PANEL AS 1448341 - Caterpillar

Hammer Line Relief Adjustment:
A relief valve (119-8331 for Single Action, 125-5806 for Combined Circuit), located on top of boom, is protecting the hammer.First, the relief valve needs to be checked. To provide standard measurement point, a gauge pressure will be mounted at the left hand side ball valve. Measurement are shown on Fig 4. This will remove the influence of the flowmeter connection to the machine. The flowmeters are very often hooked 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 steps need to be reduced to 5 or 3 bars. This is the only 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 some oil will leak through the drain line affecting the slope of the upper part (almost straight) of the curve. (DQ/DP will change)
Fig. 4 Hammer line relief characteristic curve
Fig 5: Flowmeter connectionThe relief starts to open at 195 bars. At that flow, a very small amount of oil is leaking to the drain of the relief valve. Most of the oil is still going though 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 30 bars above the average operating pressure specified by the hammer manufacturer. For some hammers, a minimum relief pressure is recommended. This number refers to the cracking pressure of the relief valve. This cracking pressure cannot be too low otherwise the relief valve will open at each hammer cycle (around 600 Hz) and may be quickly damaged. How to adjust the relief valve?Prior to the adjustment, the pressure needs to be measured by closing the flowmeter charge screw on the return line stick ball valve. The pressure measured at the high pressure stick ball valve is this time the full relief pressure. All the oil flow is going in the relief drain line. Depending on the hammer oil flow adjustment, this pressure is usually about 10 to 20 bars above the cracking pressure. In the hammer manufacturer nomenclature, this refers to the maximum allowed relief pressure.After the line relief has been adjusted, the flow must be checked again at the hammer operating pressure to make sure that no flow was leaking in the relief during the flow setting. The pressure can be adjusted from 0 bars to 320 bars to cover the requirements of any hammer available on the market place.The relief valve is presettled ex-factory at 180 bars. Flow adjustment:First step is to adjust main relief valve and the hammer relief valve to a value respectively superior and equal to the hammer