Method and apparatus for leak testing

• US 5,065,350 A
• Filed: 03/14/1990
• Issued: 11/12/1991
• Est. Priority Date: 03/14/1990
• Status: Expired due to Fees

• Current Assignee: Anthony J. Skudrna, William L. Sweet
• Original Assignee: Anthony J. Skudrna, William L. Sweet
• Inventors: Fedder, Stephen C.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Melnick, S. A.
• Application Number:
  US07/493,213
• Time in Patent Office: 608 Days
• Field of Search: 364/507, 364/506, 364/571.04, 364/571.03, 364/558, 73/49.2, 73/49.7, 73/37, 73/40
• US Class Current: 702/98
• CPC Class Codes: G01M 3/3263 using a differential pressure detector G01M3/3245, G01M3/3272 take precedence

Abstract

A method of and apparatus for testing the chamber of a test part for leaks in which the chamber is filled with gas under pressure and the differential pressure drop over a predetermined interval of time is determined. The temperature of the part being tested is determined, and a storage table of correction values corresponding to the estimated differential pressure drop attributable to the temperature of the part is provided. The correction value for the temperature of the part is selected from the storage table and substracted from the measured differential pressure drop to obtain a corrected differential pressure drop. If the corrected differential pressure drop is within a range below a predetermined amount, a fraction of it is summed back to the storage table to adjust the selected correction value.

Claims

1. A method of testing the chamber of a test part for leaks, comprising filling said chamber with gas under pressure, determining the differential pressure drop of the gas in said chamber over a predetermined interval of time, determining the temperature of the part being tested, providing a storage table of correction values corresponding to the estimated differential pressure drop of gas pressure in said chamber attributable to the temperature of the part, selecting from said storage table the correction value for the temperature of said part being tested, subtracting the selected correction value from the differential pressure drop thus determined to obtain a corrected differential pressure drop, and, if said corrected differential pressure drop is below a predetermined maximum amount, summing back to said storage table at least a fraction of said corrected differential pressure drop to adjust said selected correction value.

2. The method defined in claim 1, wherein said predetermined maximum amount is below the upper limit of leak tolerance for an acceptable part.

3. A method of testing the chamber of a test part for leaks, comprising filling said chamber with gas under pressure, determining the differential pressure drop of the gas in said chamber over a predetermined interval of time, determining the temperature of the part being tested, providing a storage table of correction values corresponding to the estimated differential pressure drop of gas pressure in said chamber attributable to the temperature of the part, selecting from said storage table the correction value for the temperature of said part being tested, subtracting the selected correction value from the differential pressure drop thus determined to obtain a corrected differential pressure drop, establishing a range of values corresponding to differential pressure drops below a predetermined maximum, determining whether the corrected differential pressure drop falls within said range, and summing back to said storage table at least a fraction of a corrected differential pressure drop falling within said range to adjust said selected correction value.

4. The method of testing defined in claim 3, wherein said storage table of correction values is initially made by filling a part which is substantially free of leaks with gas under pressure, determining the differential pressure drop of the gas in said chamber over a predetermined interval of time at a first temperature and again at a second different temperature, and developing a curve of correction values for temperatures between said first and second temperatures by plotting points representing the differential pressure drops at said first and second temperatures and constructing a line connecting said points.

5. The method of testing defined in claim 3, wherein said storage table of correction values is initially made by filling a part which is substantially free of leaks with gas under pressure, determining the differential pressure drop of the gas in said chamber over a predetermined interval of time and at a plurality of temperatures within a temperature range, and developing a curve of correction values for temperatures within said temperature range by plotting points representing the differential pressure drops at said plurality of temperatures and constructing a line connecting said points.

6. The method defined in claim 3, wherein said predetermined maximum amount is below the upper limit of leak tolerance for an acceptable part.

7. Apparatus for testing the chamber of a test part for leaks, comprising means for filling said chamber with gas under pressure, means for determining the differential pressure drop of the gas in said chamber over a predetermined interval of time, means for determining the temperature of the part being tested, means providing a storage table of correction values corresponding to the estimated differential pressure drop of gas pressure in said chamber attributable to the temperature of the part, means for selecting from said storage table the correction value for the temperature of said part being tested, means for subtracting the selected correction value from the differential pressure drop thus determined to obtain a corrected differential pressure drop, and means for determining whether the corrected differential pressure drop falls within an established range and for summing back to said storage table at least a fraction of a corrected differential pressure drop falling within said range to adjust said selected correction value.

8. Apparatus for testing the chamber of a test part for leaks, comprising means for filling said chamber with gas under pressure, means for determining the differential pressure drop of the gas in said chamber over a predetermined interval of time, means for determining the temperature of the part being tested, means providing a storage table of correction values corresponding to the estimated differential pressure drop of gas pressure in said chamber attributable to the temperature of the part, means for selecting from said storage table the correction value for the temperature of said part being tested, means for subtracting the selected correction value from the differential pressure drop thus determined to obtain a corrected differential pressure drop, and means for summing back to said storage table at least a fraction of a differential pressure drop below a predetermined maximum amount to adjust said selected correction value.