Micron Technology Turbofan - Manual (Page 10)

DRAFT
9
4.2.4 Hydraulic Oil Flow
If a Power Take Off (PTO) driven hydraulic pump is used, the pump should be chosen to
provide the calculated maximum oil flow plus losses and no more. If a larger pump were
to be used, any unused oil would have to be by-passed and would generate heat.
The specified output of the pump must match the calculated oil requirement (see sample
calculations in Sections 4.2.2 and 4.2.3)
When calculating pump output, ensure that the actual operating speed of the tractor is
taken into account. Many pumps are specified at 540 rpm nominal PTO speed. Most
tractors are driven at an engine speed corresponding to a lower PTO speed. For example,
if running at 500 rpm a pump rated at 100 l/min at 540 rpm will actually produce:
100 l/min x 500 rpm (actual) = 92.6 l/min
540 rpm (nominal)
4.2.5 Hydraulic Pressure and Hose Size Selection
When designing a system and selecting a pump, the additional pressure drop across all
hoses and fittings must be taken into account. The working pressure of all components
must be adequate for worst-case conditions, including start-up pressure surges.
All hoses, pipes and fittings must be chosen to give an acceptably low pressure drop at
the maximum operating flow rate. The procedure to select the sizes of the pressure and
return lines is as follows:
a) On all pressure lines – calculate flow through each section, then use the design table
(Table 1) to select the appropriate diameters so that the total pressure drop along any
route from the pump to a sprayhead does not exceed 3.0 bar (45 psi).
To calculate the hydraulic flow required for a specific number of Turbofan Sprayheads
running in series pairs:
• Each head and each chain runs at 8.0 l/min
• Allow 10% for pump and other hydraulic losses. Therefore flow per chain (ie 2 x
Turbofan) = 8.8 l/min
• Therefore for 6 heads (3 chains of 2) the flow required = 8.8 x 6 = 26.4 l/min
2
Alternatively if you know the maximum hydraulic flow available (and the system
pressure is 200 bar or above) then :
Maximum number of heads which can be fitted = 2 x maximum hydraulic flow available
with 2 motors in series in each chain
8.8
e.g. If flow available = 72 l/min
then maximum number of heads in series (two per chain) = 2 x 72 = 16.4 = 16 heads
8.8