The piston ring sits in a machined grooves in the piston. Clearances are essential to allow movements and thermal expansion of the piston ring. There are two types of clearances checked onboard.
Axial Clearance
It is the clearance between the ring and the groove
Measured using Feeler Gauge in four different points for each ring.
Radial Clearance
The radial clearance is the difference between the groove depth and ring width
Measured using Vernier caliper.
Butt Clearance
It is the clearance between the end butt of the ring inside the liner
To Measure the but clearance, place the ring inside the liner and impression can be taken on a paper by applying Prussian blue pate at the but ends, gap between the impressions measured using scale.
