Valve Seat of Diesel Generator Set Valve Group

Valve seat is one of the components of diesel generator set. It is a circular surface machined on the cylinder block or cylinder head. The valve cone is sealed or seated on the valve seat, which provides a sealing surface for the intake and exhaust valves to prevent gas leakage. The valve seat can also help dissipate the heat accumulated on the valve.

Types of valve seats

 

There are two types of valve seats: integrated and embedded.

 

Similar to valve guides, the integrated valve seat serves as the cylinder head

 

Part of it is directly cast; The embedded valve seat uses a metal ring as the valve seat, which is pressed into the cylinder body and needs to be ground to the correct angle. Engines with aluminum cylinder heads typically use embedded valve seats. Inlaid valve seats can be made of cast iron, hardened cast iron, high chromium steel, and tungsten chromium cobalt alloy (very hard steel).

 

To ensure the normal operation of the diesel generator set, the valve seat should be ground to a specified angle, such as 30 ° or 45 °, and there is usually an interference angle when grinding the valve. By grinding the angle of the valve cone surface to be about 1 ° smaller than the angle of the valve seat, the interference angle can be obtained.

 

For example, grind the valve to 44 ° and the valve seat to 45 °. The existence of interference angle enables the valve to cut through the deposits on the valve seat when seated, and also produces better mechanical sealing performance. As the engine runs and the valve seats wear, the interference angle will gradually disappear. The result is a good linear contact, which is conducive to transferring excessive heat from the valve and also helps the valve to seat faster into the cylinder head.

 

Replace the valve seat ring

 

The main function of the valve seat ring is to seal the valve and withstand high-speed impacts. For diesel generator sets, when the valve seat ring of the diesel generator set becomes loose, broken, burned, or deeply worn, it needs to be replaced with a new seat ring. The replacement steps are as follows:

 

1. Remove the old valve seat ring.

 

Use flat pliers to chisel off the loose and broken valve seat ring, and then clamp it out with pliers. For valve seat rings that are firmly embedded, a steel bar can be moved and welded to the inner opening of the valve seat ring. An extended old valve stem can be extended from the guide hole to knock out the valve seat ring.

 

2. Clean the surface of the seat ring hole stopper. Remove metal shavings, oxide scales, and other foreign objects from the valve seat ring hole stopper, and check if the geometric shape of the stopper is regular. If the force around the seat ring is too strong and the closing of the chamber seat ring hole is too large when using the original seat ring, a scraper can be used to scrape off a small amount around the seat ring hole to press in the new seat. It is necessary to ensure that the mating surface between the seat hole and the seat ring is complete, smooth, and free of foreign objects.

 

3. Cold shrink valve seat ring. Place the new valve seat ring in liquid oxygen and cool for 10 minutes. Use sharp nose pliers to remove it and place it in the seat hole stopper, align it, insert a special tool and press it in. The seat ring should be firmly pressed to the bottom and tightly fitted with the seat hole.

 

4. Use a flat chisel with an arc-shaped blade to firmly fix the seat ring hole along the circumference, close it, and squeeze the seat ring. Grind the valve seat ring.

 

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