MIL-P-19692E
3.3.9 Rated speed. The rated speed of the pump shall be the maximum
speed at which the detail specification requires the pump to operate
continuously at rated temperature and rated discharge pressure. The rated
speed of the pump shall be established in the detail pump specification. The
nomography on figure 1 and figure 2 show approximate practical rated speeds
for current pumps for three system pressure levels. Several system factors
such as fluid, temperature, duty cycle, contamination, expected life, etc.,
will influence the values.
3.3.9.1 Overspeed. Unless othewise specified in the detail pump
specification, all pumps shall be capable of operation at 115 percent of rated
speed for the durations and at the conditions in table V.
3.3.10 Rated endurance. Unless modified by the detail pump specifica-
tion, the rated endurance shall be 2000 hours for models in type I and type II
systems (MIL-H-5440), and 500 hours for models in type III systems
(MIL-H-8891).
3.3.11 Performance.
3.3.11.1 Torque and heat rejection. The performance requirements of
torque and heat rejection shall be specified in the detail specification. The
minimum performance requirements shall be stated as maximum input torque at
rated flow and maximum heat rejection at rated discharge pressure.
3.3.11.2 Efficiency. Where the detail specification states a required
minimum efficiency, it shall be the ratio of the output power to the input
power when the pump is operated at rated speed and maximum full-flow pressure
using the hydraulic fluid specified in the detail pump specification and
expressed as percentage. This ratio is commonly referred to as "over-all-
efficiency" and includes volumetric efficiency. For the purpose of this
specification, volumetric efficiency shall not be segregated. When calculat-
ing output power from flow and pressure change, only the net difference
between inlet and outlet pressure of the pump shall be used; the flow may be
measured in the low pressure side of the discharge line provided that
efficiency calculations compensate for fluid compressibility. Note that as
discharged pressure is increased, the compressibility of the fluid reduces
apparent pump efficiency even if pump performance itself does not change.
Variation in bulk modulus of the fluid will therefore appear as a variation in
pump efficiency.
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