534 



THE INDIA RUBBER WORLD 



[July 1, 1916. 



Cooling Calender and Mill Rolls by Refrigeration. 



THE question of keeping the rolls of calenders and mixers 

 at the proper temperature is not a difficult matter during 

 the greater part of the year. But in the summer during 

 protracted periods of hot weather, river or pond water becomes 

 too warm for cooling purposes. 



Many years ago Frank A. Magowan, then at the heyday of 

 his meteoric rubber career, installed a water tank for cooling 

 calender rolls, and chilled the water with ice during the heated 

 term. It was expensive and crude, but undoubtedly pointed the 

 way to the present practice, that of installing. small refrigerat- 

 ing plants for the same purpose. Several rubber factories have 

 recently installed water cooling plants, which makes the follow- 

 ing description of the De La Vergne plant most timely. 



The refrigerating equipment required for this purpose is quite 

 simple and is used to cool water which is circulated through 

 pipes to the rolls of the mixers 

 and calenders. The water 

 cooling expansion coils con- 

 sist of vertical pipe sections, 

 each provided with a water 

 distributing apparatus at the 

 top. The water is pumped to 

 this distributing apparatus from 

 which it flows down over the 

 outside of the vertical coils. 

 Liquid ammonia is admitted 

 at the bottom of these coils 

 through expansion valves and 

 expands upward, evaporating 

 from the liquid state into gas. 

 At the top it is drawn into 

 the suction line back to an 

 ammonia compressor. This 

 compresses this gas to a 

 pressure consistent with the 

 temperature of the cooling 



water flowing over the ammonia condensers, in which the gas 

 is turned to the liquid state. It then passes to the liquid ammonia 

 tank and from there to the expansion valves to expand again 

 from the liquid state to gas. In thus changing from liquid to 

 gas, the ammonia absorbs heat from the water and the tempera- 

 ture is therefore reduced. 



The ammonia condenser usually consists of vertical coils sim- 

 ilar to the water coolers mentioned. The cooling water flows 

 on the coils at the top and down the outside, while the hot 

 ammonia gas enters at the bottom and flows upward. Through 

 several outlets in these coils, the liquid ammonia as it con- 

 denses is drawn off and passes to the liquid ammonia tank. It 

 is desirable to obtain cooling water for the condensers at as 

 low a temperature as possible, since the cooler the water, the 

 lower the condensing pressure and a correspondingly less amount 

 of power is required to drive the compressor. 



The size of the refrigerating equipment required is determined 

 by the amount of water to be cooled, the range through which 

 it must be cooled and the final temperature. For instance, it 

 might be required to cool 200 gallons of water per minute from 

 110 degrees to SO degrees. The amount of refrigeration re- 

 quired would be determined as follows: 

 200 X 8.33 x 60 



The De La Vergne Refrig 



The final temperature of water being 50 degrees, the tempera- 

 ture of the ammonia would need to be a few degrees less than 

 this, say 45 degrees. The suction ammonia pressure correspond- 

 ing to 45 degrees would be about 65 pounds. Therefore, the 

 ammonia compressor would operate between 65 pounds suction 

 pressure and about 175 pounds condenser pressure, assuming 

 that the water flowing over the ammonia condensers had an 

 initial temperature of 75 degrees. Most refrigerating machines 

 are rated on the basis of 15 pounds suction pressure, therefore 

 to determine the proper size machine at this rating, we would 

 500 x 30 



figure ; = 190 tons at 15 pounds suction pressure 



80 

 since the tonnage varies almost directly as the absolute suction 

 pressure. This machine would have ample capacity. 



By means of the refrigerating 

 machine, the operator has abso- 

 lute control over the water tem- 

 peratures. At certain seasons 

 of the year when atmospheric 

 conditions are favorable for 

 low temperatures, the refriger- 

 ating machine can be slowed 

 down and the proper tempera- 

 ture of the ammonia main- 

 tained in order to give exactly 

 the required temperature to the 

 water to be cooled. In case of 

 an unusual demand for the cold 

 water, the refrigerating ma- 

 chine can be increased in speed 

 and the ammonia expansion 

 valve so adjusted as to give 

 just the conditions required. 

 The whole installation is very 

 simple and can be operated very 

 economically on account of the high suction pressure at which 

 the compressor operates. 



The same machine which is used for cooling the water for the 

 rolls can be used also to cool drinking water for the employes. 

 The usual arrangement consists in providing a tank in which 

 there is an ammonia e.xpansion coil for cooling the water. The 

 cooled water is circulated through the various drinking faucets 

 by a small pump. The amount of refrigeration required for this 

 work is usually quite small. 



200 



— 500 tons 



The range would be 60 degrees and since one ton of refrigera- 

 tion per twenty-four hours equals 288,000 British thermal units, 

 one ton of refrigeration per minute equals 200 British thermal 



TOTAL SULPHTE IN TtTLCANIZED 



In the following method that has been proposed by A. Hutin, 

 from 1 to 2 grams of finely divided sample is treated with 30 cc 

 of fuming nitric acid added in successive portions of 2 to 3 cc, 

 md the mixture is evaporated to a syrup on the water bath. It ii 

 then treated with 2 to 3 cc. of pure sodium hydrate solution, droi»- 

 by drop. The alkaline liquid is mixed with calcined magnesia to 

 a thick paste, evaporated to dryness at 284 degrees F., and 

 cautiously heated to avoid ignition. 



The friable residue is heated and stirred with water on the 

 water bath and the extract and washings (about 300 cc. for 1 

 gram of material) filtered, concentrated to 100 cc. and acidified 

 with hydrochloric acid. The carbonic acid is expelled and the 

 sulphuric acid precipitated with barium chloride. The final 

 solution ought to be colorless, any coloration indicating that the 

 ignition was incomplete. 



Replete with information for rubber manufacturers.— Mr. 

 Pearson's "Crude Rubber and Compounding Ingredients." 



