Inspection and repair of gas valve of marine diesel engine

Main maintenance technology of valve and valve seat

Before overhauling, measure whether the distance between the bottom surface of the valve and the bottom surface of the cylinder head exceeds the regulations. If this value differs too much, it will affect the compression ratio of the diesel engine and cause the valve and piston to collide, so the valve seat cushion must be replaced. During the maintenance, the following measurements should be made on the gas valve after long-term work: the roundness error and cylindricity error after the valve stem is worn. This error can be obtained by measuring and measuring the outer diameter micrometer. When these two errors exceed the limit of 50% of the clearance gap with the catheter, it should be scrapped and replaced; the radial runout of the outer cylindrical surface of the stem should be no more than 0.003mm. Otherwise, it should be scrapped and replaced. During inspection, place the valve tip between the spindle head and the tail pin of the lathe. The two pin pins are in the original processed valve pin hole of the valve, place the dial indicator on the carriage, and make the contact and air The cone surface is in contact. During one revolution of the valve, the maximum change of the dial indicator reading is radial runout. At this time, the valve is clamped to inspect the valve for cracks, pits, and pits. The outer surface of the valve stem is allowed to have 10 hair lines with a length of not more than 20mm. Magnetic detection and demagnetization should be performed on the conical surface and the connecting lock clamp of the valve stem. Those with cracks should be scrapped.