514 



THE INDIA RUBBER WORLD 



[Junk 1, 1917. 



The water is then discharged past the valves and out through 

 an outlet at the side of the trap, not shown. 



The Detroit separating trap illustrated in Fig. 7 differs from the 

 others in that the working parts are all on the outside and 

 therefore easy of access and observation. It is not dependent 

 upon the buoyancy of some hollow float, or the contracting or 

 expanding of certain parts, but simply upon the weight of the 

 water in the tank acting against the counter balance weight, to 

 open and close the outlet valve. There is absolutely nothing 

 inside the tank. These traps have large capacities and are quick 

 to act. 



EXPANSION TR.APS. 



The Sarco, shown in Fig. 8, is a good example of this type 

 of trap and is recommended for its extreme simplicity, being 

 operated by an expansiljle fluid that controls the valves. 



It consists of a steam pjpe body which can be screwed on 

 anywhere in a steam main or pipe, occupying very little space 

 and taking the place of an elbow or bend. In this liody a Sarco 



Fig. 8. S-\rco E.xpansion Tr.\p. 



cartridge is inserted, containing an easily expansilde fluid op- 

 erating a corrugated, hermetically sealed, tombac tube, to the 

 lower end of which is attached a piston, which carries the vahe 

 head. 



The trap is placed in position and the cartridge unscrewed a 

 few turns. When the steam has heated up the cartridge, ex- 

 panding the fluid and forcing out the piston, the cartridge is to 

 be gently screwed forward until the valve head meets the seat, 

 closing off the steam. The adjustment can then be locked and 

 the trap works automatically. As soon as water collects, the liquid 

 contracts a-nd the Valve opens. The condensation is then ejected 

 by the pressure behind it, and immediately the steam comes into 

 contact with the cartridge, there is an expansion and the trap 

 closes. 



All of the above traps are separating traps, designed primarily 

 for draining high or low pressure steam mains, vulcanizers, re- 

 ceivers, and steam separators. Their office is to hold the steam 

 in check and at the same time return condensation to the feed 

 water heater or hot well, but not to the boiler. 



RETURN TRAPS. 



Direct return systems are used to automatically return the 

 condensation directly to the boiler without loss of heat, also to 

 remove the air. The Detroit systems comprise the single system 

 when high pressures are dealt with, the double system for low 

 pressures, and the combination system when exhaust steam is 

 used for heating in the day time and live steam at night. These 

 systems require different installations, and tilting traps with 

 outside working parts are designed to meet special requirements 

 of the engineering problems. 



The following brief description of the Detroit return trap will 

 explain the operating principle of this device. 



Referring to the illustration in Fig. 9, the water enters the 

 right hand bearing through the inlet check valve, passing up 

 into the tank through the hollow trunnion and discharging, then 

 leaving by the same path, only through the outlet check 

 valve. The tank becoming two-thirds filled, its weight offsets 



Fig. 9. Dktruit Keturx Tr.-\p. 



the counterweight, and on account of the tank being supported 

 off center, it has a downward action on the tilt end. This tilting 

 action is for the purpose of opening and closing the steam and 

 air valves in 

 the right hand 

 bearing. When 

 the trap is fill- 

 ing, the steam 

 valve is closed, 

 but when dis- 

 charging it is 

 opened to allow 

 a pressure in 

 the tank to 

 force the water 

 out. The air 

 valve is opened 

 when the tank 

 is filling and 



closed while discharging. Both the steam and the air pass 

 through the upright pipe inside the tank by way of ,the right 

 hand half of the hollow trunnion. 



A return trap of different design, illustrated in Fig. 10, is the 

 Pratt & Cady trap. It consists of a body containing a float A 

 which actuates a lever B which in turn operates the rocker arm C. 

 On the outer end of the lever S is a weight D which counter- 

 poises half of the weight of the float. The rocking lever C 

 has a weight E which rolls to each end alternately as the 

 feeder fills and is emptied of water. The rolling ball acts at 

 exactly the same point every time to open and close the steam 

 valve F. The rod G connects the lever of the valve F with the 

 rocking lever C. 



In operation, water enters the inlet pipe and lifts the float 

 A, which causes the lever B to move downward at the outer 

 end. This movement is imparted to the rocker arm C by the 

 pin and catch block. When the movement of the rocker arm C 

 is sufficient, the ball E will roll to the opposite end from the 

 position shown, which suddenly tilts the arm C, giving the lever 

 G a pull which opens the steam valve F. This admits steam 

 at boiler pressure into the trap and the water is forced out 

 through the discharge pipe. 



When the water is lowered sufficiently in the trap the float 

 causes the outlet of the, lever B to rise until its motion has 

 caused the rocker C to tilt in the opposite direction, when the 

 ball will return to the position shown, closing the steam valve 

 with the same sudden motion with which it was opened 



The Bundy tilting 

 trap is designed to 

 handle water of con- 

 densation at high 

 temperature from 

 coils or other 

 sources when it col- 

 lects and returns it 

 to the boiler. 



The trap is de- 

 signed as shown in 

 Fig. 11. The yoke is 

 made with an exten- 

 sion on the upper 

 side, so that the 

 yoke approaches a ring in shape, as shown in the semi-sectional 

 view, Fig. 12. The upper section of the yoke is connected to a 

 discharge valve operated by the tilting of the bowl in unison with 

 the lower or steam valve. The latter has a vent, as shown in Fig. 

 11. Referring to Fig. 12, water enters the trunnion A in the 

 direction of the long arrow. Live steam is admitted to the bowl 

 through the valve C and the left passage of the hollow trunnion. 



F 



10. Pr.mt & C.vDV Tr.\p. 



