H45 & H45S HYDRAULIC HAMMER Pressure Reducing Valve (PRV) Caterpillar

Pressure Reducing Valve (PRV)
H45 & H45S HYDRAULIC HAMMER Pressure Reducing Valve (PRV)

Remove & Install Pressure Reducing Valve

------ WARNING! ------

Pressure may be retained in hammer. Personal injury may be caused by pieces under pressure.. Release pressure in hammer before removing valve.


The pressure reducing valve can be removed without removing the power cell from the sideplates. The pressure reducing valve is located in the valve body behind pressure and return line ports.

1. Remove spring housing (1).

2. Remove spring (3) and shims (2) from inside of spring housing (1).

4. Remove plug (6).

5. Remove spool (5) from the valve body by pushing it towards plug (6). Do not push towards spring housing (1).

3. Remove seal (6) from inside valve body located on spring housing (1) side.

NOTE: The following steps are for the installation of the pressure reducing valve.

6. Check all parts for wear and damage. If necessary, use fine emery cloth or grinding agent. Clean and oil all parts.

7. Install new seal (4) into valve body.

8. Install spool (5) into the valve body from plug (6) end only. Do not push spool too far, insert just enough to install plug (6).

9. Install shims (2) into spring housing (1) applying some grease.

10. Install spring (3) and spring housing (1) into valve body.

11. Torque plug (5) to 150 N·m (110 lb ft).

12. Torque spring housing (1) to 150 N·m (110 lb ft).

Pressure Reducing Valve Adjustment

When pre-load of the spring changes, the impact energy changes as well.

The impact energy is preset at the factory with shim plates (3 and 4).

The hammer operating pressure can be readjusted to specifications by adding or removing shim plates (3 and 4) between spring (5) and spring housing (2).

Adding shim plates increases operating pressure and removing shim plates reduces operating pressure. Always put a thick shim against the spring. Cover shims and spring with grease to stay in place during assembly

The pre-load is measured as follows:

1. Tighten the spring housing until you feel the spring (5) touch spool (2) without compressing it.

2. Measure the gap between valve body and spring housing with a feeler gauge.

3. The gap should be 1.5 mm (0.059 in).

4. Add or remove shims, as necessary, to obtain correct measurement.

5. Measure operating pressure after adjustment. Make reference to the testing and adjusting manual.

NOTE: 1 mm (0.04 in) shim changes low pressure by 3 bar (43 psi) and operating pressure by 8 bar (116 psi).

Charging Accumulators

------ WARNING! ------

Use only dry nitrogen (N2) for charging accumulators. The use of other gas may cause accumulators to explode.


1. Install a new Usit-ring (8), use existing filling plug (9) on accumulator unless plug (9) is damaged.

2. Connect charging system to the accumulator: install pin (4), adapter (5), O-ring (10), and charging device (1).

3. Close discharge valve (3) on charging device (1).

4. Open filling plug (9) through the charging device (1) three turns.

5. Carefully open nitrogen gas bottle valve (2) and set regulator (if used) to preliminary pressure of 4000 kPa (580 psi) on high pressure accumulator and to 1000 kPa (145 psi) on the low pressure accumulator.

6. Wait 10 minutes for nitrogen gas to stabilize inside accumulator.

7. Readjust accumulator pressure on charging device gauge (11) to the final specification, which is 4000 kPa (580 psi) on high pressure accumulator and 1000 kPa (145 psi) on the low pressure accumulator.

8. Torque filling plug (9) to 20 N·m (15 lb ft) maximum.

9. Release pressure from charging hose by opening discharge valve (3) on charging device.

10. Remove charging device (1), adapter (5), O-ring (10), and pin (4) from accumulator.

11. Check accumulator for nitrogen leak in Usit-ring area by filling pin area (4) with thin oil. If gas bubbles appear, discharge gas and replace Usit-ring.

12. Repeat Steps 1 through 10 if gas bubbles appear.

13. Install protective plug (6) with O-ring (7).

14. Torque plug to 150 N·m (110 lb ft)