These collect the product gases generated within the
Reformer Tubes or Cracking Tubes. The operating conditions
are different from furnace tubes as there is no firing
from outside and no reaction inside even though the
temperatures and pressures are same as furnace tubes.
However, they have to withstand severe stresses particularly
during start-ups and shut-downs due to the constraints
imposed by the tight connections. Hence, the materials
of the manifold should have supplied strentgh and
ductility at the operating temeratures as well as
thermal shock resistance.