Distribution of energy losses in pump elements
Flow section Share of total losses, %
Working wheel 45–50
Spiral ducts 10–15
Diff user ducts 10
Translation channels 20
Return channels 10
WAYS TO REDUCE HYDRAULIC LOSSES IN MULTISTAGE CENTRIFUGAL
PUMPING EQUIPMENT FOR MINING AND OIL-PRODUCING INDUSTRIES
https://nvngu.in.ua/jdownloads/pdf/2021/6/06_2021_Akanova.pd...
page 79 / PDF page 3

--------------------------------------------------
Note added at 2 óra (2022-04-16 16:44:34 GMT)
--------------------------------------------------

Troubleshooting a System Problem
Some pumping system problems are sufficiently
expensive to justify a system assessment.
Examples of these problems include inefficient
operation, cavitation, poor flow control, and
high maintenance.

Cavitation. Centrifugal pumps are susceptible to
a damaging and performance-degrading effect
known as cavitation. Cavitation occurs when the
static pressure in the pump drops below the vapor
pressure of a fluid. The liquid vaporizes in the
form of tiny bubbles; then, when the surrounding
pressure increases, the fluid returns to liquid as
these tiny bubbles collapse violently. The
collapse of the bubbles sends high-velocity water
jets into surrounding surfaces, which can damage
the impeller and erode the pump casing and
piping surfaces. When a pump experiences
cavitation, the result is accelerated bearing and
seal wear and poor system performance.
Cavitation usually occurs at high flow rates, when
a pump is operating at the far right portion of its
performance curve. However, cavitation-like
damage can also occur at low flow rates, when
damaging vortices develop in the pump. Cavitation is indicated by crackling and popping noises,
similar to the sound of marbles flowing through
a pipe. If uncorrected, cavitation can lead to
expensive repairs. For more information on
cavitation, see the fact sheet in this section titled
Common Pumping System Problems

Internal Recirculation. Internal recirculation is
another performance-degrading effect that
damages pumps in much the same way that
cavitation does. Internal recirculation tends to
occur at low flow rates when fluid leaving the
impeller forms damaging vortices. To avoid this
problem, manufacturers list the minimum flow
rates for their pumps. Operators should be aware
of this minimum flow requirement and avoid
overly restricting pump output.

Poor Flow Control. Poor flow control can result
from several conditions, including improper
pump selection and poor system design. The
performance curve characteristics of some pumps
indicate the need for careful consideration of
the variability in operating requirements. Performance curves that are relatively flat, or curves
that “droop” at low flow rates, mean that the
designer should be aware of all the operating
demands on the pump when selecting one.
https://www.energy.gov/sites/prod/files/2014/05/f16/pump.pdf

"Потери давления по длине гидролинии (путевые) определяют по формуле
...
где... r -плотность рабочей жидкост, кг/м3.

Коэффициент путевых потерь зависит от режима движения жидкости, его определяют по формулам, рекомендуемым в гидравлике:
...
где Rе – число Рейнольдса, Rе =Vжд d /n , здесь n – кинематический коэффициент вязкости жидкости".
https://portal.sibadi.org/pluginfile.php/126662/mod_resource...


"Important factors affecting pump performance are surface roughness; internal clearances; mechanical losses, such as those related to bearings, lip seals, mechanical seals, and packing; high suction specific speed; impeller trim; and the viscosity of the fluid pumped".
https://www.ijrrjournal.com/IJRR_Vol.4_Issue.8_Aug2017/IJRR0...