The purpose of this bulletin is to provide field personnel with a basic guide to
the repair of hydraulic turbine runners and large pump impellers.
Reclamation operates and maintains a wide variety of reaction and impulse
turbines as well as axial flow, mixed flow, radial flow pumps and pump-
turbines. The recommendations in this bulletin are to be used as guidelines
to help develop specific repair procedures which may be unique to a given
unit and field situation.
Unless otherwise specified discussions and recommendations concerning
turbines and runners can also be assumed to be applicable to large pumps
2. RUNNER MATERIALS
Older runners in Reclamation service are commonly cast steel conforming to
the requirements of Federal Specification QQ-S-681 class 2. This
specification specified a chemical requirement of 0.35 C, 0.7 Mn, 0.05 P, 0.06
S, 0.60 Si, 0.50 Cu, and 0.50 Ni. Physical requirements included a tensile
strength of 65,000 lb/in
and a yield strength of 35,000 lb/in
Newer runners and impellers are manufactured as one-piece castings, cast
components welded together, fabricated components welded together, or a
combination of cast and fabricated components welded together. In addition,
areas of the runner may be weld overlaid with cavitation resistant material.
The basic design of the runner will be a function of the state-of-the-art of
materials science, the cost of materials, fabrication and foundry costs, and the
anticipated duty of the machine.
The following is a description of materials commonly used for turbine
construction reprinted from EPRI AP-4719. (1)
"Carbon Steel Pipe
"Specification: ASTM A285 - Grade B; ASTM A516 - Grade 65, 70, 75;
ASTM A283 (for draft tube liner); and ASTM A36 (for draft tube liner).
"Application: These materials are used on all turbine components of
plate steel construction. They are low to intermediate strength
materials and have cavitation resistance which is typical of carbon