Spring 08 HW 3

Spring 08 HW 3 - CEE 3304 Fall 2007 HW #3 Pressure...

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CEE 3304 Fall 2007 CEE 3304, Spring 2008, HW#3 by: Amr A. El-Sayed 1 HW #3 Pressure Measurements Problem 3.12 Given : A hydraulic lift is being designed. Capacity = 20,000 lbf (10 tons). Weight of lift = 1000 lbf. Lift speed = 6 feet in 20 seconds. D = 2 to 8 inches. Piston pump data: Pressure range 200 to 3000 psig, Capacity = 5, 10 and 15 gpm. Find : a) Select a hydraulic pump capacity (gpm). b) Select a cylinder diameter (d) Solution Apply equilibrium to find the smallest bore diameter (d) that works. Then find the largest bore diameter that works by considering the lift speed requirement. Select bore and pump combinations that meet the desired specifications. Equilibrium (piston) Î 4 2 d p A p F π = × = Where F = 21, 000 lb is the load that needs to be lifted and p is the pressure on the bottom of the piston. Maximum pressure is 3000 psig so minimum bore diameter is: d
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CEE 3304 Fall 2007 CEE 3304, Spring 2008, HW#3 by: Amr A. El-Sayed 2 Required minimum diameter, () π × × × = × = 2 2 2 2 12 000 , 3 000 , 21 4 4 ft in in lb lb p F d = 0.24878 ft = 2.985 in The pump needs to provide enough flow to raise the lift in 20 seconds. The pump flow rate, H t d t H A t V Q × = × = = 4 2 Î H tQ d 4 = where A is the bore area, H is stroke (lift height), Q is the volume/time of fluid provided by the pump, and t is the time. Thus, the maximum bore diameter is: Conversion from gallons/min to cubic feet/sec: 1.0 gpm = 0.002228009 ft 3 /sec Thus, the maximum bore diameter for three pumps (to meet the lift speed specification) is given in the table below. Q, gpm H tQ d 4 = 4 2 d A = Pressure, A F p = 5 2.61 in 5.347 in 2 3927.2732 psi 10 3.69 in 10.70 in 2 1963.6366 psi 15 4.52 in 16.04 in 2 1309.1 psi Since the minimum bore diameter is 2.98 in., the 5 gpm pump will not work. The 10 gpm pump can
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This note was uploaded on 05/19/2008 for the course CEE 3304 taught by Professor Aaelsayed during the Spring '08 term at Virginia Tech.

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Spring 08 HW 3 - CEE 3304 Fall 2007 HW #3 Pressure...

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