Pressure Tests Gaseous Applications in Sealed Storages: Theory and Practice
Shlomo Navarro, Department of Stored Products, Agricultural Research Organization, The Volcani Center, P.O.Box 6, Bet Dagan 50250, Israel e-mail: vtshlo@netvision.net.il
Abstract: Pressure tests and monitoring devices described in this paper apply to structures destined for gaseous treatments to control principally insects in durable agricultural commodities including cereals. The gaseous treatments included here are: modified atmosphere (MA), controlled atmosphere (CA) and fumigation. These pressure tests are designed to estimate the permissible limits for effectively maintaining the gas composition in small, medium and large size warehouses and silos during the treatment. They are not capable however of measuring gas losses that occur by permeation through structural membranes such as concrete and plastic. Theoretical work to describe the process of gas loss from structures is well documented. This paper reviews essential considerations in measuring gastightness. However field work to correlate gas loss to pressure tests are very scarce. The described pressure tests in this paper are applicable for rigid and flexible types of structures. Variable and the constant pressure tests are fully described. In the variable pressure test, time is taken for the pressure to fall between two pressure limits while in the constant pressure test, the flow rate at a given constant pressure is measured. A table is presented for provisional ranges of the variable pressure tests to be applied in structures destined for MA, CA and fumigant treatments.
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