pumps and pumping systems  

Vacuum pumps PW, blowers DW


Rotating liquid ring vacuum pumps and blowers (commonly known as compressors) are used in various processes which demand suction and forced flows of oil-free gases, especially in the chemical, pharmaceutical, food processing, paper-making, and textile industries, as well as for the priming of impeller pumps and siphons.

PW, DW pumps are used in:

  • chemical,
  • pharmaceutical,
  • food processing,
  • paper,
  • textile industry.

It is possible to pump dry gases at temperatures of up to 150oC, and vapour-saturated gases at temperatures of up to 100oC with a 30% maximum liquid content of the working fluid demand, for operation in direct supply systems, termed "PB". When pumping saturated gases, the amount of working liquid at the input to a compressor via a line shall be reduced by the amount of liquid arriving with the gas to prevent the drive from overloading. If the mixture temperature at the pump intake exceeds the rated temperature in the PB system (which is 15oC for water), the efficiency of the gas pumped by an IP should be corrected as required. The permissible temperature of the working liquid at the compressor output should not exceed 80oC.

Various types of working liquids can be used, as required by processing, but the liquid must meet the following requirements:

  • density: 800 to 1200kg/m3,
  • viscosity: 60 mm2/s maximum at 20oC,
  • corrosivity of the working liquid: should not exceed the resilience of the compressor hydraulic stage materials.

If working liquids are used during the cycle which differ in density and viscosity from water, correct the power at the compressor shaft. Consult the manufacturer concerning drive system power. Pumped gases may include residual concentrations of non-abrasive particulates with a maximum grain size of 0.2 mm. It is recommended that filters be installed in the suction line to protect the compressor from failure. The compressors can be driven by motors rated at 50/60 Hz. Other drive transmission methods are possible provided that the drive shaft transfers the torque moment only.

Technical specifications:

Vacuum pumps
capacity 4,5 ÷ 1600 m3/h
suction pressure ps min 33 (40) hPa abs mm
mass 44,4 ÷ 1492 kg
motor power 0,75 ÷ 45 kW

capacity 7,5 ÷ 1650 m3/h
compression pressure (gauge) pt max 0,15 (0,30) MPa
mass 45,4 ÷ 1492 kg
motor power 0,75 ÷ 100 kW

Product marking structure

  P W
1 2
1 0 1 0
1 0 1
a a a
c c
e1 e2 e3 e4
i i i

a a a - pump type (two characters)
b - pump type/size (denotes successive pump rated value)
c c - pump type dimension (number of stages)
d - material execution, as in MATERIAL EXECUTION subparagraph
e1 e2 e3 e4   - constructional execution, as in CONSTRUCTIONAL EXECUTION subparagraph
h - supply completeness, as in SUPPLY COMPLETENESS subparagraph
i i i - unit selection, coded according to manufacturer's internal documents
k - product cosmetics, as in PRODUCT COSMETICS subparagraph (protective coatings)

Material execution of PW, DW pumps

PW, DW pumps are produced in six material executions

Pump elements Type of compressor Material "d"
1 3 4 5 6 7
Casing PW/DW.1
gray cast iron gray cast iron chromium cast iron tin bronze cast carbon steel austenitic cast steel
Seal casing PW/DW.1
gray cast iron gray cast iron chromium cast iron tin bronze cast carbon steel austenitic cast steel
Suction-discharge members Spacing members PW/DW.1
gray cast iron gray cast iron chromium cast iron chromium cast iron cast carbon steel austenitic cast steel
PW/DW.7 gray cast iron gray cast iron chromium cast iron tin bronze cast carbon steel austenitic cast steel
Impellers PW/DW.1 tin bronze Spheroidal cast iron special austenitic cast steel tin bronze tin bronze special austenitic cast steel
austenitic cast steel cast carbon steel austenitic cast steel
PW/DW.7 brass
Shaft PW/DW.1
stainless steel stainless steel acid-proof steel acid-proof steel stainless steel acid-proof steel
Gland seal PW/DW.1
Itamid Itamid Itamid Itamid - -
PW/DW.7 gray cast iron gray cast iron chromium cast iron chromium cast iron cast carbon steel austenitic cast steel
Soft-cord shaft seal PW/DW.1
Packing 608 type
End-face mechanical shaft seal PW/DW.1
Application of mechanical seal needs technical and trade agreements with producer

Constructional execution

Variant no
e1 e2 e3 e4
Variant name Pump
1 4 5 7
1010 Pump with cord packing  
1100 Pump with single front packing A1 "ANGA" type  
1110 Pump with single front packing A3 "ANGA" type      
1120 Pump with single front packing 2100 "CRANE" type

Supply completeness

1 - Pump with free shaft end,
2 - Pump with complete coupling,
3 - Pump with complete coupling and foundation plate,
5 - Pump, complete as in item 3 + electric motor.

The possibility of supplying vacuum pumps with accessories - vacuum system comprising:

  • vacuum pump
  • separator
  • cooler
  • fittings
  • piping
  • metering

For further information, please contact:

Janusz Sadkowski
j.sadkowski@hv.pl, tel 56 45 07 423, tel. kom. 601 647 822

Mariusz Wtorek
m.wtorek@hv.pl, tel. 56 45 07 423

Product cosmetics

  1. Standard
  2. Specjal
  3. Maritime
  4. For dry tropical climate
  5. For humid tropical climate


  • high quality,
  • guaranteed long-term, reliable operation and easily available spare parts,
  • product adjustment to individual customer's requirements,
  • constant technical supervision as well as guarantee and post-guarantee service,
  • low costs of purchase and maintenance,
  • relatively long life-time in hard working conditions.

Principle of Operation. Construction

The principle of operation of a compressor with a rotating liquid ring is as follows: Encased in cylinder "O", part of which is filled with a liquid, there is a blade impeller "W" with a hub of a large diameter. As soon as the pump is started, the rotation of the impeller causes the liquid to circulate and be pushed against the walls of the casing to form a liquid ring. If the impeller is positioned eccentrically relative to the casing, then a liquid-free gap in the form of a crescent is left around the hub; the crescent is divided by the impeller blades into several compartments. The size of the compartments will grow at first, only to decrease after the bottom position is passed. The side walls (screens) provide axial closure to the compartments; now, if two openings are cut in the side walls, one of them (suction window "S") at the beginning of the crescent and the other one (discharge window "T") at the end of it, then the expanding compartment will cause the gas to be sucked into the compartment; then, as the capacity of the compartment is reduced, the gas will be compressed and discharged. Since a portion of the liquid that forms the liquid ring is always forced outside through the discharge window together with the discharged gas, the volume of the liquid has to be made up.

The principle of operation of a pump with rotating liquid rings

The design of compressors with a rotating liquid ring is determined by the above principle of operation. The devices are rotating, valveless, positive-displacement pumps. Part of the working liquid that forms the ring is discharged together with the gas and is made up continuously. The pump consists of fixed parts such as the casing (also referred to as distance body), control disks (also called suction elements and discharge elements), side bodies closing the pump, together with bearing bodies, seals and packings, and moving parts, such as impellers, the shafts, ring seals and bearings mounted on the shaft. Both sides of the shaft are sealed with a cord packing or end-face mechanical seal.

From the point of view of their design, the blowers are not much different from single-stage vacuum pumps - they are reversible devices. The only difference between them lies in their power consumption and has been taken into account in the choice of pumps with propulsion motors. Vacuum pumps and blowers with a rotating liquid ring were first manufactured in 1950 and have been constantly improved since then. They are used in a number of factories all over Poland and abroad.

They are characterized by:

  • such features as compact design,
  • reliable operation,
  • simple maintenance (the working elements need no lubrication),
  • low operating costs.

In terms of their technical parameters, the blowers are comparable with products of reputable European manufacturers. Their assumed technical and operating parameters were validated in long-term tests.


A complete vacuum unit, or compressor unit, consists of the following elements:

  • vacuum unit,
  • working liquid separator,
  • piping,
  • valves and fittings.

All suction and discharge piping must be precisely made and accurately arranged to avoid the effect of moments and forces, exerted on the compressor flanges. To this end, the pipes should be sufficiently extended to compensate for thermal elongation of the piping; another option is to use compensation bellows. The pipes must be thoroughly cleaned to remove any corroded material and welding spits. No solid is allowed into the compressor, otherwise the rotating mechanism of the pump will be damaged. The direction of gas flow in the compressor is indicated by the arrows on the suction and discharge bodies. The openings of the piping on the suction and discharge sides and that of the working liquid inlet must be at least the size of connections. The pipe openings must not be covered up by any seals. The discharge pipe may be directed vertically not higher than 1 m off the connector pipe of the compressor. Unit hydraulic losses in the pipes should be minimized. The device is installed in either one of the three ways, depending on the type of operation:

  1. operation type

    - This type of operation is applied when water consumption is of little importance. If the pressure of water from the network is unstable and fluctuates by more than 25%, then the vacuum pump ought on its own to suck in water from the tank to which the supply of fresh water from the network is controlled by a float-type valve or by a notch in the tank. The level of water in the tank ought to be at the same height as the pump shaft. When the vacuum pump is in operation and there is no need to separate the removed water and gas on the discharge side, then the tank that separates working water may be omitted. In that case, the discharge pipe is directed to the drain.

  2. operation type

    - The working liquid is introduced in a closed circulation system. This type of operation is recommended in particular for handling caustic and noxious gases. If resistance of flow in the heat exchanger is too high, then an auxiliary pump should be provided. In the case of intermittent operation, when the pump operation for several minutes is followed by a period of time long enough to effect reduction of the temperature of the circulating liquid to a set value, the heat exchanger may be omitted.

  3. operation type

    - The working liquid is introduced in a combined system. This type operation is recommended for normal operating conditions. There is less fresh liquid than in operation type 1. To keep a compact design of the unit, the vacuum pump may be provided with a separator, mounted on the pump discharge pipe (this applies to operation types 1 and 3).

Examples of installation


Examples of installation of vacuum pumps and blowers.

Operating Requirements

  • Irrespective of the type of operation, the compressor (vacuum pump or blower) needs to take up a sufficient quantity of working liquid.

  • To reach the parameters given in this catalogue, the temperature of the working liquid discharged from the vacuum pump, as measured at the pump outlet, must be kept at or below 15oC (for water). If, for some reasons, this can not be achieved and the water is at a higher temperature a reduction of capacity will result. The capacity data given in this catalogue ought to be corrected using the k = f (t, ps) coefficient according to the chart given in the catalogue. The working point of the vacuum pump should be above the limiting curve.

  • The piping and the walls of the working liquid tank are exposed to the presence of rust and dirt, and they need cleaning as the impurities build up. If the working liquid is water with high concentrations of calcium compounds, it needs to be softened. Otherwise, the compressor has to be dismantled after at least 6 months of operation, cleaned thoroughly to remove any deposit or rinsed with appropriate chemicals, for instance 5% solution of hydrochloric acid in water, taking the usual precautions.

  • In the operation of two-stage vacuum pumps, if cavitation (noises) occurs, then the working point is below the limiting curve in the chart k = f (t, ps); in such case, the aeration valve should be in the open position during the pump operation or the temperature of the working liquid should be lowered. If these measures do not help, further operation is prohibited, otherwise the pump will be damaged as a result.

The influence of working water temperature on the suction pressure and vacuum pump capacity

single-stage pumps

two-stage pump

Conversion table of pressure and vacuum units of measure

Vacuum % 0 25 50 60 70 80 85 90 92 95 96 100
mm Hg 0 190 380 456 532 608 646 684 699 722 730 760
m H2O 0 2,58 5,16 6,20 7,23 8,26 8,78 9,30 9,50 9,81 9,92 10,33
Absolute pressure ps Torr 760 570 380 304 228 152 114 76 61 38 30 0
kp/cm2 1,033 0,775 0,516 0,413 0,310 0,207 0,155 0,103 0,083 0,052 0,041 0
mbar 1013 760 506,6 405,3 304 202,7 152 101,3 81,1 50,7 40,5 0
hPa 1013 760 506,6 405,3 304 202,7 152 101,3 81,1 50,7 40,5 0

Atmospheric pressure equals 1013 [hPa] measured at sea level at temperature of 20oC.

Table of pressure units conversing from metrical system into English/ American one

  kp/cm2 m H2O 1 Torr Ib/sq * ft Ib/sq * in in * of merc
1kp/cm3 (atm) 1 10 735,7 2048 14,225 28,965
1m H2O 0,1 1 73,57 204,8 1,4225 2,8965
1 Torr 1,3595*10-3 1,3595 * 10-2 1 2,7837 0,0193 0,03937
1Ib/sq * ft 4,883 * 10-4 4,883 * 10-3 0,3590 1 6,944 * 10-3 0,01414
1Ib/sq * in 0,07031 0,07031 51,813 144 1 2,03988
1in * of merc 0,03452 0,03452 25,4 70,7214 0,49022 1

Calculation of the vacuum pump capacity.

Calculation of the vacuum pump capacity for the set capacity of the closed container and time of emptying

Hydro-Vacuum S.A.
ul. Droga Jeziorna 8
86-303 Grudziądz
tel. 56 45 07 415
fax. 56 46 25 955
Copyright © Hydro-Vacuum S.A.

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