1. 1
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

2. 2
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."

3. 3
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

4. 4
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.

5. 5
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

6. 6
"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

7. 7
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

8. 8
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

9. 9
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

10. 10
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.

11. 11
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.

12. 12
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

13. 13
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.