Dukes Danfoss 1622 Loader Valve Requires Precision Relief Settings and Cartridge Sourcing

[MikePhua]

The 1622 Loader Valve and Its Role in Hydraulic Control
The Dukes/Danfoss 1622 directional loader valve is a compact hydraulic control unit commonly found in mid-1990s Case skid steers, including the 1845C. This valve manages loader lift and bucket tilt functions by directing hydraulic flow through spool-controlled circuits. It includes a main relief valve and two pilot-operated relief cartridges that regulate pressure in the A and B work ports.
These pilot reliefs are critical for preventing overpressure in the lift and tilt cylinders. If improperly set, they can cause sluggish operation, excessive heat, or damage to seals and hoses. The valve’s modular design allows for cartridge replacement, but sourcing compatible components and setting correct pressure values requires careful attention.
Identifying the Pilot Relief Cartridges
The original pilot reliefs in the 1622 valve are often labeled with proprietary codes, but they correspond to standard industrial cartridges. One commonly matched model is the LHRV-08, a pilot-operated relief valve with adjustable pressure settings and standard SAE port threads.
Key specifications to verify:

• Thread type: SAE-8 or SAE-10 depending on manifold block
  
• Pressure range: 2,300–2,750 psi (approx. 160–190 bar)
  
• Flow capacity: 10–15 GPM
  
• Seal material: Buna-N or Viton depending on fluid type
  
• Cartridge length and cavity depth
  

A technician in Pennsylvania tracked down the LHRV-08 as a compatible replacement but needed confirmation of the factory pressure setting. After consulting service data and field experience, a target of 190 bar was recommended for both pilot reliefs, matching the main relief’s upper threshold.
Setting Pressure and Shimming Relief Valves
Pilot relief valves are typically adjusted by shimming—adding thin washers behind the spring to increase preload. This changes the pressure at which the valve opens. For the 1622 valve:

• Start with 180 bar (2,610 psi) as baseline
  
• Add 0.010" shim to increase by ~50 psi
  
• Use hand pump and gauge to test opening pressure
  
• Ensure both A and B port reliefs are balanced within ±50 psi
  
• Avoid exceeding 2,800 psi to protect cylinder seals
  

A mechanic in Wisconsin rebuilt his loader valve and found that one relief opened 200 psi lower than the other, causing uneven bucket response. After adding a shim and retesting, the system stabilized.
Port Size and Manifold Compatibility
When replacing cartridges, port size refers to the cavity in the valve body—not the external hose fittings. Most replacement cartridges omit porting information in the model code to ensure compatibility with existing manifolds.
Tips for matching:

• Measure cavity diameter and depth with calipers
  
• Confirm thread pitch and sealing surface
  
• Use manufacturer’s cavity drawing to verify fit
  
• Avoid mixing metric and SAE threads
  

A restorer in North Carolina ordered a cartridge with incorrect porting and had to re-tap the manifold, risking contamination and misalignment. Using the correct cavity code avoided further issues.
Sourcing Parts and Navigating Obsolescence
While some suppliers like Messick’s and Coleman may list original parts, many are discontinued. Alternatives include:

• Hydraulic cartridge manufacturers (Sun Hydraulics, HydraForce, Parker)
  
• Industrial distributors with cross-reference tools
  
• eBay sellers specializing in surplus hydraulic components
  
• Custom rebuild shops with cartridge machining capability
  

A technician in Ohio contacted multiple sellers and found a matched pair of pilot reliefs with adjustable settings and proper cavity dimensions. He installed them with synthetic hydraulic fluid and reported smoother loader response.
Testing and Field Calibration
After installation:

• Warm up hydraulic system to operating temperature
  
• Use hand pump to test relief opening pressure
  
• Cycle loader arms and bucket under load
  
• Monitor for chatter, delay, or uneven movement
  
• Recheck pressure after 10 hours of operation
  

A fleet manager in Texas implemented a post-rebuild inspection protocol and reduced loader valve failures by 70% across his Case skid steer fleet.
Conclusion
The Dukes/Danfoss 1622 loader valve remains a reliable hydraulic control unit when properly maintained and calibrated. Replacing pilot relief cartridges requires attention to cavity dimensions, pressure settings, and fluid compatibility. With careful shimming, accurate testing, and smart sourcing, operators can restore full loader performance and extend system life. In hydraulic control, precision isn’t optional—it’s the difference between smooth operation and costly downtime.