Cartridge Hand Pump

Relief Valve

Primary Relief Valve and Secondary Relief Valve (Sometimes used as Primary)

Relief valves primary function is to prevent over pressurization of hydraulic system. On a double acting circuit a second relief valve will be placed after the check valve to prevent thermal expansion & over pressurization of cylinder. This could result in catastrophic failure.

Common Problems with Relief Valves

• Debris stuck on valve seat causing relief valve not to build maximum system pressure
• Adjustment screw being screwed in all the way causing the spring to compress & crack early or not be able to be readjusted to specified pressure setting. (most relief valves will start to crack 100-300 psi before full bypass)
• Torn or extruded O-rings

Check Valve

A check valve is similar to a relief valve but has a lighter spring allowing the fluid to pass through it with little pressure loss. The purpose for this relief valve in the hydraulic circuits covered in this guide is to prevent the fluid from back flowing to the pump.

Common Problems with Check Valves

• Debris stuck on valve seat
• Torn or extruded O-rings
• Silting – Debris buildup in valve causing poppet not to move freely

Normally Closed 2-Way

A Normally Closed 2-Way is nothing more than a solenoid operated check valve. When the Solenoid (coil) is activated the pilot pin retracts allowing the pressure to equalize on either side of the poppet then the poppet will retract.

Common Problems with Normally Closed 2-Way

• Debris stuck on valve seat
• Torn O-rings on nose
• Silting – Debris buildup in valve causing poppet not to move freely
• Bent Stem on valve (Stem is the portion of the valve the coil slides over)

Directional Control Valve

Directional Control Valves simply tell the hydraulic fluid where to go. By activating the Solenoid (coil) the spool will shift changing the flow path.

The tolerances between the spool & the cage are tight & overtime these tolerances can increase causing the valve to have excessive leakage. You might notice this if over time, the cycle times have been increasing where eventually you won’t be able to lift a load.

Common Problems with Directional Valve

• Electromagnetic coil not activating
• Over torqued valve (18ft-lbs. Max)
• Torn or extruded O-rings
• Debris stuck in valve
• Rust inside valve preventing spool from shifting
• Bent Stem on valve (Stem is the portion of the valve the coil slides over)

Ways to Check Directional Control Valve

• Valve not shifting
  1. Ensure valve is not bent (stem is the section of valve the coil slides over)
  2. Remove valve from manifold
  3. Use dipstick on breather to push in section 1 on nose of valve. This will manually shift the valve.
  4. If you can’t shift the valve check for debris & or replace

Trick: By removing the white wire from the start solenoid you can place the coil back on the valve & shift the valve after it has been removed from the manifold. The valve should shift just as fast as you press the button if you see the valve hesitate to shift clean valve & try again. If problem persists replace valve

• Valve stuck in activated position
  1. After removing valve check spool to see if it is covering the bottom half of the crossed drilled holes in section 2 of valve
  2. In the valves spring offset position valve should cover the bottom half of the crossed drilled holes on section 2 & 4

Load Holding Valve

The load holding valve checks both rod & bore end of cylinder, this valve is different than any other load holding valve. The solenoid (coil) operated portion allows you to retract the cylinder without having to add an orifice to restrict the flow of fluid down like you would with a dual pilot operated check valve.

Common Problems with Directional Valve

• Debris in check valves
• Bent Stem on valve (Stem is the portion of the valve the coil slides over)
• Air in system not allowing pilot operated check valve to open