METHOD TO OPERATE A VACUUM SYSTEM

Abstract

Method to operate a vacuum system comprising at least a first vacuum pump and a second vacuum pump wherein the first vacuum pump and the second vacuum pump are connectable to a vacuum chamber to maintain a set pressure inside the vacuum chamber. The first vacuum pump is a Variable Speed Drive pump wherein the first vacuum pump and the second vacuum pump are connected in series. The method comprises the steps of controlling the performance of the first vacuum pump and the performance of the first vacuum pump is controlled to be equal to or higher than the performance of the second vacuum pump while maintaining the set pressure in the vacuum chamber.

Claims

1. A method to operate a vacuum system comprising at least a first vacuum pump and a second vacuum pump, wherein the first vacuum pump and the second vacuum pump are connectable to a vacuum chamber to maintain a set pressure, wherein the first vacuum pump is a variable speed drive pump, VSD, wherein the first vacuum pump and the second vacuum pump are connected in series and the maximum pump rate of the first vacuum pump is 1.25 times to 4 times larger than the maximum pump rate of the second vacuum pump, the method comprises the steps of: controlling the performance of the first vacuum pump, wherein the performance of the first vacuum pump is controlled to be equal to or higher than the performance of the second vacuum pump while maintaining the set pressure in the vacuum chamber.

2. The method according to claim 1, characterized in that the second vacuum pump is a VSD, wherein the performance of the second vacuum pump is controlled to be reduce while maintaining the set pressure.

3. The method according to claim 1, characterized in that the first vacuum pump and/or the second vacuum pump comprise more than one vacuum pump preferably connected in parallel.

4. The method according to claim 1, characterized in that the performance of the first vacuum pump is maximized and the performance of the second vacuum pump is minimized while maintaining the set pressure.

5. The method according to claim 1, characterized in that if the pressure in the vacuum chamber is above the set pressure, the first vacuum pump is operated at maximum performance and preferably the second vacuum pump is operated in dependence on the pressure.

6. The method according to claim 1, characterized in that if the pressure in the vacuum chamber is equal to or below the set pressure, the second vacuum pump is operated at minimum performance and preferably the first vacuum pump is operated in dependence on the pressure.

7. The method according to claim 1, characterized in that the maximum pump rate of the first vacuum pump is 2 times to 4 times larger than the maximum pump rate of the second vacuum pump.

8. The method according to claim 1, characterized in that the maximum pump rate of the first vacuum pump is 1.25 times to 1.5 times larger than the maximum pump rate of the second vacuum pump.

9. The method according to claim 1, characterized in that the performance of first vacuum pump and/or second vacuum pump is increased at least above a threshold if the first vacuum pump or the second vacuum pump is running at a performance below the threshold for a predetermined time.

10. A vacuum system comprising a first vacuum pump and a second vacuum pump connectable with a vacuum chamber, wherein the first vacuum pump and preferably the second vacuum pump are connected to a control unit, wherein the control unit is adapted to carry out the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the following the present embodiments of the present invention will be described together with the accompanied drawings.

[0024] The figures show:

[0025] FIG. 1 a schematic drawing of the vacuum system according to the present invention and

[0026] FIG. 2 a flow diagram for the method according to the present invention.

DETAILED DESCRIPTION

[0027] The vacuum system according to the present invention comprises a vacuum chamber 12 to be evacuated and maintained at a set pressure. The vacuum chamber 12 is connected with an inlet 14 of the first vacuum pump 16. The outlet 18 of the first vacuum chamber 16 is connected to an inlet 20 of a second vacuum pump 22. Hence, the outlet pressure of the first vacuum pump 16 is equal to the inlet pressure of the second vacuum pump 22. The outlet 24 of the second vacuum pump 22 is connected to atmosphere or another backing pump. The first vacuum pump 16 can be built as one or more vacuum pumps connected in series or in parallel acting together. Also, the second vacuum pump 22 can be built by one or more vacuum pumps connected in series or parallel and acting together. The first vacuum pump 16 is connected to a control unit 26. Further, the second vacuum pump 22 is also connected to the control unit 26. In the present embodiment, the control unit 26 in connected to a pressure gauge 28 inside the vacuum chamber 12. By the control unit 26 the performance, i.e. volumetric flow, of the first vacuum pump 16 and/or second vacuum pump 22 can be controlled. Therein the first vacuum pump 16 is controlled to run always at the highest possible performance under which the pressure inside the vacuum chamber 12 is maintained. If the pressure inside the vacuum chamber 12 is below the set pressure, then the performance of the second vacuum pump is reduced. In particular, the first vacuum pump 16 is controlled to run always at a higher performance than the second vacuum pump 22. Thus, by the high performance of the first vacuum pump 16 the pressure at the inlet 20 of the second vacuum pump 22 is increased reducing the energy consumption of the second vacuum pump 22. Further, due to the increased inlet pressure of the second vacuum pump 22, rotational speed of the second vacuum pump 22 can be reduced without loss of vacuum in the vacuum chamber. Thus, the first vacuum pump 16 is controlled to maximize the inlet pressure of the second vacuum pump 22 by an increased performance, i.e. volumetric flow. Further, the second vacuum pump 22 is controlled to be operated at minimum rotational speed to achieve a minimized energy consumption while maintaining the set pressure in the vacuum chamber. However, the maximum inlet pressure is limited by the first vacuum pump 16. Exceeding the allowable pressure difference between the inlet and outlet of the first vacuum pump 16 would overload the first vacuum pump 16. Therefore, it is preferred to implement a first vacuum pump 16 with a maximum pump rate greater than the maximum pump rate of the second vacuum pump.

[0028] FIG. 2 shows a flow diagram of the vacuum system of FIG. 1.

[0029] In step S01 is system is turned on. Then, in step S02 it is checked whether the pressure P1 inside the vacuum chamber 12 is larger or equal than the set pressure Pset. If the pressure P1 inside the vacuum chamber 12 is larger or equal than the set pressure Pset, then in step S03 the first vacuum pump 16 is controlled to operate at the maximum performance. This maximum is depending on inlet and outlet pressure, thus also depending on the speed of the second pump. The second vacuum pump 22 is controlled to operate in dependence on the pressure P1 inside the vacuum chamber 12.

[0030] If the pressure inside the vacuum chamber 12 is below the set pressure, then in step S04 it is checked whether a stop level has been reached, i.e. P1 is equal to or larger than Pset minus Stoplevel. If the pressure inside the vacuum chamber 12 is below the stop level, then in step S06 the first vacuum pump 16 and the second vacuum pump 22 are both operated at their minimum performance.

[0031] If the pressure inside the vacuum chamber 12 is below the set pressure Pset but above the stop level, then in step S05 it is checked whether the second vacuum pump 22 is operated at minimum performance. If the second vacuum pump 22 is not operated at minimum performance, then it is returned to step S03 wherein the first vacuum pump 16 is controlled to operate at the maximum performance while the second vacuum pump 22 is controlled to operate in dependence on the pressure P1 inside the vacuum chamber 12. If the second vacuum pump 22 is operated at minimum performance, then in step S09 first vacuum pump 16 is controlled to operate in dependence on the pressure P1 inside the vacuum chamber 12 while the second vacuum pump 22 is controlled to operate at the minimum performance.

[0032] If both vacuum pumps are operated at their minimum performance, then in step S07 it is checked whether the first vacuum pump 16 or the second vacuum pump 22 is operated at minimum performance for a predetermined time. If the predetermined time has been reached, then in step S08 the vacuum system is tuned off.

[0033] The above described method is repeatedly applied in dependence on a change of the pressure inside the vacuum chamber 12.

[0034] Hence, through the method according to the present invention the first vacuum pump is usually operated at a higher performance than the second vacuum pump. Due to this configuration the inlet pressure of the second vacuum pump is maximized. Thus, the required power consumption of the second vacuum pump is reduced, thereby reducing the overall power consumption of the vacuum system.

[0035] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0036] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.