LO 7-5 Identify and explain the purpose and functions of piston rings, their construction features, and their ring shapes according to ring function

Ring Classification

Three basic types of piston rings are found in all diesel engines: compression, intermediate (a combination of compression and oil control), and oil control Figure 29. Each ring has a unique shape and is made from specialized materials to suit the ring’s particular function Figure 30. The top ring is the compression ring and helps seal gases in the cylinder. This ring is sometimes called the fire ring because it is directly exposed to combustion heat. The second ring is the intermediate ring and has both compression and oil control functions. The third ring is the oil control ring.

FIGURE 07-29: A piston with two compression rings, one intermediate ring and one oil control ring.

FIGURE 07-30: Each piston ring has a unique shape and is made from specialized materials to suit the ring’s purpose.