Volume 8 No. 2 A Newsletter from Cryogenic Industries Winter 1996

IIn recent years there has been a steadyincrease in the demand for ambient airnatural draft cryogenic gas vaporizers

for the continuous supply of gas for variedapplications. Ambient air natural draftvaporizers utilize the heat contained inthe ambient air to provide the energyrequired to vaporize the cryogens flowingthrough the units. They require no exter-nal power or additional fuel source andare easy to install. Once the liquid cryogenis connected, the vaporizer provides gasefficiently and reliably with virtually nomaintenance requirements.

The high capacity of the Cryoquip units isachieved by designing each heat transferelement with eight fins measuring 203 mm(eight inches) tip to tip, coupled withCryopquip’s wide spaced extrusion designwhich allows for more ice formation.Each element has approximately 1.55square meters of external heat exchangersurface per meter of length. Additionally,the vaporizer fin has a specially designed,patented* internal fin configuration thatresults in a very high forced convectionheat transfer co-efficient, well in excess of those found in similar look-alikevaporizers.

The limitation to the operation of thistype of vaporizer is ice build-up. As theatmospheric heat is absorbed by thevaporizer, the water content of the air(humidity) freezes onto the surface of thefin elements and forms ice (frost). Whenthe ice grows to the point where it touch-es the ice growth from an adjacent fin, thevaporizer becomes ineffective. The airflow through the unit carrying the muchneeded heat for the vaporization processis stopped by the ice formation. In order

to provide a continuous flow of vaporizedgas at an acceptable exit temperature, asecond unit has to be employed allowingthe first unit time to defrost and shed itsice. Because Cryoquip’s fin element isextruded to a high quality, very smoothsurface finish, it promotes defrosting andrapid ice shedding and minimizes thetime for defrosting. This in turn leads tothe utilization of smaller units to meetflow requirements, which reduces systemcost and improves efficiency.

However, regardless of the size of theunits, in order to provide continuous gasflow, the vaporizer(s) will require defrost-ing at some point during operation. Thelength of time that elapses between thevaporizer being on-line and providing gasflow, and being off-line defrosting, isknown as the “switching time” or “cycle

time.” There is considerable debate overhow long the switching cycle should be.Computer simulations suggest an optimumtime lies between four and eight hours.

Because ambient air natural draft vaporiz-ers’ operation is affected by the ambientconditions, ice build-up during the winteris much less than during the summer,simply because of the lack of humidity inthe winter months. (See Figure 1.) In thesummer, although the ice build-up ismuch higher, the ambient temperature is

INSIDE THIS ISSUEþ ACD prototypes a process pump

for cold box storage . . . . . . . . . . . . 2þ A computer program designs

diffuser vanes . . . . . . . . . . . . . . . . . . . 3þ Map of Cryogenic Industries’global

service & repair centers. . . . . . . . . . 4þ Cosmodyne’s MAPLE plant series

produces 8-16 tpd. . . . . . . . . . . . . . . 5þ A new service center is added

to our group. . . . . . . . . . . . . . . . . . . . 6

INSIDE THIS ISSUE

Continued on page 7

Providing the ice accumulation does not bridge the fin elements, the Cryoquip ambient air natural draft vaporizerwill continue to function.

Vaporizer ice build-up requires an analysis of switching issues for ambient air units

ACD, Inc. has supplied cryogenic pumps,turboexpanders, and compressors to theair separation industry for more thanforty years. Currently, the company isprototyping a new cold box pump thatwill be reliable, safe, and have low operat-ing costs.

The importance of compressors andexpanders in the air separation processallows the manufacturing of thesemachines to be custom designed for eachapplication. ACD’s new process pump forcold box service will have many of theadvanced features found in the turboex-panders and compressors. The reliabilityand safety features currently used inACD’s process pump will also be retainedin the new design. These include duallabyrinth seals; dry nitrogen gas purge ofthe motor/bearings; intermediate/insula-tor housings to thermally insulate thebearings from the cold fluid product; andextinguishing bronze construction.

Design Features• The new cold box pumps will be able

to connect to the cold box as an auxil-iary. (See Figure 1.) The expansionjoints, valves and piping can be sup-plied by ACD.

• The pump rotating assembly and allparts that could conceivably rub willbe part of a cartridge assembly. A keyfeature of the new design is the abilityto remove the cartridge assembly as asingle unit. (See Figures 2A and 2B.)The cartridge assembly is a smallerpackage compared to that of the entirepump and this makes replacing pumpcomponents easier.

• The cartridge assembly is attached by asingle joint. This means installationtime will be less and because there arefewer joints, it will be a safer installa-tion. The discharge, suction, vent, and

purge lines are permanently welded aspart of the cold box plumbing.

• The pump shaft is supported by oillubricated bearings which are mount-ed in a separate bearing housing. (SeeFigures 2A and 2B.)

• The motor shaft is coupled to thepump shaft so the motor can bereplaced without disturbing the bear-ing housing or the pump.

The following design features are currentlyfound on ACD’s process pumps and will beretained in the new pump design:• Dual labyrinth seal. The dual labyrinth

seal is a non-contacting seal. This sealprovides long service life and is inher-ently safe. The primary buffer gas in theseal is the product gas itself and thesecondary buffer gas is dry nitrogen gas.

• The bearings are separated from thecold product by a distance piece andinsulator plate. A slinger is mountedafter the insulator plate to assure nooxygen can enter the bearing housing.

• Continuous nitrogen gas purge of themotor and bearing housings.

• Bearing motor heaters for prolongedcool-down or stand-by modes.

• A control panel to monitor the bufferand purge gases.

Pump EfficiencyIn the past, pump efficiency has erro-neously not been considered a major fac-tor in cryogenic process pump selection.Experience has shown that ACD’s currentprocess pumps are reliable, safe, and havelow initial cost. Process pumps are runcontinuously and in some cases, have theshaft energy removed by the processrefrigeration. The operating cost of thesepumps can be very high. ACD’s newprocess pumps will have higher pumpefficiencies and consequently lower operat-ing costs. Air separation plant cold boxpumps are prime examples of why pumpefficiency should be given more considera-tion in pump selection.A cold box pump has the pump inputshaft energy removed by the process andtherefore is more expensive to operate.The following example (See Figure 3.)demonstrates the effect pump efficiencyhas on operating cost. (Assumption: Thecost of refrigeration is assumed to be thecost to produce liquid nitrogen and onlythe liquid nitrogen heat of vaporization isused to produce refrigeration.) A typical 1,000 tpd liquid oxygen plantuses a centrifugal pump to transport liq-uid oxygen (specific gravity 1.14) to the

ACD plans the next generation of cold box pumps

Typical five (5) year cost to operate the pump is:

Power Cost ($) =(kw (shaft)) ($0.05/kw-h x 24 hr/day) (365 days /yr x 5 years)

motor efficiency=92%= kw (shaft) x 2,380

Refrig. Cost ($)=(kw (shaft))(3,413 BTU/kw-h)(.24 kw/ #LN2)($0.05/kw-h x 24 hr/day)(365 days /yr x 5 years)

85.6 BTU / # LN2= kw (shaft) x 20,956

Note: The refrigeration cost (approximately 9 times that of power cost) is independent of pump flow, head and efficiency parameters, and specific gravity.

If the pump efficiency is 65%, then the kw (shaft) calculation would be:

kw (shaft) =gpm x head x specific gravity

5,303÷ pump efficiency = 39.29 kw

Total operating cost for five (5) years: Power = $ 93,510Refrigeration = $823,361Total Energy = $916,871

If the pump efficiency could beincreased to 80%, the total cost would

be reduced to $744,989 with a$171,920 savings over five years. This

is $23,337 saved per kw over a fiveyear period. The amount of savings issubstantial especially where refrigera-

tion of pump input energy occurs.

Continued on page 3

2

The program for designing impeller blades has been adaptedto the design of diffuser vanes

AAcomputer program forredesigning the vanes ofa radial diffuser in a tur-

bopump was written to satisfynew operating requirements,while not changing either thenumber of vanes or the radiallocations of the leading andtrailing edges of the vanes. (See Figure 1.) The new operat-ing requirements include speci-fied levels of performance inoff-design operation.

The computer program is amodified, upgraded version of aprogram devised previously fordesigning blades of centrifugalpump impellers. By use of twocoordinates called “G” and “H,”the complex three-dimensionalsurface of a blade (in this case, a diffuservane) can be described as though it weretwo-dimensional. The definitions of thesecoordinates are G=∫dm and H=∫rd , wherem denotes meridional length, r denotesradial length, and denotes circumferen-tial angle. The mean line of the blade isgenerated in the G-H plane with the inletand discharge blade angle specified andthe hub and shroud contours defined.The coordinates of the pressure and suc-tion sides of the vane are computed fromthe mean line and a specified elliptical orother distribution of thickness along themean line from the hub to the shroud.

The foregoing computation of the shapeof the vane is performed by one of severalsubprograms that are executed sequen-

tially in an iterative design-and-analysisprocedure. The vane-shape-generatingsubprogram generates input data for usein computing distributions of pressureand velocity in a subprogram that analyzesthe design. If the resulting blade loadingand performance, as computed by thedesign-analyzing subprogram, are accept-able, the design is structurally analyzed. A design that satisfies both performanceand structural requirements is passed to afinal subprogram that generates a practicalvane design for fabrication.

This article was taken from the July 1996issue of NASA Tech Briefs. The work wasdone by Kevin J. Lunde and Wei-ChungChen of Rockwell International Corp. forMarshall Space Flight Center.

The leading and trailing edges of a redesigned diffuser vane wereconstrained, as an explicit condition of the redesign, to lie at thesame radii as in the original design.

top of the second column (132 feet tall) at a rate of 900 gpm. The cost of the plantand power vary between locations, how-ever, for this analysis, $ 0.05 per kw-h and.24 kw of power to produce one (1)pound of LN2 are assumed.

ACD’s new cold box process pumps willuse advanced hydraulic design, machining,

and materials of construction to achievehigher pump efficiencies by incorporatingmany of the advanced features now usedin ACD’s compressor and turboexpanders.The cartridge assembly design will makereplacement easier and safer than thatused currently. The new pumps will bemore efficient and cost less to operate.

For more information, contact Greg Fox atACD, Inc.

COLD BOX

A computer program redesigns radial diffusers in turbopumps

Continued from page 2

Ed Huckstein was recently hired byPittsburgh Cryogenic Services, Inc.as that company’s Sales Manager. Hewill be responsible for increasingmarket penetration and awarenessof Pittsburgh Cryogenic Services’sales and service capabilities toindustrial gas welding distributorsand major industrial gas suppliers.

Prior to his recent hire, he was asales representative for BOC Gases.In this capacity, his efforts focusedon the company’s retail sales, bulkgas sales, on-site plant sales, andPSA plant sales. Large volume gainand significant increases in customerbase were recognized while he wasin this position.

Huckstein also worked for thePulva Corporation in the chemicalprocess industry in the industrialdevelopment of cryogenic grindingand testing. He earned a bachelor’sdegree in Business Administrationfrom Grove City College, GroveCity, PA, USA and a Master ofBusiness Administration fromDuquesne University, Pittsburgh,PA, USA.

Huckstein’s office is located in thePittsburgh Cryogenic Servicesheadquarters; he can be e-mailed at edhuck@pulsenet.com.

Manager hired for sales and

service center

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Members of

Global Service and Repair CentersGlobal Service and Repair Centers

1906 Providence CourtCollege Park, GA 30337 USAPhone: +1 770-909-0291FAX: +1 770-909-0694

530 McNicoll AvenueNorth York, Ontario M2H 2E1, CanadaPhone: +1 416-502-1950FAX: +1 416-502-1952E-mail: cryocan@istar.ca

Rheinauenstrasse 2D-79415 Bad Bellingen, GermanyPhone: +49-7635-8105-0FAX: +49-7635-8965E-mail: 101670.1042compuserve.com

767 State Route 30Imperial, PA 15126Phone: 800-327-6461 (USA only)Phone: +1 412-695-1910FAX: +1 412-695-1926E-mail: pittcryo@pulsenet.com

47 McIntosh StreetAirport West, Victoria 3042, AustraliaPhone: +61-3-9330-2444FAX: +61-3-9330-1015

64 Tianmo Shaw RoadHangzhou, 310007, ChinaPhone: +86-571-885-9026FAX: +86-571-885-9025E-mail: hci@pub.zjpta.net.cn

Lot 35, Jalan Selat Selatan 21Sobena Jaya, Pandamaran42000 Port Klang, Selangor, Malaysia Phone: +60 (3) 365-4801FAX: +60 (3) 365-4798 E-mail: jestes@pc.jaring.my

2110 S. Lyon Street, Unit HSanta Ana, CA 92705Phone: +1 714-724-8636FAX: +1 714-641-1921

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Cosmodyne adds a new family of air separation plants to its portfolio

AAnew series of air separation plantsis under development byCosmodyne–the MAPLE Series.

The MAPLE is a modular plant line witha capacity range of 8-16 tons per day ofliquid nitrogen or liquid oxygen. Theplant series is specifically designed foruse in the more remote areas of theworld where reliability, ease of mainte-nance, and portability are paramount.

Performance flexibility is fundamentalto the design of this new plant series.The MAPLE can be configured to pro-vide various production rate and purityrequirements, within the the overallperformance envelope. Both cost anddelivery are comparable to that of stan-dardized packaged plants because of thestatic fundamental design concept,which minimizes front end engineeringand manufacturing lead time.

A typical MAPLE consists of four basicmodules–the cold box, air purificationmodule, feed air compressor, and an

interconnecting piping and wiring kit.Both automatic and manual control systems are available. The modules are

sized for shipment in standard ISO con-tainers to minimize cost. This also elimi-nates the need for specialized transportand handling equipment in-country.

Following completion of manufactur-ing, each plant is fully assembled atCosmodyne’s headquarters where itundergoes thorough mechanical and elec-trical testing and complete performancespecification evaluation. Customertraining runs concurrent with this test-ing, allowing actual operating conditionsto be used for education. This puts mostof the pre-commissioning work atCosmodyne’s headquarters where it canbe done most efficiently and cost-effec-tively. This also reduces on-site assemblyand commissioning time to 10-15 days,depending on specific configuration.Overall installed cost and total time fromorder point to completion of on-sitecommissioning is substantially reduced.

For more information, contact GeorgePappagelis at Cosmodyne, Inc.

Each MAPLE plant is fully assembled and tested atCosmodyne headquarters.

A 160 ton /day oxygen gas generatorcold box was fabricated by Cryoquip forBOC Gases.The cold box will be used ina gas plant for a steel mill in Texas USA.

The cold box, jointly engineered byCryoquip and BOC was fabricated in

one piece, weighs 66 tons, andmeasures 66 feet long, 14 feet

deep, and 10 feet wide. Thebox contains pre-manufac-tured plate fin heat exchangersand large valve array anddistillation columns. Afteron-site installation, thecold box will be mountedvertically and insulatedwith perlite powderprior to start-up.Cryoquip is one of

only a handful of skilled fabricationcompanies capable of the partial

engineering and fabrication of suchcomplex cryogenic assemblies.

Cryoquip fabricates a cold box for BOC Gases

5

CryoAtlanta, Inc. has been added to theCryogenic Industries group of companies inresponse to increasing cryogenic pumpactivity in the Southeastern USA. The com-pany, located just one mile south of theAtlanta airport, is focusing its efforts oncryogenic centrifugal and reciprocatingpump repair, service, and sales.

Customer service is the first priority for thecompany, according to General Manager TomFarmer. To this end, a series of programs de-signed to aid cryogenic pump users is beingcreated, including on-site support, an ex-change program to facilitate pump repair,an extensive spare parts inventory for ship-ping efficiency, and pump training classes toeducate users on installation and repair.

CryoAtlanta serves these states in the USA:Georgia, Virginia, S. Carolina, N. Carolina,Florida, Alabama, Tennessee, Mississippi,Arkansas, Louisiana, Oklahoma, and Texas.

Tom Farmer was hiredas General Manager ofCryoAtlanta becauseof his extensive expe-rience as a servicemanager and broadtechnical knowledge.Prior to joiningCryoAtlanta, heworked as a ServiceManager for SiemensIndustrial Automation

directing the North American service cen-ter, field service, customer training, andparts inventory for gas analyzers.

Prior to that position he was SeniorInstrument Technician for Air Products andChemicals, Inc., Field Service Engineer forXerox, Corp., and Flight Test ElectronicsTechnician for Lockheed Georgia Co.Farmer was a Petty Officer 2nd Class in theUS Navy, graduating from Navy “A” Schoolin basic electronics. He also received anElectronics Technology degree fromMarietta Area Technical School, GA, USA.

CryoAtlanta, Inc. is a member of CryogenicIndustries, an authorized ACD, Inc. salesand service center, and affiliated withPittsburgh Cryogenic Services, Inc.

CryoAtlanta, Inc.1906 Providence CourtCollege Park, GA 30337 USAPhone: +1 770-909-0291FAX: +1 770-909-0694

A new service centerincreases global coverage

Members ofHEADQUARTERS:

Cryogenic Industries25720 Jefferson AvenueMurrieta, CA 92562 USAPhone: +1 909 696-7840FAX: +1 909 698-7484www.cryoind.com

EAST COAST USA: Cryoquip, Inc.Allentown, PA USAPhone: +1 610 437-1867FAX: +1 610 770-0766E-mail: lhimmie@aol.com

SOUTH CENTRAL USA:Cryogenic IndustriesHouston, TX USAPhone: +1 713 465-4910FAX: +1 713 465-6870

SOUTH AMERICA USA: Cryogenic IndustriesSan Clemente, CA, USAPhone: +1 714 498-3610FAX: +1 714 361-3438

EAST COAST USA: ACD, Inc.Allentown, PA USAPhone: +1 610 530-9060FAX: +1 610 530-9094E-mail: bdeobil@nni.com

FRANCE:Cryogenic IndustriesBättwil (Basel), SwitzerlandPhone: +41 61 731-3832FAX: +41 61 731-3833

NORTHERN EUROPE AND SPAIN: Cryogenic IndustriesLondon, England, UKPhone: +44 171 499 8036FAX: +44 171 493 4220

CHINA: Cryogenic Industries-ChinaHangzhou, ChinaPhone: +86 571-885-9026FAX: +86 571-885-9025E-mail: hci@pub.zjpta.net.cn

HONG KONG:Cryogenic Industries LimitedWanchai, Hong KongPhone: +852 2519-6078FAX: +852 2519-8012

College Park, GA USAPhone: +1 770-909-0291FAX: +1 770-909-0694

Santa Ana, CA USAPhone: +1 714 724-8636FAX: +1 714 641-1921

Santa Ana, CA USA800 525-4216 (USA Only)Phone: +1 714 261-7533FAX: +1 714 261-6285E-mail: acd@acdcom.comWeb: www.acdcom.com

Torrance, CA USAPhone: +1 310 320-5650FAX: +1 310 320-5688E-mail: cosmodyne@msn.com

Selangor, MalaysiaPhone: +60 (3) 365-4800FAX: +60 (3) 365-4798

Selangor, MalaysiaPhone: +60 (3) 365-4801FAX: +60 (3) 365-4798E-mail: jestes@pc.jaring.my

Melbourne, Victoria, AustraliaPhone: +61 3 9330-2444FAX: +61 3 9330-1015

Imperial, PA USAPhone: +1 412 695-1910FAX: +1 412 695-1926E-mail: pittcryo@pulsenet.com

Murrieta, CA USAPhone: +1 909 677-2060FAX: +1 909 677-2066

North York, Ontario, CanadaPhone: +1 416 502-1950FAX: +1 416 502-1952E-mail: cryocan@istar.ca

Cryopump AGAesch, SwitzerlandPhone: +41 61 751-6000FAX: +41 61 751-6260E-mail:101670.1042compuserve.com

Cryopump GmbHBad Bellingen, GermanyPhone: +49 7635 8105-0FAX: +49 7635 8965

6

VAPORIZER Continued from page 1

also a lot higher, leading to fast defrostand ice shedding. Also, ice build-up is notnecessarily a negative. As the ice densityincreases with time so does the thermalconductivity, providing an adequate mech-anism for heat transfer to supply the nec-essary energy for vaporization. (See Figure2.) Providing the ice accumulation doesnot bridge the fin elements, the vaporizerwill continue to function adequately.

There are many locations around theworld where ambient vaporizers willoperate continuously without anyrequirement for defrosting, eliminatingthe need for switching and for stand-byunits. Where switching from one unit toanother is required, there are a few thingsto consider. Switching can be done manu-ally or automatically, rapidly (less thaneight hours) or more slowly. Consideringthat the optimum time for efficient perfor-mance is approximately eight hours, man-ual switching is satisfactory. (Here, eighthours loosely equates to a working shiftduration, after which the units can beswitched and the stand-by unit broughton-line for the second working shift andso on.) Manual switching requires nopower; uses simple cryogenic globevalves, is simple to install, requires littlemaintenance and is reliable.

Automatic switching, however, doesrequire power (which to a certain extentdefeats one of the primary advantages ofthe ambient vaporizer), and skilled instal-lation. The more frequently the switchingsystem operates, the higher the mainte-nance, the less reliable the switchingbecomes leading to the likelihood ofinterruption of the gas flow. In the case of a back-up system, which typicallycomes on-line during power failure, auto-matic switching would be inappropriate.

There seems little advantage to rapidswitching (re: switching intervals of lessthan eight hours), and several drawbacks.First, rapid switching necessitates anautomatic system. The initial vaporizerhardware may be slightly less expensive,but the total capital outlay is not; andthere is no tolerance for error, for variableambient conditions, or accommodation offuture increased gas flow rate require-ments. In cases where there is no risk inrelying on the ambient conditions to provide quick defrosting to facilitate rapid

switching, a single, high efficiency heattransfer unit meets the process require-ments with no risk and required mainte-nance, while giving maximum reliability.

For certain high volume flow ratesrequired on a continuous basis, switchingbetween units is unavoidable. Rapidswitching though, especially in thesecases, is not desirable. Long term manualswitching offers the most reliable, flexibleextension of the concept of the low cost,

reliable and simple ambient air vaporizer.For convenience, automatic switchingmay be considered, but switching timesshould be between four and eight hoursto ensure maximum system efficiency andavoid high maintenance costs, unreliability,inflexibility and system failure.

For more information contact Bryan Smith at Cryoquip, Inc.

*US patent #5251452

Cryogenic Industries has developed a new web site. Please visitus at www.cryoind.com. This site contains an overview of ourgroup’s companies; a directory of e-mail addresses; the latestissue of FrostByte; press releases with new product information;and an e-mail form for your comments and questions.

The Cryogenic Industries site is linked to member companyACD, Inc.’s sites at www.acdcom.com, www.acdpumps.com, andwww.acdturbines.com. These sites contain detailed informationabout the ACD product line. Future links are being developedfrom the Cryogenic Industries site to Cosmodyne, Inc. andCryoquip, Inc.

http://www.cryoind.com

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Pittsburgh Cryogenic Servicescan now be reached via elec-tronic mail. Use the followingaddresses to direct your message:

pittcryo@pulsenet.com

Individual listings are as follows:carl@pulsenet.com (Carl Henningson)

mousie@pulsenet.com (Shawn Danna)

edhuck@pulsenet.com (Ed Huckstein)

dianne@pulsenet.com (Dianne Dorsek)

donman@pulsenet.com (Donald Manfredi)

Note: There are no spaces between letters andsymbols and the entire address is in lower case.

JAN 22-24 SEMICON–KOREA ’97, Seoul, KoreaContact: Semicon USA +1 415-964-5111

JAN 24-25 19th NATIONAL SEMINAR ON INDUSTRIAL GASES,All India Industrial Gases Mfg’s Association, Hyderabad, India +91 40 3321422

JAN 28-30 11th INTERSOCIETY CRYOGENIC SYMPOSIUMHouston, TX, USA +1 713-621-8833

FEB 24-26 COMPRESSED GAS ASSOCIATION ANNUAL MEETINGPhoenix, AZ, USA +1 703-412-0900

MAR (TBA) NATIONAL H2 ASSOCIATION ANNUAL MEETINGUSA (City, TBA) +1 202-223-5547

MAY 18-21 AMERICAN GAS ASSOCIATION OPERATIONS CONFERENCE & EXHIBITNashville, TN, USA +1 410-997-0763

JUL 28-AUG 1 CRYOGENIC ENGINEERING CONFERENCE/ INTERNATIONALCRYOGENIC MATERIALS CONFERENCE (CEC/ICMC)Portland, OR, USA +1 503-292-2114

OCT 28-31 OIL & GASTECH ’97International Trade Fair Equipment for the Oil & Gas Industry,Kiev, Ukraine +49 211 4560 739

Member company utilizes electronic mail

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