Method and apparatus for the leak testing of filters

An apparatus for filtering an airstream and having provisions for testing for leakage of particles of predetermined size through or around each of at least two filters mounted in series, and characterized by minimum space requirements, and comprising

• a housing defining an air passageway adapted to form a part of an air duct system having an airstream passing therethrough,
• means for sealably mounting first and second filters within the housing in a spaced apart, serial arrangement and such that the airstream passing through the housing passes serially through the first and then the second filter,
• means for selectively introducing particles of predetermined size into the airstream within the housing and immediately upstream of each filter,
• first restriction means mounted upstream of the first filter and downstream of the associated particle introducing means for partially restricting the airstream and imparting turbulence thereto, and then dispersing the airstream over the full frontal area of the first filter,
• second restriction means mounted upstream of the second filter and downstream of the associated particle introducing means for partially restricting the airstream and imparting turbulence thereto, and then dispersing the airstream over the full frontal area of the second filter,
• means mounted upstream of the second filter and downstream of said second restriction means for detecting at least a portion of any particles in the airstream to thereby permit a determination as to whether any of the particles are leaking through or around the first filter, and
• means mounted downstream of the second filter for detecting at least a portion of any particles in the airstream to thereby permit a determination as to whether any of the particles are leaking through or around the second filter,
• whereby the second restriction means is adapted to mix the airstream and leaking particles during testing of the first filter, and to mix the airstream and the particles introduced immediately upstream of the second filter during testing of the second filter.

An apparatus for filtering an airstream through a bank of filters and having provision for testing for leakage of particles of predetermined size through or around any of the filters and characterized by substantially balanced flow among the filters and by the ability to permit the immediate identification of a leaking filter in the bank, and comprising

• a housing adapted to form a part of an air duct system having an airstream passing therethrough,
• means for sealably mounting a bank of filters in parallel arrangement in said housing such that the airstream passing through the housing passes through the bank of filters,
• panel means mounted within said housing and immediately upstream of the bank of filters for dividing the housing into a separate air channel for each of the filters, and such that the airstream is divided into an isolated portion within each of the separate channels which passes through a single filter,
• means mounted within each of said separate channels for selectively introducing particles of predetermined size into the portion of the airstream passing therethrough,
• means mounted within each of said separate channels and upstream of the filter and downstream of the particle introducing means for selectively partially restricting and imparting turbulence to the flow concurrently through all of the isolated portions, and so as to obtain turbulence throughout substantially the full cross sectional area of each isolated portion and thereby mix the airstream and particles, and also achieve a substantially balanced flow among the isolated portions, said restricting means including a restriction member pivotally mounted within each channel for movement between a non-operative position wherein at least a substantial portion of the member is disposed parallel to the sides of the channel, and an operative position disposed transversely across the channel, said air channel for each of said filters being free of any substantial restriction to flow between the particle introducing means and said restriction member, and
• means mounted within said housing and downstream of said filter bank for detecting at least a portion of any particles in the airstream to thereby permit a determination as to whether any of the particles are leaking through or around any of the filters in the filter bank.