Shown is the hydraulic circuit of a load-lifting hydraulic system. The lowering

Question

Shown is the hydraulic circuit of a load-lifting hydraulic system. The lowering speed is controlled by means of a throttle-check valve. Discuss the construction and operation of this system. Redraw the hydraulic circuit in the load-lowering mode, then calculate the pressure in the cylinder rod side, PC, the inlet flow rate,Qin, outlet flow rate, Qout, pump flow rate, QP, pump output power, Nh, and the area of the throttle valve, At. Neglect the hydraulic losses in the system elements, except the throttle valve.

The flow rate through the throttling element is given by: Q = Cd At (2?P/?)^(1/2) where,

Q = Flow rate, m3/s

At = Throttle area, m2

? = Oil density, kg/m3

Cd = Discharge coefficient

?P = Pressure difference, Pa

Given
Pump exit pressure = 30 bar

Piston area AP = 78.5 cm2

Oil density = 870 kg/m3

Safety valve is pre-set at 350 bar

Piston speed = 0.07 m/s

Piston rod side area Ar = 40 cm2

Discharge coefficient = 0.611

Weight of the body = 30 kN

Explanation / Answer

A)presure in the cylinder rod

p = FA = 30 * 40 * 10-4 = 120N

b)Qout = speed * displacement / 231 = 0.003m3/sec

c)pump power = QOUT*ROWgh=0.09kw

D)Qin = 0.0101 *a*d0.5=0.15m3/sec

thoart area=0.5m3

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