Machinery Lubrication magazine published by Noria Corporation
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Figure 2. The sequence of piston ring-pack deposit formation ML PUBLISHER Mike Ramsey - mramsey@noria.com GROUP PUBLISHER Brett O'Kelley - bokelley@noria.com EDITOR-IN-CHIEF Jason Sowards - jsowards@noria.com SENIOR EDITOR Jim Fitch - jfitch@noria.com TECHNICAL WRITERS Jeremy Wright - jwright@noria.com Wes Cash - wcash@noria.com Alejandro Meza - ameza@noria.com Bennett Fitch - bfitch@noria.com Michael Brown - mbrown@noria.com Garrett Bapp - gbapp@noria.com CREATIVE DIRECTOR Ryan Kiker - rkiker@noria.com GRAPHIC ARTISTS Patrick Clark - pclark@noria.com Terry Kellam - tkellam@noria.com Josh Couch - jcouch@noria.com Greg Rex - grex@noria.com ADVERTISING SALES Tim Davidson - tdavidson@noria.com 800-597-5460, ext. 224 MEDIA PRODUCTION MANAGER Ally Katz - akatz@noria.com CORRESPONDENCE You may address articles, case studies, special requests and other correspondence to: Editor-in-chief MACHINERY LUBRICATION Noria Corporation 1328 E. 43rd Court • Tulsa, Oklahoma 74105 Phone: 918-749-1400 Fax: 918-746-0925 Email address: jsowards@noria.com MACHINERY LUBRICATION Volume 16 - Issue 1 January-February 2016 ( USPS 021-695) is published bimonthly by Noria Corporation, 1328 E. 43rd Court, Tulsa, OK 74105-4124. 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Noria shall not be liable for any inju - ries, loss of profits, business, goodwill, data, interruption of business, nor for incidental or consequential merchantability or fitness of purpose, or damages related to the use of information or recommendations provided. Machinery Lubrication 5 caused by valve guide wear and seals that are worn, cracked, missing, broken or improperly installed. The engine may still have good compression but will burn a lot of oil. Oil Flow Through the Piston Ring-pack Engine oil is designed to produce an oil film on the cylinder walls. While the oil control ring on the piston squeegees much of it off, a thin film will still remain. When the engine decelerates, high negative pressures suck oil in the combus- tion chamber and out the exhaust manifold. The problem is more pronounced when rings or cylinders are badly worn or damaged, but it can also occur if the cylinders were not honed properly (out-of-round or surface finish defects) when the engine was built (or rebuilt) or if the rings were installed improperly. Much of the oil that is transported through the piston ring-pack and along the liner usually occurs during the compression stroke. The oil control ring scrapes the oil from the cylinder wall. The scraped oil flows to the ring drain holes/cavities. Oil left behind on the cylinder wall is needed to lubricate the compression rings. Once oil moves past the compression rings, it is difficult for the oil to return to the sump. However, blow-by gases can provide a transport medium to help recycle the oil back to the sump (see Figure 1). Piston Ring-pack Deposits and Movement Piston ring-pack deposits can sharply reduce ring movement and flexing. Likewise, ring move- ment can greatly influence where deposits form and the lubricant motion (transport) within the ring-pack. This ring motion defines the resi- dence time of the lubricant in the ring-pack, which in turn affects the rate of lubricant degra- dation and where deposits will form (see Figure 2). Ring-pack temperatures can range from 195-340 degrees C. Collectively, these conditions can accelerate piston-ring-liner (PRL) wear, impair combustion efficiency, increase blow-by and reduce oil economy (more oil consumption). One way this happens is through carbon jacking. In this phenomenon, carbon buildup occurs in the ring grooves (fed by soot and oil degradation prod- ucts). The corresponding ring movement restriction increases wear, blow-by and oil consumption with the rhythm of the piston. Cylinder Wall Oil Evaporation As much as 17 percent of total oil consump- tion is associated with liner wall evaporation. The more distorted (out-of-round) and rough (surface finish) the cylinder liner, the more oil film that will remain on the liner after the power stroke. High liner surface temperatures (80-300 degrees C) will cause a loss of this oil by misting and evaporation. Light oil molecules are more prone to evaporation. These light molecules are the first to deplete, and as a result, there is less evaporative loss toward the end of the lubri- cant's service interval. Not all oils of the same viscosity are equal from the standpoint of volatility (risk of evapo- rative loss). Some lubricants may exhibit as much as a 50-percent greater loss from vola- tility than others. This is influenced by the base Oil Thermal-oxidative degradation Volatiles (evaporation) Deposits