If you have a duplex single acting reciprocating pump making 100 strokes/minute, with a 7" diameter cylinder, a 9" stroke and operating with 90% volumetric efficiency, what is the capacity of this pump?
• Formula for theoretical pump displacement per stroke for a single-acting reciprocating pump • How duplex construction changes total strokes or cylinders involved • Converting cubic inches per minute to gallons per minute (gpm), remembering 1 gal = 231 in³
• First, find the volume displaced by one stroke of one cylinder using the area of the piston and the stroke length. How do you calculate piston area from diameter? • For a duplex pump that is single-acting, how many cylinders are delivering fluid, and how does that affect total displacement per minute? • After you get the theoretical gpm, how do you apply 90% volumetric efficiency and compare to the choices?
• Be clear on whether the given 100 strokes/minute is per cylinder or total for the pump assembly. • Confirm the area calculation for a 7" diameter: use ( A = \pi d^2 / 4 ) and keep units in square inches. • After you find flow in in³/min, divide by 231 in³/gal and then apply 0.90 for volumetric efficiency before matching with the choices.
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