CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
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Figure 8.1 Powerhouse floor plan at the Jhankre mini-hydro scheme
The minimum wall thickness of the stone masonry walls
(mud mortar) should be 450mm. If funds are available at
least the external surface of the walls should be plastered
in cement-lime mortar (12mm thick, 1:1:6 mix) to keep
away moisture from rain.
The penstock pipe should not normally be built into the
powerhouse wall, otherwise the wall could be damaged by
vibration from the turbine. The recommended solution is
to leave an oversized opening in the wall; an alternative is
to place a bigger pipe outside the penstock pipe where it
passes through the wall. At Jhankre mini-hydro the wall
was locally thickened to act as a support pier for the penstock
pipes entering the powerhouse.
The clear height of the building should be 2.5m to 3m.
For larger schemes, provision must be made for lifting
equipment that cannot be lifted by hand. A crane is
expensive; more appropriate is a block and tackle supported
by a beam or temporary A-frame.
CGI sheets should be used for the roofing, since they are
relatively fire resistant and leak proof.
The floor of the powerhouse should be 300mm to 500mm
above the outside ground surface to prevent dampness and
rainwater entering. Drains should also be provided outside
the powerhouse.
Doors and windows should open outwards for safety in
case of fire or flooding.
8.4 Design of machine foundation
The design of the machine foundation is similar to that of an
anchor block, but simpler. The most significant forces that the
machine foundation can experience are as follows:
Photo 8.4 Construction of Jhankre mini-hydro machine foundation.