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PRINCIPLES OF CALCULATION FOR THE HYDRAULIC

The following examples of calculation here on the side are fundamental for the employment of hydraulic systems.

Lifting force of a hydraulic cylinder

The lifting force of a hydraulic cylinder drift from the pressure p (Bar) applied in the hydraulic cylinder on piston.

Formula:
F(kg) = p(bar) . A(cm² )
[per g = [(10 N.m) : s²]]

where:
F = acting force on cylinder ( kg)
p = operating pressure (bar)
A = piston area inside cylinder in cm² resulting from piston diameter:
A (cm²) = [d (mm)². 3,1416] : 400

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Example: Individualization of the operating pressure

With a cylinder it should be lifted a load of 72 t.
Which operating pressure is it necessary?

A (cm²) = [d (mm)².3,1416] : 400
with a piston diameter d = 130 mm
A = (130².3,1416) : 400 cm²=132,7 cm²
Per F(kg) = p(bar) . A(cm 2 ) it is obtained upon conversion
p(bar) = F (kg) : A (cm²) where F = 72 t = 72.000 kg
p = 72.000 : 132.7 bar = 542 bar.

Result: the necessary operating pressure is of 542 Bar.

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Example: Calculation of the weight of the lifted load

With a cylinder a load is lifted of which weight is not known. The manometer points out an operating pressure of 520 Bar. To calculate the weight of the lifted load is used the following formula:

A (cm²) = [d (mm)² . 3,1416] : 400
with a piston diameter -> d = 45 mm
A = (45² . 3,1416) : 400 = 15,9 cm²
F (kg) = p(bar) . A(cm² )
F = (520 . 15,9) kg = 8270 kg

Result: The lifted load weighs 8270 kgs.

Operating a hydraulic cylinder with a manual pump, the cylinder completes to every pumped a certain stroke that depends from the area of the piston and from the capacity of the pump to every pumped. For the two- phase pumps is had to set for the movement of the cylinder without load the low pressure capacity BP and for the movements under load the high pressure capacity AP.

Formula:
S(mm) = [V (cm³).10.] : A (cm²)

where:
v = cylinder speedy mm/s
Q = pump capacity l/min
A = piston area inside cylinder cm 2

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Example: Calculation of the loading move to pump act

A cylinder is operated with a manual pump. Which move does the load complete to every pumped act?
-> A= 15,9 cm²

S(mm) = [V(cm³).10] : A (cm²)

Pump activation

With a capacity to every pump stroke
V = 3,5 cm³
S =( 3,5 .10) : 15,9 mm = 2,2 mm

Result: To every operation the load makes a move of 2,2 mm

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Example: How much pump actions are necessary for extending the whole cylinder

A cylinder (stroke H=50 mm) is operated with a manual pump. A wasted stroke must be performed L = 30 mms. How much pump operation are there necessary for getting the complete extension of the cylinder?

-> A = 132,7 cm² (as example 1)
For the wasted stroke it values
S BP (mm) =[V BP (cm³).10] : A (cm²)

With a capacity to every pump stroke
-> V BP = 32cm³
-> S BP = (32.10) : 132,7 mm = 2,4 mm

Number pump operation for the waste stroke : the waste stroke is divided by stroke to every pump action:
PB BP = L (mm) : S BP (mm) = 30 : 2,4 = 13 pump action
For the stroke under loading:
S AP (mm) =é V AP (cm³).10] : A (cm²)

With a a capacity to every pump stroke
-> V AP = 3 cm³
-> S AP =(3.10) : 132,7 mm = 0,23 mm

Number pump operation for under loaded stroke: the remaining stroke is divided by the complete stroke to every pump action:
PB A = [H(mm) - L(mm)] : S AP(mm)= [50-30] : 0,2 =87 pompate

Result: In total = PB BP + PB AP = 13 + 87 = 100 pump action.

Extension speedy

The extension speedy of a hydraulic cylinder activates with a electric pump depends from the area of the piston and from the capacity of the electric pump. For the two- phase pumps is had to set for the movement of the cylinder without load the low pressure capacity BP and for the movements under load the high pressure capacity AP.

Formula:
v(mm/s) = [Q(l / min).166,67] : A (cm²)

where:
v= cylinder speedy mm/s
Q= pump capacity l/min
A= piston area inside cylinder cm 2

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Example: what speedy does a cylinder extend if activated by electric pump

A cylinder is operated with an electric pump. How speed does the cylinder complete its extension?

-> A = 132,7 cm² (as example 1)
v(mm/s) = [Q(l / min).166,67] : A (cm²)
per capacity pump -> Q = 1,8 l/min
V= 1,8.166,67 : 132,7 mm/s= 2,2 mm/s

Result: The cylinder extension speedy is of 2,2 mm/s.