In modern high capacity sulfuric acid plants particularly in
areas where cooling water conditions are severe, the elimination
of most gasketed joints is desirable, to minimize the possibility
of leaks which are recognized as the result of bolt corrosion.
This corrosion eventually reduces the cross section area of
the shank of the bolts holding sections together to a point
where there is not enough metal to maintain the gasket seating
stress. When this occurs, the affected bolts relax and cause
a separation at the gasket which results in an acid leak.
The development of gasketless, permanent sealing joint provides
a remedy for such conditions.
This closure is called push nipple joint, and consists of a
mating machined surface in the section port to accommodate a
finely machined cast iron cylindrical nipple. The nipples are
ground slightly convex on the exterior, and the section surface
is slightly tapered. When the joint is made up with the usual
bolts drawing the adjacent sections together over the nipple,
the nipple distorts sufficiently in compression to exert sufficient
force against the section to provide a tight joint that no longer
depends on the bolting for its integrity.
View of nipple showing details.
Assembly detail of push nipples and ports, dimensions shown