Check And Repair Valve Lifters And Push Rods Of Diesel Generators

When the diesel generator is running, because the valve lifter of the unit performs both linear motion up and down, and rotational motion, its rod body and spherical surface (or plane) will inevitably wear out naturally. When the valve tappet is in use, although compressive stress is generated under pressure, it is generally not easy to bend and deform due to the thickness and shortness of the rod body. However, due to the long working hours of the generator valve lifters, wear is still inevitable.

1. Common failure forms.

(1) The valve lifter wears due to friction with the guide tube or guide hole (column wear), which increases the fitting clearance.

(2) The surface of the column bottom is worn. Fatigue spalling.

2. Inspection and maintenance.

(1) The fitting clearance between the valve lifter and the guide hole is usually between 0.03-0.01mm and cannot exceed 0.15mm. The rule of thumb is: there should be a little resistance when pushing the tappet to the guide hole with the thumb, and then shake it a little by hand, so as not to feel shaking. If the fitting clearance is greater than 0.10mm, the fitting size can be restored by plating thickening and reaming.

(2) When the bottom surface of the tappet is uneven or the spherical surface has wear marks, it can be ground with a fine emery cloth. Grinding sand or whetstone can also use a grinder to eliminate the unevenness of the plane and restore the original shape.

Check and repair the valve pusher and rocker arm of the diesel generator as follows:

1. The common failure form of diesel generator push rod.

(1) Hit straight with a hammer.

(2) The upper pit and the lower ball are worn, usually repaired by surfacing or replacement.

2. Common failure forms of diesel generator rocker arm.

(1) The rocker arm indenter has been worn into a pit shape.

In general, the impact surface of the valve stem should protrude by 4.2mm, and the minimum value after wear should not be lower than 3.2mm. If it is too low, surfacing and necessary surface heat treatment should be carried out.

(2) The rocker arm hole bushing and shaft are worn.

The rocker hole bushing is generally matched with 0.025~0.065mm. If the wear is too large and the fitting clearance exceeds the limit of use, the shaft should be thickened and chrome-plated, ground to the standard size, and then re-lined. If there is no obvious wear on the journal, and the bushing is greatly worn, replace the bearing bush with a new one without grinding the journal, and then find the appropriate fit gap according to the size of the axle.

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