Sch 80 Vs Sch 40 with small diameters
Sch 80 Vs Sch 40 with small diameters
(OP)
Dear all,
All pipes with small diameter (<2") that I´ve used were always Sch80 despite that their process conditions allowed in some cases Sch 40 (cheaper option).
Reasons that I´ve always heard to justify this are on one hand that welded union is less problematic with Sch 80, and on the other hand that availability of the stock in case of Sch 40 may be also a problem in case of a big stock.
The fact is that I´ve followed this common practices all times assuming that they were right, but I wonder if the use of Sch 40 (cheaper option) may be interesting in some cases, asumming of course that it is technically possible to use a Sch 40.
Any clarification about this topic?
Thank you in advance for your help.
Kind regards.
All pipes with small diameter (<2") that I´ve used were always Sch80 despite that their process conditions allowed in some cases Sch 40 (cheaper option).
Reasons that I´ve always heard to justify this are on one hand that welded union is less problematic with Sch 80, and on the other hand that availability of the stock in case of Sch 40 may be also a problem in case of a big stock.
The fact is that I´ve followed this common practices all times assuming that they were right, but I wonder if the use of Sch 40 (cheaper option) may be interesting in some cases, asumming of course that it is technically possible to use a Sch 40.
Any clarification about this topic?
Thank you in advance for your help.
Kind regards.





RE: Sch 80 Vs Sch 40 with small diameters
Based on my experience, the overwhelmingly common industry practice is to specify minimum SCH 80 for 2" NPS and smaller.
RE: Sch 80 Vs Sch 40 with small diameters
RE: Sch 80 Vs Sch 40 with small diameters
Sch80 is no more available than sch40 in carbon steel, and no more available than sch40S or sch10S in common stainless grades. And of course, the normal form for sch10S is welded rather than seamless.
Some firms like to simplify their internal maintenance inventory by standardizing on the heaviest schedule. They value the additional mechanical robustness against corrosion and abuse offered by the heavier pipe as well. They of course don't use 150# stainless fittings either, favouring 3000# or in some cases, even butt-welding everything. Is that good value for money? Doing so definitely costs more, and whether or not that additional cost offers useful, meaningful value is a matter of debate to say the least. For a substantial new build with large amounts of pipe 2" and below, applying your maintenance stockroom's standardization to the specs used for that big new project is definitely going to represent a significant amount of additional cost with a benefit which is questionable at best.
I would agree with you that for welded carbon steel services, and for threaded carbon steel without internal coating, sch80 makes an insignificant cost difference relative to using sch40 and provides a much longer service life by providing more corrosion allowance. But in galvanized 150# threaded services, using sch80 pipe is a waste in my opinion.
RE: Sch 80 Vs Sch 40 with small diameters
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Sch 80 Vs Sch 40 with small diameters
RE: Sch 80 Vs Sch 40 with small diameters
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat