Leak Detection

摘要

"Leak tight" and "hermetic" are rather nebulous or misleading terms. Webster defines tight as "so close in structure as not to admit liquid." Hence, a leak-tight article would be one through which a liquid would not pass. Similarly, hermetic is defined as "Made perfectly close or air-tight." Hence, a hermetic article would be one through which air could not pass. Actually both of these definitions are perfectionistic and neither can be strictly realized in practice. There is no such thing as an impervious barrier and leak tightness is but a relative term. As an extreme example, consider a barbed wire fence. You would, no doubt, consider this cow-tight, but certainly it would not prevent the passage of chickens, mice or anything smaller. On the opposite end of this relative scale, a thick piece of steel plate, as impervious as it may seem, will allow the passage of gas molecules. The rate of passage may be so small that the flow of gas could not be detected or measured with existing equipment. However, he gas will still pass through the steel.