SEAL-DUST 2291081 - Caterpillar

Hammer Flow Adjustment
The next step is to hook up a flow meter to measure the oil flow and line relief characteristic curve.
Fig.12: Flow meter connectionThe plugs on the stick ball valves can be removed so that the pressures can be measured at both sides (hammer supply and return line). Using the flowmeter charge screw and the Allen screw on the solenoid valve under the platform (see fig. 11), adjust the pump flow so that the right hammer flow is delivered at the normal hammer operating pressure (example: 180 l/min at 150 bars). The right flow for a hammer setting is usually 10% under the maximum specified by the hammer manufacturer. This setting will provide both high hammer performance and durability.As the oil flow is a function of the oil temperature, it is recommended to adjust the oil flow at normal working oil temperature, around 50°C.When adjusting the hydraulic load with the flowmeter screw, the load increase may be too smooth to influence the pressure sensors of the excavator. For this reason, it is always recommended to check the flow with start and stops at the hammer operating pressure.When the flow is properly adjusted, the pilot pressure may be easily recorded by connecting a pilot pressure gage to the regulated output of the solenoid valve 116-4416 (shown in fig. 11). This pressure may be used to easily check that the hammer flow has not been modified after the installation made by the dealer.Hammer Relief Adjustment
Once the flow has been adjusted, the relief valve needs to be adjusted. To provide standard measurement point, a pressure gage will be mounted at the left hand side ball valve as shown Fig. 12. This will remove the influence of the flowmeter connection to the machine. Those connections are very often made with quick disconnects and these parts usually generate pressure drop that could affect the relief characteristic curve.In order to determine what is the cracking point of the relief pressure, it is recommended to plot the following chart by taking flow at free flow, 50 bars, 60, 70,.. up to the cracking pressure where the pressure gaps need to be reduced to 5 or 3 bars. This is the only right way to determine the right cracking pressure by looking at the slopes of the different segments of the graph. At the cracking pressure, the relief starts to open. This means that the some oil will leak through the drain line affecting the slope of the upper part (almost straight) of the curve (Delta Q/Delta P will change).
Fig.13: Hammer line relief characteristic curve.In the above case, the relief starts to open at 195 bars. At that flow, a very small amount of oil is leaking to the drain of the relief 6C-6746. Most of the oil is still going through the flowmeter. This is called the cracking pressure. This pressure must be slightly higher than the maximum pressure generated by the hammer working under normal conditions. This maximum pressure is usually