160 MARKET DAIRYING 



cock at the bottom is uS'ed to blow out the sediment that 

 is liable to block the opening between it and the boiler. 

 When this occurs the gauge becomes a false indicator. 

 Frequent blowing out is therefore necessary. The cock 

 next to the blow-out admits the water from the boiler. 

 The cock above this admits the steam. When the glass 

 breaks shut off the water first, then the steam. Always 

 have a few extra glasses on hand so that the broken one 

 can be immediately replaced. Owing to its tendency to 

 clog, the gauge can not always be relied upon, hence the 

 use of water cocks placed next to the glass gauge. 



Water Gauge Cocks i There are three of these used. 

 The water level should be kept as near as possible to the 

 middle cock. It should never go below the lower cock, 

 nor above the upper. These cocks should be opened 

 many times during the day, and so long as steam issues 

 from the upper and water from the lower cock, the water 

 level is all right. 



Steam Gauge. This shows the number of pounds of 

 steam pressure per square inch on the boiler by means 

 of a pointer moving around a dial. Below the dial is a 

 loop which contains water to prevent injury to the gauge 

 from the hot steam. The steam gauge is liable to get 

 out of order and will then fail to show the true pressure. 

 Such a condition is indicated by the safety valve. 



Safety Valve. This is placed on top of the steam 

 chamber and permits the escape of steam when the steam 

 pressure reaches the danger limit. It is an indispensable 

 boiler attachment as without it the boiler would be a 

 dangerous thing. There are two kinds of safety valves, 

 the "pop" and "ball and lever" types. The former is 

 considered the more desirable because it is not so easily" 



