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Class 300 nipple (sched.80) Vs thickness calculation

Class 300 nipple (sched.80) Vs thickness calculation

Class 300 nipple (sched.80) Vs thickness calculation

(OP)
Hi,

I was hoping to get some help here.

A class 300 nipple (2 in sched. 80) I chose for my design (Class 300), is capable of holding 1500 psig of pressure from (-29 to 66 Celsius). However when I calculate this nipple as per B31.3 having into account: 12.5% under tolerance allowance, 0.118 Corrosion Allowance (sea water), and h=.06597 in thread depth I just don't meet the minimum thickness required.

What do you usually do in this situation?

JJAV1983

RE: Class 300 nipple (sched.80) Vs thickness calculation

1. Check my calculations and ALL assumptions used in those calculations. Have somebody second check me, and my assumptions, if this is a design or size I've used before. Or that the company has used before.

2. Change material - SStl will reduce the required corrosion allowance, for example. That induces a whole lot of other problems though.

3. Use a thicker fitting of the original material (higher class fitting = thicker wall).

RE: Class 300 nipple (sched.80) Vs thickness calculation

Corrosion allowance is the killer. You need to go thicker or reduce the corrosion allowance. If your service is sea water, your choice of threaded construction is questionable already.

RE: Class 300 nipple (sched.80) Vs thickness calculation

I concur with Moltenmetal. I have run into this before with nipples and had to go to a thicker material to make it work.

RE: Class 300 nipple (sched.80) Vs thickness calculation

(OP)
Thank you for all you answers, increasing the thickness of the fitting to sched.160 eliminates the problem, now I comply with B31.3

RE: Class 300 nipple (sched.80) Vs thickness calculation

The wouldn't us sch80 for 1500 psi. I dnt use B31.3 but I don't think you need to consider Mfg undertolerance on small dia pipe.

General Blr. CA,USA

RE: Class 300 nipple (sched.80) Vs thickness calculation

Manufacturing dimensional tolerances need to be considered on pipe of all sizes, unless you buy special tolerance pipe or cherry-pick and do verification measurements on the pipe you buy.

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