Pipe Category and Hydrotest 1

[LeitoGM]

Hi All,

I am new in the piping design world, and I was asked to design a spool with a hydrotest package for a gas line operating at 1,200 psi at a north region in Canada.

I choose the following materials for the spool:

· The pipe can be a NPS 1 XS A-106 (WT 0.133 in)

· A NPS 2: NPS 1 reducer made of A-105N

· Weld neck flanges - ANSI 600 – A105N

· A ¾ “ TOR – 3000# - A105N

I did not specify which Category to use I II or III, since I am a bit confused as to what the categories really represent

From what i read on CSA Z662, categories I, II, III represent the notch toughness and different exposed temperatures (I might me wrong).

Therefore, since this spool piece is in a facility and can experience temperatures as low as -45 C, would it be saved to assume that a Category II or Category III pipe is required?

Also, Table 5.3 in CSA Z662 indicates pipe types and their limitations in category, so how come a pipe made out of A-106 is not applicable to Cat II and Cat III applications?

I would really appreciate any advice or comment.

Thank you

 

[SNORGY]

Proven notch toughness properties are not required in these small line sizes and thicknesses. Category I pipe (A106B Ana A105N) is acceptable.

For your information:

Category I = no proven notch toughness required
Category II = proven notch toughness required both in terms of absorbed energy in a Charpy impact test (or DWTT) as well as in the percent shear area measured on the Charpy impact test (or DWTT) specimens (minimum 60% shear area averaged across three specimens with no single specimen below 50%).
Category III = proven notch toughness required as measured by absorbed energy only, with no measurement of shear area on fracture surface.

Thus, Category I is the least stringent, Category III is more stringent, and Category II is the most stringent.

Study CSA Z662 Clauses 4 and 5 and CSA Z245.1 carefully for details.

 

[LeitoGM]

Hi Snorgy,

Thank you so much for replying to my thread at 11pm and I really appreciate your feedback!

I will review Z662 and Z245.1 as you recommended.

Cheers

 

[SNORGY]

Some folks impose notch toughness proven materials in small bore pipe below 4" NPS and below 6 mm wall thickness just to avoid the optics and contradiction between ASME B31.3 and CSA Z662 with respect to material selection below an MDMT of -29 C. The truth is that Z662 does not mandate proven notch toughness properties in small bore thin wall pipe, and that 323.2.2 (b) in ASME B31.3 would lead to the same conclusion (albeit for different reasons). Bear in mind that Z662 is more concerned about crack initiation and propagation in the longitudinal direction along tbe axis of the pipe, whereas B31.3 is concerned about cracking in general. Regardless, my interpretation is that you need not worry about proven notch toughness here if you are designing and building to Z662.