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By S. L. Aaroe

"TYRETHANE PRODUCTSTyrethane® is the family brand name which has been adopted by The W. S. Tyler Company of Canada, Limited to identify its polyurethane products. Since we have been manufacturing Woven Wire Cloth for over one hundred years and have been the innovator for most of the product improvements and developments of that industry, it is only natural that our first and primary efforts involve the use of Tyrethane® as a screening medium. The product is ideal for application in the mining industry and other operations where the rate of wear on existing media is exceptionally high.In the event that you have already had some experience with polyurethane it should be poirted cut that there are many grades of the material. The polyurethane used in Tyrethane® Products will be compounded in a variety of chemistries and different heat treatments will be used to develop best mechanical properties to handle specific applications. However Tyrethane® will not be a ""cure all"" but when it is properly applied as a screening medium it will assist by lowering the unit cost for screened materials.Prior to an explanation of the advantages of Tyrethane® let's review the conventional screening media whose applications may be considered as good candidates for replacement by Tyrethane®.1.,Woven Wire Cloth.2.,Perforated metal screens.3.,Rubber faced perforated metal screens.4.,Perforated rubber screens.5.,Cast steel screen segments and weldiments.6.,Profile wire.In most cases a Tyrethane® section is designed for a one for one replacement of the material now being used. It is rarely necessary to modify the screening equipment to enable you to install the Tyrethane® Product although it may be desirable to take some steps to improve the service life of hold down components such as Clamping Strips or Tension Members. Those parts can be encapsulated in polyurethane if necessary.To fabricate the Tyrethane® section we have three basic building blocks. They are: (1) Small molded segments having square or slotted openings, (2) Reinforcing material and (3) the raw liquid polyurethane."

Jan 1, 1976

By Kul Bhushan

This paper presents the results of lateral load tests on 0.61-m to 1.27-m (24 to 50-inch) diameter drilled and cast-in-place piers in San Diego area residual/formational soils. The test piers were installed and tested in the following soils: Decomposed Granitic Rock (Ktd), Stadium Conglomerate (Tst), and Friars Formation (Tf). Lateral loads of up to 845 KN (190 kip) were applied to the piers in residual granitic soils, and loads up to 1780 KN (400 kip) were applied to the piers in Stadium Conglomerate and Friars Formation. The tests were conducted by jacking against adjacent piers and monitoring the lateral load and lateral deflection at the ground line. Test results indicate that ultimate lateral pile capacities of up to 1800 KN (400 kip) can be obtained for 0.61 m (24-inch) drilled piers with penetration of 3 to 6 m (10 to 20 ft) in the residual/formational soils tested. Lateral load analyses using p-y curves for very dense sand significantly overestimate the observed lateral deflections. For lateral load analyses using dense sand p-y curves, p-multipliers that increase the lateral soil stiffness (p-y curves) by 2 to 8 times are required to match the load-deflection behavior measured in the test piles. When applied to the dense sand p-y curves, the p-multipliers provide a more accurate prediction of load-deflection behavior in the residual/formational soils, and can result in shorter required pier penetration and significant savings in foundation cost.

Jan 1, 2002

Discussion of the paper of C. M. YOUNG, presented at the St. Louis meeting, October, 1917, and printed in Bulletin No. 129, September, 1917, pp. 1369 to 1384. CARL SCHOLZ, Chicago, Ill.-Mr. Young was kind enough to' allude to the development of a mine in which I am now engaged. Several months ago the Burlington Railroad decided to open a mine in the field Which they own in Franklin County containing some 15,000 acres .(6070 ha.) of coal, ranging in thickness from 8 to 12 ft. (2 to 3.6 m.). This proposition in itself is attractive to any mining engineer, but with the backing of a large company I saw an opportunity to do some novel work in the construction line, and for several months I have been investigating and working on the problem of developing what I hope will be the largest and best equipped mine in the State of Illinois. The shaft will be sunk at a place where the coal lies at a depth of 600 ft. (182 m.) and conditions both of the surface and of the coal are ideal in every way; the seam is almost level, and we had only 7 ft. (2 m.) of surface clay to go through. We are going to hoist by skips in order to reduce the rope speed. I believe that is a long step in the direction of economy, because we not only double the output of the mine by hoisting the contents of two cars atone time, but we reduce the proportion of dead weight. In our case there will be 20 tons of coal and 18,000 lb. of skip, or 55 per cent. net and 45 per cent. tare. That, of course, necessitates less than half the rope speed for the same tonnage, and we all know that speed means power and power means cost. Skip hoisting permits the use of solid-end gate cars, which is an advantage. The cost of these cars will be in the neighborhood of $250 apiece; They are well built, with roller-bearing wheels of the most up-to-date type, spring draw-bars, and refinements of-that character which are necessary to move the loads most advantageously.

Jan 1, 1918

By Fuming Wang, Xi Chen, Shuai Liu, Changrong Li, Dan Wu, Yaxu Zheng

The effects of B content and austenitizing temperature on hardenability and toughness of Cr–Mo alloy steel have been studied. The results show that the hardenability is deteriorated with increasing B content and austenitizing temperature. With increasing temperature, more and more B containing particles were dissolved in austenite and increase the amount of B atoms segregating at grain boundaries. Moreover, the coarsening grains reduce area of grain boundaries and also increase the amount of B atoms at unit grain boundary, excessive B atoms segregating at grain boundaries promotes precipitation of M2B, which accelerates ferrite nucleation and reduces hardenability. The main elements in M2B phase are Fe, Cr, Mo and B. The B atoms segregating at grain boundaries during austenitizing promote precipitation of M2B during tempering which deteriorate toughness significantly.

Mar 1, 2018

By J. E. Dutrizac

Fracture-exposed surfaces of sphalerite samples having five different solid solution iron contents ranging from 0.0 wt% to 14.8 wt% Fe were leached for 15 to 120 s at 100°C in 0.3 M Fe(S04)1.5 -0.3 M H2S04 media. The reacted samples were examined using X-ray photoelectron spectroscopy (XPS) which provides chemical state information on the first few nanometers of the solid surface. Surface compositions show that the leaching rate increases with increasing solid solution iron content of the sphalerite. Detailed evaluation of high resolution S2p spectra show that the leaching progresses via the formation of polysulphide species. Disulphide species were not detected in any of the experiments. Examination of the Zn2p and Fe2p spectra indicate little change in the chemical states of these elements over the duration of the experiments. Longer leaching times resulted in the generation of elemental sulphur. The ratios of elemental sulphur to dissolved ferrous ions and zinc suggest that less than 5% of the sulphide is oxidized to sulphate. Morphological studies showed that the elemental sulphur commonly formed at a few isolated sites, such as the grain boundaries. Furthermore, euhedral sulphur crystals were often identified. These observations suggest that at least part of the elemental sulphur forms via dissolved sulphide species which are oxidized in solution by ferric sulphate.

Jan 1, 2003

By Lloyd A. Morley

This final report concludes the documentation under Grant G0155003 and details research not covered under foregoing report volumes. The first chapter lists all other reports. The following chapters are divided into three major research tasks: Continuous Safety Monitoring Systems, Battery and Battery-charging Safety, and Mine Power System Transients. The monitoring chapter discusses the prediction of power-system failures. The battery chapter details work on battery-box stresses, battery chargers, and the elimination of electrocutions. The final chapter covers transient instrumentation, distribution transients sources and suppression, and utilization transients on mine power systems.

Jan 1, 1981

Jan 1, 1970

By J. A. C. Fortescue

"Reconnaissance geochemical mapping, based on the chemical analysis of waters, stream, and / or lake sediments had its origin in geochemical prospecting surveys carried out in New Brunswick during the 1950s. More recently, reconnaissance geochemical surveys carried out by government agencies for mineral resource appraisal purposes have been seen as a special case of regional geochemical mapping which is carried out with the aim of describing geochemical patterns f or elements which may he interpreted for mineral resource appraisal, environmental or geological purposes. The interpretation of pal/ ems on regional geochemical maps is based on the concepts of landscape geochemistry, in this paper, the regional approach 10 geochemical mapping is described with reference to an experimental regional geochemical survey which was completed in southwest Ontario during 1981-82. II is concluded, on the basis of data pal/ems for one element only (i.e. arsenic), that the new approach has much potential for solving modern problems in geoscience.""If things don 'I alter they will stay as they are... An old adage.IntroductionDuring the past hundred years topographic, geological, and geophysical maps have been made for all, or nearly all, of Ontario. During the past thirty years these maps have become related as components of what is now called geoscience. Geoscience maps at the regional (i .e. 1 :250,000) scale are often used together to solve general problems in earth science especially in relation to prospecting, or mineral re source appraisal."

Jan 1, 1986

By Allen F. Agnew

Detailed stratigraphic studies in the Wisconsin-Illinois-Iowa district have made it possible to map the folds and faults that controlled the deposition of the zinc-lead ore. Prospecting on the basis of this mapping and prospecting in lower zones that are potentially ore-bearing have led to discoveries of ore. GEOLOGIC studies for the Federal and State governments in the Wisconsin-Illinois-Iowa zinc-lead district were begun in 1835, and subsequent surveys were made in the three states at intervals until 1916, see Table I. The current study of the district, Fig. 1, by the U. S. Geological Survey was begun in 1942 in the hope that a systematic investigation would help increase production of zinc and lead, then in extremely short supply. Major emphasis of the USGS program was on detailed mapping of the geologic structure and ore deposits. Preliminary maps and reports covering localities of intensive mining activity have been published during the course of this study, Fig. 2. By 1950 the objectives of the study by the USGS were revised; 71/2-min quadrangles of relatively unprospected localities as well as intensively mined localities are now being mapped in Wisconsin. Since 1945 the investigation in Wisconsin has been made in cooperation with the Wisconsin Geological and Natural History Survey, and since 1951 the geologic mapping of areas of particular interest in Iowa has been performed in cooperation with the Iowa Geological Survey. At intervals since 1943 the Illinois State Geological Survey has mapped the geologic structure and ore deposits of localities in the Illinois part of the mining district, see Fig. 2. Geology was applied by mining company personnel as early as 1853, but only sporadically, with periods of greater application between 1890 and 1925. Much of the so-called geologic work was in reality mining engineering. Since 1946 the major mining companies in the district have employed geologists who have successfully applied geologic techniques in the search for ore. History of Mining Occurrence of galena in the district was known as early as 1658 or 1659, when French explorers heard of lead mines that were apparently in the vicinity of Dubuque, Iowa. In 1690 a trading post was established near Dubuque to obtain galena. The first significant attempt at mining by white men took place in 1788 when the Indians granted to Julien Dubuque mining rights for 20 miles along the west side of the Mississippi River, including the vicinity of Dubuque, Iowa. By 1805 lead was being mined near Galena, Ill. In 1819 permanent settlement of the region was begun, and most of the important lead-producing areas had been found by 1830, see Fig. 3. Lead production in the Wisconsin-Illinois-Iowa district between 1830 and 1871 far exceeded that of any other district in the U. S.' Smithsonite was first mined in 1859, and sphalerite was mined as early as 1867. After 1873 the production of sphalerite exceeded that of smithsonite. In 1873 annual zinc production from the district first equaled lead production, and from then until 1893 production of zinc and lead was roughly the same. Since 1893 the ratio of zinc to lead mined has generally ranged between 5:l and 20:l. In 1942 the Wisconsin-Illinois-Iowa zinc-lead district ranked 14th among zinc-producing districts of the U. S. From 1946 until February 1953 the dis-

Jan 1, 1956

By J. M. Mutmansky

Procedures for the determination of the operating point that results when a fan is connected to a mine and placed in operation have been a source of confusion for decades. A variety of techniques has been proposed, often to the detriment of the practicing ventilation engineer trying to apply the techniques to the multitudinous mine/fan matching problems encountered in the engineering of mine ventilation systems. This paper proposes some different assumptions and definitions that simplify the solution of problems in determining the operating point. As a result, a set of procedures is provided for determining the operating point of a mine/fan system when the outlet areas of the mine and fan are known. To establish a major simplification in the development of procedures for the determination of the operating point for a mine/fan combination, the authors suggest that the mine pressures be redefined and then used in such a manner that the conservation of energy is ensured. This provides the basis for the recommendation that the fan operating point be determined using the fan total pressure and the system total pressure characteristics. This procedure can be applied to fans in the blower, booster, and exhaust positions equally well and to both single-fan and multiple-fan networks. Another advantage is that the method is applicable to fans with or without an evase.

Jan 1, 1984

By J. Méndez-Nonell

The thermodynamic and chemical properties of SrSO4 and SrS in a gaseous flow of CO and CO2 at high temperature are discussed. The thermodynamic analysis of the system was made using data from the literature. The results obtained from the thermodynamic analysis were experimentally verified using the thermogravimetric technique. The experimental results suggest the formation of a complex compound between SrO and SrSO4. It was also found a change in the chemical mechanism of the process between SrSO4 and CO-CO2 and in the chemical mechanism of the process between SrS and pure CO2.

Jan 1, 1995

By V. S. Sastri, Elboujdaini. M.

"Economics of wear in mining industry and methods by which wear cost may be reduced will be discussed.IntroductionCanada loses more than $5 billion annually due to friction and wear (Table 1). It is estimated that about $1.3 billion, or about 25% of the losses, could be saved through better application of existing technology (Table 2). It should be noted that the costs given in Table 1 and 2 refer to 1986. The losses due to friction and wear and the savings would be much higher in 1996. Tribology combines the many branches and specialties in science and technology concerned with understanding and combatting friction and wear. Specifically, tribology is concerned with the design and manufacture of sliding and rolling bearings, piston rings, gears, cutting tools and other devices in which surfaces interact, in sliding or other relative motion. Tribology is concerned with the correct use of materials for interacting solid surfaces, with the interaction of the surfaces with the lubricants, with the chemistry, physics and use of lubricants. It is concerned with the reduction of friction and wear and the avoidance of associated failures in machinery. Similar tribological components such as bearings are used in different technologies and similar tribological problems such as abrasive wear occur in different industries. Thus, tribology is in itself a generic science and technology, concerned with the generation and dissemination of knowledge on friction, wear and lubrication, and the application of the knowledge, to a wide range of industrial products and equipment, from ploughs to space equipment, from prosthesis to engines, from washing machines to railways, from computers to power stations, from paper mills to mines. Avoidable losses due to friction and"

Jan 1, 1997

By K Kongolo, M K. Kalenga

It is well known that the electrochemical precipitation of metals from aqueous solutions is conducted by the electrochemical standard potential scale. This scale indicates the order of nobility of different metals. Consequently, the standard potential scale shows the nocivity of metals when they are present as impurities in aqueous solutions containing metals. In the hydrometallurgy of cobalt, nickel and zinc are co-deposited during cobalt electrodeposition. Nickel has almost the same chemical, physical and electrochemical properties as cobalt. Furthermore, the electrochemical potential of nickel is relatively higher than that of cobalt. For this reason nickel is preferentially reduced at the cathode in the presence of cobalt. The presence of small amounts of zinc in solution leads to contamination of cobalt electro won. In spite of its lower electrochemical potential in comparison to cobalt, zinc is reduced on the cathode because of its higher hydrogen-overvoltage. But, in the hydrometallurgy of zinc, small amounts of cobalt present into solution will contaminates the zinc reduced at the cathode. This is easily explained by the fact that cobalt is more electropositive than zinc. The co-deposition mechanism of sulphur at the cathode is not yet well understood. Great attention has to be paid to the mechanism of co-deposition of sulphur during cobalt electrolysis..This work aimed to investigate the influence of some parameters on the co-deposition of nickel, zinc and sulphur during cobalt electrowinning. The following parameters have been investigated : Co2+ concentration in the electrolyte, current density and ammonium sulphate (NH4)2SO4 additions. It has been established that important nickel, zinc and sulphur co-deposition takes place at relatively low Co2+ concentration in solution. The behaviour of these elements with regard to the cathodic phenomena has been established.

Jan 1, 2005

By Jamie Delgado, Marco Arelano

The changes of bench angles in an Open pit mine has a strong economical impact in the “mining business”, particularly in its cash flow related both to the decrease as well as to the increase of the global bench angle or the inter-ramp angle. The global vision of bench optimization process currently developed by Compafila Minera Zaldivar (CMZ), includes the interconnection of different processes driving to the completion of the designs. Thus five very influential areas are recognised such as: (1) The physical Surrounding terrain, (2) the strength parameters, (3) the observational model, (4) the acceptability criteria and (5) the operational considerations. One of the important variables affecting this process is Drilling and Blasting (D&B). Increasing the bench angle requires to optimisation of D&B. To achieve this efficiently controlled sub processes must be defined. Three (3) steps can be defined: (a) design parameters, (b) explosive energy distribution and (c) operation results. To control and improve said steps quantitative evaluations of D&B must be performed. One valid evaluation is the “near field vibration monitoring technique” (at bench level). With the application of damage criteria, measurements and modelling of particle velocity a proper definition and optimisation of stages (a), (b) and (c) was achieved, The use of this methodology has enabled to CMZ to successfully increase the inter-ramp angle in three degrees thus obtaining a saving of US$ 36 million in the waste material removed. Also, the efficient control of the bench slopes has resulted in the improvement of the fragmentation operational results. This has resulted in a 26Oh increase in the ore processing by saving energy in the primary crusher due to its performance improvement.

Jan 1, 2001

By X. H. Li, F. Xie, Q. Zhang, Z. H. Shen, S. Mao

"There is abundant rare-earth element(REE) in our country, but it is very fragmented in the earth's crust, and it is very difficult to mining or mining cost is extremely high. There are few of industrial value rare-earth deposits. There is a lot of concomitant rare-earth deposits, and the comprehensive utilization value is high. There is very rich carlin-type gold resource, associated with a certain amount of REE in the southwest of Guizhou province. In order toutilize comprehensively the resources, this paper conducts the study on the occurrence characteristics of REE in the ore. By the chemical analysis, the gold grade is 3.35g/t, the organic carbon 0.81%, the total REE 0.022%, which is a high carbon fine disseminated gold ore. By the optical microscope and XRD analysis, the major minerals are quartz, pyrite, calcite, limonite, arsenopyrite, mica, kaolinite, clay minerals, etc. In addition, there is a large amount of carbonaceous materials, such as organic carbon, graphite, which is harmful on leaching of gold. By the scanning electron microscopy analysis, there are thorium, lanthanum and neodymium, ytterbium, persimmon and other REE in the ore. Gravity separation shows that REE could be enriched to lighter material mainly, which indicates that REE disseminate closely with lighter materials.INTRODUCTION Carlin-type gold ore is important gold resource in the world, which are mainly distributed in Nevada and its vicinity, as well as the two Golden Triangle of Yunnan, Guizhou, Guangxi and Sichuan, Shanxi, Gansu province in China(Su W.C. et al.,2009; Xia G.X.,1996).Guizhou carlin-type gold ore is the second largest gold resource in the world(Muntean J L et al.,2011), distributing along the southwestern margin of the Yangtze plate, mainly mineralizing in the neopaleozoic-early mesozoic(Xie Z J et al.,2017). Many large gold deposits have been found in southwest in Guizhou in twentieth century, such as Zimuyou,Getang, Lannigou, Shuiyindong and Laowanchang gold deposit, and so on, and the gold reserves reach over 100 tons(Xia Y. et al.,2009).There is a certain amount of rare-earth resource in the carlin-type gold ore in the southwest in Guizhou province, and the current researches might mainly focus on characteristics of REE from the angle of geological mineralization(AnanyevY.,2015), not from the angle of separation and enrichment."

Jan 1, 2018

By A. MacG. Robertson

A cone penetrometer has been used to assess the level of stress existing in hydraulically placed mine backill. The test apparatus was fabricated at the mine and consisted of a steel cone, connector rods and a hydraulic jack. Testing was carried out from a manway passing through the centre of the stope. The cone was pushed horizontally into the fill, both at right angles and parallel to the orientation of the stope walls, and the resistance to penetration was measured. Corrections were made to allow for friction along the rods. In a cohesionless sand, such as mine fill, the point resistance should be directly related to the in situ stress. The stresses in mine backfill are due to o the self weight of the fill o convergence of the footwall and hangingwall of the stope. Silo theory was used to estimate that component of the in situ stress due to the self weight of the fill. The difference between the stress predicted by silo theory and the stress estimated from the cone resistance was assumed to be due to convergence of the stope walls.

Jan 1, 1986

By William H. Schiffbauer

The Bureau of Mines is conducting research that is aimed at making the mining industry more efficient in term of both productivity and the health and safety of the worker. As part of this research the Bureau of Mines has integrated a testbed composed of computer and related peripheral hardware to form an intelligent base for performing autonomous mining machine experiments. Although this particular application was con- figured for use on a Joy 16 CM mining machine, its generic structure facilitates its attachment to a variety of mining machine types. The multitasking multiuser computer can be set up for other applications by changing a bubble memory cartridge. The Joy 16 CM implementation includes 96 digital input-output (1-0) ports, 32 analog inputs, 8 analog outputs, 2 serial data channels, and 1 printer port. Operation of the machine can be performed either through a local terminal or remotely through a modem hookup. This report describes a testbed for autonomous mining machine experiments (TAMME)--its hardware, software, and complete system integration--so that it can be used as a foundation for other applications.

Jan 1, 1988

By Charles E. Wait

IT is said by some that the occurrence of a deposit of sulphide of antimony in Southwestern Arkansas has been known for fifteen or twenty years. Whether or not such is the case I am not prepared to say, but I am not able to find any record of such a discovery, or any analysis of antimony ore obtained from that section, published at so early a period. The present discoveries, that seem to be attracting some attention, date back to the winter of 1873-74. At that time a vein of ore was found by Mr. Robert Wolf, in honor of whom the vein was named, and still is called, "the Wolf lode." At the time of the discovery the ore was unknown to the prospector, and its composition was not thoroughly understood in that locality until samples were sent to several analytical chemists, who pronounced it sulphide of antimony-stibnite. Since the discovery of this ore there have been three mines opened, and a number of interesting minerals of the antimonial series have been found. I have had an unusually good opportunity to collect specimens from these mines; and it is owing to the constant inquiry concerning the character of these ores that I have collected for publication the results of quite a number of analyses, sufficient I trust to clearly point out their composition. This is one of the few localities in the United States where antimony ore is found in workable quantities; I say workable quantities, because two different shipments of ore have been made to English reduction works, and in both cases excellent returns were made. The discovery of these deposits will, it is hoped, give rise to a prosperous and remunerative industry at no distant day, and when fully developed they may yield ore in sufficient quantity to supply the regulus for the home demand, thus adding wealth not only to those interested, but also to the State of Arkansas. The three mines are situated in the northern part of Sevier County, and may be reached by the St. Louis, Iron Mountain and Southern Railway to Fulton, thence by wagon-road to Columbus, Nashville, Centre Point, and to the mines. During most seasons of the year the

Jan 1, 1880

By C. J. Toberman

Improvements in fine (28x0) and ultrafine (200x0) coal cleaning is an acknowledged goal with potential benefits in both steam and metallurgical coal markets. This work focuses on adaptation to fine coal flotation of FLOTE, a computer simulation model of the froth flotation process originally developed in the hard minerals field. FLOTE describes the flotation of solids based on particle surface activity, composition, and size. The quasi steady state model was applied to predict flotation performance at an Eastern Kentucky, full scale metallurgical coal preparation plant. Parameter estimation and model testing used detailed flotation test data from a five stage rougher flotation bank. Overall grade/recovery predictions compared well with known plant performance under variation of principally feed grade, plant throughput and reagent addition; however, grade/ recovery predictions for each cell weaken under overloading conditions. Analysis of grade/recovery over a range of sizes is presented. Suggested model improvements and extensions are discussed.

Jan 1, 1984

By John F. Wiss

A series of controlled experiments was conducted at four surface coal mines to study the effects of certain blast parameters upon the ground and air vibration. Preliminary scale-model blasts were conducted at a quarry to provide basic data. It was found that the amplitudes of the ground and air vibration were controlled by the maximum explosive weight per delay. Either cube root or square root scaling could be used for the seismic amplitudes, and cube root scaling could be used for the overpressure amplitudes. Both amplitudes were not significantly affected by the total charge weight per blast, the attitude of the boreholes, or the charge length or diameter. The overpressure amplitudes were affected by the charge depth, the use of cover over surface detonating cord, and the use of adequate stemming. The length of the delay intervals and the spacing of holes were important in determining the potential for reinforcement of the amplitudes in certain directions from the blasts. In downwind directions from the blast, the attenuation of the overpressure with distance decreases. Surface terrain did not significantly affect the overpressure amplitudes within the range investigated. The type of overburden affects the generation of both amplitudes and the propagation of the seismic amplitudes. Spectral analysis of the ground and air vibration is reported. A scaled distance of 300 ft/lb1/3 should produce a peak particle velocity of less than 1 ips and an overpressure of less than 128 dB linear peak. For square root scaling, a scaled distance of 75 ft/ lbl/2 should limit the ground vibration to less than 1 ips.

Jan 1, 1978