628 HYDRAULICS AND ITS APPLICATIONS 



to be handled. One of the best of this type, the Drum Pump, is 

 illustrated in section in Fig. 300. 1 Here P is the revolving piston, which 

 carries two projecting ribs, these gearing into suitable slots on the 

 revolving drum D. The piston and drum are geared together by 

 external gear wheels, and at each rotation of the piston a volume of 

 liquid = 2 IT E A cubic feet is delivered, where R = mean radius of the 

 projecting rib and A = its projected area on a diametrical plane. The 

 pump is built in sizes to deliver up to about 700 gallons per minute. 



EXAMPLES. 



(1) Sketch the displacement curve for a five-cylinder single-acting 

 pump having cranks at 72 and, assuming zero acceleration in the pipe 

 line, determine the proportion of the delivery per revolution which enters 

 the air vessel per cycle. 



Answer. '0013. 



(2) Assuming no air vessels, determine the critical speeds at which 

 separation will occur on the suction and delivery sides respectively of the 

 following pump : 



/Cylinder diameter = 10 inches. 



Cylinder stroke =18 inches. 



1 Diameter of suction pipe = 5 inches. 



I Diameter of delivery pipe = 4 inches. 



Length of connecting rod = 3 feet. 

 Length of suction pipe : 40 feet. 

 Length of delivery pipe = 250 feet. 



Suction lift = 10 feet. 



Delivery lift = 180 feet. 



. | On suction stroke 21*7 revolutions per minute. 



I On delivery stroke 20-7 revolutions per minute. 



(3) Assuming the pump of example (2) to run at forty revolutions per 

 minute, determine at what point in the stroke shock will take place, and 

 assuming all connections, etc., to be rigid, and neglecting the effect of the 

 opening of the delivery valves, determine the maximum hammer pressure 

 then produced. 



Answer. 99 '3 per cent, of stroke. 



Hammer pressure 834 Ibs. per square inch. 



(4) Determine the discharge coefficients for a pump of 6-inch stroke, 



, . connecting rod 4 . piston area 



having a ratio - n = -=- ; a ratio 5 = 



crank length 1 ' suction pipe area 



length of suction pipe = 63 feet, when running at fifty revolutions 

 minute, and when the delivery pressure is respectively 



(a) 5 Ibs. per square inch. 



(b) 10 Ibs. per square inch. 



1 By courtesy of the Drum Engineering Company, Bradford. 



