Method of operating a vacuum system

Abstract

A method of operating a vacuum system, the 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 driven 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.

Description

Technical Field

[0001] Vacuum technology is widely used in various technologies and applications. Typically, in these applications, a vacuum system is connected to a vacuum chamber to be evacuated. This usually requires the vacuum system to lower the pressure within the vacuum chamber below a given set point. Background Technology

[0002] Vacuum systems typically include vacuum pumps. However, it is well known that vacuum systems include two vacuum pumps, with the first vacuum pump configured to achieve either low or high vacuum. The first vacuum pump works in conjunction with a second vacuum pump, or a backing pump. The backing pump is configured to provide high-quality flow rates and is capable of achieving a low vacuum (coarse vacuum). During the evacuation of the vacuum chamber, the backing pump typically first evacuates the vacuum chamber to a certain vacuum level, i.e., reduces the pressure to a certain level. Then the first vacuum pump begins to generate the necessary low pressure equal to or below a given setpoint. Typically, both vacuum pumps operate at a constant maximum speed, thereby providing their highest possible volumetric flow rates. Thus, on the one hand, rapid evacuation of the vacuum chamber is guaranteed due to the pump performance provided, while the pressure within the vacuum chamber can be maintained below the setpoint. However, due to this configuration, high power consumption of the vacuum system occurs.

[0003] Furthermore, variable speed driven pumps (VSDs) are known, which involve vacuum pumps with adjustable rotational speeds in order to control the performance of the vacuum pump. The performance of a VSD can be controlled between maximum and minimum performance. Summary of the Invention

[0004] The object of the present invention is to provide a vacuum system and a method for operating such a vacuum system, which can be operated in an energy-efficient manner to maintain a vacuum in a vacuum chamber.

[0005] The solution to this problem is provided by the method of operating the vacuum system according to claim 1 and the vacuum system according to claim 11.

[0006] According to the present invention, the vacuum system includes at least a first vacuum pump and a second vacuum pump, wherein the first and second vacuum pumps are connectable to a vacuum chamber to maintain a set pressure. The first vacuum pump is a variable speed driven pump (VSD). The first and second vacuum pumps are connected in series. The inlet of the first vacuum pump is connectable to the vacuum chamber, and the outlet of the first vacuum pump is connectable to the inlet of the second vacuum pump. The outlet of the second vacuum pump can be connected to the atmosphere or another backing pump. The maximum pumping rate of the first vacuum pump is 1.25 to 4 times the maximum pumping rate of the second vacuum pump.

[0007] The preferred method of operating a vacuum system according to the present invention, as described above, includes the step of controlling the performance of a first vacuum pump, wherein the performance of the first vacuum pump is controlled to be equal to or higher than the performance of a second vacuum pump, while maintaining a set pressure in the vacuum chamber. The first vacuum pump is defined as a vacuum pump directly connected to the vacuum chamber. Furthermore, performance can be defined as the ratio between the actual mass flow rate through the respective vacuum pump and the maximum mass flow rate through the respective vacuum pump. Alternatively, performance can be defined as the volumetric flow rate or relative volumetric flow rate of the vacuum pump, i.e., the ratio between the actual volumetric flow rate of the respective vacuum pump and the maximum volumetric flow rate. Alternatively, performance can be defined as the ratio between the actual rotational speed of the respective vacuum pump and the maximum rotational speed of the respective vacuum pump.

[0008] It has been noted that the power consumption of a vacuum pump is related to its rotational speed and inlet pressure. Therefore, for a set inlet pressure, the power consumption of the vacuum pump can be reduced by decreasing its rotational speed. Furthermore, the present invention has noted that the backing pump, i.e., the second vacuum pump, is typically the largest energy consumer in such a vacuum system. This is because the second vacuum pump is usually configured to rapidly evacuate the vacuum chamber, resulting in a high-quality flow rate through it. However, with the present invention, the first vacuum pump is controlled to operate at a higher performance than the second vacuum pump, while the pressure in the vacuum chamber is maintained at or below the set pressure due to the combined action of the first and second vacuum pumps. Therefore, the inlet pressure of the second vacuum pump increases, while the rotational speed of the second vacuum pump decreases, resulting in a reduction in the power consumption of the second vacuum pump. According to the present invention, assuming the set pressure is maintained, the inlet pressure of the second vacuum pump is maximized while the rotational speed of the second vacuum pump is minimized to achieve the effect of minimizing power consumption without overloading either of the vacuum pumps.

[0009] Specifically, the first vacuum pump is a Roots pump, a molecular drag pump, or a turbomolecular pump.

[0010] Specifically, the second vacuum pump is a screw pump, vortex pump, rotary vane pump, claw pump, etc.

[0011] Specifically, the second vacuum pump is a VSD (Vacuum-Depressant), where its performance is controlled to decrease while maintaining the set pressure. Therefore, if the first vacuum pump is controlled to increase its performance, this typically results in a decrease in pressure within the pressure chamber. However, to further reduce the energy consumption of the vacuum system, the second vacuum pump can be controlled to decrease its performance while maintaining the set pressure and compensating for any increase in the performance of the first vacuum pump.

[0012] Specifically, the first vacuum pump and / or the second vacuum pump comprises more than one vacuum pump preferably connected in parallel. Therefore, the first vacuum pump and / or the second vacuum pump are constructed as one or more vacuum pumps operating together. Each vacuum pump connected in parallel includes a common inlet and a common outlet. At least one of the vacuum pumps in the first vacuum pump or at least one of the vacuum pumps in the second vacuum pump is constructed as a VSD (Vacuum-Dedicated Surface Pump). Thus, for example, if the first vacuum pump comprises two vacuum pumps, one of these two vacuum pumps can always operate at maximum performance, while the other vacuum pump of the first vacuum pump can be operated according to the method described above. The same applies to the second vacuum pump. Of course, all vacuum pumps of the first vacuum pump and / or all vacuum pumps of the second vacuum pump can be controlled in the same manner.

[0013] Specifically, while maintaining the set pressure, the performance of the first vacuum pump is maximized and the performance of the second vacuum pump is minimized. If the vacuum chamber is evacuated and the vacuum system is operating at the set pressure of the vacuum chamber, the first vacuum pump operates at maximum performance, while the second vacuum pump operates at minimum performance. Therefore, the power consumption of the second vacuum pump can be significantly reduced, thereby reducing the total energy consumption of the vacuum system.

[0014] Specifically, if the pressure in the vacuum chamber is higher than the set pressure, the first vacuum pump operates at maximum performance, and preferably, the second vacuum pump operates according to the pressure. Therefore, the second vacuum pump is operated to meet the application requirements so that the desired vacuum below the set pressure is achieved in the vacuum chamber quickly enough.

[0015] Specifically, if the pressure in the vacuum chamber is equal to or lower than the set pressure, the second vacuum pump operates at minimum performance. Therefore, energy consumption of the vacuum system can be minimized. Preferably, the vacuum pump then operates according to the pressure inside the vacuum chamber. Thus, if the pressure in the vacuum chamber is equal to or lower than the set pressure, the first vacuum pump operates according to the pressure inside the vacuum chamber to meet application requirements and maintain the desired pressure in the vacuum chamber.

[0016] Specifically, the maximum pumping rate of the first vacuum pump is two to four times that of the second vacuum pump. Therefore, the maximum pumping rate of the first vacuum pump is greater than that of the second vacuum pump, thus providing a sufficiently fast evacuation time for the vacuum chamber.

[0017] Alternatively, the maximum pumping rate of the first vacuum pump is 1.25 to 1.5 times that of the second vacuum pump. Therefore, by having a maximum pumping rate that is equivalent to or slightly higher than the maximum pumping rate of the second vacuum pump, it is easy to maintain an operating state where the performance of the first vacuum pump is selected to be higher than that of the second vacuum pump. Thus, it is possible to achieve a situation where the first vacuum pump is always running, thereby reducing the power consumption of the second vacuum pump and also reducing the power consumption of the entire vacuum system.

[0018] Specifically, if the first vacuum pump and / or the second vacuum pump operate at a speed below a threshold for a predetermined time, the performance of the first vacuum pump and / or the second vacuum pump increases to at least above the threshold. If the first vacuum pump or the second vacuum pump operates at a speed below the threshold, the lubrication of the bearings of the first vacuum pump or the second vacuum pump may become insufficient. Therefore, increased wear or damage to the bearings of the first vacuum pump or the second vacuum pump may occur. To avoid this situation, the speed (i.e., performance) of the first vacuum pump or the second vacuum pump is increased above the threshold, respectively, to ensure adequate lubrication of the bearings of the respective vacuum pumps.

[0019] Furthermore, the present invention relates to a vacuum system as described above. In particular, a first vacuum pump, and preferably a second vacuum pump, is connected to a control unit, wherein the control unit is adapted to perform the method as described above. Attached Figure Description

[0020] In the following text, along with the appendix Figure 1 The present invention will now be described in its current embodiment.

[0021] The attached diagram shows:

[0022] Figure 1 This is a schematic diagram of a vacuum system according to the present invention, and

[0023] Figure 2 This is a flowchart of the method according to the present invention. Detailed Implementation

[0024] The vacuum system according to the invention includes a vacuum chamber 12, which is evacuated and maintained at a set pressure. The vacuum chamber 12 is connected to the inlet 14 of a first vacuum pump 16. The outlet 18 of the first vacuum chamber 16 is connected to the inlet 20 of a second vacuum pump 22. Therefore, 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 the atmosphere or another backing pump. The first vacuum pump 16 can be configured as one or more vacuum pumps connected in series or parallel and operating together. Furthermore, the second vacuum pump 22 can be composed of one or more vacuum pumps connected in series or parallel and operating together. The first vacuum pump 16 is connected to a control unit 26. Additionally, the second vacuum pump 22 is also connected to the control unit 26. In this embodiment, the control unit 26 is connected to a pressure gauge 28 within the vacuum chamber 12. The performance, i.e., the volumetric flow rate, of the first vacuum pump 16 and / or the second vacuum pump 22 can be controlled by the control unit 26. The first vacuum pump 16 is controlled to always operate at its highest possible performance, at which the pressure within the vacuum chamber 12 is maintained. If the pressure inside vacuum chamber 12 falls below the set pressure, the performance of the second vacuum pump degrades. Specifically, the first vacuum pump 16 is controlled to always operate at a higher performance level than the second vacuum pump 22. Therefore, due to the high performance of the first vacuum pump 16, the pressure at the inlet 20 of the second vacuum pump 22 increases, thereby reducing the energy consumption of the second vacuum pump 22. Furthermore, due to the increased inlet pressure of the second vacuum pump 22, its rotational speed can be reduced without losing vacuum in the vacuum chamber. Therefore, the first vacuum pump 16 is controlled to maximize the inlet pressure of the second vacuum pump 22 through increased performance (i.e., volumetric flow rate). Furthermore, the second vacuum pump 22 is controlled to operate at a minimum rotational speed to achieve 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 will overload the first vacuum pump 16. Therefore, it is preferable that the first vacuum pump 16 has a maximum pumping rate greater than the maximum pumping rate of the second vacuum pump.

[0025] Figure 2 It shows Figure 1 The flowchart of the vacuum system.

[0026] In step S01, the system is turned on. Then, in step S02, it is checked whether the pressure P1 inside the vacuum chamber 12 is greater than or equal to the set pressure Pset. If the pressure P1 inside the vacuum chamber 12 is greater than or equal to the set pressure Pset, then in step S03, the first vacuum pump 16 is controlled to operate at maximum performance. This maximum value depends on the inlet and outlet pressures, and therefore also on the speed of the second pump. The second vacuum pump 22 is controlled to operate according to the pressure P1 inside the vacuum chamber 12.

[0027] If the pressure inside vacuum chamber 12 is lower than the set pressure, then in step S04, it is checked whether the stop level has been reached, i.e., P1 is equal to or greater than Pset minus Stoplevel. If the pressure inside vacuum chamber 12 is lower than the stop level, then in step S06, both the first vacuum pump 16 and the second vacuum pump 22 operate at their minimum performance.

[0028] If the pressure inside vacuum chamber 12 is lower than the set pressure Pset but higher than the stop level, then in step S05, it is checked whether the second vacuum pump 22 is operating at minimum performance. If the second vacuum pump 22 is not operating at minimum performance, the process returns to step S03, where the first vacuum pump 16 is controlled to operate at maximum performance, and the second vacuum pump 22 is controlled to operate according to the pressure P1 inside vacuum chamber 12. If the second vacuum pump 22 is operating at minimum performance, then in step S09, the first vacuum pump 16 is controlled to operate according to the pressure P1 inside vacuum chamber 12, while the second vacuum pump 22 is controlled to operate at minimum performance.

[0029] If both vacuum pumps are operating at their minimum performance, in step S07, it is checked whether the first vacuum pump 16 or the second vacuum pump 22 has been operating at minimum performance for a predetermined time. If the predetermined time has been reached, the vacuum system is shut down in step S08.

[0030] The above method is repeatedly applied based on the pressure changes within the vacuum chamber 12.

[0031] Therefore, by means of the method according to the invention, the first vacuum pump typically operates with higher performance than the second vacuum pump. Due to this configuration, the inlet pressure of the second vacuum pump is maximized. Consequently, the required power consumption of the second vacuum pump is reduced, thereby reducing the overall power consumption of the vacuum system.

Claims

1. A method for operating a vacuum system, said 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 connected to a vacuum chamber to maintain a set pressure. The first vacuum pump and the second vacuum pump are variable-speed driven pumps. The vacuum chamber, the first vacuum pump, and the second vacuum pump are connected in series, such that the vacuum chamber is connected to the inlet of the first vacuum pump, and the outlet of the first vacuum pump is connected to the inlet of the second vacuum pump. The maximum pumping rate of the first vacuum pump is 1.25 to 4 times the maximum pumping rate of the second vacuum pump. The method includes the following steps: The performance of the first vacuum pump is controlled, wherein, while maintaining the set pressure in the vacuum chamber, the performance of the first vacuum pump is controlled to be equal to or higher than the performance of the second vacuum pump. If the pressure in the vacuum chamber is higher than the set pressure, the first vacuum pump operates at maximum performance, and the second vacuum pump operates according to the pressure in the vacuum chamber.

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

3. The method according to claim 1 or 2, characterized in that, The first vacuum pump and / or the second vacuum pump may include more than one vacuum pump.

4. The method according to claim 1 or 2, characterized in that, While maintaining the set pressure, the performance of the first vacuum pump is maximized and the performance of the second vacuum pump is minimized.

5. The method according to claim 3, characterized in that, The more than one vacuum pump is connected in parallel.

6. The method according to claim 1 or 2, characterized in that, If the pressure in the vacuum chamber is equal to or lower than the set pressure, the second vacuum pump operates at minimum performance.

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

8. The method according to claim 1 or 2, characterized in that, The maximum pumping rate of the first vacuum pump is 1.25 to 1.5 times that of the maximum pumping rate of the second vacuum pump.

9. The method according to claim 1 or 2, characterized in that, If the first vacuum pump or the second vacuum pump operates for a predetermined time with performance below a threshold, then the performance of the first vacuum pump and / or the second vacuum pump is improved to at least above the threshold.

10. The method according to claim 6, characterized in that, If the pressure in the vacuum chamber is equal to or lower than the set pressure, the second vacuum pump operates at minimum performance, and the first vacuum pump operates according to the pressure in the vacuum chamber.

11. A vacuum system comprising a first vacuum pump and a second vacuum pump capable of being connected to a vacuum chamber, wherein the first vacuum pump and the second vacuum pump are connected to a control unit, wherein the control unit is adapted to perform the method according to any one of claims 1 to 10.

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