Scroll Vacuum Pump and Method of Maintenance Including Replacing a Tip Seal of a Scroll Vacuum Pump

Patent metadata

Field	Value
Publication number	US-2016201674-A1
Application number	US-201615074635-A
Country	US
Kind code	A1
Filing date	Mar 18, 2016
Priority date	Apr 30, 2013
Publication date	Jul 14, 2016
Grant date	—

Abstract

A scroll pump has a tip seal between an axial end of the scroll blade of one of stationary and orbiting plate scrolls of the pump and the plate of the other of the stationary plate and orbiting plate scrolls. The scroll pump may have a ballast gas supply system and use the operation of the ballast gas supply system to assess the condition of the tip seal. Alternatively, the scroll pump may have two pressure sensors that sense pressure at two locations spaced along a compression mechanism of the pump to assess the condition of the tip seal.

First claim

What is claimed is:

1 . A method of operating and maintaining a scroll vacuum pump, the method comprising:
running the scroll pump while the pump is connected to a system, at an inlet of the scroll pump, to discharge fluid from the system; while the scroll pump is discharging fluid from the system, sensing a first pressure proportional to a first fraction of the compression ratio of the pump and a second pressure proportional to a second fraction of the compression ratio of the pump; calculating a monitored pressure value based on both the first and second sensed pressures; comparing the monitored pressure value based on the first and second sensed pressures with a reference pressure value; and changing a tip seal, interposed between an axial end of a scroll blade of one of stationary and orbiting plate scrolls and a plate of the other of the stationary plate and orbiting plate scrolls of the scroll pump, at a point in time after the monitored pressure value and the reference pressure value differ by at least a predetermined amount.

2 . The method of claim 1 , further comprising periodically supplying a ballast gas into a compression mechanism of the scroll pump at a location adjacent a downstream end of the compression mechanism with respect to the direction of fluid flow through the pump, while the scroll pump is being run to discharge fluid from the system,
the compression mechanism constituted by a series of pockets of the scroll pump defined between stationary and orbiting scroll blades of the pump, and wherein the sensing of the first pressure comprises sensing the pressure of the fluid at a location along the direction of fluid flow during a state in which no ballast gas is being supplied into the compression stage, and the sensing of the second pressure comprises sensing the pressure of the fluid at said location during a state in which ballast gas is being supplied into the compression stage at said location adjacent a downstream end thereof.

3 . The method of claim 2 , wherein the calculating of the monitored pressure value comprises calculating a ratio of the first and second sensed pressures.

4 . The method of claim 2 , wherein the calculating of the monitored pressure value comprises calculating a difference between the first and second sensed pressures.

5 . The method of claim 2 , wherein the sensing of the first and second pressures each comprises sensing the pressure of the fluid at the inlet of the scroll pump.

6 . The method of claim 1 , wherein the sensing of the first pressure comprises sensing the pressure of fluid in the compression mechanism of the pump at a first location immediately upstream of one portion of the compression mechanism with respect to the direction of flow of fluid through the pump, and the sensing of the second pressure comprises sensing the pressure of fluid in the compression mechanism of the pump at a second location immediately downstream of said one portion of the compression stage with respect to the direction of flow of fluid through the pump.

7 . The method of claim 6 , wherein the calculating of the monitored pressure value comprises calculating a ratio of the first and second sensed pressures.

8 . The method of claim 6 , wherein the calculating of the monitored pressure value comprises calculating a difference between the first and second sensed pressures.

9 . A scroll pump comprising:
an inlet portion having a pump inlet into which fluid is drawn by the pump, and an exhaust portion including a pump outlet through which fluid is exhausted from the pump; a frame; a stationary plate scroll fixed to the frame and including a stationary plate, and a stationary scroll blade projecting from the stationary plate; an orbiting plate scroll including an orbiting plate, and an orbiting scroll blade projecting axially from the orbiting plate, the stationary scroll blade having the form of a spiral including a plurality of successive wraps emanating from a central portion of the stationary plate, the orbiting scroll blade having the form of a spiral including a plurality of successive wraps emanating from a central portion of the orbiting plate, and the stationary and orbiting scroll blades being nested; a tip seal interposed between an axial end of the scroll blade of one of the stationary and orbiting plate scrolls and the plate of the other of the stationary plate and orbiting plate scrolls; an eccentric drive mechanism supported by the frame, and the orbiting plate scroll being coupled to the eccentric drive mechanism so as to be driven by the eccentric drive mechanism in an orbit about the longitudinal axis of the pump, wherein during the orbital motion of the orbiting plate scroll relative to the stationary plate scroll, a series of pockets are simultaneously defined between the nested stationary and orbiting scroll blades, the series of pockets constitute a compression mechanism of the pump, each of the pockets is selectively and sequentially placed in open communication with the pump inlet and the pump outlet, and a compression process in which fluid trapped in the pocket is compressed occurs between a point in time at which the pocket is in open communication with the pump inlet and a later point in time at which the pocket is in open communication with the pump outlet; pressure sensors operatively associated with the compression mechanism at first and second points, respectively, spaced along the direction of flow of fluid through the pump, wherein the pressure sensors sense a first pressure of the fluid in the compression mechanism at a first location immediately upstream from one part of the compression mechanism and sense a second pressure of the fluid in the compression mechanism at a second location immediately downstream from said one part of the compression mechanism, respectively; and control means configured to calculate a monitored pressure value based on both the first and second sensed pressures, to compare the monitored pressure value with a reference pressure value, and to output a signal, indicative of a need to replace the tip seal, when the monitored pressure value and the reference pressure value differ by at least a predetermined amount.

Assignees

• Agilent Technologies Inc

Inventors

• Calhoun John

Classifications

• F04C2270/86

  Detection · CPC title

• F04C28/28 Primary

  Safety arrangements; Monitoring · CPC title

• F04C2230/85

  Methods for improvement by repair or exchange of parts · CPC title

• F04C27/005

  Axial sealings for working fluid · CPC title

• F04C2230/80

  Repairing methods · CPC title