Home | Looking for something? Sign In | New here? Sign Up | Log out

Kamis, 09 Desember 2010

Air, how load-sensing reduces heat.

/ On : 22.08/ Thank you for visiting my small blog here. If you wanted to discuss or have the question around this article, please contact me e-mail at mozabani@yahoo.com
Hello again Air,

In your past couple of hydraulic maintenance emails,
I explained how to accurately assess the condition
of a hydrostatic transmission using case drain flow.

Today I want to switch gears and talk about
a type of hydraulic control in widespread use,
but not well understood: load sensing.

Load sensing is a term used to describe a type of
variable pump control used in open circuits. It is
so called because the load-induced pressure downstream
of an orifice is sensed and pump flow is adjusted to
maintain a constant pressure drop (and therefore flow)
across the orifice.

The 'orifice' is usually a directional control valve
with proportional flow characteristics. But a needle
valve or even a fixed orifice can be employed,
depending on the application.

In hydraulic systems that are subject to wide fluctuations
in flow and pressure, load-sensing circuits can save
substantial amounts of input power.

A load sensing circuit typically comprises a
variable displacement pump, usually axial-piston design,
fitted with a load sensing controller, and a directional
control valve with an integral load-signal gallery.

The load-signal gallery is connected to the load-signal port
on the pump controller. The load-signal gallery in the
directional control valve connects the A and B ports of
each of the control valve sections through a series of
shuttle valves.

This ensures that the actuator with the highest load pressure
is sensed and fed back to the pump control.

To read the rest of this story - with diagrams,
point your browser to

Yours for better hydraulics knowledge,

Brendan Casey
Author of 'Insider Secrets to Hydraulics'


If you no longer wish to receive the valuable guidance
provided by the 'Inside Hydraulics' newsletter
and associated mailings, point your browser to this page:


1195 Hay St
PO Box 1029
West Perth, Western Australia 6872
6 (189) 380-6659

Delivered By Infusionsoft