1. Principle of Gradual Increase in Main Pump Displacement: During the no-load operation of the hydraulic pump,
components such as bearings and distributor plates inevitably generate heat due to friction. This heat is gradually
transferred to the surrounding hydraulic oil, causing the hydraulic oil temperature to gradually rise and the viscosity
to gradually decrease. After a period of time, a small angle change can be made to the hydraulic pump swashplate
to allow the hydraulic oil to flow, thereby delivering the hotter hydraulic oil to the hydraulic circuit. The oil in the
hydraulic motor and pipelines gradually heats up due to convection and conduction. The preheating process is
completed when the hydraulic oil in the entire pumping system reaches its operating temperature.
2. Operation Method of Gradual Increase in Main Pump Displacement: Due to the difference between open and
closed systems, the operation method of gradually increasing the displacement of the main pump is also divided
into two types.
(1) For concrete pump trucks with open systems, the pumping displacement is gradually increased from "zero".
At this time, the directional valve starts to work, and the hydraulic oil after the directional valve flows back to the
oil tank, causing the oil temperature of the entire pumping hydraulic system to gradually rise. The displacement
increase must be gradual, and each displacement level should be maintained for at least 2-3 minutes until the
normal pumping displacement is reached. The entire process takes approximately 15-20 minutes.
(2) For small pump trucks with closed systems, start pumping at the lowest displacement setting. Maintain for
5-8 minutes, and then directly set to the normal pumping displacement.