NOTES ON CREOSOTING. 



175 



Of the various methods of creosoting which have been 

 suggested at different times, only three are important. These 

 are by pressure, by boiling, and by simple immersion. 



I. In the pressure method, the necessary plant consists of 

 three parts— a boiler or receiver for the timber, a storage tank 

 for the creosote oil, and a duplicate pump — vacuum and 

 pressure. The size of the boiler must naturally vary with the 

 material to be operated upon, but one made of malleable iron, 

 26 to 28 feet long and 4 ft. 6 ins. in diameter, is a useful type. 

 At the bottom of the boiler there should be two rails on 

 which run trolleys used for carrying the timber. This is an 

 enormous advantage as compared with the method of moving 

 the wood in and out of the boiler by hand. The filled boiler 

 should be closed by a cast-iron swing door, hung by an over- 

 head derrick. The storage tank should stand alongside the 

 boiler, and its proportions should vary with those of the 

 boiler. 



The boiler is filled with wood and closed up. The vacuum 

 pump is then applied and the air is thus exhausted. The 

 result is that the creosote is forced upwards into the boiler 

 by atmospheric pressure from the storage tank, which stands 

 about six feet below the boiler. In about twenty minutes' time 

 the boiler is partially filled with creosote, and a tap is turned to 

 shut off the storage tank. The vacuum pump is then dis- 

 connected and the pressure pump applied. Its valves are so 

 arranged that the oil is forced forward, but is prevented from 

 falling back into the storage tank. Pumping may be continued 

 for two or three hours, according to the dryness of the timber, 

 until the pressure gauge registers 90 lbs. to the square inch. 

 Then the door is swung open to allow the surplus creosote to 



