Class 300 nipple (sched.80) Vs thickness calculation 1

[JJAV1983]

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

 

[racookpe1978]

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).

 

[moltenmetal]

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.

 

[AVis2]

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

 

[JJAV1983]

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

 

[GenB]

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

 

[moltenmetal]

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.