How to inspect precision components of diesel engines?
Precision components and spare parts are expensive and costly in ship diesel engine repair work. Proper maintenance and repair of precision components in diesel engines can not only save costs but also greatly help with the lifespan of moving parts in diesel engines. Here is a brief introduction to how to properly inspect precision components:
1, The main forms of damage in precision components
(1) Plunger sleeve coupling
(2) Excessive wear on the cylindrical mating surface
(3) The working surface of the cylinder is worn, and the surface near the spiral groove of the plunger is particularly severe; The heavily worn part of the sleeve is near the oil hole
(4) Wear increases the fit clearance, reduces the pump oil pressure, causes poor atomization, and insufficient combustion; The degree of wear of the components varies, and the pump oil pressure and injection volume are different, resulting in imbalanced power of each cylinder
Reason: Due to impurities in the oil, small gaps between components, improper oil temperature, sudden changes in oil temperature, inaccurate installation, etc
2, Plunger working surface pitting
Mainly occurring on the working surface near the inclined groove
(1)At the moment when the oil return hole opens, high-pressure fuel rushes out,
(2) When the pressure inside the sleeve drops sharply and the oil pressure at the edge of the spiral groove drops to the corresponding fuel evaporation pressure at that temperature, bubbles are generated; The subsequent fuel pressure wave causes the bubbles to collapse, resulting in pitting corrosion
(3) Pulling marks on the cylindrical mating surface and biting of the mating parts
(4) There are impurities in the fuel, small fitting gaps, improper heat treatment of the mating material, etc., which can cause longitudinal tensile marks on the mating surface, causing the mating parts to jam or bite.
3, Oil outlet valve and valve seat accessories
Function: Pressure storage check and pressure reduction
The main forms of damage to the oil outlet valve and valve seat components are:
(1) Excessive wear on the working surface.
Excessive wear on the guide surface, pressure reducing flange, and sealing cone surface; Excessive wear on the sealing cone surface and inner hole of the valve seat.
Excessive wear on the fitting surface leads to an increase in fitting clearance, an increase in pump oil volume, and incomplete combustion; Excessive wear on the sealing surface leads to a decrease in sealing performance, resulting in high-pressure fuel backflow and a decrease in fuel injection pressure.
(2) The valve is in a normally open state due to occasional jamming, jamming, or inadequate closure of the components.
4. Needle valve and needle valve body accessories
(1) Wear on the cylindrical mating surface of needle valve fittings
The clearance increases, the fuel injection pressure decreases, and the atomization is poor; The different wear of needle valve components in each cylinder results in varying fuel injection rates, which affects the power balance and low load stability of diesel engines
(2) Wear on the fitting surface of the needle valve coupling cone
The cone fitting surface of the needle valve coupling is an important sealing surface. Under normal circumstances, to ensure sealing and quickly cut off fuel, the cone fitting surface should meet the following requirements:
The cone angle θ ′ of the needle valve is 0.5-1 ° larger than the cone angle θ of the seat surface
Cone sealing tape (valve line) width h=0.3-0.5mm
The narrower the annular sealing strip, the better the sealing performance.
Excessive wear on the conical mating surface causes the sealing ring to widen, interrupt or blur, the needle valve position to move downwards, the lift to increase, and the impact is severe, exacerbating the wear and damage of the mating surface.