Doosan DE08TS - Piston assembly; Piston inspection; Piston rings

DE08TS Diesel Engines Maintenance
Piston assembly
1. Disassemby of piston assembly
Disassemble piston according to the disassembly
process.
2. Piston inspection
a. Visual check
Visually check the pistons for cracks, scuff or
wear, paying particular attention to the ring
groove.
b. Clearance between the piston and cylinder
liner
• With an outside micrometer, measure the piston
outside diameter at a point 13mm away from the
lower end of piston skirt in a direction at a right
angle to the piston pin hole.
• Using a cylinder bore gauge, measure cylinder
liner inside diameter at 3 points (cylinder top ring
contacting face, middle, and oil ring contacting
face on BDC) in a direction at an angle of 45°.
Take the mean value with the largest and small-
est values excepted.
• The clearance is computed by subtracting the pis-
ton outside diameter from the cylinder liner inside
diameter. Replace either piston or cylinder liner,
whichever damaged more, if the clearance is
beyond the specified limit.
<Clearance between piston and liner>
3. Piston rings
a. Visual check
Replace the piston rings with new ones if detected
worn or broken when the engine is overhauled.
b. Piston ring gap
• Insert the piston ring into the upper portion of the
cylinder liner bore so that it is held at a right angle
to the cylinder liner wall.
• Measure the piston ring gap with a feeler gauge.
• Replace piston rings with new ones if the gap is
beyond the limit
2
EAMD067I
47
Standard N 110.833 ~ N 110.897 mm
Standard Limit
N 111 ~ N 111.022 mm N 111.122 mm
Standard 0.103~ 0.139 mm
Standard Limit
Top ring 0.40 ~ 0.60 mm 1.5 mm
2nd ring 0.40 ~ 0.60 mm 1.5 mm
Oil ring 0.30 ~ 0.50 mm 1.5 mm