Chapter 14. -PIPING, FITTINGS, AND VALVES 



147.104X 

 Figure 14-8.— Bimetallic steam trap. 



STRAINERS AND FILTERS 



Strainers are fitted in practically all piping 

 lines to prevent the passage of grit, scale, dirt, 

 and other foreign matter which could obstruct 

 pump suction valves, throttle valves, or other 

 machinery parts. 



Figure 14-9 illustrates three common types 

 of strainers. Part A shows a bilge suction 

 strainer located in the bilge pump suction line 

 between the suction manifold and the pump. 

 Any debris which enters the piping is collected 

 in the strainer basket. The basket can be re- 

 moved for cleaning by loosening the strongback 

 screws, removing the cover, and lifting the 

 basket out by its handle. Part B of figure 14-9 

 shows a duplex oil strainer of the type com- 

 monly used in fuel oil and lubricating oil lines, 

 where it is essential to maintain an uninterrupted 

 flow of oil. The flow may be diverted from one 

 basket to the other, while one is being cleaned. 

 Part C of figure 14-9 shows a manifold steam 

 strainer. This type of strainer is desirable 

 where space is limited, since it eliminates 

 the use of separate strainers and their fittings. 

 The cover is located so that the strainer basket 

 can be removed for cleaning. 



Metal-edge filters are used in the lubrica- 

 tion systems of many auxiliary units. A metal- 

 edge filter consists of a series of metal plates 

 or disks. Turning a handle moves the plates or 



disks across each other in such a way as to re- 

 move any particles that have collected on the 

 metal surfaces. Some metal- edge type filters 

 have magnets to aid in removing fine particles 

 of magnetic materials. 



VALVES 



Every piping system must have some means 

 of controlling the amount and direction of the 

 flow of the contained fluid through the lines. 

 The control of fluid flow is accomplished by the 

 installation of valves. 



Valves are usually made of bronze, brass, 

 iron, or steel. Steel valves are either cast or 

 forged, and are made of either plain steel or 

 alloy steel. Alloy steel valves are used in high 

 pressure, high temperature systems; the disks 

 and seats of these valves are usually surfaced 

 with Stellite, an extremely hard chromium-co- 

 balt alloy. 



Bronze and brass valves are not used in 

 high temperature systems. Also, they are not 

 used in systems in which they would be exposed 

 to severe conditions of pressure, vibration, or 

 shock. Bronze valves are widely used in salt 

 water systems. The seats and disks of bronze 

 valves used for sea water service are often 

 made of Monel, a metal that is highly resistant 

 to corrosion and erosion. 



Many different types of valves are used to 

 control the flow of liquids and gases. The basic 

 valve types can be divided into two groups, 

 stop valves and check valves. Stop valves are 

 those which are used to shut off— or partially 

 shut off— the flow of fluid. Stop valves are con- 

 trolled by the movement of the valve stem. 

 Check valves are those which are used to per- 

 mit the flow of fluid in only one direction. Check 

 valves are designed to be controlled by the 

 movement of the fluid itself. 



Stop valves include globe valves, gate valves, 

 plug valves, piston valves, needle valves, and 

 butterfly valves. Check valves include ball-check 

 valves, swing-check valves, and lift-check 

 valves. 



Combination stop-check valves are valves 

 which function either as stop valves or as check 

 valves, depending upon the position of the valve 

 stem. 



In addition to the basic types of valves, a 

 good many special valves which cannot really 

 be classified either as stop valves or as check 

 valves are found in the engineering spaces. 

 Many of these special valves serve to control 



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