76 



vSvVI':KT1{NI-:i1 CONOIJNSI';!) AIlLK CoNniCNSINn 



ufacturer, as short as possible and with few and easy bends. The 

 grade of the suction pi])e should be tmiform in order to avoid air 

 pockets. 



Fig. 25. Dry-vacuum pump 



Courtesy of Buffalo Foundry & Machine Company 



The water should be turned into the condenser before the 

 vacuum pump is started. The pump should not run at a higher 

 speed than is necessary to secure the required vacuum. Excessive 

 speed means high steam consumption and heavy wear and tear on 

 the pump. The amount of water supplied to the condenser should 

 be regulated to suit the requirements. Ordinarily, and with a 

 vacuum of twenty-five to twenty-six inches, the temperature of the 

 condenser discharge should be about 110 degrees F. A lower tem- 

 perature would cause excessive and uneconomic use of water. The 

 basin on the vacuum cylinder should be kept filled with water to 

 prevent admission of air to the cylinder through the stuffing box, 

 and the spray pipe or jet in the condenser should be inspected often 

 to make sure that the perforations are not clogged. The stuffing 

 box of the cylinder should be well packed with a good quality of 

 packing and the steam cylinder well oiled. Start the pump slowly. 

 Belt-driven pumps, especially those equipped with a fly-wheel, insure 

 greater uniformity of speed than direct-acting, steam-driven pumps. 

 Steam-driven pumps should be furnished with a high grade gov- 

 ernor. The vacuum pump should have a capacity proportionate to 

 the size of the vacuum pan, amount of heating surface, steam pres- 

 sure and temperature of condensing water. 



Science and Practice of Evaporating in Vacuo. — Purpose of 

 Condensing in Vacuo. — The important advantages gained by evap- 



