SUPERHEATED STEAM IN MARINE PRACTICE. 185 



EQUIPMENT NECESSARY FOR SUPERHEATED STEAM OPERATION. 



52. Equipment to handle superheated-steam, some of which may not be con- 

 sidered for saturated-steam installation, is confined to the following: — 



1st. Lubricating-oil pump and pipes. 

 2d. Filters. 

 3d. Pyrometers. 



4th. Mixing pipes for leading saturated steam to main steam pipe and super- 

 heated steam to auxiliary steam pipe. 



53. An oil pump, driven from some convenient part of the engine, is required 

 to feed oil in a steady and regular manner. Inexpensive pumps are on the mar- 

 ket, and are reported as being reliable in service. Many of them are so arranged 

 that the oil container is not under pressure, thus permitting a renewal of the oil 

 supply without trouble or danger. In modern practice, the oil is introduced into 

 the steam pipe between the throttle valve and the engine. The delivery end of the 

 oil pipe fitting extends into the steam pipe, so that the current of steam entrains 

 the oil and it is atomized before reaching the wearing parts. This feature has 

 been found very important. 



54. Filters are, of course, necessary where there is any possibility of oil being 

 taken into the boilers. A large proportion of steamers using saturated steam in 

 condensing engines are at present equipped with filters. It is believed that in a 

 good many ships the filtering apparatus now installed, particularly with proper at- 

 tention given to cleaning, is adequate to prevent oil reaching the boilers. A num- 

 ber of recently built ships, using high superheat, have had two filters arranged in 

 series, and reports from engineers on such boats indicate that oil does not get into 

 the boilers so as to cause any damage or give trouble. No matter how good filters 

 may be, they will not keep oil out of the boilers unless attended to. With a double 

 filter installation, the first filter is generally inspected and cleaned about every two 

 days while at sea. The second filter does not require attention oftener than about 

 once a week. 



55. Pyrometers are desirable for measuring the temperature of the steam at 

 various points. It appears, at the present time, common practice to have one py- 

 rometer indicating the temperature of steam at the engine stop valve, also to have 

 other pyrometers at points nearer the superheater for indicating the temperature of 

 the steam where it leaves the superheating apparatus. A pyrometer to register the 

 temperature of steam in the intermediate-pressure chest is also frequently applied. 

 Various types of pyrometers which measure these temperatures accurately are 

 available and are reliable instruments; the electric pyrometer, especially, appears 

 to have been developed in a satisfactory manner for marine practice. The infor- 

 mation given by the pyrometer is important, and makes it possible to determine : — 



1st. How far superheat is being carried through the engine. 



2d. Whether any boiler is being properly or improperly fired. 



3d. By showing a reduction in steam temperature, gives warning of an impend- 



