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A PLACE OF PILGRIMAGE FOR ENGINEERS

Water-Injected Screw Compressors at Philips in Hamburg

"The new compressed-air station in use at Philips Semiconductors in Hamburg-Lokstedt

has meanwhile turned into some kind of place of pilgrimage for interested engineers

because we are generating compressed air here with water-injected and water-lubricated

screw compressors made by GVM in Crimmitschau", says B.Eng. Frank Reetze. This GVM

concept is unique all over the world in the opinion of the manager of HEW Contract

Betriebsgesellschaft Lokstedt mbH (HCL). He concedes it a development lead of at least 8

to 10 years.

As from the mid-nineties, Philips intended to focus exclusively on the core business line in

their Hamburg Semiconductors Factory. Therefore, a full-service contract was concluded in

1998 with HEW Contract Betriebsgesellschaft Lokstedt (HCL), a subsidiary of Hamburg

Electric Power Company (HEW) covering the whole power supply including compressed-air

supply. So, the previous power supplier is also fully responsible for additional compressed-

air supplies to Philips.

Frank Reetze says: "We can offer maximum benefit to our clients only with highly-efficient

solutions. Now, we have implemented a pilot solution at Philips in close co-operation with

GVM for particularly economic generation of 100 % oil-free compressed air. This solution

might be unique all over the world with regard to size and constructive design."

The old compressed-air station operated with two-stage oil-free compressing screw

compressors with oil-lubricated transmission and with fixed numbers of revolutions. This

caused high pressure fluctuations and high power consumption for driving and for cooling of

the compressors.

The station required huge maintenance efforts and had reached the end of its service

lifetime. Therefore, Frank Reetze considered a short-term replacement as urgently

necessary: "Philips Semiconductors play a leading role among the Top 12 of semiconductor

technology and does not only anticipate quality on a world-wide scale from their suppliers

but also uninterrupted supply over 365 days with 8760 running hours per year. Actually, 36

hours maximum are available to us per year for maintenance and servicing work altogether

between Christmas and New Year – in the future, 0 hours only. Even in such cases, we have

to maintain supply by sufficient redundancies."

Four PIONEER screw compressors of the CWS 250-PW model

The n+1 Philosophy

In the redevelopment of compressed-air station, Philips gained benefit from the profound

knowledge of the HCL service partner and of the former naval engineer Reetze who had

been in charge of planning and erecting large industrial plants as management consultant

prior to his work at HEW. To implement his revolutionary concept of 100 % oil-free

compressed-air generation at Philips, Frank Reetze chose four water-injected screw

compressors of GVM Gesellschaft für Schraubenverdichter und

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Schraubenmotorentechnologie mbH in Crimmitschau (model CWS 250-10 PW, driving power

250 kW each, rate of delivery 2400 Nm3/h each). All four packages were conceived for load-

demand operation and for 100 % compatibility with frequency inverters. In normal

operation, three compressors are running in partial-load demand operation with a duty of

approx. 80 % in parallel. The fourth package functions as reserve in stand-by operation. In

case of malfunctions in a package, this concept prevents supply deficiencies in the network

by start and run-up of stand-by package. An automatic circulation circuit with 24-hours cycle

ensures uniform utilization of all compressors. Variations from setpoint values are reported

in the central control room already at an early stage "before Philips can discern them". The

new station functions at a constant maximum pressure rating reduced by 0.5 to 8.0 bars and

is by 0.5 bars beyond the line pressure of 7.5 bars required by Philips. Thanks to the

maximum pressure reduction by 0.5 bars, an energy saving of approx. 3 % as compared to

the old station is achieved that was scrapped immediately after putting the new station in

operation in April 2001.

Ingeniously Simple

Already in the planning stage, Frank Reetze noticed: "The ingeniously simple GVM concept is

just the right thing for supply of the highly-sensitive semiconductor production with purest

compressed-air. All utilities and media must be available at a higher purity in powers of ten

than in any other industrial sector. We must meet this extremely high demand on economy

and availability with an optimal cost-to-benefit ratio as we contribute essentially to the

world-wide competitiveness of Philips semiconductor products with the quality standard of

our compressed-air supply. Therefore, we supply the whole Philips site through only one

network with 100 % oil-free compressed air generated by four GVM compressors".

All this was preceded by a tailor-made invitation to bid, both

• directed to other bidders of conventional techniques (dry-running screw compressors

and packages with oil-injected cooling and successive treatment to 100 % oil-free

compressed air)

• and to GVM (100 % oil-free compression by water-injected screw compressors).

After careful investigation, Manager Reetze found out "that the ingeniously simple GVM

technique of cooling by water injection features the ideal solution. According to our

estimates, these packages require between 8 and 12 % less electric power in full-load

operation than conventional oil-free – so-called dry-running – screw compressors. This value

was confirmed meanwhile by practice.

Further, GVM holds a unique position in the market according to our experience and has got

a development lead of approx. 8 to 10 years.

As there has not yet been a station in which the 250 kW packages desired by us ran with

frequency inverters, our specialist engineer and our management tried and tested the GVM

technology in the Crimmitschau factory. Further, we saw GVM packages with smaller

performance parameters under practical conditions of run."

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Thoroughly Sound

Frank Reetze praises the single-stage design of GVM compressors without any need for

additional transmission (direct drive of male rotor), the largely dimensioned carbon slide

bearings, the very low specific power demand and the easy-to-service construction. He

forecasts an almost unlimited service lifetime for the packages. He was also deeply

impressed by the almost isothermal compression principle at compressed-air temperatures

of max. 40°C as compared to 180°C max. for conventional screw compressors. Nonetheless,

the compressed air for Philips is cooled-down prior to intake in the plant network for

reasons of economy in order to feed the condensation water produced in the cooling towers

to compensate for the evaporation rate. Further, Frank Reetze appreciates the principle of

100 % oil-free compression as HCL was certified according to ISO 14000 – an essential

condition for co-operating with Philips: "Participating in the world-wide "Eco-Version"

scheme, Philips want to reduce the use of lubricants and chemicals as far as possible. Oils

not required for our packages need not to be purchased or disposed of. This saves money

and preserves environment."

Revolutionary Technology

In conventional screw compressors, oil is injected into the air end from a closed circuit. Said

oil dissipates the major portion of heat produced during compression, performs sealing jobs,

and lubricates the bearings. First tests with water-injected compressors were already

performed in Japan and in the United States more than ten years ago. According to the

belief of Eng. Günter Kirsten, the "brain" of GVM, these solutions could not come out

because they were constructed as single-stage dry-running compressors and a transmission

to synchronize the rotors was required. Further, bearings and transmission were oil-

lubricated and housing, bearing caps and rotors were made from stainless steel or bronze.

FU control unit

Four frequency-inverter control panels

Compressed-air intake measurement

As opposed to this, GVM emerged from KCS Verdichtertechnik in 1985 offers after a more

than 10 years development period 36 water-injected package models proven in practice

(maximum pressure ratings 8 / 10 and 13 bars above atmospheric, rates of delivery ranging

from 0.59 to 33.8 and/or from 0.49 to 33.5 m³/min).

"We have profoundly investigated the various problems of water injection already at a very

early stage and solved then in field tests over at least one summer and two winter seasons",

says Kirsten, dealing with the development of screw compressors for more than 30 years.

Meanwhile, GVM tested more than 400 packages world-wide under practical conditions and

warrants for perfect function under any operational and climatic conditions.

Slide Bearings, Water Lubrication

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The water-injected GVM screw compressor packages (internationally patented) offer 100 %

oil-free compression according to Pneurop 6611/1 Class 1, slow peripheral speeds of male

rotors (12 to 60 m/sec.) and single-stage standard compression ratios of up to 14. Core of

the maintenance-free PIONEER air end are the patented polyceramic rotors, proven for

more than 15 years. The GVM air ends function without any transmission as the male rotor

drives the female rotor. Further, the free motions in such packages must be essentially

smaller as the kinetic viscosity of water is about one dimension smaller than the associated

value of oil. The rotors are running axially and radially in hydrodynamic slide bearings

lubricated with circulation water of approx. 2 bars below the discharge end pressure. The

thrust bearing cast on the male rotor – a new feature of screw compressors – guarantees an

almost unrestricted lifetime thanks to the minimum axial and radial bearing load of about

0.3 N/mm² only (end pressure 10 bars above atmospheric).

As the polyceramic rotors with their new profiles are made from patented materials

according to patented techniques, lubrication of tooth meshing, cooling, and gap caulking

can be performed by controlled water. As the thermal capacity of water is two times higher

than oil and water can be atomized much easier than oil, the temperature in the

compression cycle rises only by max. 10°C – even at compression ratios of 20 in one end.

However, this minimum heating requires a weight excess of water that is about 12 to 16

times higher than the air taken-in. The packages are connected to a drinking-water

connection and the internal water treatment facility generates the required water quality. If

fully desalted water is available as with Philips, the internal water treatment ceases and the

Ion-Clean system mixes the water quality from drinking and fully desalted water. These

packages only require little maintenance as the regeneration of the internal mixed-bed ion

exchanger becomes superfluous.

"Normal and non-treated drinking water involves considerable corrosion and sedimentation

hazards and, therefore, cannot be used to operate the packages. Further, chemical

composition and conductivity of drinking water vary at different locations in the world.

Thanks to long-term and wide-range tests performed under practical conditions, we have

the knack of the water topic. This is acknowledged by many packages, running to the entire

satisfaction of our clients", outlines developer Kirsten from GVM.

Water treated by reversed osmosis or distilled or de-ionized water will lose its purity within a

few hours due to the absorption of minerals and other ions from the machine system and

the air taken-in. In particular, the CO2 anion causes substantial sedimentation, calcification or

changes of pH value. Therefore, circulation water is permanently treated, supervised and

controlled in pre-defined limits in the GVM packages by the patented Ion-Clean system.

Further, the various atmospheric take-in conditions must be mastered.

Master control

The germ concentration in the gas and water circuits, an argument repeatedly raised against

water injection, lies only within a range from 1 to 106 KBE according to experience from

long-time tests carried out in various institutes and in practice (as compared to the

permitted germ concentration of about 100 KBE in clean rooms). In shopping centers, the

germ concentration index may often rise up to 2000 KBE.

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Electrochemical Polarization Device

As the gas to be compressed enters and leaves the package with a definite equal water

amount, the cooling water amount in the system remains almost constant in the closed

circulation-water circuit so that the GVM system can be called a quasi-closed system. To

compensate for the water intake (condensation) or water loss (evaporation), the circulation

circuit is of open configuration with a level-controlled water inlet and a level-controlled

condensation water drain. That is why the GVM packages can be used in all climatic zones

without any problems.

The internal circulation-water treatment and control facility ensures a conductivity between

10 and 20 µS / 23°C in the water circuit irrespectively of climatic conditions and drinking

water quality. This means, all ions and salts as well as CO2 dissolved in the water are

controlled within the pre-defined limits. The high-value polarization device made from

highest-grade aluminum and carbon (lifetime of electrodes over 10 years) functions without

external power source.

The polyceramic rotor pair – the strong core of each GVM compressor

Further, the charged ions absorb ions of other polarity being in the water circuit. A highly-

efficient particle filter (international patents pending) contributes essentially to the high

operating safety of all GVM packages. Particles extracted from the water circuit are held

back in the matrix even at pressure and system fluctuations. A Delta-P alarm system with

package shutdown function is to safeguard the whole system.

Energy Savings of up to 20 %

The sound-absorbent single-stage GVM compressors are delivered ready-for-use with all

incorporated control, monitoring, and cooling facilities. As to smaller packages, drive takes

place via narrow V-belt and, as to the packages from 30 kW, via elastic coupling directly onto

the male rotor of air end. Water and gas systems are interconnected by means of rustproof

materials.

Thanks to the almost isothermal compression principle and the cease of additional re-

cooling facilities, energy savings of up to 20 % can be achieved as compared to other

compressor systems: a largely dimensioned cooler in the water circuit restricts the

temperature rise during the compression cycle in air-cooled packages to about 14°C only, in

water-cooled packages, to 5 – 10°C only above the temperature of cooling medium.

All GVM packages are operated in standard configuration with a full-load/no-load control

with relief feature, however, they can also be operated with speed control via frequency

inverter – as shown by the HCL-Philips example. An intake controller ensures relieved start-

up and prevents current peaks in conjunction with an economically favorable start cycle. All

important states of operation are continuously detected and reported. A supervising and

safety system with shutdown function controls all important system parameters.

Huge Potentials

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"Our experience made so far confirms the correctness of our decision made. GVM offers safe

and reliable water-injected screw compressors proven in practice for the first time in the

market. We forecast a bright future to this compressor concept. Meanwhile, we are engaged

in further contracting projects through our ten agencies in Germany, covering water-injected

GVM compressors e.g. for use in foodstuff, pharmaceutical, chemical, and automotive

industries. I could even imagine that the water-injected GVM compressors can substitute in

the long run oil-injected screw compressors same as so-called dry-running packages thanks

to their safe and economic operation and the low energy and maintenance costs", says

Frank Reetze.

Talk to us and request more information.

GVM

A corporation of TCI AG

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100 % OIL-FREE COMPRESSED AIR FOR 500 € PER YEAR ONLY

Water-Injected Screw Compressors at WEMA Plauen

Sound principles of yesterday might be obsolete today. This applies also to the answer to

the question whether an "average" machine building company needs 100 % oil-free

compressed air. "Too expensive and also not necessary" has been the answer given so far.

For 4 years, the medium-sized business with 440 employees has been generating 100 % oil-

free compressed air by means of water-injected screw compressors made by GVM in

Crimmitschau for good reasons. And this to a minimum extra price of only 500 € per year

as compared to the "oil-lubricated" compression technique with a maximum residual oil

content of about 4 mg/m³ usual so far. Already now, experts of the compressed-air scene

consider the world-wide unrivalled GVM compressors to be the future substitute of oil-

lubricated and dry-running options.

100 % oil-free compressed air, that is, compressed air without the smallest portion of oil has

been a predominant vital precondition in pharmaceutical and foodstuff industries, in

chemical and electronic industries and even for power stations so far. Further, 100 % oil-free

compressed air is an integral part of the technical equipment of any hospital. There are

important reasons for that:

• 100 % oil-free compressed air is indispensable in many sectors as residual oil portions in

compressed air may cause destruction of production facilities and/or of the products.

• Residual oil portions in compressed air may cause important damages to the health of

men due to oil-containing inhaled air or eating of contaminated products, in extreme

cases, they may lead to death.

• 100 % oil-free compressed air favors almost trouble-free function of the ever more

sensitive compressed-air components (controls, cylinders, measuring devices etc.).

The answer to the question whether 100 % oil-free compressed air is not only advisable but

also necessary in the individual case supposes a great deal of expertise in the field of

compressed-air technology, responsibility, impartiality and freedom from bias of the

consultant. Meanwhile, 100 % oil-free compressed air is not more expensive than

compressed air with a residual oil content of about 4 mg/m³ provided it is generated using

the adequate technology. In general, there are several possibilities at hand to generate 100

% oil-free compressed air:

1. Oil-Lubricated Compression

When generating 100 % oil-free compressed air by means of oil-lubricated piston or screw

compressors, filtration in a charcoal filter station is required prior to intake in the network.

This will not only cause additional investment, maintenance, and disposal costs. An

acceptable risk due to uncontrolled saturation of charcoal filter station or an oil inrush can

never be excluded when choosing this solution. If, however, oil or residual-oil containing

compressed air enters into a hitherto 100 % oil-free piping system, dreadful consequences

may occur. The oil portions do not only settle on the walls of network, They may also cause

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long-term breakdowns at the consumers, a complete replacement of network and, under

circumstances, total loss of products. Inhaled air in a hospital containing oil residues would

be a disaster.

2. "Dry-Running" Compression

100 % oil-free compressed air can also be generated directly, that is, without downstream

filtration by means of 100 % oil-free compressing, so-called dry-running piston or screw

compressors. In such systems, the actual compression process takes place on the basis of

appropriate technological concepts without oil as lubricant and/or sealing agent. However,

these compressors call for an essentially higher design expenditure as the bearings must still

be oil-lubricated but hermetically sealed off the compression area. Further, 100 % oil-free

compressing screw compressors also require air ends of extremely high precision as oil is not

used any more as sealing agent between both rotors and between rotors and housing wall.

This results in essentially higher maintenance, servicing and spare parts costs, shorter

lifetimes of air ends, and supply risks due to occurring total breakdowns of air ends.

Therefore, generation of 100 % oil-free compressed air by means of oil-free compressing

piston and screw compressors is now and then a compromise with increased investment and

follow-up costs and increased risks.

3. Water-Injection Cooling

Whoever wants to eliminate the risks of oil-lubricated/oil-injected compression with

successive treatment and the economic disadvantages and risks of the so-called dry-running

compression process will encounter the alternative of 100 % oil-free compressed-air

generation by means of water-lubricated and water-injected screw compressors made by

GVM Compressors GmbH in Crimmitschau.

The company Werkzeugmaschinenfabrik Vogtland Plauen, a machine-tools factory, has been

using these compressors successfully for 4 years, producing 100 % oil-free compressed air at

an extra price of 500 € per year only as compared to oil-injected screw compressors

(investment and energy costs included).

Water-injected screw compressors have already been offered in the United States and Japan

for more than 10 years. However, the could not come out on top due to their important

flaws with regard to constructive design and materials technology. The final breakthrough

was made by KCS Verdichtertechnik owned by Eng. Günter Kirsten, a company from which

GVM Compressors GmbH, now domiciled in Crimmitschau/Saxony, arose in 1985. GVM

Compressors GmbH is an associate company of TCI TechnoCap International AG in Leipzig.

Günter Kirsten has been developing oil-injected screw compressors for over 30 years. Based

upon this experience, GVM offers now after an over 10-years time of development:

• 36 water-injected screw compressors, proven in practice (rates of delivery from 0.59 to

40 m³/min, driving power up to 300 kW, maximum pressure ratings 8/10 and 13 bars

above atmospheric).

Technology Proven World-Wide

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After comprehensive field tests and the test of more than 400 packages under practical

conditions, GVM warrants for perfect function of its water-injected and water-lubricated

screw compressors under any operating and climatic conditions prevailing world-wide.

Such compressors have been used successfully at Werkzeugmaschinenfabrik Vogtland GmbH

in Plauen since 1998.

This company, founded in 1881, was the biggest manufacturer of knitting frames in Europe

around 1922 with more than 6,000 employees. Nowadays, about 450 employees are

producing special-purpose machines, modular transfer lines, and manufacturing systems.

"We are quite an average machine building company but we are especially proud of our

highly-modern technologies, of our know-how, and of our more than 50-years experience in

special-purpose machine construction", says B.Eng. Uwe Emmerich, Manager for

Infrastructure / Administration.

B.Eng. Uwe Emmerich

The highly-modern compressed-air station with three water-injected GVM screw

compressors to supply the entire factory area with 100 % oil-free compressed air also ranks

among these progressive technologies. Two compressor packages (model CWF 75-8 PA, rate

of delivery 12.5 m³/h each) are to supply compressed air for the 6 bars network. One

package of the model CWF 90-11 PA is to feed the separate 10 bars network. The original

intention was to generate compressed air conventionally using oil-injected screw

compressors with a maximum pressure rating of 6 and/or 10 bars and a residual oil content

of 4 mg/m³ max. Appropriate quotations were invited from five bidders and one also

encountered the GVM water-injected compressors as an option.

Uwe Emmerich says: "In case of long-term considerations, for instance, over a period of 10

years, energy costs of a compressed-air station amount for about 90 % of the total cost.

Therefore, any consideration of investment costs in the decision to purchase would have ben

unjustifiable. However, this cost item was higher for GVM packages as compared to the oil-

injected ones of the competitors. As to the long-term effective energy costs, the GVM

packages evidently held rank 1 thanks to their essentially smaller energy demands.

In the overall result of investment and 10-years energy costs, the water-injected GVM screw

compressors were more expensive only by about 500 € per year than the cheapest bidder of

oil-injected packages. As we saw the great advantage of 100 % oil-free compressed air

almost for free, we decided to buy three GVM compressors. Meanwhile, four years are over

and we have not yet regretted this choice till now".

2 CWF 75-8 A compressors, 1 CWF 90-11 PA compressor

Proven for Four Years

As a matter of course, they took a rather skeptical view of the GVM technology right at the

beginning. The other bidders only offered oil-injected compressors, forecasting a "bright

future" for water-injected compressors, however, this was only a marginal topic for their

own companies. "After personal talks with Günter Kirsten, the developer of GVM packages

and manager of GVM Compressors GmbH and talks in the Crimmitschau factory, we were

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entirely convinced of the water-injected compression technology although we took a critical

view of this technical concept", says Uwe Emmerich.

"We additionally got here the great advantage of 100 % oil-free compressed air at an

excellent cost-to-benefit ratio with minimized extra price. So, we dot not only enhance safe

function of our compressed-air consumers. We also preserve the health of our employees as

their inhaled air is not polluted any more by the residual oil content of escaping compressed-

air. Further, 100 % oil-free compressed air also enhances the cleanliness in our factory

thanks to the cease of oil mist. These compressors have been running without any troubles

since the commissioning of GVM packages four years ago. Meanwhile, we also think that the

GVM water-injection concept features an ingenious and forward-pointing idea".

The theoretical compressed-air demand of Werkzeugmaschinenfabrik Vogtland amounts to

40 m³/min, the actual demand is at an average of about 20 m³/min. However, this actual

demand may undergo very big fluctuations as a function of current jobs so that on-peak

work has to be performed almost without reserves. That is why Uwe Emmerich already

thinks of a fourth GVM package of the model CWF 90-8: "We started our compressed-air

supply four years ago with GVM packages and – supported by the good experience acquired

so far – we are going to continue with GVM".

CWF 90-11 PA compressor with external air-water heat exchanger

After expiration of the first three-years servicing contract, a new agreement was meanwhile

concluded in which GVM guarantees a 24-hours response time. The packages were installed

in a largely dimensioned compressor room. The water circuit of every GVM compressor is

cooled in an external air-cooled unit. Prior to intake in the networks, the compressed air is

dried in two refrigeration dryers – separated into 6 bars and 10 bars maximum pressure

rating. Largely dimensioned weather protection gratings for admission air and two

thermostat-controlled exhaust air fans are to maintain an optimal room temperature

between 20°C and 30°C all over the year.

Revolutionary Concept

GVM screw compressors offer 100 % oil-free compression according to Pneurop 6611/1

Class 1. The patented polyceramic male and female rotors were tested under toughest

conditions of practice over more than 15 years. The rotors are running axially and radially in

hydrodynamic slide bearings. The thrust bearing cast for the first time on the male rotor

(peripheral speeds of 12 to 60 m/sec.) has got an almost unrestricted lifetime thanks to the

minimum axial and radial bearing load (about 0.3 N/mm² only at an end pressure of 10 bars

above atmospheric).

Lubrication of bearings and tooth meshing, absorption of an important portion of heat

produced during compression, and gap caulking take place by means of controlled

circulation water. As the thermal capacity of water is two times higher than oil, the

temperature in the compression cycle rises only by max. 10°C – even at compression ratios

of 20 in one end. As the rotors are driving mutually, a transmission is not required. As to

packages from 30 kW, the male rotor is driven directly via elastic coupling, as to smaller

packages, via narrow V-belts.

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Energy Savings of up to 20 %

The sound-absorbent single-stage GVM compressors are delivered ready-for-use with all

incorporated control, monitoring, and cooling facilities and operated in standard

configuration with a full-load/no-load control with relief feature (optionally, speed-

controlled via frequency inverter). An intake controller ensures relieved start-up and

prevents current peaks in conjunction with an economically favorable start cycle. All

important states of operation are continuously detected and reported. A supervising and

safety system with shutdown function controls all important system parameters. Water and

gas systems are interconnected by means of rustproof materials.

Thanks to the almost isothermal compression principle and the cease of additional re-

cooling facilities, energy savings of up to 20 % can be achieved. Thanks to a largely

dimensioned cooler in the water circuit, the temperature rises during the compression cycle

in air-cooled packages to about 14°C only, in water-cooled packages, to 5 – 10°C only above

the temperature of cooling medium.

View into a CWS 300-8 PW screw compressor, 300 kW, 40 m³/min

The water-injected GVM packages can be directly connected world-wide to any drinking-

water connection. The internal Ion-Clean system treats the drinking water continuously to

obtain circulation water, guarantees the constant water quality required, and prevents

important corrosion and sedimentation hazards in case of non-treated drinking water.

The germ concentration in the gas and water circuits, an argument repeatedly raised against

water injection, lies only within a range from 1 to 106 KBE according to experience from

long-time tests carried out in various institutes and in practice. The GVM circulation-water

circuit is quasi-closed. In a quasi-closed circulation-water circuit, the cooling water amount

remains almost constant as the gas to be compressed enters and leaves the package with a

definite equal water amount. GVM packages can be used in all climatic zones and for any

drinking-water quality as water intake (condensation) or water outlet (evaporation) are

compensated for by open and level-controlled water inlets and condensation water drains.

The internal Ion-Clean circulation water control facility ensures that the conductivity is

always maintained between 10 and 20 µS / 23°C. A high-value polarization device made from

highest-grade aluminum and carbon (lifetime of electrodes over 10 years) polarizes all ions

circulating in the circuit to positive polarity and prevents any formation of sediments, even

in smallest form. A special water filter is to remove all circulating particles.

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TECHNOLOGY OF THE FUTURE

Water-Injected Screw Compressors in Use at Apollinaris

There is only one thing of importance for Thomas Ritz: the use of 100 % oil-free

compressed air only. And, meanwhile, he affirms his statement: "If the cost-to-benefit

ratio is sound, we will only use water-injected screw compressors made by GVM in

Crimmitschau. We have been using 100 % oil-free compressed air in our production for

decades to prevent any potential troubles as far as possible", says the plant engineer of

Apollinaris & Schweppes GmbH & Co. in Bad Neuenahr-Ahrweiler. And Thomas Ritz knows

what he is talking about because he is aware of all possibilities of oil-free compressed-air

generation – no matter whether so-called dry-running piston or screw compressors or –

since spring 2001 – water-injected GVM screw compressors are concerned.

At present, Apollinaris is the most renowned and reputable mineral-water brand in Germany

almost 150 years past the foundation of business in 1853 with an awareness level of over 90

% and is also consumed in over 50 countries all over the world. The legendary slogan "The

Queen of Table Waters" and the red triangle were already registered in 1894 as trademarks

still being used. Since 1956, Apollinaris belongs to Dortmunder Union-Schultheiss-Brauerei

AG (since 1988, Brau und Brunnen AG). In 1991, the merger with Schweppes GmbH

Hamburg and Schweppes AG Austria took place. Schweppes beverages are consumed even

in 190 countries all over the world.

Plant engineer Thomas Ritz believes that a reliably functioning compressed-air supply is an

indispensable requirement for trouble-free operation in Bad Neuenahr-Ahrweiler. That is

why he does not run a risk in this respect. In general, compressed air is required as control

air where a usual residual oil content of e.g. 4 mg/m³ max. would be acceptable. However,

even here one goes for 100 % oil-free compressed air not to jeopardize the perfect function

of control valves. For safety reasons, one does not want to hear of compressed air generated

by oil-lubricated piston compressors or oil-injected screw compressors which has then to be

treated by suitable filtration to reach 100 % oil-free quality because any acceptable risk must

be avoided. Further, compressed air is used to pre-load tanks. That is why such compressed

air must be 100 % oil-free as production means are kept in these tanks.

To maintain perfect function, the control valves need a minimum pressure rating of 6.0 bars.

Therefore, the compressed-air station was configured for a maximum pressure rating of 6.5

bars. Until spring 2001, this station was comprised of:

• two oil-free compressing piston compressors (year of construction around 1975, rate of

delivery 6.5 m³/min each), and

• three two-stage oil-free compressing screw compressors, year of construction 1978/80

(rate of delivery about 15 m3/min each).

Opting for GVM

For reasons of energy policy, however, Thomas Ritz was not very happy with this situation

because all packages ran in intermittent operation with a considerable share of inevitable

idle times during which the screw compressors still absorbed about 30 % of electric power

but did not generate any compressed air. "What we needed was a new concept for our

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compressed-air station to reduce power cost in this sector as far as possible. In spring 2001,

we investigated the market for more economic solutions and invited some quotations

covering oil-free compressing piston and screw compressors. In this respect, we also

encountered the water-injected screw compressors from GVM in Crimmitschau.

As a matter of course, we first took a rather skeptical view of the GVM concept. In

comparative cost accounting, however, these compressors held the first place, taking into

consideration investment, energy, and servicing costs. Thereupon, we decided in spring 2001

to install a water-injected GVM compressor of the CWS 110-8 PW model."

Speed-Controlled Peak-Load Package

This package is operated as peak-load package via frequency inverter. It has got a driving

power of 110 kW and delivers a rate of 18.3 m³/min of 100 % oil-free compressed air at 100

% duty and a maximum pressure rating of 8 bars. Thomas Ritz was particularly impressed by

four features regarding these GVM packages:

1. The revolutionary concept of water-injection cooling ensured generation of 100 % oil-

free compressed air.

2. The packages require less electric power, well below the demands for comparable

dry-running screw compressors.

3. Thanks to the technical concept, particularly high lifetimes and minimized technical

maintenance can be anticipated from the compressors.

4. Controlled via frequency inverter, the packages can be operated over a particularly

wide power range according to demands and very economically without any idle

times.

Unrivalled World-Wide

The technical concept of GVM screw compressors with water injection to generate 100 % oil-

free compressed air is unrivalled all over the world. Experts in the field concede a

development lead of at least 8 to 10 years to this concept and forecast a bright future. The

GVM company arising from KCS Verdichtertechnik in 1985 offers 36 packages proven in

practice after more than 10 years of development with maximum pressure ratings of 8/10

and 13 bars (rates of delivery 0.59 – 40 and/or 0.49 – 40 m³/min). In full-load operation,

these packages require up to 20 % less electric power that oil-free – so-called dry-running –

screw compressors. Meanwhile, GVM tested more than 400 packages under practical

conditions world-wide and warrants for perfect function under any operating and climatic

conditions.

Slide Bearings, Water Lubrication

The screw compressors with internationally patented water-injection cooling offer 100 % oil-

free compression according to Pneurop 6611/1 Class 1, slow peripheral speeds of male

rotors of 12 to 60 m/sec. only and single-stage standard compression ratios of up to 14. Core

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of the maintenance-free PIONEER air end are the patented polyceramic rotors, proven for

more than 15 years. This air end functions without any transmission as the male rotor drives

the female rotor. The thrust bearing cast on the male rotor – a new feature of screw

compressors – guarantees an almost unrestricted lifetime thanks to the minimum axial and

radial bearing load of about 0.3 N/mm² only (end pressure 10 bars above atmospheric).

The polyceramic rotors with their new profiles are made from patented materials according

to patented techniques. That is why lubrication of tooth meshing, cooling, and gap caulking

can be performed by controlled circulation water that is also used for lubrication of axial and

radial hydrodynamic slide bearings. As the thermal capacity of water is two times higher

than oil and water can be atomized much easier than oil, the temperature in the

compression cycle rises only by max. 10°C – even at compression ratios of 20 in one end.

Water Treatment

The packages are connected to a drinking-water connection. This drinking water is

permanently treated, supervised, and controlled within pre-defined limits in the GVM

packages by means of the patented Ion-Clean system,

1. as non-treated drinking water involves considerable corrosion and sedimentation

hazards and, due to the ever varying chemical composition and conductivity, cannot

be used to operate the packages;

2. as water treated by reversed osmosis or distilled or de-ionized water will lose its

purity in the compressor system already within a few hours due to the absorption of

minerals and other ions from the machine system and the air taken-in.

In particular, the CO2 anion causes substantial sedimentation, calcification or changes of pH

value.

Further, the various atmospheric take-in conditions must be mastered. The germ

concentration in the gas and water circuits, an argument repeatedly raised against water

injection, lies only in between 1 and 106 KBE according to experience from long-time tests

carried out in various institutes and in practice (as compared to the permitted germ

concentration of about 100 KBE in clean rooms).

CWS 110-8 PW compressor package with frequency inverter

Electrochemical Polarization Device

The gas to be compressed enters and leaves the package with a definite equal water

amount. As the cooling water amount in the system remains almost constant in the closed

circulation-water circuit, the GVM system can be called a quasi-closed system. An open

circulation circuit with level-controlled water inlet and condensation water drain is to

compensate for the water intake by condensation and water outlet by evaporation. That is

why the GVM packages can be used in all climatic zones of the world without any problems.

Electronic control

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The internal circulation-water treatment and control facility ensures a conductivity between

10 and 20 µS / 23°C in the water circuit irrespectively of climatic conditions and drinking

water quality. This means, all ions and salts as well as CO2 dissolved in the water are

controlled within the pre-defined limits. The high-value polarization device made from

highest-grade aluminum and carbon (lifetime of electrodes over 10 years) functions without

external power source.

Further, the charged ions absorb ions of other polarity being in the water circuit. A highly-

efficient particle filter (international patents pending) contributes essentially to the high

operating safety of all GVM packages. Particles extracted from the water circuit are held

back in the matrix even at pressure and system fluctuations. A differential-pressure alarm

system reports and variation of the preset limit value and shuts the package down.

View into the compressor

Energy Savings of up to 20 %

The sound-absorbent single-stage GVM compressors are delivered ready-for-use with all

incorporated control, monitoring, and cooling facilities. Smaller packages are driven via

narrow V-belt. As to the packages from 30 kW, drive takes place via elastic coupling directly

onto the male rotor of air end. Water and gas systems are interconnected by means of

rustproof materials.

Thanks to the almost isothermal compression principle and the cease of additional re-

cooling facilities, energy savings of up to 20 % can be achieved as compared to other

compressor systems. A largely dimensioned cooling system in the water circuit restricts the

temperature rise during the compression cycle in air-cooled packages to about 14°C only, in

water-cooled packages, to 5 – 10°C only above the temperature of cooling medium. All GVM

packages are operated in standard configuration with a full-load/no-load control with relief

feature, however, they can also be operated with speed control via frequency inverter – as

shown by the Apollinaris example. An intake controller ensures relieved start-up and

prevents current peaks in conjunction with an economically favorable start cycle. All

important states of operation are continuously detected and reported. A supervising and

safety system with shutdown function controls all important system parameters.

Base Load/Peak Load/Stand-By

The new GVM package, speed-controlled via frequency inverter, is in use at Apollinaris as

demand-dependent peak-load compressor. Two other oil-free compressing screw

compressors with fixed speed from the old stock are operated to full load separately or

jointly as base-load compressors according to demands in permanent operation. The third

oil-free compressing screw compressor from the old station was scrapped after putting the

new GVM package into operation as he did not function reliably and economically any more

for reasons of age and high repair and spare parts costs. The two old piston compressors

(rate of delivery 6.5 m³/min each) are currently used as emergency and additional base-load

units when the higher rate of delivery of the two base-load compressors (15 m³/min each) is

not required. This concept is used on seven days a week around the clock because

compressed air is also needed off the production time.

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View into a CWS 300-8 PW screw compressor, 300 kW, 40 m³/min

The compressed air is dried in a refrigeration dryer (compression dew point + 3°C). A new

dryer was installed together with the GVM compressor in spring 2001 whose output delivery

rate was chosen so that it can dry the compressed air generated by two dry-running screw

compressors and the GVM compressor without any overloads. In addition, two other elder

refrigeration dryers are used as stand-by units. The compressors and dryers needed as a

function of demand are currently activated manually yet. Fully-automatic changeover is in

the pipeline.

Side view of air end and package

Additional GVM Compressor

Thomas Ritz from Apollinaris & Schweppes GmbH in Bad Neuenahr-Ahrweiler knows that the

almost 25 years old oil-free screw compressors must soon be replaced with new

installations, too, not to jeopardize reliability and economy of compressed-air supply. That is

why the plant engineer looks forward to the future already today. "The new GVM package

has been running here since spring 2001. Our experience with this package are so good that

we are inclined to purchase a second water-injected GVM compressor to substitute one of

the two still existing oil-free compressing screw compressors in the near future. We will then

operate this GVM package as base-load compressor with fixed speed and without frequency

inverter. As a matter of course, we will also investigate the market again prior to our

decision to purchase and invite quotations for other compressor systems to draw

comparisons.

When the cost-to-benefit ratio of the new water-injected GVM package is sound again, we

could even opt for such a package once again.

According to our own experience gained over years, we are aware of the advantages and

disadvantages of oil-free compressing piston and screw compressors. And now, we know the

water-injected screw compressors from GVM for almost one year. Right at the beginning, we

took a rather skeptical view of this concept. However, this skepticism was completely

unfounded. Meanwhile, the technical concept of water-injection cooling has stood its

ground with us." Further, according to experience gained so far, the maintenance

expenditure for such packages is essentially reduced as compared to oil-free compressing

two-stage screw compressors. For the replacement of air ends after about 25,000 hours of

operation alone – that is, after three years respectively – Apollinaris had to pay over 20,000

€ each on the nail.