December 1, 1920 



THE INDIA RUBBER WORLD 



163 



on the end of a dead or stagnant line attached at the proper point 

 in the system which takes care of this point very satisfactorily. 

 It also serves as a liquid seal and insures the exclusion of air. 

 The expansion tank being vented to the atmosphere does not per- 

 mit the building up of high pressure. A number of tests have 

 shown the oil in the expansion tank lo lie about 300 degrees lower 

 than the oil in circulation. 



CIRCULATION OIL 



It is verj' important that the circulating oil used should be care- 

 fully selected. It must have a high flash point and be free from 

 all impurities. Viscosity and specific heat arc also of importance. 

 A number of tests show the specific heat increases with tempera- 

 ture on a straight line, its value being .62 at 550 degrees F. 

 CONSTRUCTION OF PIPE LINES 



The transmitting lines for the circulating fluid are one of the 

 most difficult and expensive features in a system of this kind. 

 Ample provision must be made at all points for the expansion 

 produced, which amounts approximately to 1/32-inch per linear 

 foot. As hot oil of this nature is an exceedingly fugitive material, 

 all castings and pipe joints must be so designed that there is no 

 possibility of leakage. A pipe line constructed in the same man- 

 ner as for steam would be merely a source of expense and trouble. 

 It is practically impossible to use threaded joints above two inches, 

 and sheet packings thus far have proved to be useless for the 

 flanges. .\s the pressure is comparatively small, namely from 10 

 to 20 pounds per square inch, standard weight steel piping is 

 satisfactory. There is no corrosion as the oil actually preserves 

 the pipe. Steel flanges, screwed and welded to the pipe, prevent 

 leakage at that point, and special design metal gaskets take care 

 of the flanges. It is advisable to avoid joints as much as possible, 

 so pipe bends and offsets are substituted for fittings. These parts 

 in addition reduce friction, and vibration caused by cohimn inertia. 



FUEL 



Compounds requiring temperatures that make it necessary to 

 use an oil circulating system generally require also a uniform 

 temperature in the heat applied. For this reason fluid types of 

 fuel are used, and the most satisfactory results are obtained with 

 either oil or gas. 



It is probable, however, in the absence of either of these kinds 

 of fuel that the absorber could be coal fired, and with proper 

 attention make possible the maintenance of reasonably close tem- 

 perature regulation. 



APPLICATIONS 



Installations for fluid heat transmission have been found useful 

 in rubber factories in a variety of lines. Some twenty years 

 ago the India Rubber, Gutta Pcrcha & Telegraph Works at 

 Silvertown, England, installed a complete rubber drying plant, 

 using oil heat. The saving in time over air drying or even steam 

 heated rooms was very great. The only criticism offered by 

 rubber men was that the intense heat softened the rubber too 

 much. As the finished goods did not suffer, this pomt was 

 ignored. 



Following the Silvertown lead, oil heating plants were estab- 

 lished in France, Germany and Russia for drying rubber. One 

 was also planned for an .'\merican factory. Just at this juncture 

 came the vacuum dryer which in compactness, ease of installa- 

 tion and quick results fairly outclassed the oil dryer and handi- 

 capped it in what would have been a very general adoption by 

 rubber manufacturers. 



Nevertheless, the system has a fairly wide use in heating 

 compounds for electric tape, and "dope" for insulated wire, and 

 indeed for a variety of heating in special lines. 

 USED IN "RUBBER ROOFING" 



Here the saturant is maintained as high as 425 degrees F., 

 which is sometimes required. This temperature is easily obtain- 

 able. Due to the uniform temperature the machines can be oper- 

 ated at constant speed, and because of the high saturant tempera- 



tures that can be carried the felt can run through the saturant at 

 ma.ximum speed, thus increasing the hourly production and insur- 

 ing a product of the highest quality and uniformity. 



The hot circulating oil at approximately 475 degrees to 500 de- 

 grees F. can be passed through pipe coils set inside the tanks, 

 which is the general practice in the asphalt field, or through jack- 

 eted tanks if necessary. 



After the felt is saturated, it is allowed to cool and then passed 

 on to the coating machine. The coating is a bitumastic material 

 that flows on the saturated felt at a lower temperature and forms 

 a protective coating, in reality hermetically sealing the prepared 

 felt from the weather. The coating tank temperature ranges from 

 250 degrees to 350 degrees F. 



Both saturating and coating tanks operate from one oil heating 

 system and the temperatures of each are independently controllable 

 by special oil by-pass valves installed at each piece of apparatus. 



The study of the transfer of heat is also very interesting here. 

 The conductance of the film between the pipe coil and the liquid 

 asphalt is about ten B.t.u. per square foot per hour, per degree 

 F. difference and because the conductances of the pipe and the film 

 on the oil side is so high compared to this value, the overall 

 coeflicient is practically ten. 



MANUFACTURE OF MINERAL RUBBER 



In the manufacture of mineral rubber an uncarbonized blend 

 of asphalt heavy oil residue is desired that shall be intimately 

 mixed and of definite melting point. No better system of heat- 

 ing such ingredients has been devised than fluid heat transmission 

 by circulation of the oil in the jacket of a double-walled kettle. 

 INSULATION 



A plant manufacturing rubber-covered electric wire formerly 

 operated on steam and could not maintain above 280 degrees F. 

 in eleven dipping and polishing kettles. They were using 125 

 pounds steam pressure. Today the oil system operates at 14 

 pounds pressure and the required temperature of 325 degrees F. 

 in tanks is uniformly maintained. Production has increased about 

 50 per cent and the quality has been vastly improved. 



POOLING WAGES FOR VOLUME PRODUCTION 

 When it became necessary, a few months ago, to reduce tire 

 production temporarily, owing to the slump in the automobile 

 industry. The B. F. Goodrich Co., Akron, Ohio, laid off about 

 4,000 of the 29,000 operatives employed earlier in the year and 

 began running three-hour shifts five days a week. In an effort 

 to retain as many men as possible, the company decided to adopt 

 a plan which had been used in a small way in one of the mechan- 

 ical goods departments, with the result that the new system has 

 increased output per man and is more satisfactory to both em- 

 ployes and the company. 



The plan provides for "pooled" operations by various depart- 

 ments and payment is made on the basis of a certain volume of 

 production, shared proportionately by the various members of 

 each department. For example, the compounding department 

 is told to deliver a specified amount of various compounds. 

 The department is paid a fixed sum for each ton of compound 

 delivered and the operatives of the department share propor- 

 tionately in this payment. In other words, the men are not 

 paid by the hour or day, nor do they operate on a piece-work 

 basis. It is more or less a matter of volume. If eighty men 

 in one group can deliver as much compound as one hundred 

 men in another group, the members of the first group will re- 

 ceive individually more money than those of the second. This 

 increases personal eflficiency, for the men themselves see to it 

 that no one shirks. At the same time, the company can regu- 

 late production in a more satisfactory manner than heretofore. 



For the first seven months of the calexdah year 1920 

 Belgian exports of rubber to ihc United States were 432 tons, 

 valued $333,300. 



