Schedules are the different "standard pipe wall thicknes" that various manf. offers. They should be he same regardless of the mill.
Most companies that uses pressurerised pipes will have their own "piping standard" where the approved types of materials and pipes/pipe sizes are listed. This will usually include the corresponding schedule.
If you are to do this on your own you need to calculate your required wall thickness (ASME) and for the NB in mind find the nearest schedule with a higher wall thickness.
Remember that schedules are usually only used for "process piping" in order to reduces the number of different pipetypes. For longer pipelines any wall thickness can be ordered.
See whether following steps help you get your answer.
First calculate pipe thickness based on yr. reqd. Code formule.
say if you are considering ANSI B 31.3.
where Pipe material is Carbon Steel
Design Presure : 300 psig
Pipe Size (OD) : 6"
Allowable stresses : 20000 psi
Y : 0.4
A : 0.125 inch
E : 0.85
calculated thickness will come as "t" : 0.053 inch
Add allowance to this. i.e.
t + A = 0.053 + 0.125 = 0.178 inch
Consider Mill tolerance of 12.5 %
T = 0.178/(1-12.5/100)= 0.178/0.875 = 0.2034 inch
Now refer Pipe dimensional code ANSI B 36.10
for Nominal pipe size - 6"
Sch 10 - 0.134 inch
Sch 40 or std - 0.280 inch
There is no Sch 20 or Sch 30 for 6" pipe size.
How do PSI (for Pipe Fittings) and Schedule (for Pipe) Relate?
PSI (pounds per square inch) is the amount of pressure a pipe fitting can endure. Schedule refers to the thickness of pipe.
While there are no steadfast rules relating psi to schedule, we have made general recommendations throughout the pipe fitting section of our catalog. Note: Regardless of material, all pipe OD's are the same. Due to different manufacturing methods and tolerances, however, pipe ID and wall thickness may vary slightly from what's shown in table below.
Schedule 10 is the thinnest-wall pipe we offer. It's lightweight, but definitely not light duty. Schedule 40 is the most common pipe wall thickness. Great for all-around use. Schedule 80 is a thicker, heavier pipe. Use it in high-pressure applications where greater mechanical strength is required. Schedule 160 is the thickest, heaviest pipe. Use it for your most demanding applications where pressures and temperatures run high.
How is the pipe schedule and the material related. If I specify 2 1/2" schedule 40 carbon steel pipe - do I still have to specify the material? Or is saying 2 1/2" ASME SA-106B sched 40 pipe redundant?
