Discuss NFPA CWBSP Exam Topic 4 Question 18

A 4 in. (102 mm) nominal diameter Schedule 10 sprinkler main is to be supported from the structure utilizing a trapeze

hanger with a span of 8 ft (2.4 m). Using Schedule 40 pipe for the trapeze hanger, what is the minimum diameter pipe

that should be used?

A1.5 in. (40 mm)

B2 in. (50 mm)

C2.5 in. (65 mm)

D3 in. (75 mm)

Suggested Answer: B

For supporting a 4 in. Schedule 10 sprinkler main with a trapeze hanger spanning 8 ft, a Schedule 40 pipe of at least 2 in. in diameter is typically recommended. This size provides adequate strength for the span and weight of the sprinkler main.

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29 comments · newest first

Lakeesha 10 months ago

Totally agree, 2.5 in. seems like the sweet spot!

Olga 10 months ago

Definitely 2 in. for that span, anything bigger seems unnecessary.

Madalyn 10 months ago

I think 3 in. is overkill for a trapeze hanger.

Alverta 10 months ago

Wait, are we sure 1.5 in. can handle that load?

Nana 11 months ago

Schedule 40 is usually stronger, so I'd go with 2.5 in.

Abel 11 months ago

I’m leaning towards 3 inches because I remember the need for extra support over longer spans, but I’m not entirely confident.

Tesha 11 months ago

I feel like the answer might be 2.5 inches, but I can't recall the exact calculations we did in class. It’s tricky with the different schedules.

Marleen 11 months ago

I think we practiced a similar question where we had to calculate the support requirements based on pipe sizes. I want to say it was around 2 inches, but I could be wrong.

Carmelina 12 months ago

I remember something about using a larger diameter for the trapeze hanger to support the load properly, but I'm not sure what the minimum should be.

Allene 12 months ago

This seems like a tricky one. I'll need to make sure I understand the difference between Schedule 10 and Schedule 40 pipe, and how that affects the design.

Kanisha 12 months ago

Okay, I think I can handle this. I'll start by calculating the weight of the 4-inch sprinkler main and then use that to determine the minimum diameter of the trapeze hanger pipe.

Melissa 1 year ago

Hmm, I'm a bit unsure about how to approach this. I'll need to review my notes on pipe sizing and structural support calculations.

Fausto 1 year ago

This looks like a straightforward structural design problem. I'll need to consider the load on the trapeze hanger and the allowable stresses in the pipe material.

Allene 1 year ago

Is there an option for 'all of the above'? I mean, who doesn't love a good game of 'Guess the Pipe Diameter'? It's like a sprinkler version of 'The Price is Right'!

Desiree 1 year ago

I'm going to have to go with B. 2 in. (50 mm). Anything bigger and I'd be worried about the trapeze hanger looking like a jungle gym instead of an actual support system.

Lonny 1 year ago

↳ replying to Desiree

I think C) 2.5 in. (65 mm) might be a safer option for extra support.

Avery 1 year ago

↳ replying to Desiree

I agree, B) 2 in. (50 mm) seems like the right choice for the trapeze hanger.

Abel 1 year ago

D. 3 in. (75 mm) all the way! Go big or go home, am I right? I'd rather have a hanger that could bench-press a truck than one that's just barely holding on.

Vanda 1 year ago

↳ replying to Abel

B: Yeah, I agree. It's always better to over-engineer than under-engineer when it comes to safety.

Gracia 1 year ago

↳ replying to Abel

A: I think I would go with option D, 3 in. (75 mm) as well. Better safe than sorry!

Arminda 1 year ago

I agree with Paris, C) 2.5 in. (65 mm) seems like the most appropriate choice

Paris 1 year ago

I'm leaning towards C) 2.5 in. (65 mm) because of the span of the trapeze hanger

Latricia 1 year ago

I disagree, I believe the correct answer is B) 2 in. (50 mm)

Jenelle 1 year ago

Hmm, I'm leaning towards C. 2.5 in. (65 mm) just to be on the safe side. Better to have a bit of extra strength than to risk the whole system collapsing, you know?

Annice 1 year ago

I'm pretty sure it's B. 2 in. (50 mm) seems like the right size for a trapeze hanger supporting a 4 in. (102 mm) main. Anything smaller would be too weak, and anything larger would be overkill.

Mozell 1 year ago

↳ replying to Annice

Yeah, D) 3 in. (75 mm) would be too large and unnecessary for this application.

Hubert 1 year ago

↳ replying to Annice

Agreed, using a smaller diameter pipe would not provide enough support for the sprinkler main.

Martina 1 year ago

↳ replying to Annice

I think you're right, B) 2 in. (50 mm) sounds like the best choice for the trapeze hanger.

Remona 1 year ago

I think the answer is A) 1.5 in. (40 mm)

NFPA CWBSP Exam - Topic 4 Question 18 Discussion