Leak Detection System and Method
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Leak Detection System and Method The most sensitive technology for valve quality control Date: July 2015, updated in January 2024

exposed to atmospheric air, where, generally speaking, there is a 5 PPM helium content. The following patented method is used to test all ASDevices valves during development and for quality control during manufacturing. Sensitivity could be increased by using a helium cylinder instead of relying on the helium content of atmospheric air. Such a leak detection system is calibrated by pumping atmospheric air or helium into the mass spec, through a calibrated leak orifice. It is mainly useful for a “capillary” type leak. Here we classify leaks into two large categories, i.e., capillary and...

Considering all the above-mentioned facts, we have designed a leak detection and measuring system based on N2 instead of helium. This system is suitable for capillary and permeation type leaks, as we will demonstrate here. Figure 2 shows one possible embodiment of the system. System Description Testing Valve First, the Valve Under Test, i.e., VUT, is installed into the system. Here an ON/OFF valve of any type is shown, i.e., could be a diaphragm-based, ball, globe, etc. The size is not an important issue, since the purge argon flow is adjusted accordingly. The inlet of the VUT is connected...

valves will have a longer waiting time. During the N2 inlet pressure stepping sequence, the PED measures N2 signal and reports it to the signal processing subsection. If there is a diminution of the slope value of the signal S, N2 is flowing through a leakage passage of VUT. Here the differential value could be measured to report the PPM of N2 and transform it in the desired leak rate engineering unit. A band could be defined above the slope signal where the leak rate could be acceptable (see Figure 4). Before each pressure increase, the system baseline is re-zeroed, so that monitoring is...

During the execution of a leak-finding procedure, the signal value may decrease and go under scale because the atmospheric or residual N2 is being purged out by the action of argon flowing and purging the outlet side of VUT. At this point, it becomes necessary to set back the signal on scale by offsetting it, at a predetermined value. For example, 50% of the scale, other values will work too. It may be desirable to change this value based on operating conditions, mainly the valve size, or the dead volume to be purged. These affect the rate or speed of the purging effect. So, when the signal...

AUTO ZERO GAIN CONTROL GAIN CONTROL GRAPHICAL DISPLAY Figure 2 – Leak detection possible embodiment. SIGNAL PROCESSING OPTIONAL GAS RECYCLING SYSTEM Visual Indication DIGITAL I/0: • Control various ON/OFF valves, like V1, V2 and V5 ANALOG I/0: • Read various parameters like pressure and flow • Control V5, PC1, V3

Bill of Material for Figure #2 PC1: High-pressure electronic pressure controller based on a proportional EDV-1. PT1, PT2, PT3: Absolute pressure transducer V1: Diaphragm type stream selection valve, ASDevices EDVS-4. V2, V4: Diaphragm type 3-way switching valve ASDevices EDV-3. V3: Tight shut-off proportional valve based on ASDevices EDV-1. V5: Diaphragm-based proportional valve based on ASDevices EDV-1. V6: Diaphragm-based ON/OFF valve, ASDevices EDV-1. CV1: Check the valve to prevent back flow when using the recycling system. PF: Particle filter. TRAP: Tube having proper gettering...

Figure 7 – Leak Detection Sensitivity Comparison Leak Detection Techniques Bubble test (soap painting) NB: A leak rate of 1.E-14 atm cc/s would need 3 million years to pressurize a cube of 1cc from complete vacuum to atmospheric pressure. Bubble test (He, alcohol) Water immersion (bubble test) Acoustical Pressure decay (without pressure differential) Pressure decay (withpressure differential) Vacuum decay Thermoconductivity Halogen sniffer Helium sniffer (inside-out) Helium leak test outside-in Vacuum chamber helium leak test (inside-out) 1.E+02 Leak Rate (mbar l/s or atm cc/s) References...