1. Improper application of maintenance data of self feeding mixer
In the maintenance of self loading mixer, it is an important reason that the maintenance data can not be selected scientifically. For example, the width of the contact surface between the valve and the valve seat is specified as 1-2.2mm for the inlet valve and 1.5-2.5mm for the exhaust valve. However, in the actual maintenance, many people think that it is better to be wider than narrow, and they are used to choosing the upper limit or close to the upper limit value, because the width of the working face of the newly repaired valve is close to the service limit. Another example is the valve foot clearance, which is generally 0.2-0.25 mm. However, in maintenance and adjustment, it is considered that a larger clearance is better than a smaller one. Therefore, if the valve foot clearance is used beyond the upper limit, it will not only reduce the engine power, but also cause knocking noise and early damage.
2. Smooth grinding of valve
In the maintenance of the self feeding mixer, if the valve is ablated, pitted and sunken, it should be polished. Generally, it is carried out on the polishing mill. Four problems should be paid attention to during the operation: first, ensure that the valve head is concentric with the rod, otherwise, straighten it first; second, the smaller the smooth grinding vehicle can grind out the complete conical surface, the smaller the better; the third is to improve the surface finish as much as possible; the fourth is to ensure that the valve head is concentric with the rod, otherwise it should be straightened first The depression at the end of the valve stem should be ground smooth.
3. Hinge pin of valve guide
Since the loading mixer, the fit clearance between the valve stem and the valve guide is the key to determine the service life of the valve guide. Therefore, when replacing a new valve guide, the fit clearance should be strictly controlled when the pin is hinged, and the lower limit of the clearance specified for each mixer model can effectively prolong the service life.
4. Grinding of valve
Since the loading mixer, the grinding of valve can be divided into two situations: one is that there are only slight pitting between the valve and the valve seat, which does not need to be polished and reamed; the other is that both the valve and the valve seat are polished and grinded after hinge pin. The former is first ground with full gold steel sand, after grinding off the pitting points, then grinding with fine emery, and then coated with oil for grinding until the sealing meets the requirements and the width meets the requirements. The latter can only be ground when the sealing performance can not meet the requirements. However, attention must be paid during operation, and it is strictly forbidden to knock the valve up and down, otherwise concave sand marks will appear, which will affect the maintenance quality. Concrete mixer engine failure is not terrible, terrible is that the maintenance is not correct, the performance of the engine will only get worse and worse.
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