SHOP MANUAL
HYDRAULIC
Ch 5 page 6 Ch 5 page 7
HYDRAULIC
Hydraulic System Description
For optimum efficiency and performance, the new system is still using variable displacement pump- and load
sensing technology for the operation of bin lifting-, steering-, brake- and fan control systems as its predecessor.
The new system has reduced the complexity further with fewer components, better packaging by the integration
of several sub functions into one main manifold, less connecting points for simplified installation and reduc-
tion of potential leakage points. The entire hydraulic system is fed by one large variable displacement pump.
Although less complex, the new one pump system offers increased lifting flow and by using an “on-demand”
maximum flow boost function only when lifting, the pump margin pressure setting has been possible to reduce,
(now 20bar), what reduces energy losses, heat generation and emissions further while saving fuel
Hydraulic System Components
The hydraulic system consists of the following components:
1. Variable displacement piston pump;
Maximum displacement 145cc.The pump has maximum pressure and load sensing delta-P controller. The
maximum pressure is factory set at 280bar. LS delta-P is set at 20bar at engine idle speed and no flow output
(i.e. standby setting)
2. Main control manifold assembly;
It has included a control section with electro-hydraulic pilot controlled three position spool operated bin lift func-
tion and lift cylinder pressure protection. The manifold also incorporates functions for steering priority, steering
maximum pressure limitation, brake charging, brake- and parking brake pressure control, fan activation and
speed control, diff lock pressure control, engine exhaust brake pressure control, pilot pressure supply, bin float
function, pump de-stroking damping and pump pressure spike protection.
The manifold also acts as a junction block for connection and distribution of various supply- and tank lines.
It also offers gauge ports for various important control pressures. Many of those control pressures are
routed to an external test block, [Item 8], for easy access.
3. Brake Pressure Accumulators;
The 2,15 Litre parking brake accumulator is placed on the left side of the cab front wall along with the 3,3 Litres
front service brake accumulator. The two 3,3 Litre rear service brake accumulators are placed on the right side
of the cab front wall. The accumulators are from Doosan Infracore Norway factory loaded with Nitrogen (N
2
).
4. Return Filter
The hydraulic return filter has as function filter all hydraulic oil that returns to the tank. The filter head for the
return filter is built with two non-return valves (0,2 bar) and a by-pass valve.
5. Steering Unit
Displacement: 250 cm³ (15.25 in³ / rev), Rated oil flow: 25 L/min (6.60 U.S. gal / min) and the amplification factor
is 8. This means that total displacement is 160 cm3 x 8 = 1280 cm3 per steering wheel revolution.
The Steering Master Valve is located on the cab front wall (firewall). Access is obtained by tilting the cab.
6. Steering Amplifier
In the flow amplifier system, it is a combination between steering and working hydraulics.
A priority valve is built into the flow amplifier. The priority valve ensures that the steering system has first priority
on oil flow from the hydraulic pumps, which enters the flow amplifier.
The oil flow which is not used for steering, are sent to tank.
If the steering wheel is not turned, the entire oil flow is directed to the tipping valve.
The principle applied to the controlled operation of the flow amplifier, called “load sensing”. As name suggest ,
it is a system in which the load is used in this system, to control the priority valve in the flow amplifier, so that
oil flow and pressure precisely matches momentary demands.
7. Steering Cylinders
The Steering Cylinders are located on each side of the articulation hinge and are resposible for the front frame
turning. Their specificatios are:
DA40 DA30
• Double acting;
• Cylinder Diameter 115mm; 100mm
• Piston diameter 70mm; 63mm
• Stroke 550mm 515mm
• End cushion.
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