the pipe’s header and drop diameter sizes:• What is the end-use application’s flow requirements?• Do the flow requirements change over time?

– Change with pressure?• How many use points are in the system?• Will there be additional equipment added to the pipe

system in the future?– Consider this flow in the sizing of the main header

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VIP - LN2 flow vs pipe size

Length equivalent is length of pipe plus fitting factorsValve = 40 feet / Elbow or tee = 20 feet / 1 foot flex = 3 feetOne foot vertical rise = 0.35 psi pressure drop for nitrogen serviceBased on 5 psi pressure drop

140 GPM48 GPM25 GPM8 GPM1 GPM500’160 GPM54 GPM28 GPM10 GPM2 GPM400’185 GPM63 GPM32 GPM11 GPM2 GPM300’

225 GPM78 GPM40 GPM14 GPM3 GPM200’325 GPM110 GPM56 GPM20 GPM4 GPM100’

3” PS2” PS1-1/2” PS1” PS½” PSLen Eq

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VIP Design considerationsRouting• Define carefully because changes are difficult, time consuming

and costly– Useful to make the initial design, then re-visit the site with

the drawing to confirm the design will work• Be careful of obstructions (vents, electrical, pipes, etc.)

– Be sure to ask about any obstructions that may not be present at the time of design, but may be installed before the VIP is installed

• Minimize fittings to control cost (elbows, tees, bayonets, etc.)and improve system flow performance

• Flex can be used to make installation easier, or work around an obstruction such as a support beam, etc.

– Especially useful at connection points to the tank and/or end use equipment

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VIP Design considerationsSection lengths• Longer sections generally reduce total system cost and

heat leak• 20 foot sections are optimal for manufacturing and

shipping• Consider installation issues

– Moving into building, lifting, walls, etc.• Consider shipping• May consider section breaks in places to accommodate a

future addition in specific places• There are some minimum dimensions for various fittings

based on manufacturing requirements

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VIP Design considerationsSection connections• Bayonets

–Shrink fit design - “MVE”–Close tolerance design - “CVI”–Field joints

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O-ring

Female bayonet (sectioned)Clamp

Shrink fit nose Male bayonet

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Vacuum jacketed valves

Y-PatternT-Pattern

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Non-jacketed cryogenic valves• Although they are not vacuum

insulated, they still need to have an extended stem so that the resulting ice ball does not grow to the valve packing

– When valve packing gets too cold, it could leak nitrogen to the environment

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Gas traps• Used in intermittent use drops to

control heat leak and frost.• Allows use of non-VJ valves. • Not recommended for high flow

applications due to its pressure drop• Not recommended for continuous

use applications

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VIP Design considerationsEnd connections• Bayonets

– Most efficient– Easy to install

• Pipe threads– Will result in ice ball– Readily available connections to various equipment

• ANSI flanges– Will result in ice ball– Need to use low temperature gasket material

• Pipe stub ends– Will result in ice ball– Requires welding on-site at installation

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Relief valves & risers• Relief valves are required in any spot where liquid can be trapped

(between any two valves)– Consider protection at the inlet and outlet of the pipe system

• Does the supply/use equipment have protection?• Confirm pressure rating of relief valve needed

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Future expansion• Less expensive to add “futures” than to modify

or replace system later• Consider future expansion when sizing pipe• Typically accommodated by placing a caped

bayonet at location where expansion may take place.

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VIP System Measurement

Location of tank and use pointsArchitectural structure of buildingLocate clearest path from tank to use pointsEstablish elevationsDesign system with maximum length sections minimizing elbows & teesEstablish flow rates to support pipe sizingEstablish use pattern

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VIP System Measurement

Establish saturation pressure requirement at use pointCombine design, sizing and flow to establish pressure dropRecommend tank operating pressureMeasure and document the pipe routingEstablish installation procedures and material / equipment list

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VIP System Installation

Off loading the truck• Watch for damage

–Notify driver and document any damage immediately before driver leaves!

• Consider checking section vacuums

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Reading the print and assembling the puzzle• Isometric drawing – not to scale• Section numbers on print match section

numbers on labels–VS-1, VS-2, VS-3, etc

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Supports / hangers• Support every 10 feet• J-hangers or cushioned pipe clamps

– Uni-strut (www.tyco-unistrut.com)– Flex-strut (www.flexstrut.com)

• External bellows pipe needs to be able to move along its axis

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Installation equipment & supplies• Halocarbon grease to lubricate bayonet o-rings• Standard hand tools (wrenches, small hammer)• Consider need for manlift, forklift, crane• Field joints require welding and evacuation

equipment

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Installation labor• Generally need at least two people to install any

system–Systems with longer sections, bigger

diameters, many sections, welding, etc will require more people on-site

• System with bayonets require less time and skill• System with field joints require welding and

evacuation

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Proper bayonet assembly• Clean and inspect bayonets• Lubricate and install o-ring• Engage bayonets (do not twist)• Install V-retainer and tighten nut• Bayonets should slide together easily

– If it is difficult, it is likely due to not having the pipe sections aligned properly

– Do NOT force them together

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Proper slope• If the system contains a Cryovent to keep the

pipe filled with liquid, the pipe must rise continuously towards the Cryovent.–Any gas bubbles must rise to the Cryovent–Any high spots will trap gas–Rise ~1” per 50’

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Pressure / leak test• Do not exceed MAWP of pipe• If testing at more than 90% of MAWP,

temporarily replace relief valves• Use clean, dry gas, preferably nitrogen• Leak test all joints or do pressure decay test

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Start up• Preferably isolate Cryovents• Fill slowly to minimize pressure spike• Open use point valves until there is a continuous

stream of liquid• It will be several hours before system is stable• Once system is stable, open cryovents

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Maintenance• Monthly visual inspection of piping

–Look for sweating, frost and leaks–Check relief valves (installed & set point)

• If there are questions or issues, call Chart–Provide PN and VS number from label

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Maintenance• Before disconnecting any bayonet or

component, verify that all pressure has been released for the system.

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VIP Accessories

Cryovent• Keeps the VIP system filled with LN2 during periods of

no useage– Provides quick response when the system needs

liquid• Float driven valve• Installed on tee, at highest point, near use point• Pipe must rise continuously towards Cryovent

– Gas bubbles must get to the Cryovent

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VIP Cryovent

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VIP AccessoriesAPPS-160 Phase separator• Allows using a single storage

tank to supply a high pressure GN2 application and a low pressure LN2 application

– Lowers pressure of LN2– Sits next to supply tank– Outlet Feeds VIP system with

a vacuum insulated bayonet connection

– Operates up to 50 psig– 15 GPM max

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Python Pipe

Python Pipe Product• Good alternative to foam insulated copper pipe• 1” & 2” pipe size in stock, 3” special order• Straight, rigid lengths from 2’ to 20’ (even feet)• Flex sections with 6’ of flex• Pre-insulated cover kits in straight, elbow & tee

configurations

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Python Pipe

Higher heat leak means higher cost of operationEnd use system is much more efficient for customer, providing higher quality liquid and reducing losses

Foam insulation should be stripped off and re-applied to keep its efficiency

Extremely low maintenance

Plastic outer jacket and foam is easily damagedStainless steel outer jacket for durability and aesthetics

Over time will condense moisture on outer jacket and ultimately may grow mold

Will not condense moisture on outer jacket

Foam insulated pipe requires significantly larger OD for the insulation, requiring more space and higher cost of installation (wall penetrations and supports)

Smaller outer jacket means less space required for the installation and less cost for wall penetrations and pipe supports

As moisture leaks past the plastic cover, it soaks into the foam making it even less efficient. Eventually need to replace the foam!

Stainless steel outer jacket is not affected by moisture from ambient

Poor-moderate thermal performanceExcellent thermal performance (at least 5 times better than foam)

Foam Insulated PipePYTHON

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Standard Python Joints

T-joint

Elbow joint

Straight joint

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Python pipe

Design• Inner & outer – stainless steel pipe, schedule 5• Static vacuum – factory evacuated and sealed• Field welded, pipe stub end joints

–All weld joints are insulated in the field• 400 psig MAWP

–External bellows design

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Python pipe

System design considerations• Even foot increments• Minimize joints to maximize efficiency• Over-all length will shorten 3-1/2” per 100’ when

filled with LN2

–Consider this when providing installation• Wall/roof penetrations• Connections to equipment

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Python pipe

Installation• Hang sections• Weld joints (manual TIG on schedule 5 SS pipe)• Leak test joints• Install joint covers

Download - VJ Piping Design

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