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Suitability of carbon steel pipes at low temperatures

Suitability of carbon steel pipes at low temperatures

Suitability of carbon steel pipes at low temperatures

(OP)
Hi.

I have some doubts regarding suitability of carbon steel pipes at low temperatures in reference with 323.2.2 of ASME B 31.3. Please bear with me as the list of questions is a bit long.

First I am placing some data related to the subject from ASME B 31.3.

(a)    Para. 323.2.2(c) states that a listed material may be used at a temperature lower than the minimum shown in Table 323.2.2 A ( including Notes ), unless prohibited in Table 323.2.2, Table A-1 , or elsewhere in the Code, and provided that the base metal, weld deposits, and HAZ are qualified as required by the applicable entry in Column B of table 323.2.2.

(b)    A-3(b) in Table 323.2.2 mentions the requirement of impact tests of weld deposits for Design Min. Temp. below -29 deg. C except as provided in Notes (3) & (5) of this Table.
    
(c)     B-3 in Table 323.2.2 mentions the requirement of impact tests of base metal, weld deposits and HAZ  at  Design Minimum Temperature  below  Min. Temp. in Table A-1 or Fig. 323.2.2A  except as provided in Notes (3) & (5) of this Table.

(d)    Para. 323.2.2(d)(1) states that carbon steel pipes can be used at or above -48 degree C ( if the conditions in this para. are met ) without any impact test.

(e)    Para. 323.2.2(d)(2) states that carbon steel pipes can be used below -48 degree C without requiremet of impact test, if conditions in Note (3) of Table 323.2.2 are met.

(f)    Note (4) of Fig. 323.2.2A states that a welding procedure for the manufacture of pipe or components shall include impact testing of welds and HAZ for any design minimum temperature below -29 deg. C, except as provided in Table 323.2.2A, A-3(b).



I have the following questions :

(1)    Am I correct in understanding that all the carbon steel pipes can be used without requirement of impact test of base metal, weld deposits and HAZ for Design Min. Temp. at or above -29 deg. C. ?

(2)    A-3(b) of Table 323.2.2, mentions that for Design min. temp. below -29 deg. C, impact test is not required except as provided in Notes (3) & (5) of this Table. This case happens for curves C & D when the Design Minimum Temperature lies above the curve, but below -29 deg. C. So, if conditions in Notes (3) & (5) are not satisfied, impact test of weld deposits will be required. However, Para. 323.2.2(b) mentions that if the Design minimum metal temperature-thickness combination is on or above the curve in Fig. 323.2.2A, impact testing is not required. So, what is correct in this case ( para. 323.2.2(b) or A-3(b) of Table 323.2.2 ) ?

(3)    Point (d)  related to para. 323.2.2(d)(1) mentioned above, allows pipe to be used at temperatures at or above -48 deg. C without any impact test if conditions in this para. are satisfied. However, according to me, combined interpretation of points (a) , (b) & (c) is that, for pipes to be used at temperatures below the curves in Fig. 323.2.2A or below -29 deg C, conditions in Notes (3) & (5) of Table 323.2.2 have to be satisfied.  In such a scenario, does para. 323.2.2(d)(1) precede  A-3 and B-3 of Table 323.2.2  or vice versa ?

(4)    Point (e)  related to para. 323.2.2(d)(2) mentioned above, allows pipe to be used at temperatures below -48 deg. C without any impact test if conditions in Note (3) of Table 323.2.2 are satisfied. However, from points (a), (b) & (c), for these temperatures, conditions in Notes (3) & (5) of Table 323.2.2 have to be satisfied. In such a scenario, does para. 323.2.2(d)(2) precede  B-3 of Table 323.2.2  or vice versa ?

(5)    Except for the case ( Design minimum temperature above the curves C & D of Fig. 323.2.2A, but below -29 deg. C ) that I mentioned in question (2) above, is my interpretation correct that in accordance with Note (4) of Fig. 323.2.2A ( see point (f) above ), no additional  impact testing is required for any Design minimum temperatures below -29 deg C, but or above -104 deg C ( in accordance with Note (3) of Table 323.2.2 ) except for the mandatory one done during manufacturing stage ?

(6)    In paras. 323.2.2(d)(1)  &  323.2.2(d)(2), there is no mention of Note (5) of Table 323.2.2. However, para.  323.2.2(c) makes a reference of Table 323.2.2 which makes a requirement of use of Note (5) for such lower temperatures.

(7)    A-3(b) & B-3 of Table 323.2.2 mention that impact test is not required for carbon steel pipes if conditions in Notes (3) & (5) of this Table are satisfied. I understand Note (3). I am a bit confused regarding Note (5). It states that " Impact tests are not required when the maximum obtainable Charpy specimen has a width along the notch of less than 2.5 cm ( 0.098 in. ). Under such circumstances, the design minimum temperature shall not be less than the lower of -48 deg. C or the minimum temperature of the material from Table A-1". Is Note (5) of Table 323.2.2,  a part of Note (4) of Fig. 323.2.2A ? If it is, then this note is taken care of already during manufacturing and we need to take care only about Note (3). Am I right ?

I would really appreciate answers to my queries.

Thanks.....

Amatuerepipe


 

RE: Suitability of carbon steel pipes at low temperatures

Might be worth a cross link to ASME forum.  

RE: Suitability of carbon steel pipes at low temperatures

(1) No, because a material might be governed by Curve A.

(2) Refer to the restriction on welding consumables in A-3 (b).  That is the differentiator.

(3)  The tabulated temperature limits are based on achieving the full design stress ratio.  If the stress ratio is reduced, so too can the temperature at which impact testing is not required.  

I give up with the rest as you need to be more conversant with fracture theory.  

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04
 

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