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# test quest.

Member Posts: 1
This question appears in a prep book for a civil service test. (Steamfitter)

If a 2" diameter pipe discharges 20 gallons of fluid per minute, a 4" diameter pipe under similar conditions (such as internal friction and pressure head) would discharge APPROXIMATELY 64 gallons of fluid pre minute.

It's a true/false question. Is there a formula to arrive at the answer?

• Member Posts: 249
try one of these

There are several equations here, maybe one of them will help you.

http://www.efunda.com/formulae/fluids/calc_pipe_friction.cfm#calc
steam newbie
• Member Posts: 645
False

Area of 4" is 6 times 2" ?
• Member Posts: 22,910
square

the area of a pipe cross section is proportional to the square of the actual inside diameter.  If we assume that the actual inside diameter of a 4 inch pipe is 4 inches -- it isn't, but it's not too far off -- and that of a 2 inch pipe is 2 inches, then the proportion is as 16 (the square of 4) is to 4 (the square of 2); therefore the 4 inch pipe has 4 times the area of the 2 inch.

To be more exact you would need to know the kind of pipe to which you are referring -- e.g. sched. 80 CI, Type K copper, ABS... etc. etc. and then look up the actual inside diameters for those nominal sizes.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 813
Formula

Q = A x V where Q = cubic feet per min. A = internal area of pipe in square feet and

V = velocity in feet per min. Q x 7.48 will give answer in gallons per min.

4" Sched. 40 has 3.77 times the area of 2" Sched. 40
bob
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