MTS Series 505G2 SilentFlo Hydraulic Power Unit Model 505G2-11 - Manual (Page 48)

Model 505G2.07/.11 SilentFlo™ HPU 48
Adjusting the Auto-Cooling Level
Adjusting the Auto-
Cooling Valve to
correspond with a
change in HPU output
pressure
Perform the following procedure whenever the HPU will be operated with a
change in output pressure for longer than 10 minutes.
The following procedure assumes that Steps 1 through 3 of “Adjusting the HPU
output pressure level” have already been completed.
1. With the HPU running in high, loosen the nut on the Auto-Cooling Valve
located on the control manifold (see the previous figure).
2. Adjust the Auto-Cooling Valve to shift at the desired level.
• When increasing the output pressure, adjust the Auto-Cooling Valve
clockwise to the desired shift level.
• When decreasing the output pressure, adjust the Auto-Cooling Valve
counterclockwise to the desired shift level.
Note The number of turns required to reach the transition level will depend on
the how much the output pressure is changed. For example, going from
an output pressure of 21 MPa (3000 psi) to 14 MPa (2000 psi) may
require as much as three full turns on the Auto-Cooling Valve before you
approach the transition level.
While adjusting the Auto-Cooling Valve, listen to the pump. When the valve
shifts a sudden change in pitch will be heard from the pump. Reversing the
valve adjustment a number of times will aid in identifying the proper
setting. Make a final counter-clockwise adjustment, an increase in pump
pitch will be heard that corresponds with the opening of the valve. Stop
adjusting at this point.
An alternative to listening for a change in pump pitch is to hold the return
line hose at the manifold while making the valve adjustment to feel when
the resultant flow stops or starts.
Important Adjustment of the Auto-Cooling Valve to a level too close to the
desired output pressure may cause an unstable condition
characterized by rapid valve shifting. This condition will produce an
audible flutter and can be seen as an erratic movement of the
needle on the pressure gage.
Adjustment of the Auto-Cooling Valve at or above the desired
output pressure may prevent the valve from shifting and result in
the HPU overheating.
Adjustment of the Auto-Cooling Valve that results in the valve
shifting at a level substantially below the desired output pressure
may result in reduced flow to the system.
3. Confirm the Auto-Cooling Valve setting by slowly cycling the HPU Output
Pressure Control. Decrease the HPU output pressure and note a decrease in
pump pitch when the valve closes. At the point when the valve closes, the
pressure on the gage will momentarily hesitate during the adjustment.
Increase the pump output pressure to the desired pressure setting and note an
increase in pump pitch when the valve opens. Once again the pressure gage
will show a momentary hesitation when the valve opens.
4. If necessary, repeat Steps 2 and 3 until the Auto-Cooling Valve is stable and
the HPU cools properly.