( b) Intermediate structure. The intermediate structure of a power house may be defined as that
part of the power house which extends from the top of the draft tube to top of the generator foundation.
This structure contains two important elements of the power house, one is the scroll case which feeds
water to the turbine. The generator foundation rests on the scroll-case which is embedded in the con-crete. The other galleries, adits and chambers also rest on the same foundation. Scroll or spiral case is a
part of the turbine and it distributes water coming from penstock uniformly and smoothly through guide
vanes to the turbine. The scroll case is required only in case of reaction turbine. In case of impulse
turbine the place of scroll case is taken by the manifold supplying water to the jets.