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How to Lubricate Steam Cylinders Plug Pistons Inefficient—Proper Lubrication Eliminates Piston Ring Trouble—Cases Cited—No Danger of Oil in Feed Water LUG pistons and hoods are obso- pis. and inefficient. In the early days of reciprocating steam en- gines, low steam pressures were em- ployed. This low pressure wet steam was not at all efficient as we know steam engine efficiencies today with high pressure superheated steam. Even with the low steam pressures, on some installations, much trouble was expe- rienced with excessive wear and break- age of piston rings particularly in the high pressure cylinders. In order to overcome this trouble many plug pis- tons and hoods were installed in high pressure cylinders to replace piston rings and some are still in use. While the ring trouble was over- come the plug piston did not solve the engineering problem. The fuel con- sumption reflects the tightness of the pistons working in the cylinders, and the plug or hood type cannot be fitted steam tight. While a loosely fitted pis- ton minimizes actual wear it is con- ducive to gross inefficiencies on ac- count of heavy steam leakage. The excessive wear of piston rings with eventual breakage is due in most cases to lack of correct lubrication and some owners and engineers are appar- ently willing to sacrifice maximum op- erating efficiency and economy with the plug piston for groundless fear of getting cylinder oil into the boilers. y= ‘Ti SS Spee ZN 4 \ =X [7 SSSA Ny N NY NJ R A N K cosassant Sissssmssssass mo Se SSL) "Ob 4 Zul ae \ AN SAN ~ ANAS g = 4 ili ddbbddddbidrinpiitisidissids 3 WAAAARAABARRRARAN SSSA TSS ATES bs Lttbddbebbidddbsiididdidiz SS 77 / (pdddhedededdadddddediaddidddhd 7,7 pddddaddadadiadddddc SS sass By O. M. Gordon Under present conditions when every conceivable economy counts there is no place for the wasteful plug piston or hood in any reciprocating engine. Piston rings will give lower fuel con- sumption, but we must consider their service value from the practical oper- ating viewpoint Various Types of Piston Rings There are many types of piston rings all of which are superior to the plug piston from an economy standpoint. In the accompanying illustration Fig. 1 is a cross section of a high pressure valve, valve chest, cylinder and piston. Figs. 2, 3. and 4 are cross sections of different type high pressure piston rings. In Fig. 1 it can be easily visualized what would happen if the piston rings were removed and a hood or plug piston installed that could not possibly be steam tight while traveling in the cylinder. With the piston rings it is also obvious that mechanical friction is set up “as indicated by grunts and groans every stroke of the piston. This frictional noise is also common with plug pistons and hoods, and means loss of power in addition to excessive wear of working parts. It is a matter of universal knowl- edge when metal is rubbed on metal, excessive heat is generated and wear of the metal takes place. The amount of wear is proportional to the actual Fig. 2—Ramsbottom piston packing rings SS s SSS iS Z| KScss EA UN Z \ eee z SYZZZZZZZZZZLALANN REA | EW imma NS TT 3% Z 4 [aac SS SN | oe Oe A, OD / ! Guanrrerit ed | Be ye ae —* a Ys : Baie eid Y 4 tee oe eo) Y TEN Y ates EO" anereoacay hd | YW : Fig. 1—High pressure cylinder with piston valve SS Fig. 3—Piston packing ring with expansion restricted by a shoulder when quill faces pressure forcing the moving pieces to- gether plus the speed and character of materials. To eliminate or minimize the wear of working parts fluid fric- tion must replace mechanical friction and this cannot be done by inject- ing by hand periodically a mixture of graphite and oil, or tallow, through the antiquated tallow cup or hand pump. Lubrication is the science of sepa- rating moving metal parts by introduc- ing and maintaining a suitable film of lubricant between the parts or replac- ing mechanical friction with fluid friction. There are a few marine in- stallations where the steam is so wet no internal lubrication is considered necessary except by swabbing the valve stems and piston rods, but such instal- lations obviously do not operate effi- ciently. Efficient Steam Cylinder Lubrication Swabbing rods and valve stems is not only wasteful of oil but highly in- efficient in other respects.. The cylin- der oil reaching cylinders and valves by this method is not distributed: over the cylinder walls and valve surfaces and most of this oil passes through the engine without actually lubricating, with the result that more swabbing is necessary and much of the oil collects in the filter box or hot well and some ‘(Continued on Page 58) e SS LM Fig. 4—Double type piston ring, with spiral spring to produce expansion steam flow Diagrams to Illustrate Steam Piston Ring Arrangements and Effective Lubrication to Minimize Wear and Trouble MARINE REVIEW—September, 1931 33