Page 549 - Mechatronics with Experiments

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JWST499-c07
JWST499-Cetinkunt
ELECTROHYDRAULIC MOTION CONTROL SYSTEMS 535
Pressure drop (psi)
100
Teat fluid
Mobil DTE 25 (HYD, Oil)
200 SUS @ 105° F
2 Specific gravity = 0.873
6
Diameter 4 5 8
10
10
2.3
12 16
14 20
1

.1 1 5 10 100
Flow rate (gpm)
FIGURE 7.93: Pressure drop (loss) in pipes and fittings (turns, elbows, T-connections,
cross-connections) as a function of fluid viscosity, pipe diameter and length, flow rate, fitting
shape, and pipe inner surface roughness). There are similar graphs available from hydraulic
pipe and fiting manufacturers based on measured data. Reproduced with permission from
Parker Hannifin.

For the pressure drop from pump output to the input of the main valve,

p loss−1−3 = p loss (Q, l, d, RF, straight pipe 1) (7.424)
+p (Q, l, d, RF, T connector) (7.425)
loss
+p (Q, l, d, RF, straight pipe 3) (7.426)
loss
For the pressure drop from pump output to the input of the relief valve,
p = p (Q, l, d, RF, straight pipe 1) (7.427)
loss−1−2 loss
+p (Q, l, d, RF, T connector) (7.428)
loss
+p (Q, l, d, RF, straight pipe 2) (7.429)
loss
For pressure drop from output of the relief valve to tank

p = p (Q, l, d, RF, straight pipe 4) (7.430)
loss−4−5 loss
For pressure drop from output of the main valve to tank
p = p (Q, l, d, RF, straight pipe 6) (7.431)
loss−6−7 loss
+p (Q, l, d, RF, Right angle connector) (7.432)
loss
+p loss (Q, l, d, RF, straight pipe 7) (7.433)
For each section, the pressure losses can be estimated as a constant value once the
nominal flow rate and geometric properties of the piping are determined using the look-up
tables and graphs provided by pipe-fitting suppliers.
Therefore, for the rest of the analysis, if we know the pressure at the pump output
(p (t)) and the tank (return reservoir) pressure (p ), we can determine the pressures at the
s
t
relief valve input and output, main valve input and output. That way, we estimate the flow