# Pipe Schedule and Pressure Ratings
**URL:** https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681
**Category:** Factual Questions
**Created:** [November 5, 2001, 10:13pm UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681 "2001-11-05T22:13:06Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Trucido](https://boards.straightdope.com/u/Trucido)
#### Post date: [November 5, 2001, 10:13pm UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681/1 "2001-11-05T22:13:06Z")
I have been searching (google and a number of other sources) for a table that gives the pressure rating of various types of steel pipe. I keep running into the ANSI standards, but can’t find these either.
So, where can I find such a reference? Failing that, what’s a rough estimate for the maximum sustained pressure on schedule 80 and 120 A53 carbon steel in 2 and 4 inch OD?
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### Author:  [@Phil\_Saoud](https://boards.straightdope.com/u/Phil_Saoud)
#### Post date: [November 5, 2001, 11:26pm UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681/2 "2001-11-05T23:26:18Z")
I don’t know of any sources on the internet that give the information that you’re looking for. I’m sure they exist though. I’ll do some checking and let you know. In the mean time, the pressure rating is still probably 125#, even though schedule 80 is heavier than standard weight piping. BTW, I fairly certain that the piping you’re asking about is 2" and 4" ID, not OD.
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### Author:  [@Ferrous](https://boards.straightdope.com/u/Ferrous)
#### Post date: [November 6, 2001, 12:07am UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681/3 "2001-11-06T00:07:59Z")
Hmm, I have some books here at the office that might have it…perhaps I’ll try to find it later. I haven’t tried any internet searches, but I’m surprised there’s not an ANSI site. You could also try ASME (Amer. Soc. of Mechanical Engineers.)
FWIW, we routinely use SCH 40 (for 2.5" nom and above) and SCH 80 (2" and below) for pressures up to 300 PSIG. The fittings (elbows, tees, etc.) are rated for 3000#, though, so I suspect the pipe would be good for quite a bit higher too.
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### Author:  [@Strainger](https://boards.straightdope.com/u/Strainger)
#### Post date: [November 6, 2001, 12:18am UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681/4 "2001-11-06T00:18:32Z")
I’ll assume Grade B, which seems to be the most common, and has a [yield strength (F[sub]ty[/sub]) of 35 ksi](http://www.usstubular.com/products/seamslp.htm). Now, the dimensions for 2" and 4" [Schedule 80 and 120 pipe](http://members.aol.com/expertpipe/steelpipe.htm) are as listed below.
```auto
Schedule 80 OD ID Thickness
2" 2.375" 1.939" .218"
4" 4.500" 3.826" .337"
Schedule 120
2" (doesn't exist in this size)
4" 4.500" 3.626" .437"
```
Now, apply the formula p=2F[sub]ty[/sub]t/ID (thin wall assumption, [Cite.](http://www.engineersedge.com/pipe_bust_calc.htm)) where p=allowable pressure before yielding occurs and t=pipe wall thickness. (Assumes a Safety Factor of 1). We have:
```auto
Schedule 80 p (psi)
2" 7870
4" 6166
Schedule 120
4" 8436
```
You can plug values into the aforementioned link and specify your own safety factors. It rounds to the nearest 1000 psi.
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### Author:  [@Engineer\_Don](https://boards.straightdope.com/u/Engineer_Don)
#### Post date: [November 6, 2001, 12:19am UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681/5 "2001-11-06T00:19:41Z")
Mark’s Standard Handbook for Mechanical Engineer’s has all the tables you would need. Basically, Schd 40 is standard pipe, and schd 80 is extra strong. The schedules determined by a formula,
Schedule Number = 1000 x Operating Pressure (psi) / Allowable Stress of the material (psi) x Quality Factor (0.80 for most steels).
If you know the allowable stress for 120A53 then you can calculate the max pressure fairy easily.
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### Author:  [@Trucido](https://boards.straightdope.com/u/Trucido)
#### Post date: [November 6, 2001, 12:28am UTC](https://boards.straightdope.com/t/pipe-schedule-and-pressure-ratings/91681/6 "2001-11-06T00:28:33Z")
I really appreciate the reponses! Strainger’s laid it out as clearly as I could want, but I’m going to hit the engineering library for a copy of that handbook.