National Crane Published 10-30-2014 Control # 040-09 5-45
1400H OPERATOR AND SERVICE MANUAL SERVICE
Adjusting the Relief Valve Pressure Settings
The control valves supplied with this crane are equipped
with adjustable relief valves. After time of use, it may be
necessary to make some adjustment in pressure because of
spring weakening, etc. See the “Specifications” section for
correct pressure setting.
Important: If the machine does not perform properly
first consult the trouble diagnosis chart in this section.
Do not adjust any relief valve setting without first
checking the current setting with a pressure gauge.
Never adjust any relief valve setting above its
specified setting as this could allow the machine to
operate in such a manner as to endanger personal
safety.
If the machine does not perform properly at these
pressures, the problem is not the relief valve and no
attempt should be made to readjust the setting. If the
relief valves are set to higher pressures than those
specified, the warranty on the machine is void. Also the
machine could operate in a manner such as to endanger
personal safety.
Adjustment of port relief, on individual work sections of
the control valve, or main relief, on inlet section of the control
valve:
1. Remove seal disc in top of port relief.
2. Clean grease out of port relief cavity.
3. Turn adjustment screw in for increased pressure or back
adjustment screw out for decreased pressure setting.
4. Fill port relief cavity with grease.
5. Install seal disc, replace with new disc if necessary.
Never set pressure above recommendations.
Tightening Torques (maximums)
1. Main Relief Valve ................................30 lb-ft (41 Nm)
2. Port Relief Valve..................................35 lb-ft (47 Nm)
3. Port Relief Cavity Plug ........................35 lb-ft (47 Nm)
4. Assembly Studs-initial torque..............11 lb-ft (15 Nm)
Final torque.........................................20 lb-ft (27 Nm)
5. Cavity Plug..........................................30 lb-ft (41 Nm)
6. Standard Check Valve.........................50 lb-ft (68 Nm)
7. Check Valve ........................................30 lb-ft (41 Nm)
8. Metering Orifice...................................50 lb-ft (68 Nm)
9. Damp/Check Valve Cartridge................8 lb-ft (11 Nm)
10. Steel Plugs (SAE#12) .........................60 lb-ft (81 Nm)
11. Steel Plugs (SAE#10) .........................50 lb-ft (68 Nm)
12. Steel Plugs (SAE #8)...........................40 lb-ft (54 Nm)
13. Cavity Plug..........................................35 lb-ft (47 Nm)
14. Pressure Reducing Valve
Cavity Plug .........................................30 lb-ft (41 Nm)
15. Spool Control Spring ............................50 lb-in (6 Nm)
16. Hydraulic Cap Capscrews....................50 lb-in (6 Nm)
17. By-Pass Unit .......................................50 lb-ft (68 Nm)
18. Hi/Lo Flow Unit....................................50 lb-ft (68 Nm)
19. Pressure Gauge Port ..........................50 lb-ft (68 Nm)
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