TECHNOLOGY
Compressor Design Holds Maintenance Down Spring-loaded compression rings mean longer ring life for nonlubricated reciprocating compressors With application of nonlubricated reciprocating compressors in the chemical process industries on the rise, one approach to keeping maintenance low that chemical process firms might well consider comes from Joy Mfg. The company's T-Block construction for nonlubricated compressors holds promise of cutting the number of shutdowns usually required for replacing compression rings. With the chemical process industries market for nonlubricated compressors increasing, Joy, as well as other compressor manufacturers, are looking at this market segment with more than usual interest, and Joy, for one, is getting set to push for increased sales in this area. The Pittsburgh firm is banking on the advantages of its TBlock design to make inroads here, credits this design for most of its rise in nonlube sales to other industries. For example, Joy points out that its nonlubes now account for about 50% of its reciprocating compressor sales. In the chemical process industries,
sales of nonlubes will probably account for 15 to 20% of an estimated $80 million these companies will spend on reciprocating compressors in 1963. Joy says its T-Block piston overcomes many of the limitations of conventional designs. Main features of the T-Block are that the piston is centered in the cylinder bore at all times and that compression rings can wear a half inch before replacement. T-Block piston rings are generally made of carbon or glass-impregnated Teflon. The rings are fitted together from four sections which interlock to form a circle. Each of these sections is spring loaded against the cylinder wall by four expander plungers which not only press the ring against the wall but in turn support the piston. As the four ring segments wear, the combination of spring and gas pressure causes them to expand by riding-out on each other so that no gap develops in the ring. Since the ring always fits snugly against the cylinder wall, the output
efficiency of the compressor remains constant over the life of the rings. The 1 / 2 inch of ring wear means longer ring life and fewer shutdown periods. T-Block compressors have operated for more than 30,000 hr. on one set of compression and wear rings, according to Joy, compared to 8000 hr. for conventional rings. The four spring-loaded expander plungers also center the piston in the cylinder. This eliminates the problem of piston hop and reduces the possibility of metal-to-metal contact between the piston and cylinder, Joy claims. Eliminates Gas-Leak. The "gapless" feature of the "T"-Block also has plus values in addition to maintaining compressor output efficiency constant over the life of the rings. Blowby or leakage of compressed gases back into the suction side of the piston is eliminated. Blowby causes erosion of parts and kiting or climbing compressor temperatures. And excessive temperature is the culprit responsible for early
INSTALLED. Joy Mfg. Co., Michigan City, Ind., uses a ring compressor to install its T-Block piston rings in a compressor. T-Block rings reduce maintenance in reciprocating compressors, keeping compressor efficiency high throughout life of compression rings
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§ny@®iw UCARSIL Metal Protectants Achieve Outstanding Results Union Carbide's m i c r o - t h i n s i l i c o n e metal protectants are making significant contributions to industry. Easily a p p l i e d and c o l o r l e s s , new UCARSIL Metal Protectants form a continuous pinhole-free film, only 0.1 mil thin, that effectively resists corrosion. They form the strongest film-to-metal bond yet observed. Additional benefits include unusual flexibility, thermal stability, and resistance to impact and underfilm corrosion. Sylvania Electric Products Inc., for example, used Union Carbide's silicone metal protectants on the copper and aluminum waveguides for two 60-foot parabolic antenna complexes, part of the U.S. Army's ADVENT system for communicating by synchronous satellites. Employing microwave frequencies, this system will be capable of handling more than 100 voice messages and several
thousand teletype signals simultaneously. At the heart of the ground electronic system are waveguides, which enable engineers to conduct microwave frequencies. And it is here that Sylvania uses UCARSIL R-101 Protectant to prevent metal corrosion. Corrosion products on untreated waveguides caused power losses. Because silicone protected metal remains free of tarnish and corrosion, the waveguides retain high efficiency in the piping of microwaves. In applying the micro-thin pinhole-free protectant, Sylvania plugged up one end of a waveguide, poured in R-101, plugged the other end, and swished. Excess R-101 went back in a bottle for future use. Of course, UCARSIL Metal Protectants can also be applied by spraying, dipping and brushing.
and general applications is available from your Silicones Man. See him soon! And in the meantime, complete and mail the coupon below.
UNION CARBIDE WINS 1963 ANNUAL COPPER AND BRASS ACHIEVEMENT AWARD The I n d u s t r i a l Achievement Award of the Copper and Brass Research Ass o c i a t i o n was r e cently presented to Union Carbide for the development of these silicone metal protectants, cited as the year's outstanding contribution to advancing the use of copper, brass, bronze, and other copperbase alloys.
UCARSIL Metal Protectants are economical to use, offering positive protection for one or two pennies per square foot. Other possible uses are on printed circuits, tubes and similar electronic gear. As the originator of these protectants, and the leading innovator in silicone technology, Union Carbide is constantly developing new products to do a better job. Information on silicones for metals
UNION CARBIDE
lye U N I O N C A R B I D E and U C A R S I L are registered
trade marks of Union Carbide Corporation.
Silicones Division Union Carbide Corporation Dept. 3G25-1303, 30-20 Thomson Ave. Long Island City 1, New York In Canada: Union Carbide Canada, Ltd. Bakélite Division, Toronto 12. Please send me data on
NAME_ TITLE_ COMPANY. ADDRESS_ CITY_ STATE_
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WHAT'S NEW IN V I N Y L S Carboxylated polyvinyl a c e t a t e copolymer RESYN® 2 8 - 1 3 0 0 A resin in bead form with solubility and adhesion properties to excite any chemist interested in pigment binding, protective coatings, tex tile finishes, adhesives—
SEGMENTED. The rings are fitted from four sections which interlock to form a circle. Each section is spring-loaded by four expander plungers to press the ring against the wall and support the piston. As they wear, the sections rideout on each other so that no gap develops in the ring
• Soluble in a wide variety of solvents such as alcohols, esters, ketones, chlorinated hydrocarbons. • Soluble in dilute aque ous alkali. Varying amounts of alkali lets you change resin's solubility, flexibility and tacki ness. • Product can be made both solvent and water-soluble. Provides advantages of fastdry solvent system with watersoluble polymer. 9 Films of c o n t r o l l e d s o l u b i l i t y can be c a s t f r o m solution —ranging from waterresistant to water-soluble. • Product has outstand ing adhesion to variety of sur faces. APPLICATIONS H e r e ' s w h e r e R E S Y N 28-1300 seems likely to be most interest ing: Wash-Off Coatings for t e m porary protection of construction materials, autos, etc. · Pigment Binder · Textile Sizes · Emulsifier Protective Colloid · GreaseResistant Coatings * Repulpable Adhesives · Thickener · Casein Modifier · Cement Mortar Admix W a n t a closer look at Resyn 28-1300? For c o m p l e t e i n f o r m a tion, write N A T I O N A L — your p r i m e s o u r c e f o r vinyl a c e t a t e polymers and copolymers.
RESINS NATIONAL STARCH and CHEMICAL CORPORATION 7 5 0 Third Avenue, New York 1 7 ( D e p t . C)
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failures; including valves in many cases. Other advantages to T-Block con struction are: • Ring wear can be measured with out removing the piston by sighting into the cylinder bore and measuring the arc lengths of the four segments. • The wear or bull ring in T-Block compressors is a fail-safe feature since the piston is constantly centered by the four spring-loaded expander plungers. Nine U.S. firms manufacture nonlubricated reciprocating compressors in a wide range of sizes for the CPI. Major manufacturers are Chicago Pneumatic Tool Co., Clark Division of Dresser Industries, Cooper-Bessemer, Gardner-Denver, Ingersoll-Rand, Joy, Nor walk, Pennsylvania Pump and Compressor, and Worthington Corp. Design improvements over the years and the advent of Teflon compression rings have combined to erase much of the hesitancy on the part of design engineers to use nonlubricated recips. Even so, the higher capital investment and maintenance costs for nonlube recips tend to limit their use in the CPI to installations where it is essential that compressed gases contain no oil. New CPI Uses. Nonlubes have long been used in instrument air service to eliminate the problem of plugged ori fices in pneumatic instruments. To day, the CPI uses nonlubes for a variety of jobs such as compressing oxygen, chlorine, acetylene, hydro gen, butadiene, ethylene, and vinyl chloride. Nonlube recips are also called for in cases where oil may poison catalyst beds. Major criticism of nonlubricated recips are their higher initial cost and
maintenance requirements. Nonlubes cost about 2 5 % more than lubricated compressors of comparable size. Maintenance costs vary, depending upon speed and load on the pump and the cleanliness of gases being com pressed. But maintenance engineers have learned to expect repairs for non lubes to run 20 to 100% more than for lubricated compressors on the average. Most nonlubes made today are of the reciprocating type. Rapid wear of compression rings is a nagging problem. Attrition of the rings can cause metal contact between the piston and cylinder wall and ex tensive damage to the compressor. Manufacturers have found a number of ways to solve this problem in recent years. Improved graphite and Teflon ring materials have helped greatly. Another technique almost universally used by the industry is to place a wide ring of graphite or Teflon between the compression rings. This rider or wear ring, since it is wider, wears more slowly than the compression rings. Free-Floating Pistons. Another technique used by compressor manu facturers, especially in the large (over 24-in.) compressors, is free-floating piston construction. Free-floating pis tons use an assembly that keeps the piston centered in the cylinder regard less of ring wear. Nonlubricated reciprocating com pressor manufacturers are hard pressed to meet the demands for higher pres sure operation being made by the process industries. All manufactur ers say they are constantly working to increase compressor pressures. Cooper-Bessemer says it has developed commercial nonlube recips capable of developing pressures to 5000 p.s.i.
