It is necessary to preheat the engine before leaving the small mixer. However, when the mixer truck arrives at the construction site, the upper part of the pumping system must be preheated, otherwise the normal construction will not be possible. What does the main oil pump maintain before and after the mixer is preheated?
The usual way to preheat the mixer truck body is to turn on the body to get power when the engine is running. When the hydraulic pump works passively for a period of time, the hydraulic oil temperature rises to the specified value, the hydraulic oil viscosity reaches the normal working state, and the car body preheating is completed. This accepted preheating operation seems simple, but it is not. If the preheating operation of the mixer car body is carried out in the correct state, the wear and failure rate of the car body hydraulic system can be effectively reduced. On the contrary, incorrect preheating behavior will inevitably increase equipment wear. Next, we will introduce the correct operation method of mixer preheating.
At the early stage of preheating, the main oil pump must keep running dry
There are generally four types of hydraulic pumps in the hydraulic system installed on the concrete mixer, namely, the main oil pump, the balance pressure pump, the mixing pump and the boom pump. From the working principle of the hydraulic pump, except that the mixing pump belongs to the gear pump, the other three pumps belong to the swashplate piston pump. In comparison, the performance of the swashplate piston pump is better than that of the gear pump, with higher precision and higher price. Therefore, more attention should be paid to it.
For mixer trucks with different working principles, the operation method of dry running the main oil pump is different. At present, there are two kinds of common concrete pumping hydraulic systems - open system and closed system. It is not convenient to introduce the principles, differences and characteristics of the two systems here. We only introduce the operation method to keep the swashplate of the main oil pump from tilting according to the principle.
(1) For the concrete mixer with open system, the pumping displacement can be set at "zero" position when the upper power take-off is opened. The setting method may be slightly different according to the brand and service life of the mixer.
(2) For the closed system concrete mixer, the method is relatively simple, that is, when the power take-off of the vehicle body is opened, the pumping stops.
At the later stage of preheating, the main oil pump gradually increases its displacement
During the idling process of the hydraulic pump of the small mixer truck, the bearing, oil distribution plate and other components will inevitably heat up due to motion friction. The heat is gradually transferred to the surrounding hydraulic oil, so that the temperature of the hydraulic oil gradually increases and the viscosity gradually decreases. After a period of time, the swashplate of the hydraulic pump can be adjusted to a small angle change to make the hydraulic oil flow, so as to send the hydraulic oil with higher temperature into the hydraulic circuit. Due to convection and conduction, the oil in the hydraulic motor and pipeline gradually heats up. The preheating will not be completed until the hydraulic oil of the whole pumping system reaches the operating temperature.
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