Eaton Hydrokraft PVW 250, Руководство по эксплуатации

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Assembly and installation
22
HYDROKRAFT OPERATION MANUAL PVW 250+360
E-PUIO_II001-E April 2021 www.eaton.com
5.10 Suction line
To avoid cavitation damage, the inlet pressure should be at
or slightly above 1 bar absolute at all times. Smaller pumps
can tolerate some degree of vacuum but larger pumps must
have a minimum pressure of 1 bar absolute at the inlet.
Guideline for suction line diameter:
v max oil (suction line) < 1 m/sec
250 cm
3
/r & larger = 1 bar (14.5 psi) MINIMUM
Avoid long vertical suction lines, sharp elbow joints or
small diameter lines.
The suction line should be of the largest possible diameter,
reducing to inlet port size at or near the port itself. It should
also use swept bends rather than sharp elbow joints.
Suction filters and strainers should not be fitted as the
pressure drop required to draw fluid across them further
lowers the inlet pressure.
5.11 Atmospheric pressure
The sensitivity of the pumps to inlet conditions is
even more relevant at greater altitudes and lower
atmospheric pressures.
5.12 Acceleration of oil in suction line
Consider the effect of drawing oil along a suction line
under conditions of rapidly changing swash angle.
As the pump moves from zero flow to maximum flow,
fluid has to be accelerated from low speed (or rest) by the
pressure difference acting across it.
The pressure required to accelerate the fluid is determined
by the length of the inlet line, the fluid density, the inlet
flow velocity and the on-stroke response time of the pump.
To reduce or avoid this negative pressure, the length of
the inlet line could be reduced in order to reduce the
mass of fluid to be accelerated.
Or, if this is not possible, the on-stroke response time
of the pump could be increased either by using the
slow on-stroke adjustment option or a ramp signal if
electronically controlled.