June i, 1904.] 



THE INDIA RUBBER WORLD 



309 



SCIENTIFIC VULCANIZATION METHODS. 



BY CHARLES J. TAGI.IABUE. 

 I. — PIPING DEFECTS AND REMEDIES. 



THERE are a great variety of helps to the heater man in 

 the way of semi automatic devices, but none of them are 

 effective unless vulcanizer or press is so placed and piped that 

 its skilful handling always results in even cures. And even 

 then the problem is no easy one. And just here it might be well 

 to catalogue a few of the ordinary defects that a steam expert 

 finds in very many rubber factories. 



Overtaxing the capacity of the main steam line is a usual de- 

 fect, and is often supplemented with other faulty piping. 

 Then, too, in many cases a long heater is supplied with steam 

 from one connection, usually at the head. This arrangement 

 does not insure uniform heating, as the end nearest the steam 

 inlet heats quickest, and it is possible to have the heater at the 

 start quite hot at one end, and cold at the other. An attempt 

 to improve on this by running a perforated steam pipe on the 

 inside of the heater tends to equalize the heat, but usually the 

 area of the perforations is not considered, and the steam is not 

 delivered uniformly from end to end. 



All long heaters should be provided with three or four steam 

 inlets suitably spaced to insure rapid and uniform distribution 

 of the heat. Heaters are rarely provided with blow-offs on 

 the upper side, for the release of the air when starting up; 

 consequently air is trapped in the heater, and irregular curing 

 results. The safest and best way is to provide a large exhaust, 

 open it wide when steam is turned on, and, when the steam es- 

 capes in good volume, close it ; this will relieve the heater 

 quickly of air, and cause the steam to circulate rapidly and 

 uniformly. 



Steam with a large amount of water in suspension is not as 

 hot as dry steam, and retards the cure, besides making the 

 goods wet. It should be the aim, therefore, to cure goods in 

 as dry steam as possible. There are three factors in the ac- 

 complishment of this end; namely, dry incoming steam, the 

 rapidity of the circulation, and the quick discharge of the wet 

 steam and condensation. 



When steam is turned into a large heater, the condensation 

 is very rapid ; a fog forms and gradually condenses. This fog 

 and the condensation should be discharged rapidly to equalize 

 the heat so that the goods will be subjected to the same tem- 

 perature for the same length of time ; therefore it is necessary 

 to open the discharge valve wide. No traps, of any kind should 

 be used at first. When the steam leaves the discharge pipe 

 bluish in color, it indicates that the fog has been dispelled, and 

 the discharge valves can then be throttled to permit the water 

 to pass out freely; or at this stage of the curing, a good trap 

 can be used to advantage, and will effect some economy. 



In this connection the matter of piping is very important. 

 Some introduce the steam at the bottom and some at the top ; 

 both methods have merit, but a combination of the two is 

 preferable. Steam entering at the top only, does not rid the 

 heater of air quickly. Steam entering at the bottom only, 

 must pass through the fog, and is deprived of its heat and dry- 

 ness. The best way is to have top and bottom inlets. Turn- 

 ing on the bottom inlets first will force the air out of heater at 

 the top blow-off very rapidly. After heater is thoroughly freed 

 of air, close the bottom inlets and open those on top. The fog 

 being heavier than the dry steam entering from the top inlets, 

 will settle at the bottom and be blown out. Frequently the 

 steam before entering the heater passes through a steam sep- 

 arator, removing the entrained water, and greatly facilitating 

 operations. 



The proper piping of presses and distribution of steam in 

 them is as important as in the case of heaters. The mains and 

 supply lines should be ample, and in case of large belt and 

 packing presses, there should be sufficient steam inlets to in- 

 sure quick and uniform steam distribution. The steam space 

 in a platen though small is nevertheless required to heat a 

 large amount of metal and exposed surfaces. This causes rapid 

 condensation and necessitates careful manipulation of the dis- 

 charge to keep the platens free of water or wet steam. Unless 

 this is attended to very carefully, the lower platens are apt to 

 fill with water and cause the goods to be undercured on one side. 

 As in the case of heaters, when first starting up a press, it is well 

 to open the discharge valve wide, dispensing with a trap, after 

 which the valve can be throttled or trap used. 



The proper application and use of the thermometer also 

 merits careful consideration. The bulb of the thermometer 

 should not project inside of a heater, as it is apt to be struck 

 and broken. It should be held in a special fitting, provided 

 with a vent cock, which should be wide open when the heater is 

 first started, and afterwards throttled so that just sufficient 

 steam escapes to keep up a good circulation around the ther- 

 mometer bulb. In place of the special fitting just mentioned, a 

 nipple and tee can be used with the vent cock or valve screwed 

 in the side outlet of the tee. 



On presses, the thermometer being placed on the side, it is 

 oftentimes impossible to screw them directly into the platen ; 

 hence it is necessary to use the special fitting just mentioned, 

 manipulated in the same way. In many mills a nipple with a 

 coupling is screwed into the top of the heater or side of the 

 press, and the thermometer screwed into coupling ; such a con- 

 dition is a constant source of danger, since the thermometer 

 cannot possibly indicate the true temperature, as the air 

 pockets in the fitting, and steam cannot circulate freely around 

 the bulb, causing the thermometer to read 10 or 20 degrees too 

 low. Another matter of carelessness observable is the fact 

 that thermometers are constantly used having the columns sep- 

 arated — that is, small particles of mercury being lodged in the 

 tube above the main column and no attention is paid to these 

 separations or allowance made for them. They however create 

 a considerable error, and should be corrected as soon as ob- 

 served. The best remedy is to use gas filled thermometers in 

 which the mercury column can never separate. On long heat- 

 ers it is desirable to have two or three thermometers in order 

 to note the temperatures in different parts. A thermometer 

 near the door (if it be the only one) is not well placed, because 

 the radiation of heat by the uncovered door lowers the tem- 

 perature. On long presses, it is equally desirable to have two 

 or three thermometers on both the upper and lower platens. 



Where pressure gages only are used for curing, it is not un- 

 usual to find no two gages indicating alike. This is easily ac- 

 counted for, since it is known that Bourdon springs cannot re- 

 tain their accuracy for any length of time, and require to be 

 constantly tested and adjusted. Such gages are frequently ten 

 points in error. A mercury pressure gage is the only form 

 which is reliable. Steam control of a heater or press should 

 always be done by temperature observation, as it is the heat 

 that effects the cure, and experience has proven that the best 

 results can be obtained when thermometers are employed. 



When gages only are used on a press they are misleading, 

 because, should the platens fill with water, the gage will not in- 

 dicate the fact ; but where thermometers are used such a con- 

 dition can be quickly detected. Recording thermometers or 

 gages are also desirable adjuncts to a heater as they give a rec- 

 ord of the work done, and are a check upon carelessness. 



As previously stated, the hand control of a heater or press is 



