Cryopump drain and vent

• US 9,186,601 B2
• Filed: 04/20/2012
• Issued: 11/17/2015
• Est. Priority Date: 04/20/2012
• Status: Active Grant

• Current Assignee: Sumitomo (SHI) Cryogenics of America, Inc. (Sumitomo Heavy Industries Limited)
• Original Assignee: Sumitomo (SHI) Cryogenics of America, Inc. (Sumitomo Heavy Industries Limited)
• Inventors: Longsworth, Ralph
• Primary Examiner(s): DUKE, EMMANUEL E
• Application Number:
  US13/451,712
• Publication Number:
  US 20130276467A1
• Time in Patent Office: 1,306 Days
• Field of Search: 62/555, 62/82, 622/68, 622/69, 624/75
• US Class Current: 1/1
• CPC Class Codes: B01D 8/00 Cold traps; Cold baffles pumps for evacuating by condensing or freezing F04B37/08

Abstract

A means of rapidly melting a large quantity of type II cryogen in a cryopump that is configured to contain the liquid in the warm cryopanel with the inlet to the cryopump facing up or sideways, and venting the liquid and gas in a controlled way. Rapid melting is preferably accomplished by flowing a purge gas that will condense on the cryodeposit. By not allowing the liquid to drain onto the vacuum housing the evaporation rate is limited and the maximum pressure in the cryopump can be controlled by the purge gas flow rate.

Claims

1. A method of removing cryodeposits from a second stage cryopanel assembly,

the second stage cryopanel assembly being contained in an interior space disposed within a first stage cryopanel assembly in a cryopump attached to a vacuum chamber,

the cryodeposits comprising group II cryogens,

the first stage cryopanel assembly comprising an inlet to the interior space, the inlet facing between up and sideways;

the method comprising the steps of;

(a) orienting a tube that is connected to a first vent valve to remove from the lowest point in the first stage cryopanel assembly a first and a second liquid waste;

(b) isolating the cryopump from the vacuum chamber;

(c) stopping cryogenic refrigeration operation of the cryopump;

(d) introducing a purge gas and a second gas having a lower normal boiling point than the purge gas, the purge gas being selected from group II cryogens;

(e) melting the cryodeposits with the purge gas into a first liquid waste while the purge gas condensing into a second liquid waste by the cryodeposit;

(f) containing the first liquid waste and the second liquid waste within the first stage cryopanel;

(g) increasing a pressure in the interior space by introducing more second gas; and

(h) removing from the cryopump the first liquid waste, the second liquid gas, and the second gas through the tube into the first vent valve, and removing from the cryopump only the uncondensed purge gas through a second vent valve,

wherein the first vent valve opens automatically at a first pressure above atmospheric pressure and the second vent valve opens automatically at a pressure higher than the first pressure.

2. The method of claim 1, wherein when a cryodeposit is partially melted, the following steps are performed

(i) stopping a flow of the purge gas,

(j) collecting in the interior space the first liquid waste and the second liquid waste;

(k) introducing into the interior space enough second gas to force the first liquid waste and the second liquid waste through the first vent valve,

(l) repeating steps (i)-(k) until all of the cryodeposit is removed from the second stage cryopanel assembly.

3. The method of claim 1, wherein by controlling a flow rate of the purge gas and the second gas into the interior the maximum pressure in said cryopump is controlled.

4. A method of removing at least one cryodeposit from a second stage cryopanel assembly,

the second stage cryopanel assembly being contained in an interior space disposed within a first stage cryopanel assembly in a cryopump attached to a vacuum chamber, the at least one cryodeposit comprising at least one group II cryogen, the first stage cryopanel assembly comprising an inlet to the interior space, the inlet facing between up and sideways;

the method comprising the steps of;

(a) orienting a tube that is connected to a first vent valve to remove from the lowest point in the first stage cryopanel assembly a first and a second liquid waste;

(b) isolating the cryopump from the vacuum chamber;

(c) stopping cryogenic refrigeration operation of the cryopump;

(d) introducing a purge gas, the purge gas being selected from group II cryogens;

(e) melting the at least one cryodeposit with the purge gas into a first liquid waste while the purge gas condenses into a second liquid waste by the at least one cryodeposit;

(f) containing the first liquid waste and the second liquid waste within the first stage cryopanel;

(g) increasing a pressure in the interior space by introducing one of the same purge gas and a second gas having a lower normal boiling point than the purge gas; and

(h) removing from the cryopump the first liquid waste, the second liquid waste, and a partial amount of purge gas through the tube into the first vent valve, and removing from the cryopump a balance of the gas in the cryopump through a second vent valve;

wherein the first vent valve opens automatically at a first pressure above atmospheric pressure and the second vent valve opens automatically at a pressure higher than the first pressure.

5. The method of claim 4, wherein when the at least one cryodeposit is partially melted, the following steps are performed

(i) stopping a flow of the purge gas,

(j) collecting in the interior space the first liquid waste and the second liquid waste;

(k) introducing into the interior space enough second gas to force the first liquid waste and the second liquid waste through the first vent valve,

(l) repeating steps (i)-(k) until all of the at least one cryodeposit is removed from the second stage cryopanel assembly.