Hydraulics and Fluid Mechanics in ME
In a single casing, multistage pump running at constant speed, the capacity rating is to be slightly lowered. It can be done by

Not possible
Designing new impeller
Some other alterations in the impeller
Trimming the impeller size to the required size by machining

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Hydraulics and Fluid Mechanics in ME
A compound pipe of diameter d1, d2 and d3 having lengths l1, l2 and l3 is to be replaced by an equivalent pipe of uniform diameter d and of the same length (l) as that of the compound pipe. The size of the equivalent pipe is given by

l/d⁵ = (l₁/d₁⁵) + (l₂/d₂⁵) + (l₃/d₃⁵)
l/d⁴ = (l₁/d₁⁴) + (l₂/d₂⁴) + (l₃/d₃⁴)
l/d² = (l₁/d₁²) + (l₂/d₂²) + (l₃/d₃²)
l/d³ = (l₁/d₁³) + (l₂/d₂³) + (l₃/d₃³)

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