PE Problem #4

6/6/2018

Determine the required thrust block volume (in cubic feet) for a 45-degree elbow serving a wet 6-inch schedule 10 pipe in sandy silt with a 50% safety factor added. The water within the pipe has a maximum pressure of 140 psi and the block material has a density of 150 pounds per cubic foot.
a. 28 cubic feet
b. 31 cubic feet
c. 44 cubic feet
d. 63 cubic feet

Solution | Posted 06/07/18

3 Comments

Shafeeq

6/6/2018 07:46:53 am

b 31.4 cubic feet (Ref MeyerFire PE Prep Guide Equation 5.20)

Colleen

6/6/2018 09:48:33 am

B). 31 cubic feet (I got 31.4 like SHAFEEQ)

I used eqsn A.10.6.1d in NFPA 13, Vg=[Sf x PA x sin(theta)]/Wm

with Sf=1.5, P=140 psi, A=pi*(6.357/2)^2 (using actual inside diameter for 6" S10 pipe per HFPE appendix), theta=45, Wm=150

I assume the info about sandy silt is extraneous information (Bearing strength, Sb was not required in this eqsn) and A). is a distractor since it does not account for the actual inside diameter.

Diaa

6/7/2018 11:42:39 am

B) 31.42 ft3

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