WO2005035989A1 - Improved water-injected screw-type compressor - Google Patents

Improved water-injected screw-type compressor Download PDF

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Publication number
WO2005035989A1
WO2005035989A1 PCT/BE2004/000144 BE2004000144W WO2005035989A1 WO 2005035989 A1 WO2005035989 A1 WO 2005035989A1 BE 2004000144 W BE2004000144 W BE 2004000144W WO 2005035989 A1 WO2005035989 A1 WO 2005035989A1
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WO
WIPO (PCT)
Prior art keywords
water
type compressor
screw
pressure
motor
Prior art date
Application number
PCT/BE2004/000144
Other languages
French (fr)
Inventor
Anton Van Hal
Original Assignee
Atlas Copco Airpower N.V.
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Filing date
Publication date
Application filed by Atlas Copco Airpower N.V. filed Critical Atlas Copco Airpower N.V.
Publication of WO2005035989A1 publication Critical patent/WO2005035989A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/28—Safety arrangements; Monitoring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/06—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for stopping, starting, idling or no-load operation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/0007—Injection of a fluid in the working chamber for sealing, cooling and lubricating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/02—Lubrication; Lubricant separation
    • F04C29/021—Control systems for the circulation of the lubricant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/04—Heating; Cooling; Heat insulation
    • F04C29/042—Heating; Cooling; Heat insulation by injecting a fluid

Definitions

  • the present invention concerns an improved water- injected screw-type compressor.
  • the invention concerns a water- injected screw-type compressor which is mainly composed of a compressor element with a housing in which are provided two co-operating screw-shaped rotors; an inlet line in which is provided an inlet valve; an outlet line in which has been incorporated an air receiver which also serves as a water separator; a lubrication pipe which is connected to the above-mentioned air receiver and which opens into the rotor chamber of the compressor and at the bearings of the above-mentioned rotors .
  • the air receiver When the compressor is operational, the air receiver will be put under pressure and the water which is situated at the bottom in the air receiver will be sent back to the compressor element under the influence of said pressure for lubricating the rotors and the bearings.
  • the injected water is pressed back to the air receiver, together with the compressed air, via the outlet line, whereby the injected water is separated from the air in this air receiver.
  • the present invention aims to remedy the above-mentioned and other disadvantages by providing an improved water-injected screw-type compressor with an improved water lubrication of the bearings, which has for a result that these bearings have to be replaced far less frequently, so that the operating costs of such an improved water-injected screw-type compressor will be lower than those of the known screw-type compressors with a comparable capacity.
  • the invention concerns an improved water-injected screw-type compressor which is mainly composed of a compressor element with a housing in which are provided two co-operating screw-shaped rotors that are driven- by means of a motor with a constant or variable drive; an inlet line in which is provided an inlet valve; an outlet line in which is incorporated an air receiver which also serves as a water separator; a lubrication pipe which is connected to the above- mentioned air receiver and which opens into the rotor chamber of the compressor element and at the bearings of the above-mentioned rotors, whereby a non-return valve is incorporated in the above-mentioned lubrication pipe which is spanned by a branch in which is incorporated a water pump with a driving motor.
  • An advantage of the improved water-in ected screw- type compressor according to the invention is that, at times when the pressure in the air receiver is not sufficient for an effective lubrication of the bearings, the above-mentioned water pump can be turned on, so that water from the air receiver can be pumped to the bearings under a sufficient pressure and with a sufficient flow, so that an effective lubrication is at all times provided for and the life of the bearings is notably lengthened, and, as a consequence, the screw-type compressor has to be stopped far less frequently for maintenance and repairs .
  • the water pump will preferably be activated at least when the compressor is started and when the pressure in the air receiver is situated under a certain minimum limit, for example in case of lengthy idle running. Besides, the water pump will preferably be switched off as soon as the pressure in the air receiver is sufficient to guarantee an effective lubrication of the bearings, so that no energy is unnecessarily ' spilled for driving the pump.
  • Figure 1 represents an improved water- inj ected screw-type compressor 1 which is mainly composed of a compressor element 2 with a housing 3 in which are provided two co-operating screw-shaped rotors 4 whose shaft 5 is bearing-mounted in water- lubri cat ed hydrodynamic and hydrostatic bearings 6 and which are driven by means of a motor 7.
  • the compressor element 2 is provided with an inlet line 8 in which has been provided an inlet valve 9 and which is connected to an inlet filter 10 on its entry.
  • an outlet line 11 which is composed of the parts 11A, 11B and 11C respectively, whereby an air receiver 12 is provided between the parts 11A and 11B which is provided with a safety valve 13 on its output onto which the part 11B of the outlet line 11 is connected and whereby, between the part 11B and the part 11C, is provided an air cooler 14 which is equipped with a ventilation screw 15.
  • a water-cooled cooler can be connected, which can then be cooled by means of a secondary cooling water system.
  • the air receiver 12 is provided with a central conductor 16 which makes the compressed air flow through the air receiver 12 in a tangential manner.
  • a lubrication pipe 17 which is composed of the parts 17A, 17B and 17C, whereby, between the parts 17A and 17B, is provided a non-return valve 18 and whereby, between the part 17B and the part 17C, is incorporated a water cooler 19 which is cooled by means of the above-mentioned ventilation screw 15 of the air cooler 14 or by means of a secondary cooling water circuit in the case of a water-cooled cooler.
  • the lubrication pipe . 17 opens into the rotor chamber 20 on the one hand, which is confined by the housing 3 of the compressor element 2, and, via the branches 21 and 22 on the other hand, at the above-mentioned bearings 6 of the compressor element 2.
  • the lubrication pipe 17 opens in a central distribution chamber from where the water is distributed via internal channels to the rotor chamber 20 and to the bearings 6.
  • the air receiver 12 is connected to a chamber 24 in the housing 3, via a passage in the lid by means of a control line 23, consisting of a part 23A, a part 23B and an internal channel 23C, which chamber 24 forms a guide for a far end of the inlet valve 9, which far end is made as a piston 25.
  • a solenoid valve 26 having two positions, which, in one position, forms a connection between the lines 23A and 23B, and in the other position cuts off the line 23A and simultaneously connects the line 23B to the ambient air via an opening 27.
  • the above-mentioned internal channel 23C is connected to a chamber 28 in the housing 3 of the compressor element 2, whereby this chamber 28 is further connected to the above- mentioned rotor chamber 20 via a channel 29 which opens next to the inlet of the compressor element 2 and whereby a relief valve 30 is provided in this chamber 28 which cuts off the above-mentioned channel 29 by means of a spring 31-
  • the channel 29 is connected to the above-mentioned inlet line 8 by means of a bypass line 32.
  • the invention provides for a water pump 33 with a pump drive 34, which water pump 33 is provided in a branch 17D which spans the above-mentioned non-return valve 18 in the outlet line 17A.
  • a control element 35 is provided to control the motor 7 of the compressor element and of the pump drive 34, and to this end, it is connected to the motor 7 and to the pump drive 34 by means of electric conductors 36.
  • This control element 35 may for example consist of a microprocessor or the like and a memory in which has been stored accompanying software which provides for the general control of the compressor.
  • the control element 35 is also connected to two pressure sensors, a pressure sensor 37 measuring the pressure in the air receiver 12 and which is provided for example on the control line 23A, and a pressure sensor 38 measuring the injection pressure of the water and which is provided for example at the output of the lubrication pipe 17C respectively.
  • Figure 1 represents the screw compressor 1 as loaded, whereby the compressor element 2 is being driven by means of the motor 7, with a fixed or variable drive, and whereby the solenoid valve 26 is activated, such that, as described in detail in Belgian patent No. 1,012,655 in name of the present applicant, control pressure is sent from the air receiver 12, via the control line 23A, the solenoid valve 26 and the internal channel 230, to the chambers 24 and 28, as a result of which the inlet valve 9 is pushed open and the relief valve 30 is closed, so that a pressure is built up in the air receiver 12.
  • the pressure in the air receiver 12 forces the water which is situated at the bottom of the air receiver 12 through the lubrication pipe 17, over the non-return valve 18 and through the water cooler 19, to the compressor element 2, where the water under pressure is injected into the rotor chamber 20 in order to lubricate the rotors 4, and via the branches 21 and 22 into the bearings 6 for the hydrodynamic lubrication of these bearings .
  • the pressure in the air receiver 12 which is measured by means of the pressure sensor 37, is sufficient to obtain an effective lubrication of the compressor element 2 and of the bearings 6, the water pump 33 will be switched off by the control element 35.
  • the control element 35 will switch on the water pump 33 in order to avoid that the compressor element 2 and the bearings 6 would be lubricated insufficiently because the pressure in the air receiver 12 is too low, such that, in this case, the water pump 33 delivers the driving force for the lubrication of the compressor element 2 and the bearings 6.
  • This situation may occur for example in case of a lengthy idle running of the screw-type compressor 1 and when the compressor is being started and stopped.
  • the control element 35 When the pressure in the air receiver 12 then rises again, for example when the screw-type compressor 1 switches again from idle running to loaded running, the control element 35, as soon as the pressure in the air receiver 12 has reached a certain maximum value which is sufficient to obtain an effective lubrication of the compressor element 2 and of the bearings 6, will switch off the water pump 33 again, so that no energy is unnecessarily wasted for driving the water pump 33.
  • injection pressure which is measured by means of the pressure sensor 38 can be used as an input signal of the control element 35 in order to control the water pump 33 being switched on and off in an analogous manner as a function of a certain preset maximum and minimum value to be reached.
  • the signal of the pressure sensor 37 as well as the signal of the pressure sensor 38 is taken into account for the control .
  • the water pump ' 33 will be started immediately, before the motor 7 of the compressor element 2 is excited.
  • a motor 7 can be applied for example a conventional motor with a constant rotational speed, as well as a motor with a variable speed, whose rotational speed is frequency-controlled for example, and which can then be started after a fixed preset time, or when a signal is transmitted by one of the sensors, as soon as a certain pressure has been reached.
  • the solenoid valve 26 will be de-activated, as a result of which the control line 23A will be cut off in the known manner and the chambers 24 and 28 will be connected to the environment via the control lines 23B and 230 and the opening 27 in the solenoid valve 26, as a result of which the inlet valve 9 will be closed and the relief valve 30 will be opened, such that the compressor element 2 is being driven in an idle manner .
  • control element 35 can be programmed such that the motor 7 is shut down under these circumstances so as to save energy and is started up again as soon as the pressure in the air receiver 12 has dropped to a minimum value .
  • the flow and the lift of the water pump 33 are preferably selected such that, taking the characteristics of the water-injected screw-type compressor 1 and of its components into account, such as for example the- rotational speed of the motor 7 , the diameters of the lines and the like, the flow of the water pump 33 during the starting up will always be somewhat smaller than the flow of the water which is being pressed out by the compressor element 2, in order to avoid any damage resulting from water that is accumulated in the compressor element 2 and in the bearings 6, and to make sure that there is always a controlled pressure and flow in the compressor element 2 and in the bearings 6.
  • the motor 7 and the pump drive 34 are excited during a pre-set period of time by the control element 35, whereby this time has been selected sufficiently long in order to make sure that, reckoning with the above- mentioned difference in water flow, any water which is possibly present in the compressor element 2 will be evacuated before setting the motor 7 at a higher operational speed, in order to avoid any damage resulting from what is called water hammer caused by the powerful hydraulic forces that would result from a non- compressible medium such as water being compressed.
  • the water pump 33 will be started first and, after a short period of a few seconds, as soon as a certain pressure has been built up, the motor 7 will be started and driven at a reduced speed, lower than the normal regime speed, during a short time span of a few seconds before switching to a loaded condition by exciting the solenoid valve 26 and before switching to a higher regime speed.
  • the reduced rotational speed and the time span of this reduced rotational speed are selected such that, again reckoning with the characteristics of the screw-type compressor 1 and its components, the flow delivered by the water pump 33 will always be somewhat smaller than the flow of the water that is being pressed out by the compressor element 2, such that water hammer in the compressor element is prevented, and just a sufficient amount of lubrication and pressure of the bearings will be nevertheless guaranteed.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)

Abstract

Improved water-injected screw-type compressor which is mainly composed of a compressor element (2) with a housing (3) in which are provided two co-operating screw-shaped rotors (4) which are driven by means of a motor (7); an inlet line (8) in which is provided an inlet valve (9); an outlet line (11) in which is incorporated an air receiver (12) which also serves as a water separator; a lubrication pipe (17) which is connected to the above-mentioned air receiver (12) and which opens in the rotor chamber (20) of the compressor element (2) and at the bearings (6) of the above-mentioned rotors (4), characterised in that a non-return valve (18) is incorporated in the above-mentioned lubrication pipe (17) which is spanned by a branch (17D) in which is incorporated a water pump (33) with a pump drive (34).

Description

Improved water-injected screw-type compressor,
The present invention concerns an improved water- injected screw-type compressor.
More particularly, the invention concerns a water- injected screw-type compressor which is mainly composed of a compressor element with a housing in which are provided two co-operating screw-shaped rotors; an inlet line in which is provided an inlet valve; an outlet line in which has been incorporated an air receiver which also serves as a water separator; a lubrication pipe which is connected to the above-mentioned air receiver and which opens into the rotor chamber of the compressor and at the bearings of the above-mentioned rotors .
When the compressor is operational, the air receiver will be put under pressure and the water which is situated at the bottom in the air receiver will be sent back to the compressor element under the influence of said pressure for lubricating the rotors and the bearings. The injected water is pressed back to the air receiver, together with the compressed air, via the outlet line, whereby the injected water is separated from the air in this air receiver.
Such compres sors are very efficient in practice because of the intensive cooling of the water which is also used as a cooling medium.
However, extended experimental research has shown that, under certain circumstances, for example when starting up the compressor and in case of lengthy idle running, the pressure in the air receiver is insufficient to guarantee an efficient lubrication of the above- mentioned bearings, and that, under these circumstances, the bearings may be slightly damaged, as a result of which their life is considerably shortened.
Partly due to this, the bearings in the known water-injected screw-type compressors have to be periodically replaced with a certain frequency, 'which is disadvantageous in that the screw-type compressor concerned must be stopped and in that this replacement naturally has an influence on the operating costs of the screw-type compressor.
The present invention aims to remedy the above-mentioned and other disadvantages by providing an improved water-injected screw-type compressor with an improved water lubrication of the bearings, which has for a result that these bearings have to be replaced far less frequently, so that the operating costs of such an improved water-injected screw-type compressor will be lower than those of the known screw-type compressors with a comparable capacity.
To this end, the invention concerns an improved water-injected screw-type compressor which is mainly composed of a compressor element with a housing in which are provided two co-operating screw-shaped rotors that are driven- by means of a motor with a constant or variable drive; an inlet line in which is provided an inlet valve; an outlet line in which is incorporated an air receiver which also serves as a water separator; a lubrication pipe which is connected to the above- mentioned air receiver and which opens into the rotor chamber of the compressor element and at the bearings of the above-mentioned rotors, whereby a non-return valve is incorporated in the above-mentioned lubrication pipe which is spanned by a branch in which is incorporated a water pump with a driving motor.
An advantage of the improved water-in ected screw- type compressor according to the invention is that, at times when the pressure in the air receiver is not sufficient for an effective lubrication of the bearings, the above-mentioned water pump can be turned on, so that water from the air receiver can be pumped to the bearings under a sufficient pressure and with a sufficient flow, so that an effective lubrication is at all times provided for and the life of the bearings is notably lengthened, and, as a consequence, the screw-type compressor has to be stopped far less frequently for maintenance and repairs .
The water pump will preferably be activated at least when the compressor is started and when the pressure in the air receiver is situated under a certain minimum limit, for example in case of lengthy idle running. Besides, the water pump will preferably be switched off as soon as the pressure in the air receiver is sufficient to guarantee an effective lubrication of the bearings, so that no energy is unnecessarily ' spilled for driving the pump.
In order to better explain the characteristics of the invention, the following preferred embodiment of an improved water-injected screw-type compressor according to the invention is described as an example only without being limitative in any way, with reference to the sole accompanying figure 1, which schematically represents an improved water-injected screw-type compressor according to the invention.
Figure 1 represents an improved water- inj ected screw-type compressor 1 which is mainly composed of a compressor element 2 with a housing 3 in which are provided two co-operating screw-shaped rotors 4 whose shaft 5 is bearing-mounted in water- lubri cat ed hydrodynamic and hydrostatic bearings 6 and which are driven by means of a motor 7.
The compressor element 2 is provided with an inlet line 8 in which has been provided an inlet valve 9 and which is connected to an inlet filter 10 on its entry.
On the outlet of the compressor element 2 is connected an outlet line 11 which is composed of the parts 11A, 11B and 11C respectively, whereby an air receiver 12 is provided between the parts 11A and 11B which is provided with a safety valve 13 on its output onto which the part 11B of the outlet line 11 is connected and whereby, between the part 11B and the part 11C, is provided an air cooler 14 which is equipped with a ventilation screw 15.
Instead of said air cooler 15, also a water-cooled cooler can be connected, which can then be cooled by means of a secondary cooling water system.
Onto the piping part 11C can be connected compressed air consumers which are not represented in the figures .
The air receiver 12 is provided with a central conductor 16 which makes the compressed air flow through the air receiver 12 in a tangential manner.
At the bottom of the air receiver 12 is connected a lubrication pipe 17 which is composed of the parts 17A, 17B and 17C, whereby, between the parts 17A and 17B, is provided a non-return valve 18 and whereby, between the part 17B and the part 17C, is incorporated a water cooler 19 which is cooled by means of the above-mentioned ventilation screw 15 of the air cooler 14 or by means of a secondary cooling water circuit in the case of a water-cooled cooler.
The lubrication pipe .17 opens into the rotor chamber 20 on the one hand, which is confined by the housing 3 of the compressor element 2, and, via the branches 21 and 22 on the other hand, at the above-mentioned bearings 6 of the compressor element 2.
In practice, the lubrication pipe 17 opens in a central distribution chamber from where the water is distributed via internal channels to the rotor chamber 20 and to the bearings 6.
The air receiver 12 is connected to a chamber 24 in the housing 3, via a passage in the lid by means of a control line 23, consisting of a part 23A, a part 23B and an internal channel 23C, which chamber 24 forms a guide for a far end of the inlet valve 9, which far end is made as a piston 25.
Between the parts 23A and 23B of the control line 23 is provided a solenoid valve 26 having two positions, which, in one position, forms a connection between the lines 23A and 23B, and in the other position cuts off the line 23A and simultaneously connects the line 23B to the ambient air via an opening 27.
The above-mentioned internal channel 23C is connected to a chamber 28 in the housing 3 of the compressor element 2, whereby this chamber 28 is further connected to the above- mentioned rotor chamber 20 via a channel 29 which opens next to the inlet of the compressor element 2 and whereby a relief valve 30 is provided in this chamber 28 which cuts off the above-mentioned channel 29 by means of a spring 31-
The channel 29 is connected to the above-mentioned inlet line 8 by means of a bypass line 32.
The invention provides for a water pump 33 with a pump drive 34, which water pump 33 is provided in a branch 17D which spans the above-mentioned non-return valve 18 in the outlet line 17A.
A control element 35 is provided to control the motor 7 of the compressor element and of the pump drive 34, and to this end, it is connected to the motor 7 and to the pump drive 34 by means of electric conductors 36.
This control element 35 may for example consist of a microprocessor or the like and a memory in which has been stored accompanying software which provides for the general control of the compressor. In the given example, the control element 35 is also connected to two pressure sensors, a pressure sensor 37 measuring the pressure in the air receiver 12 and which is provided for example on the control line 23A, and a pressure sensor 38 measuring the injection pressure of the water and which is provided for example at the output of the lubrication pipe 17C respectively.
The working of the improved water- in j e c ted screw- type compressor 1 according to the invention is very simple and as follows.
Figure 1 represents the screw compressor 1 as loaded, whereby the compressor element 2 is being driven by means of the motor 7, with a fixed or variable drive, and whereby the solenoid valve 26 is activated, such that, as described in detail in Belgian patent No. 1,012,655 in name of the present applicant, control pressure is sent from the air receiver 12, via the control line 23A, the solenoid valve 26 and the internal channel 230, to the chambers 24 and 28, as a result of which the inlet valve 9 is pushed open and the relief valve 30 is closed, so that a pressure is built up in the air receiver 12. The pressure in the air receiver 12 forces the water which is situated at the bottom of the air receiver 12 through the lubrication pipe 17, over the non-return valve 18 and through the water cooler 19, to the compressor element 2, where the water under pressure is injected into the rotor chamber 20 in order to lubricate the rotors 4, and via the branches 21 and 22 into the bearings 6 for the hydrodynamic lubrication of these bearings .
If the pressure in the air receiver 12, which is measured by means of the pressure sensor 37, is sufficient to obtain an effective lubrication of the compressor element 2 and of the bearings 6, the water pump 33 will be switched off by the control element 35.
If, however, the pressure measured by the pressure sensor 37 drops below a certain preset minimum value, the control element 35 will switch on the water pump 33 in order to avoid that the compressor element 2 and the bearings 6 would be lubricated insufficiently because the pressure in the air receiver 12 is too low, such that, in this case, the water pump 33 delivers the driving force for the lubrication of the compressor element 2 and the bearings 6.
This situation may occur for example in case of a lengthy idle running of the screw-type compressor 1 and when the compressor is being started and stopped.
When the pressure in the air receiver 12 then rises again, for example when the screw-type compressor 1 switches again from idle running to loaded running, the control element 35, as soon as the pressure in the air receiver 12 has reached a certain maximum value which is sufficient to obtain an effective lubrication of the compressor element 2 and of the bearings 6, will switch off the water pump 33 again, so that no energy is unnecessarily wasted for driving the water pump 33.
Also the injection pressure which is measured by means of the pressure sensor 38 can be used as an input signal of the control element 35 in order to control the water pump 33 being switched on and off in an analogous manner as a function of a certain preset maximum and minimum value to be reached.
In the given example, the signal of the pressure sensor 37 as well as the signal of the pressure sensor 38 is taken into account for the control .
When starting the screw-type compressor 1 after a period of standstill, there will be practically no pressure in the air receiver 12.
In this case, the water pump' 33 will be started immediately, before the motor 7 of the compressor element 2 is excited. As a motor 7 can be applied for example a conventional motor with a constant rotational speed, as well as a motor with a variable speed, whose rotational speed is frequency-controlled for example, and which can then be started after a fixed preset time, or when a signal is transmitted by one of the sensors, as soon as a certain pressure has been reached.
In the case of a motor 7 with a' constant rotational speed, as soon as the injection pressure has reached a certain minimum limit of for example half a bar within a certain time span of a few seconds, the motor 7 will be started in star connection. If, however, the above-mentioned minimum limit is not reached within said time span, the motor 7 will not start, in order to prevent the compressor element 2 from being driven without any water pressure or flow.
Subsequently, we will switch from a star connection to a delta connection, and the solenoid valve 26 is simultaneously excited, so that the inlet valve 9 is opened and the relief valve 30 is closed, as a result of which the compressor element 2 will function entirely loaded in the known manner. As soon as the pressure has reached a preset value of for example 5 bar, the water pump 33 will be switched off to save energy.
As soon as the operating pressure in the air receiver 12 reaches a preset upper limit, the solenoid valve 26 will be de-activated, as a result of which the control line 23A will be cut off in the known manner and the chambers 24 and 28 will be connected to the environment via the control lines 23B and 230 and the opening 27 in the solenoid valve 26, as a result of which the inlet valve 9 will be closed and the relief valve 30 will be opened, such that the compressor element 2 is being driven in an idle manner .
If necessary, the control element 35 can be programmed such that the motor 7 is shut down under these circumstances so as to save energy and is started up again as soon as the pressure in the air receiver 12 has dropped to a minimum value .
The flow and the lift of the water pump 33 are preferably selected such that, taking the characteristics of the water-injected screw-type compressor 1 and of its components into account, such as for example the- rotational speed of the motor 7 , the diameters of the lines and the like, the flow of the water pump 33 during the starting up will always be somewhat smaller than the flow of the water which is being pressed out by the compressor element 2, in order to avoid any damage resulting from water that is accumulated in the compressor element 2 and in the bearings 6, and to make sure that there is always a controlled pressure and flow in the compressor element 2 and in the bearings 6.
During the start-up of the compressor element 2, the motor 7 and the pump drive 34 are excited during a pre-set period of time by the control element 35, whereby this time has been selected sufficiently long in order to make sure that, reckoning with the above- mentioned difference in water flow, any water which is possibly present in the compressor element 2 will be evacuated before setting the motor 7 at a higher operational speed, in order to avoid any damage resulting from what is called water hammer caused by the powerful hydraulic forces that would result from a non- compressible medium such as water being compressed. In the case of a motor 7 with a variable speed, also the water pump 33 will be started first and, after a short period of a few seconds, as soon as a certain pressure has been built up, the motor 7 will be started and driven at a reduced speed, lower than the normal regime speed, during a short time span of a few seconds before switching to a loaded condition by exciting the solenoid valve 26 and before switching to a higher regime speed.
By first driving the motor 7 for a short period at a reduced rotational speed, one can be sure that all the water is removed from the compressor element 2 before switching to a higher regime speed whereby the compressor element 2 would be irrevocably damaged if not all the water were evacuated. After the start-up, the pressure in the air receiver 12 will rise and, as soon as this pressure or the injection pressure has reached a certain preset value, the water pump 33 will be switched off.
The reduced rotational speed and the time span of this reduced rotational speed are selected such that, again reckoning with the characteristics of the screw-type compressor 1 and its components, the flow delivered by the water pump 33 will always be somewhat smaller than the flow of the water that is being pressed out by the compressor element 2, such that water hammer in the compressor element is prevented, and just a sufficient amount of lubrication and pressure of the bearings will be nevertheless guaranteed.
The present invention is by no means limited to the above-described embodiment represented in the accompanying drawings; on the contrary, such an improved water-injected screw-type compressor according to the invention can be made in all sorts of shapes and dimensions while still remaining within the scope of the invention .

Claims

Claims ,
1.- Improved water-injected screw-type compressor which is mainly composed of a compressor element (2) with a housing (3) in which are provided two co-operating screw-shaped rotors (4) which are driven by means of a motor (7); an inlet line (8) in which is provided an inlet valve (9); an outlet line (11) in which is incorporated an air receiver (12) which also serves as a water separator; a lubrication pipe (17) which is connected to the above-mentioned air receiver (12) and which opens in the rotor chamber (20) of the compressor element (2) and at the bearings (6) of the above- mentioned rotors (4), characterised in that a non- return valve (18) is incorporated in the above-mentioned lubrication pipe (17) which is spanned by a branch (17D) in which is incorporated, a water pump (33) with a pump drive (34) .
2.- Improved water-injected screw-type compressor according to claim 1, characterised in that it is provided with a control element (35) for controlling the motor (17) of the compressor element (2) and of the pump drive (34) , whereby this control element (35) is configured such that, when starting up the screw compressor (1), the pump drive (34) is first activated for a certain period of time before the motor (7) of the compressor element (2) is excited.
3.- Improved water-injected screw-type compressor according to claim 2, characterised in that it is provided with a.- pressure sensor (37) for measuring the pressure in the air receiver (12) , which pressure sensor (37) is connected to the control element (35), and in that, during the start-up of the screw-type compressor (1) , the motor (7) of the compressor element (2) will be only exerted as soon as the measured pressure has reached a preset minimum limit.
4.- Improved water-injected screw-type compressor according to claim 3, characterised in that the above- mentioned preset minimum limit of the pressure is in the order of magnitude of half a bar.
5.- Improved water-injected screw-type compressor according to claim 3, characterised in that the control element (35) will not start the motor (7) when the above- mentioned preset minimum pressure is not reached within a certain preset time span.
6.- Improved water-injected screw-type compressor according to claim 5, characterised in that the preset time span is in the order of magnitude of a few seconds .
7.- Improved water-injected screw-type compressor according to claim 3, characterised in that the water pump (33) is switched off as soon as the pressure in the air receiver, measured by- the above-mentioned pressure sensor (37), exceeds a certain preset maximum value .
8.- Improved water-injected screw-type compressor according to claim 2, characterised in that it is provided with a pressure sensor (38) for measuring the injection pressure of the water, which pressure sensor (38) is connected to the control element (35), and in that the water pump (33) is switched off as soon as the injection pressure of the water exceeds- a certain preset maximum value.
9.- Improved water-injected screw-type compressor according to claim 1, characterised in that it is configured such that the flow of the water pump (33) during the start-up is always somewhat smaller than the flow of the water which is being pressed out by the compressor element (2) .
10.- Improved water-injected screw-type compressor according to claim 9, characterised in that, during the start-up of the compressor element (2) , the control element (35) excites the motor (7) and the pump drive (34) during a preset period, whereby this time is selected sufficiently long, such that, reckoning with the above-mentioned difference in water flow, any water which is possibly present in the compressor element (2) would be evacuated.
11.- Improved water-injected screw-type compressor according to claim 7, characterised in that the motor (7) of the compressor element (2) is a motor with a variable speed, and in that, when starting up the screw-type compressor (1), the speed of this motor (7) is adjusted such at a reduced rotational speed by the control element (35) that, taking into account the characteristics of the components of the screw-type compressor (1), the flow delivered by the water pump (33) is always somewhat smaller than the flow of the water which is being pressed out by the compressor element (2) .
12.- Improved water-injected screw-type compressor according to claim 2 r characterised in that the control element (35) is configured such that the water pump (33) is switched on as soon as the pressure, measured by the pressure sensor (37) and/or the pressure measured by the pressure sensor (38) , drops/drop respectively below a certain preset minimum value.
PCT/BE2004/000144 2003-10-15 2004-10-12 Improved water-injected screw-type compressor WO2005035989A1 (en)

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CN102162457A (en) * 2011-05-12 2011-08-24 上海英格索兰压缩机有限公司 Air inlet valve of screw air compressor with halt check function
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US20140308148A1 (en) * 2013-04-12 2014-10-16 Hitachi Industrial Equipment Systems Co., Ltd. Water Lubricated Screw Compressor
WO2015035478A1 (en) * 2013-09-11 2015-03-19 Atlas Copco Airpower, Naamioze Vennootschap Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
WO2018054857A1 (en) * 2016-09-21 2018-03-29 Knorr-Bremse Systeme für Nutzfahrzeuge GmbH Screw compressor for a utility vehicle
CN109458344A (en) * 2017-09-06 2019-03-12 久益环球地表采矿公司 Lubricating system for compressor
US11680588B2 (en) 2020-04-21 2023-06-20 Joy Global Surface Mining Inc Lubrication system for a compressor

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CN102162457A (en) * 2011-05-12 2011-08-24 上海英格索兰压缩机有限公司 Air inlet valve of screw air compressor with halt check function
US20140308148A1 (en) * 2013-04-12 2014-10-16 Hitachi Industrial Equipment Systems Co., Ltd. Water Lubricated Screw Compressor
US9732751B2 (en) * 2013-04-12 2017-08-15 Hitachi Industrial Equipment Systems Co., Ltd. Water lubricated screw compressor
BE1021737B1 (en) * 2013-09-11 2016-01-14 Atlas Copco Airpower, Naamloze Vennootschap LIQUID-INJECTED SCREW COMPRESSOR, CONTROL FOR THE TRANSITION FROM AN UNLOADED TO A LOAD SITUATION OF SUCH SCREW COMPRESSOR AND METHOD APPLIED THEREOF
KR101905281B1 (en) 2013-09-11 2018-10-05 아틀라스 캅코 에어파워, 남로체 벤누트삽 Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
CN105612352A (en) * 2013-09-11 2016-05-25 阿特拉斯·科普柯空气动力股份有限公司 Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
JP2016530450A (en) * 2013-09-11 2016-09-29 アトラス コプコ エアーパワー, ナームローゼ フェンノートシャップATLAS COPCO AIRPOWER, naamloze vennootschap Liquid injection type screw compressor, controller for shifting screw compressor from unloaded state to loaded state, and method applied thereto
WO2015035478A1 (en) * 2013-09-11 2015-03-19 Atlas Copco Airpower, Naamioze Vennootschap Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
AU2014321166B2 (en) * 2013-09-11 2017-12-14 Atlas Copco Airpower, Naamloze Vennootschap Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
US10704550B2 (en) 2013-09-11 2020-07-07 Atlas Copco Airpower, Naamloze Vennootschap Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
KR20160058838A (en) * 2013-09-11 2016-05-25 아틀라스 캅코 에어파워, 남로체 벤누트삽 Liquid injected screw compressor, controller for the transition from an unloaded state to a loaded state of such a screw compressor and method applied therewith
CN109790839A (en) * 2016-09-21 2019-05-21 克诺尔商用车制动系统有限公司 Screw compressor system for commercial vehicle
WO2018054857A1 (en) * 2016-09-21 2018-03-29 Knorr-Bremse Systeme für Nutzfahrzeuge GmbH Screw compressor for a utility vehicle
US11085447B2 (en) 2016-09-21 2021-08-10 Knorr-Bremse Systeme Fuer Nutzfahrzeuge Gmbh Screw compressor for a utility vehicle
CN109458344A (en) * 2017-09-06 2019-03-12 久益环球地表采矿公司 Lubricating system for compressor
CN109458344B (en) * 2017-09-06 2024-04-12 久益环球地表采矿公司 Lubrication system for compressor
US11680588B2 (en) 2020-04-21 2023-06-20 Joy Global Surface Mining Inc Lubrication system for a compressor

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