Appeal No. 1998-0425 Page 23
Application No. 08/272,527
said diffusion elements having central and boundary
portions
with enhanced volumetric compression ratios, said central
portions having volumetric compression ratios of about 2 to
about 20% relative to the portions of the elements surrounded
thereby and said boundary portions having outwardly and
downwardly inclined upper surfaces at an angle of depression
of about 35 to about 60 degrees relative to the horizontal and
having volumetric compression ratios of about 10 to about 35%
relative to the portions of the elements surrounded by said
boundary portion;
said diffusion elements each having a bubble release
pressure of about 5 to about 10 inches of water gauge and a
coefficient of variation not greater than about 0.25, said
coefficient of variation being based on the values of bubble
release pressure measurements at, at least, about 5 equally
spaced points along each of two mutually perpendicular
reference lines extending across said surface and through the
center thereof;
said plenums, mounted on said piping at elevated
positions relative to said bottom surface, each comprising
gastight enclosures that enclose the lower surface of said
diffusion elements and include upstanding walls facing and
adjacent to the sides of the diffusion elements, the
peripheries of said elements having annular steps formed about
the upper portions of the peripheral surfaces of the diffusion
elements for positioning sealing O-rings on said annular step
for sealing contact with the respective plenums and elements,
said sealing O-rings being comprised of resilient, elastomeric
material; and
retaining rings indirectly in contact with said elements
at their respective peripheries for securing said elements
around their entire peripheries to their respective plenums,
said retaining rings including upright, cylindrical walls and
flanges which at least partly overlie the sealing O-rings,
said flanges restraining upward movement of said sealing O-
rings and elements, whereby said upward force on said elements
acts upwardly on said sealing O-rings and against said sealing
O-rings, for increasing the sealing integrity of said sealing
O-rings and preventing escape of gas from the plenums at the
sides of the elements.
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