Tronair 5731, Operation & Service Instructions

Page: 19 / 119

Model: 5731
Hydraulic Power Unit
08/2016 | Rev. 08 Page | 14
5.0 OPERATION (continued)
5.6 BLEEDING AIR FROM SYSTEM
Rapid fluctuations of the pressure gage and flow-meter are indications of cavitation or entrapped air in the hydraulic lines
and/or components. Air may enter the system when:

Operating the unit with insufficient oil in the reservoir.

Changing a component on the aircraft.

Changing hose connections and/or couplings.
5.6.1 To Easily Purge the Unit of Air
a. Fill reservoir to recommended level.
b. Open bypass valve.
c.
Place reservoir selector valve in “Hydraulic Power Unit” position.
d. Start unit and adjust flow control to maximum position.
NOTE: If fluid is not flowing, shut off HPU and reference 8.2 No Flow in Trouble Shooting section of Technical
Manual
e. Run unit for five (5) minutes and shut off.
f.
If additional bleeding is required, connect the pressure and return hoses together and open all pressure and return ball
valves at the rear of the HPU. Start the HPU and slowly close the bypass valve (
system pressure should remain under
200 psi (approximately 14 bars) . Allow fluid to flow at full flow for five (5) minutes, then shut the HPU off.
WARNING!
Failure to open the return ball valves will cause hose or valve rupture. Property damage and personal
injury can result.
5.7
DUAL SYSTEM OPERATION (Option C)
The dual system option allows control of fluid flow to aircraft with two hydraulic systems. The systems consist of two sets of
hoses and valves located in the pressure and return systems. The valves are mounted on the rear of the hydraulic power unit
and are of the 90
o
ball type. The valves are open when the operating handle is in line with the valve.
Although both systems may be operated simultaneously, usually only one system is required at any one time. If both valve
sets are open simultaneously, the pump output will be divided between the two systems. Also, cross flow between aircraft
reservoirs may occur if a reservoir level or pressure differential exists. Select valve positions prior to starting machine.
5.7.1 To Operate the Dual System
a. Before starting machine, open pressure and return valves of the same system.
WARNING!
Ensure pressure and return hoses of the same system are paired and used together.
b. After completing tests on one system, shut the machine off before selecting the second system.
WARNING!
NEVER open or close dual system valves without shutting off the Hydraulic Power Unit. Damage to the
aircraft system or reservoir may result if either return line valve is closed while the machine is running.
5.8
HAND PUMP OPERATION (Option M)
The Hand Pump Option allows for filling the reservoir (low pressure) or static testing of components or system (high pressure).
The hand pump circuit is separate from the main hydraulic system; a separate filter and hose are attached to the back panel of
the HPU.
5.8.1 To Operate the Hand Pump
a. Remove the pump handle from inside the front access door. (Reference Figure 5.3.6

Hand Pump Controls )
b. Insert the end of the pump handle through the front panel opening into the hand pump relief screw.
c.
Turn the pump handle clockwise to close the relief screw.
d. Insert the pump handle onto the hand pump arm through the front panel slot.
e. Pump the handle using an up and down motion. Observe the hand pump system pressure on the hydraulic control panel
( Figure 5.3.3 Hydraulic Control Panel ). The pump is an automatic two stage pump. 500 psi (34.47 bar) can be produced
with high fluid flow and 5,000 psi (344.74 bars) can be produced with low fluid flow.
f. Turning the relief screw in a counter-clockwise direction releases hydraulic pressure in the hand pump system.
Pressurized Fluid! Before disconnecting the hand pump pressure hose, ALWAYS open the relief screw valve to
relieve any residual pressure in the hydraulic system.
5.0 Operation continued on following page.