This type of diaphragm
has no flange. An O-ring is molded to the bottom of the
sidewall. Unlike the other types of diaphragms, the Type
O is put into convolution by folding the sidewall back
onto itself. The bead is then squeezed into a groove machined
into the bonnet half of the hardware. This type enables
the greatest reduction in hardware diameter, while keeping
a full stroke potential.
Type
OA
This diaphragm type
is second generation to the Type O. It fits into identical
hardware. It differs from the Type O in that its sidewall
attaches to the inside diameter of the O-ring and the
fabric is on the outside, requiring the head corner radius
to be inverted for installation. The Type OA tends to
be easier to install but basically the difference is a
personal preference.