Preheating Techniques for Small Pump Trucks

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.