The V-type concrete mixer is refitted on the chassis of a general truck, and a flywheel power take-off is reserved. The mixing device mostly uses the power take-off transmission shaft to drive the hydraulic pump, and the mixing device provides power. The hydraulic system of mixing device generally adopts closed system. When the vehicle is started, if the power takeoff and the engine flywheel are engaged, the hydraulic pump will rotate with it. Under the condition of high viscosity of hydraulic oil, if the hydraulic pump is under load, it will have difficulty in oil absorption, or even "empty suction", and the hydraulic pump will be excessively worn due to poor lubrication. At the same time, the hydraulic motor and drum reducer will also operate passively under the condition of poor lubrication, resulting in serious wear. This is the fundamental reason why the mixing device must be preheated.

小型混凝土搅拌车液压系统的输出转矩和功率与负载有关，液压泵排量越大，混凝土罐体总质量越大，所形成的阻力也越大。若启动时，搅拌筒操作手柄未置于空挡位置，则启动阻力较大，该阻力将会造成发动机马达启动困难，耗费更多的电能，也可能造成启动马达过早损坏。

The output torque and power of the hydraulic system of small concrete mixer are related to the load. The larger the displacement of the hydraulic pump, the greater the total mass of the concrete tank and the greater the resistance. If the operating handle of the mixing drum is not in the neutral position during startup, the starting resistance is large, which will make it difficult to start the engine motor, consume more electric energy, and may also cause premature damage to the starting motor.

在罐体静止状态下启动发动机时，飞轮取力器依然带动取力器传动轴和液压泵转动，增加的启动负荷只是取力器传动轴和液压泵的空转阻力，这个阻力与整个转罐传动系统的阻力相比明显降低了很多，所以液压泵柱塞体和柱塞的磨损可以降低到较低程度。而且，由于液压泵不作功，液压马达和转罐减速机也就不工作，所以也不会形成磨损。因此，在罐体静止状态下启动发动机，是所有小型混凝土搅拌车降低发动机启动负荷的较佳方法。在罐体静止状态下启动发动机，能使整个转罐系统在磨损降低的同时，将液压油的温度逐渐升高，黏度逐渐降低。

When the engine is started under the static state of the can body, the flywheel power takeoff still drives the power takeoff transmission shaft and hydraulic pump to rotate. The increased starting load is only the idling resistance of the power takeoff transmission shaft and hydraulic pump. This resistance is significantly reduced compared with the resistance of the whole can transmission system, so the wear of the plunger body and plunger of the hydraulic pump can be reduced to a low degree. Moreover, since the hydraulic pump does not work, the hydraulic motor and drum reducer will not work, so wear will not be formed. Therefore, starting the engine in the static state of the tank is a better method for all small concrete mixer trucks to reduce the starting load of the engine. Starting the engine when the tank is stationary can make the whole can system gradually increase the temperature of the hydraulic oil and reduce the viscosity while reducing the wear.

液压泵空转一段时间之后，可以让罐体缓慢转动，给液压马达和管路中的油液进行预热。同时，转罐减速机也开始自我预热。直到整个转罐系统的油液都达到工作温度，预热工作即结束需要特别提出的是，搅拌装置预热期间严禁过早、过快提高发动机转速。应在启动后低速运转10min后，再加载运转。具体的发动机转速和预热时间控制，要根据环境温度和小型混凝土搅拌车状况因地制宜。一般说来，环境温度越低，空载预热的时间应越长。同时须注意，预热操作程序不可以违背设备使用说明书的相关规定。

After the hydraulic pump idles for a period of time, the tank can rotate slowly to preheat the oil in the hydraulic motor and pipeline. At the same time, the drum reducer also starts self preheating. Until the oil of the whole drum system reaches the working temperature, the preheating work is over. It should be specially pointed out that it is strictly prohibited to increase the engine speed too early and too fast during the preheating of the mixing device. It shall be loaded for operation after running at low speed for 10min after startup. The specific engine speed and preheating time shall be controlled according to the ambient temperature and the condition of small concrete mixer truck. Generally speaking, the lower the ambient temperature, the longer the no-load preheating time should be. At the same time, it must be noted that the preheating operation procedure must not violate the relevant provisions of the equipment operation manual.