- Leaktesting machines and installations
- Systems for preparation and recovery of test gas
A leak may be considered a ‘chink’ through which gas leaks, in a system understood to be hermetic. In terms of dimensions, a leak is quantified by indication of the quantity of gas (expressed in volume) leaking, with a given ΔP at the sides of the leak, in one second. A gas flow takes place in a channel if, between the channel’s extremities, a pressure difference is maintained. The capacity of a channel to enable passage of the gas flow depends not only on the pressure difference between the two extremities of the channel but also on the channel’s geometric characteristics. A magnitude (conductance) is therefore adopted. This is defined as the relation between the gas flow and the pressure difference between the extremities of the channel: C = Q / (p1 - p2) expressed as m3/s or l/s.
where n is the number of moles of gas contained in volume V at pressure p and absolute temperature (Kelvin degrees [K]), and R is the gases constant (8.31441 j·mol-1·K-1). In this manner, if the pressure is a constant of the system, the equation is obtained, with the flow dependent upon gas volume variation, on pressure and on time:
The unit of measurement for the leakrate (Q) according to the International System (SI) is Pa·m3/s. The mbar·l/s unit is a permissible unit of measurement of flow, according to the SI, since it is linked to the former unit of measurement by multiples.