UCS-6 (b)(3) 1

[israr1]

Hey folk,
I was going thru UCS-6 & got stuck to it.

As per UCS-6 (b)(3), SA 36 (plate) can be used for pressure vessel provided thickness does not exceed 5/8in.

Question 1: Why code allows SA 36 only upto thickness of 16mm and why not more than 16mm?
What is the basis for setting limit to 16mm?

Question 2:
For NON STAMPED vessels,can we use ASME SEC VIII DIV 1 for SA 36 having thickness more than 5/8in.
OR
Does it mean that we cannot use ASME SEC VIII DIV.1 for vessel whether it is stamped or non stamped if thickness criteria of UCS-6(b)(3)is not met i.e(thickness
exceeding 5/8 in.)?.

Provide your thought process.

 

[metengr]

Question 1: Why code allows SA 36 only upto thickness of 16mm and why not more than 16mm?
What is the basis for setting limit to 16mm?

Because ASTM A36/ASME SA 36 is a structural steel specification versus a pressure retaining specification, and the Section VIII, Div 1 standards committee decided to limit this material to a thickness of 16mm, most likely based on past experience and assurance of mechanical properties through thickness for pressure retaining applications.

For NON STAMPED vessels,can we use ASME SEC VIII DIV 1 for SA 36 having thickness more than 5/8in.

Since the vessel will not be stamped, it is not a code vessel. So, you are not required to follow Section VIII, Div 1. It becomes a contractual matter as to what you want to pick and chose for ASME Section VIII, Div 1.

 

[israr1]

metengr,

Thank you very much for your instant reply.

Quote:
"Since the vessel will not be stamped, it is not a code vessel. So, you are not required to follow Section VIII, Div 1. It becomes a contractual matter as to what you want to pick and chose for ASME Section VIII, Div 1."

Kindly refer
(b) S t e e l pl at e s conforming to S A - 3 6 , SA/ CSA‐G40.21 38W, and SA-283 Grades A, B, C, and D may be used for pressure parts in pressure vessels provided
all of the following requirements are met:
(3)With the exception of flanges, flat bolted covers, and stiffening rings, the thickness of plates on which strength welding is applied does not exceed 5/8 in.(16 mm)


UCS-6 states that SA 36 may be used for pressure parts provided it satisfies all (3) requirements, one from three is regarding thickness.

So if we are not satisfying thickness requirement than we cannot use SA 36 for pressure parts so it does not matter whether it is stamped or not
Thats my understanding for UCS-6

Kindly correct me if i am wrong.

Regarding thickness limitation, i searched in many handbooks but have not found any apposite / authentic reason for it.
Please share if you make it out first.

 

[metengr]

israr1;
What I was trying to reply for your question 2 is this... If one chooses to not stamp the vessel, it is not a code vessel. We have had vendors fabricate vessels that were not stamped, and as such, they were not ASME Section VIII, Div 1 vessels despite following most of the rules regarding construction with the exception of stamping.

So, you are free to use the rules of Section VIII, Div 1 and exceed the thickness of A 36 for pressure retaining purposes because the vessel will not be stamped and is therefore not a Section VIII, Div 1 code vessel.

 

[MJCronin]

israr1...

What is the maximum operating pressure expected for this non-code vessel that you are planning ?

MJCronin
Sr. Process Engineer

 

[weldstan]

As a former steel maker, both A-36 and A-283 were considered the bottom of the barrel with regard to quality and uniformity of chemistry and mechanical properties. We routinely downgraded heats of steel to these specifications when they did not meet the criteria of the original ordered specification. The only thing lower was "fence post" as a salable product. After that - scrap.

This is not to say that A-36 cannot be purchased to a high quality level equivalent A-515 or A-516. It can be.

 

[israr1]

Thank you very much guys.

So far from above i understand that SA 36 can be used for thickness over 5/8in for non stamped vessel.

Mjcronin,

Operating pressure is around 50 psig @ 160F.
Also Vessel ID=3m & length=9m.