EP3280915A1 - Vacuum pump system - Google Patents

Abstract

A vacuum pump system (4, 5, 6) comprising a plurality of vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) which are connected to one another in parallel and each connected on an inlet side to a chamber (40, 0, 60), having an outlet line (41) which is connected on the outlet side of the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62), and an intermediate line (42) which connects the inlet side of at least one vacuum pump (P41, P42, P43, P44, P45, P51, P52, P61, P62) to the outlet line (41), characterized in that all the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) are switched to be in parallel during a pumping out period and at least one of the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) is switched to be in series with the other vacuum pumps as a backing pump during an idle period.

Description

 Vakuumpumpensvstem

The present invention relates to a vacuum pump system for evacuating a chamber, in particular a process or lock chamber.

Vacuum pump systems for the regular evacuation of large chambers are known from the prior art, Figure 1. Frequently, for this purpose, vacuum pumps, which operate dry-compressing used. These are typically combinations of backing pumps, such as screw pumps, claw pumps or multi-stage roots pumps, and Roots pumps arranged in series with them. In large pump systems, several pumps and several Roots pumps are connected in parallel.

Typically, such pump systems in lock chambers, such as loadlock or unloading, z. B. used in coating equipment. In these facilities, a chamber in a short time, z. B. Abpumpzeit 20 seconds to 120 seconds, from atmospheric pressure to a transfer pressure of typically about 0.1 mbar to 10 mbar, are pumped down. Following this, a vacuum pump is separated from the chamber to be evacuated by a valve on the inlet side and runs in end pressure mode for some time, typically one to ten times the pumping time. Other typical applications are large process chambers for the heat treatment or refining of metals. In this case, typical pump down times are 2 to 30 minutes. Thereafter, a low gas flow must continue to be pumped, which, however, is much smaller than the gas flow necessary to realize the Abpumpzeit. A typical holding time for this operating pressure is two to ten times the pumping time.

In such applications, the vacuum pump system must be very large to realize the short Abpumpzeit. During an idle time or during a hold time, however, large pumping system pumping speeds are not necessary. As a result, unnecessarily high energy expenditure of the pump is required during the idling period, during the holding time.

To reduce a high power consumption of pump systems during the idle or hold time, various approaches are known.

Some pump systems with pre- and / or Roots pumps are temporarily shut down. The disadvantage in this case is that the pumps are cold, which has a negative effect on the life of the components. Also coverings can stick together and block the rotors. With short idle or hold times, the pumps often have to be re-accelerated, which costs more power and requires very large sized motors. Switching off pumps is therefore unusual.

From the prior art is also known that on the outlet side of each fore pump, an additional smaller auxiliary pump is arranged in series, Figure 3. This can, for. B. be an ejector or other smaller forepump. In addition to the auxiliary pump, a switching valve or non-return valve with a sufficient cross-section usually has to be arranged in order to avoid too high pressures between the pre-pump and the auxiliary pump during the pump-down time. A disadvantage of these solutions is the high number of additional Pump. In addition, very small auxiliary pumps, such as ejectors, can not reduce the backing pump outlet pressure fast enough to achieve sufficient power savings with a short idle or hold time. The auxiliary pumps also require energy for operation.

A further solution, which is known from the prior art, is that a small number of further large backing pumps can be arranged as large auxiliary pumps on the outlet side of the backing pumps, FIG. 2. These are connected in series via a pipeline system to the backing pumps. In this case as well, at least one valve with a sufficient cross-section usually has to be arranged parallel to the auxiliary pump in order to avoid excessively high pressures between the pre- and auxiliary pumps during the pump-down time. A disadvantage of this solution is the additional acquisition and operating costs and the space required for the auxiliary pumps.

The object of the present invention is to provide an improved pump system which receives less power, especially during idle and hold times.

This object is achieved by a pump system having a plurality of vacuum pumps connected in parallel with each other and each connected to an inlet side of a chamber, FIG. 4. The pump system also has an outlet conduit connected to the outlet side of the vacuum pumps , Furthermore, the pump system has an intermediate line connecting the inlet side of at least one of the vacuum pumps with the outlet side. During a pump down time, all the vacuum pumps are connected in parallel, and during one idle and / or hold period, at least one of the vacuum pumps is connected as a backing pump in series with the other vacuum pumps.

Due to the parallel connection of all backing pumps of a pump system during the pump down time, the full suction capacity is available for the pumpdown process Available. The vacuum pump system also has switching means both in connections between the inlet sides to the chambers and in an intermediate line. These switching means may include valves, for example. During idling or holding time, one of the vacuum pumps can thus be connected as a backing pump in series with the other vacuum pumps. This is realized by appropriate switching of the switching means by blocking or releasing the connection in such a way that the vacuum pumps are arranged correspondingly differently to one another in series or in parallel. As a result, the outlet pressure of the vacuum pumps is lowered quickly and the power consumption is significantly reduced. However, the pumps continue to run so that they can be used for the next pump down cycle without any loss of time.

It is therefore not necessary to switch off certain pumps, so that the pumps remain warm and continue to be fully operational. Another advantage arises from the fact that the drives do not have to be designed for frequent acceleration and no additional pumps are required. An additional expense for the pump system according to the invention is limited only to relatively small-sized pipes and switching means, such as valves, as well as modifications to a pump control.

Due to the reduced energy consumption of the pump system, the pumps are operated relatively cold, so that the life of conventional wear parts is significantly increased, such as oil, bearings, seals, power electronics in the drive. Furthermore, this reduced energy consumption due to reduced waste heat also reduces the costs for the air conditioning of the installation site and the cooling of the pumps. The reduced pressure in the outlet during operation further avoids the condensation of vapors in the pumps, which can reduce corrosion damage.

In the case where at least one vacuum pump is connected in series as a fore pump, a very low end or working pressure can be achieved. This allows special process steps without additional pumps. For example, such a leak detection in the system before the actual process operation is possible because a leak detection usually requires a low working pressure. During an idling or holding time realized according to the invention, the sound level of a pump system also drops because most of the pumps have lower noise emissions when the load is reduced.

The pump system according to the invention allows a high degree of redundancy, because the failure of individual pumps in such a composite enables a continuation of the process. All pumps can therefore do their job without auxiliary pumps. Furthermore, several pumps can be integrated so that they can be used as an auxiliary pump. In addition to a reduction in power consumption and thus reduced operating costs, the CO 2 balance for such an application according to the invention is also improved.

For the operation described according to the invention, it is particularly preferred that the vacuum pumps, which are to be connected in series as backing pumps, meet certain technical requirements. It is particularly preferred that these vacuum pumps are sealed so that they can work safely with greatly reduced outlet pressures without gas or oil leakage. In this case, outlet pressures of the backing pumps during idling or holding operation in a range from 10 mbar to 500 mbar are particularly preferred. In addition, it is particularly preferred that the thermal behavior of the pumps allows safe operation at a greatly reduced outlet pressure. This aspect particularly concerns the gap heights, oil viscosity and bearing lubrication.

Furthermore, it is particularly preferred that oil-lubricated spaces are sealed from a working space so that even with very fast cycles no strong Ölverschleppung takes place. Furthermore, shaft seals should preferably be designed so that they do not wear prematurely due to the rapidly changing pressure differences. One possibility in this regard is the use of compensating pipes between oil-lubricated spaces and the working space, which have an oil separator.

Further advantageous embodiments and further developments are specified in the following figures. However, the resulting respective features are not limited to individual figures or embodiments. Rather, one or more features of the above description may be combined with single or multiple features of the figures in addition to further developments.

Show it :

Figures 1 to 3 embodiments according to examples of the prior art, and

Figures 4 to 6 embodiments of the invention.

FIG. 1 shows a vacuum pump system 1 with a lock chamber 10 and parallel-connected pumps PI-P5, which are each connected to the lock chamber on their inlet side. Furthermore, the vacuum pump system 1 has valves VI - V5, whereby the connection can be separated from the pump inlets of the pumps PI - P5 to the lock chamber 10. The illustrated vacuum pumping system is known in the art. During a pump down time, valves VI - V5 are open. The pumps PI - P5 take a lot of power during the pump down time and run at full speed. The pressure in the lock chamber drops continuously.

During an idle time, the valves VI-V5 are closed and the pumps PI-P5 run at full speed, the current consumption substantially equaling that of the operation at a final pressure, and still relatively is high. The pressure in the lock chamber is equal to a transfer pressure.

During a holding time, valves VI - V5 are open and pumps PI - P5 operate at a low working pressure.

The vacuum pump system shown in FIG. 2 is known from the prior art. The pump system is extended by a relatively large sized auxiliary pump P26 and the check valves CV1 - CV5 (Check Valve: Check Valve, CV).

The parallel-connected pumps P21 - P25 are connected to a chamber 20. During a pump down time both the valves V21 - V25 and the check valves CV21 - CV25 are open. The inlet pressure of the additional auxiliary pump P26 is approximately equal to the outlet pressure of the auxiliary pump.

During an idle time, valves V21 - V25 are closed. As a result, the check valves CV21 - CV25 close. The inlet pressure of the auxiliary pump P26 in this operation is substantially smaller than the outlet pressure of the auxiliary pump P26.

FIG. 3 shows a configuration known from the prior art of a vacuum pump system for a lock chamber 30 with small auxiliary pumps P33 and P34. For example, an ejector pump can be selected for the auxiliary pumps.

During a pump down time, the valves V31 and V32 and the check valves CV31 and CV32 are opened. The inlet pressures of the auxiliary pumps P33 and P34 are approximately equal to the outlet pressures of the auxiliary pumps P33 and P34. During an idle time of the pump system 3, the valves V31 and V32 are closed.

The check valves CV31 and CV32 are also closed during an idle time. The discharge pressures of the auxiliary pumps P33 and P34 during the idling time are substantially greater than the inlet pressures of these auxiliary pumps P33 and P34.

FIGS. 4 to 6 show embodiments of the vacuum pump system according to the invention.

The vacuum pump system shown in FIG. 4 has five parallel-connected vacuum pumps P41, P42, P43, P44, P45. The inlets of the vacuum pumps P41, P42, P43, P44, P45 are connected to a vacuum chamber 40. Between the respective vacuum pump P41, P42, P43, P44, P45 a valve V41, V42, V43, V44, V45 is provided. The outlet sides of pumps P41, P42, P43, P44, P45 are connected to a common outlet 41 via check valves CV41, CV42, CV43, CV44, CV45.

In a connecting line 42 in which a valve V46 is arranged, in the embodiment of the vacuum pumping system of FIG. 4, the pump P41 can be connected in series with the pumps P42, P43, P44, P45.

The vacuum pump P41, which should be used as a pre-pump and as an auxiliary pump, can generally be made smaller than the other vacuum pumps. Thus, the power consumption in idle or in holding mode is further reduced. FIG. 4 shows a vacuum pump system in which the valves V41-V45 are open during a pump-down time and the valve V46 is closed. Furthermore, the check valves CV41 - CV45 are open during the pump down time. During the idle time, valves V41 - V45 are closed, V46 is open. The CV41 check valve may be open in this mode as long as the pump system is evacuated by the P41 pump. After that it will be closed. The check valves C42 - C45 are closed in idling mode. The reduction of power consumption during idling is up to 40% in some embodiments. In particular, the described series connection of the vacuum pump can also be used as a backing pump to improve the production of light gases. Furthermore, this pump circuit can also be used to control the chamber pressure or the process flow. The auxiliary pump ensures that the working pressure range is safely reached. The backing pumps can then be safely controlled in a very wide speed range.

FIG. 5 shows a minimal configuration for lock chambers. By way of example, in the exemplary embodiment of FIG. 5, a pump system is selected with only two vacuum pumps P51, P52. These have a common inlet line, which is connected via a valve V52 with a vacuum chamber 50. Only the outlet of the vacuum pump P52 is connected to the common outlet 51 via a check valve CV51. The outlet of the pump P51 is directly connected to the common outlet 51. Through an additional line 52, in which a valve V51 is arranged, which leads from the outlet of the pump P52 to the inlet of the pump P51, in the idling time the pump P51 can evacuate the other pump 52 from both sides. However, in the example of FIG. 5, the pumps P51 and P52 can not be connected in series.

FIG. 6 shows, analogously to FIG. 5, a minimal configuration for process chambers. During the hold time, V61 is open so that P62 and P61 are evacuated from both sides. During the pump down time, V61 is closed so that the process chamber can be evacuated in a short time. In both embodiments of the vacuum pump systems 5 and 6 could parallel to the Pumps P52 and P62 other pumps are arranged and operated accordingly.

The solutions described here could be realized for combinations with two and more forepumps. The number and size of the pumps can each be freely adapted to the application. The Roots pumps in series with the backing pumps do not affect the solutions in principle. Therefore, they were not shown in the examples.

Claims

claims A vacuum pump system (4, 5, 6) having a plurality of vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) connected in parallel with each other and each having an inlet side to a chamber (40, 50, 60) are connected to an outlet line (41, 51, 61) connected to the outlet side of the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) and one Intermediate line (42, 52) connecting the inlet side of at least one vacuum pump (P41, P42, P43, P44, P45, P51, P52, P61, P62) to the outlet line (41), characterized in that during a pump down time all the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) are connected in parallel, and during an idle time, the inlet side of at least one of the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62 ) as a forepump is connected to the outlet side of the remaining vacuum pumps. 2. Vacuum pump system according to claim 1, characterized in that during the idle time, the vacuum pump whose inlet side is connected to the outlet side of the remaining vacuum pumps, is connected in series with the other vacuum pumps. The vacuum pump system according to claim 1 or 2, characterized in that the outlet side of the vacuum pump is connected to the outlet pipe (41, 51, 61) via a check valve (CV41, CV42, CV43, CV44, CV45, CV51, CV61). 4. Vacuum pump system according to one of claims 1 to 3, characterized in that before each of the vacuum pumps (P41, P42, P43, P44, P45, P51, P52, P61, P62) a valve (V41, V42, V43, V44, V45, V52) is arranged and in particular a further valve (V46, V51, V61) in the intermediate line (42) for controlling a parallel and series connection of the individual vacuum pumps (V41, V42, V43, V44, V45) with each other. 5. Vacuum pump system according to claim 1 to 4, characterized in that the at least one of the vacuum pumps whose inlet side is connected at idle to the outlet side of the remaining vacuum pumps and in particular connected in series with the other vacuum pumps, is smaller in size than the other vacuum pumps.