GB1338318A - Leak detector unit - Google Patents

Abstract

1338318 Leak testing CROSS CO 6 Jan 1972 [18 Nov 1971] 584/72 Headings G1N and G1S A leak detecting apparatus comprises means for rapidly pre-filling a workpiece to be tested for a predetermined time, means for maintaining a test pressure substantially the same as and preferably slightly lower than the pressure in the workpiece after pre-filling, and a flow-meter for detecting the flow required to maintain the test pressure. Compressed air passes through main valve 14 and filter 15 to a reducing regulator 38. During pre-filling, compressed air passes through a regulator 41, a pre-fill/test valve 51 and a test/vent valve 56 to the workpiece 50. During testing, the test pressure is maintained by an air flow through a regulator 43, flowmeter 17, and valves 54, 51 and 56. After a test, the workpiece is vented through valve 56, valve 54 being closed during the venting. The flowmeter comprises a laminar flow element, the pressure across which is measured and amplified by amplifier 49, the amplified output being applied to pressure operated switch 49, to a pressure gauge 62 and optionally to a data processing unit. To test the calibration of the apparatus a pair of test orifices are provided, one orifice 34 representing a just acceptable leak and the other orifice representing a non-acceptable leak. To initiate a test manually push button 57 is actuated, a holding circuit provided by relay 1 C R then bridging the push button until the end of the test. Relay 1 C R also operates solenoid valve 56 to its fill position, and valve 54 to its open position. Prefilling then occurs for an interval determined by time switch 2 T R, closure of which shifts solenoid valve 51 to its test position via relay 2 C R. The test continues for an interval determined by time switch 3 T R. Closure of switch 3 T R causes a reject or accept lamp 28, 29 to be lit according to whether or not pressure switch 49 has operated. When switch 3 T R closes either relay 4 C R or 5 C R is actuated which causes relay 1 C R to be de-energised so that valve 54 moves to its closed position, valve 56 moves to the vent position and switch 2 T R opens allowing valve 51 to move to the pre-fill position, the apparatus then being ready for the next test cycle. For automatic testing on an assembly line, a test cycle is initiated by each workpiece engaging a trip switch 63, and ended by a time switch 1 T R set according to the line speed. In the modification of Fig. 6, a gross leak test is carried out after the prefilling but prior to the normal leak test by closing the testfill valve 114 and detecting any large pressure changes in the system. A stabilisation chamber 122 is connected into the system. In a further modification, Figs. 7 and 8 (not shown), the calibration of the apparatus is automatically checked at the end of each test cycle by means of an orifice 201 connected to valve 56. The orifice is set to represent an unacceptable leak and if the apparatus doesn't detect it as such, it is automatically closed down and a fault signal given.