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what does schedule pipe mean? schedule 40, schedule 80Helpful Member!(13) 

Guest (visitor) (OP)
11 Mar 00 16:38
I am studying for the lubrication engineers exam and need to know more about "schedule pipe" what it means and what do they mean by schedule 40 and schedule 80
Helpful Member!(4)  mbeychok (Chemical)
11 Mar 00 21:47

The pipe schedule refers to the pipe wall thickness. The higher the schedule, the thicker is the pipe wall. For example:

2-inch nominal size steel pipe: schedule 40 has a wall thickness of 0.154 inches and schedule 80 has a wall thickness of 0.218 inches.

4-inch nominal size steel pipe: schedule 40 has a wall thickness of 0.237 inches and schedule 80 has a wall thickness of 0.318 inches.

As you can see, the relationship between schedule and wall thickness changes with the
pipe nominal size.

Table 6-6 in Perry's Chemical Engineers' Handbook (Sixth Edition) provides the schedule thicknesses for steel pipe nominal sizes ranging from 1/8 of an inch to 30 inches. I am sure similar tabulations are available in other books as well.

Milton Beychok
Air Pollution Dispersion Modeling
Visit my website to learn about "Fundamentals of Stack Gas Dispersion", the most comprehensive book on air dispersion modeling of continuous, buoyant air pollution plumes. The site includes published peer reviews and the complete Table of Contents.

Krpan (Mechanical)
27 Jun 01 9:10
What is the difference between pipes SCH 40 and SCH 40S?
Helpful Member!(4)  butelja (Mechanical)
27 Jun 01 15:45
The schedules that end in S (5S, 10S, 40S, & 80S) are for stainless steel pipe.  In MOST smaller pipe sized (<8") schedule 40 and schedule 40S have the same wall thickness.  In larger diameter pipes, they do not.  Also, there are no schedule 5 or 10 carbon steel pipes until you get into very large (>14") sizes.
nadeemqureshi (Mechanical)
9 Sep 01 12:25
Can any one tell me the exact defination of Nominal Pipe
Helpful Member!  Guest (visitor) (OP)
18 Oct 01 15:48
Nominal pipe size refers to the basic size of the pipe.  For example, a 2" nominal pipe is not really 2" in diameter.  Its typically larger by a tenth of an inch or so, but its refered to as 2" nominal for simplicity.  Its the same basis applied to lumber.  A 2x4 is actually 1.75" x 3.75", but the nominal size of the wood is 2x4
kulwinder (Marine/Ocean)
19 Oct 01 7:15
i want to know how pipes specification are given in its nominal diameter & schedule? Which will have maximum outside diameter, a 20 mm extra strong,
or 20 mm heavy strong or 20mm double heavy strong  pipe?
Helpful Member!(2)  MarkMark220 (Petroleum)
1 Nov 01 17:01
Good luck with your tests.
This should be a little more definitive for you.
Pipe schedules indicate approximate values of the expression 1000 x P/S where P is the service pressure and S is the allowable stress, both expressed in pounds per square inch.

Here's a tip for you.  When calculating the working pressure of pipe almost everyone forgets to take into account the standard manufacturer's allowance on wall thickness which is 12.5%.  Therefore any calculation you derive should be multiplied by .875 to ensure a correct answer.  That is of course unless you can guarantee that the wall thickness is consistently the nominal given or greater and in this economy that just isn't going to happen.
CC9513493 (Mechanical)
20 Dec 01 20:47
Dear sirs
If You need more information about this subject.You can consult The Standard ANSI/ASME B36.10 for C.S, and 36.11 for S.S.
Table For schedule, wall thicness, weight of Pipes for each nominal diameter.

Helpful Member!(2)  TD2K (Chemical)
24 Jan 02 20:44
Kulwinder, pipe schedule is independent of the OD.  For example, 2" sch 40, 80 or 160 pipe all are 2.375" OD.  The ID decreases though as the wall thickness goes up.

For 14" and larger pipe, OD = nominal pipe size.  For 12" and under, the actual OD > nominal pipe size.
ROBERTOBE (Marine/Ocean)
19 Feb 02 15:26
MarkMark220 wrote:

Pipe schedules indicate approximate values of the expression 1000 x P/S where P is the service pressure and S is the allowable stress, ...... the standard manufacturer's allowance on wall thickness which is 12.5%....

Can you explain it to me with an example: What schedule I need for a pressure of 50 bar or 750 psi?
TD2K (Chemical)
19 Feb 02 16:11
Robertobe, the following example from "CASTI guidebook to ASME B31.3 modified to 750 psig (their example used 600 psig)

Let's say you were using A-53B, Sh for this pipe is 18,900 at 500F.

Schedule = 1000 * P / Sh = 1000*750/18,900 or 39.68.  You would use the next size commercial pipe which is schedule 40.  If you included the standard 12.5% allowable variation in wall thickness, you'd have to choice a higher schedule than 60.

Note, this method is no longer used to actually size pipe, you should use the equations in the appropriate code to determine your minimum thickness, taking into account allowable manufacturing variations and corrosion allowances.
Jaiswal (Structural)
15 May 02 3:55
manufactures's allowance on thickness of pipe is on positive side or negative?
Dikkala (Mechanical)
17 Nov 02 17:57
Mfr tolerance on thickness is plus or minus 12.5%
tariacuri (Chemical)
3 Dec 02 12:05
dear sir, if you want to check existens schedules for comercial steel and associated characterĂ­stics you can find this information on CRANE TECHNICAL PAPER No. 410     " FLOW OF FLUIDS THROUGH VALVES, FITTINGS, AND PIPE" pp b-16 thru b-19 for diameters from 1/8" to 36".
vmartins (Chemical)
15 Jan 03 12:58
This is my first time on this site and I just wanted to post a question in this forum so, I found this link and I hope someone can help.

I was wondering if anyone knew who sells schedule 40 pipe to companies in the natural gas industry. As small as 1".?
Either a muanufacturer or supplier in Canada or the U.S.?

if you can't post a response here, please contact me at

I would really appreciate any feedback!
d23 (Petroleum)
15 Jan 03 13:21

You can try the two links below.

In the future you may want to post your questions on a new thread not just add to an existing one.  Your question will be reviewed by more people giving you more answers.

Hope this helps!
slc2000 (Mechanical)
2 Feb 05 14:28
TD2K, in your reply to Robertobe, where can I find the allowable stress (i.e. 18,900 in your example) for different pipe?  Does this number apply to all A53 pipe?  If so, what is the number for 316SS pipe?
TD2K (Chemical)
4 Feb 05 1:14
Wow, this is a blast from the past.

First, this is an obsolete method to size what pipe you need.  That said:

Allowable stresses can be found in B31.3 and likely a bunch of other reference materials.  

The values will vary depending on the grade of A53 you are using.  A53 GrF for example at 500F is limited to 400F at a value of 13,800.  A53 GrA is 16,000 at 500F.

316SS has a value of 17,900 at 500F.  316L has a value of 14,400 at 500F.

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