Detecting leaks in gas-filled pressure vessels using acoustic resonances

Published: May 06, 2016

Author(s)

Keith A. Gillis, Michael R. Moldover, James B. Mehl

Abstract

We demonstrate that a leak from a large, unthermostatted pressure vessel into ambient air can be detected an order of magnitude more effectively by measuring the time dependence of the ratio p/f2 than by measuring the ratio p/T. Here f is the resonance frequency of an acoustic mode of the gas inside the pressure vessel; p is the pressure of the gas, and T is the kelvin temperature measured at one point in the gas. In general, the resonance frequencies are determined by a mode-dependent, weighted average of the square of the speed-of-sound throughout the volume of the gas. However, the weighting usually has a weak dependence on likely temperature gradients in the gas inside a large pressure vessel. Using the ratio p/f2, we measured a gas leak (dM/dt)/M ≅ -1.3×10-5 h-1 = 0.11 year-1 from a 300-liter pressure vessel filled with argon at 450 kPa that was exposed to sunshine-driven temperature and pressure fluctuations as large as (dT/dt)/T ≅ (dp/dt)/p ≅ 5×10-2 h-1 using a 24-hour data record. This leak could not be detected in a 72-hour record of p/T. (Here M is the mass of the gas in the vessel and t is time.)
Citation: Review of Scientific Instruments
Volume: 87
Issue: 5
Pub Type: Journals

Keywords

leak, leak detection, pressure vessel, acoustic resonance, resonance frequency
Created May 06, 2016, Updated November 10, 2018