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Hydraulic excavator technical support
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Terminology Slew [see illustration]
Slew - Swing - Turn - Superstructure rotation - (often confused with the movement of a offset boom)
Fault category
Loss of braking - Poor uphill performance - Slow slew/swing - loss of speed - lacking power - Lubrication loss.
Slew systems for excavators follow similar principles for most excavator manufactures, smaller machines have a motor and transmission [see illustration] combination as the size increase so the transmission and motor are separate components. Larger machines are often equipped with two slew motors and transmission. Today the braking of the slew motion is in effect changing the slew motor to that of a pump, this combined with the fluid being forced over a relief valve brake's & stops the slew motion.
The negative brake will apply after the slew motion is at a standstill maintaining the superstructure position in relation to the undercarriage, the brake requires pressure to release relying on spring force to apply.
A slew transmission leaking lubricant from the bottom seal often indicates an impending slew ring bearing failure.
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