by the relief valve; well? sometimes is not. If there are lines that are not connected to the relief valve in certain moments, they are not protected.
We are going to talk this time about the intensification of the pressure in hydraulic cylinders when the flow is controlled, meter-out.
The rod of the hydraulic cylinder is extending at a speed controlled by the meter-out flow control. In the graphic, the flow is coming from the pump to the back of the cylinder and the reading in the pressure gauge is the pressure relief valve setting. The flow control that is reducing the flow that exits the rod side of the cylinder creating a back pressure that is higher than the relief valve setting.
A x Pin = Ar x Pout + Load
A= Area of the piston
Ar= Area annular (A - rod area)
Pin= Inlet pressure or relief valve pressure setting
Pout= Outlet pressure before the flow control.
The worst case scenario is when the load is insignificant or very low and the rod diameter is big compared to the piston diameter. Taking the load off the formula, we have that the force from the left is equal to the force from the right, or:
A x Pin = Ar x Pout so, Pout = Pin x A/Ar
Knowing that Ar is always smaller than A, then Pout is always going to be higher than pin. Now, the question is how much higher?
It is inversely proportional to A/Ar or in other words, the bigger the rod against the piston, the higher the pressure intensification.
Let's put an example:
A cylinder has: 4" piston diameter, 3" rod.
Then, A = 12.56 sq inch. Ar = 12.56 - 7.06 = 5.5 sq inch
If Pin = 2,000 psi, then Pout = 2000 x 12.56/5.5 = 4,567 psi a lot higher than 2,000 psi.
In the following video, the relief valve pressure setting is 85 psi. The intensified pressure goes up to 125 psi.
If the load is not neglected, then it lowers the intensification effect.
Whenever you have meter-out flow meters and low loads, you can expect pressure intensification.
Hydraulics Knowledge POLL
BLOGS Latest Posts
→ NEW GENERATION BENT AXIS PISTON PUMPS AND MOTORS
04.05.2013 19:25 0
Çelebi Hidrocel ® Axial Piston Pumps, Axial Piston...Memo63 → Motor Hidraulico vs Motor Electrico
03.14.2013 02:14 0
Hola todos Espero alguien pueda ayudarme. Deseamo...Hydraperm → Hydra-Perm-Co Ltd - PERMCO UK, European & Middle Eastern Distributors
08.29.2012 18:15 0
// Hydra-Perm-Co Ltd is an international...nefacio → Consulta sobre cañería de salida de bomba
08.24.2012 00:23 0
Hola, tengo una consulta sobre la elección del dia...kobra → Bienvenidos a KOBRA Paintball fields
07.22.2012 03:30 0
// Puede visitar nuestro sitio en Face...ventas → Vendo bomba de pistones marca DYNAPOWER mod 120 PV serial 895425
06.29.2012 02:45 0
// Estamos ofreciendo la bomba de piston...juanqui → SERMATER; SERVICIO DE REPARACION Y MANTENCION DE MAQUINARIA PESADA EN TERRENO
06.16.2012 08:10 0
// SATISFACEMOS LAS NECESIDADES DE REPAR...
Motor Hidraulico vs Motor Electrico
Buenos dias, Para empezar, es mejor saber cual es ...