The manufacturing process for the suction tube is similar to the process of
manufacturing the spiral, as detailed in section 2.1. The following plans
should be used in manufacturing the suction tube: Plans 02 and 02-1,
along with the general assembly plan EG.
2.3. Turbine wheel manufacture
See plan 03.
A. Materials.
• Chrome-nickel cast stainless steel (13% chrome and 4% nickel)
from the foundry. The use of stainless steel is recommended given
its greater resistance to corrosion caused by cavitation.
• Electrodes. The electrodes used to weld the blades to the turbine
wheel hub are E308-16 (AW Oerlicon Stainless Steel)
• Other. Grinding disc, files and fine and coarse abrasive paper.
B. Method
Manufacture of the turbine wheel begins with preparation of the models
and moulds as an initial step. The models are produced in accordance with
the plans, taking into consideration the tolerance values for contraction of
the cast metal, and are in general made from wood, as the cheapest
material, or other options such as: resin, fibreglass or aluminium. In this
case models have been used for the blades and for the hub, which are
cast separately. The blades are bead-welded to the hub using electrical
welding equipment and stainless steel electrodes. The welding is
performed blade by blade, taking into consideration the correct positioning
of the defined angle. Once all the blades are in position they are welded
completely to the hub, avoiding any overheating which could warp the
parts, while also taking care to keep the blades in their correct position.
After the blades have been welded to the turbine wheel, final finishing
involves polishing those parts of the wheel which will be in permanent
contact