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MDE-4334C Atlas Start-up and Service Manual · April 2008
Hydraulic/Mechanical Components
Pumping Unit
Servicing the Rotor and Shaft Assembly
The rotor and shaft assembly is the heart of the pumping unit. It creates the flow and pressure
supplied by the pump.
Figure 7-29: Rotor and Shaft Assembly
• Wear eye protection. Residual pressure and entrapped fuel may still be present
and may drain or spray while removing parts.
• Fire and explosion could result in severe injury or death.
• Test and close the shear valves involved. Shut off power to the unit.
• Remove parts slowly. Collect fuel in approved containers.
• Clean up all spills promptly.
WARNING
Service Tips
• The normal failure mode for pumping elements is excessive wear. Occasionally, a seizure
in the bore can result. Wear/seizure can result in either lower or very low flow, or less
commonly motor stalling, and very occasionally noise.
• If the pumping elements appear with minimal wear and the symptom is noise or low flow,
usually there is an installation issue starving the pump or an issue with the Bypass/PRV,
Control Valve, or a component downstream.
• Avoid introducing contamination into the unit while inspecting or replacing pumping
elements, including the rotor and shaft. Always use the strainer provided and ensure that it
is not clogged.
• Some pumping elements have grooves in the blades manufactured, on purpose. While
replacing blades, always install new blades in the same orientation.
• A shot of clean oil in the bore after replacing the pumping elements will aid in priming and
initial start-up.
• Excessive belt tension may cause failure of the pumping elements or bearings.
