FPPE
Mechanical
- Mar 4, 2022
- 162
Hi,
We are designing two heat exchangers with a required MDMT of -45°C.
The first of these is a BJU where all the main components subjected to pressure (shell barrel, body flanges, tubesheet, exchanger tubes, nozzles pipe, bolts and nuts) are made of materials that fall under paragraph UCS-66(g) which states:
"(g) Materials produced and impact tested in accordance
with the requirements of the specifications listed
in Figure UG-84.1 (Figure UG-84.1M), General Note (c),
are exempt from impact testing by the rules of this Division
at minimum design metal temperatures not more
than 5°F (3°C) colder".
Figure UG-84.1M), General Note (c) states:
"Material produced and impact tested in accordance with SA-320, SA-333, SA-334, SA-350, SA-352, SA-420, impact tested SA/AS 1548 (L
impact designations), SA-437, SA-540 (except for materials produced under Table 2, Note 4 in SA-540), and SA-765 do not have to satisfy
these energy values. See UCS-66(g)."
The only components that do not fall under this definition are the reinforcing pads of nozzles and lifting lugs and the wear plates of support saddles, which are in SA 516 Gr. 70 Normalised, which in any case do not exceed 13 mm, so we fall into the -48°C section of Figure UCS-66M (Curve D).
1) Is it correct to say that, considering only the above, we are not in impact test condition for this exchanger, both for materials and welding procedures, because the welding materials were also ordered with the impact test at -50°C?
2) If the materials are mentioned in the General Notes (c) of Figure UG-84.1M, is it correct not to assign a curve to each right material, but only to exempt the impact test by referring to the note "Exempted for UCS-66(G)"? And in the case of SA 516 Gr. 70 exempting with the note "Exempted for UCS-66(a) Figure UCS-66M"?
3) In the drawing datasheet under 'Material Impact Test' is it correct to write 'NO' referring to the notes above, or should we write 'YES' because the materials we are using are impact tested anyway, regardless of UCS-66?
4) The SA 516 Gr. 70 was ordered with impact test at -46°C, also mentioned in the material certificate, does this not exclude the need to enter Figure UCS-66M? Logically if we order a material that has already been tested (even if not required by the material specification in ASME II) at a lower temperature than the required MDMT we should benefit in some way also in the Mechanical Calculation Report, so we think, please correct us if incorrect.
The other heat exchanger is a BXU and like the first is made of low-temperature materials, except for the channel where the barrel and elliptical head are made of SA 516 Gr. 70 with a thickness of 24 mm (the flange is made of SA 765 Gr. II):
Governing thickness per UCS-66(a)(1)(-a)(-1) is 24 mm --> SA 516 Gr. 70 Normalised (Curve D) --> MDMT Figure UCS-66M is -36 °C (above requested MDMT of -45°C), but with PWHT we can consider a -17°C reduction in calculated MDMT ---> MDMT adjusted per UCS-68(c) is -53 °C --> Impact Test Exemption per UCS-68(c).
Can we state in the Mechanical Calculation Report and in drawing the Impact Test is exempted per UCS-68(c) or we have to consider only UCS-66?
Tubes of the bundle are in SB 163 N08825 (welded to weld overlay part in Inconel 625 of tubesheet in SA 765 Gr. II), how can we calculate the tubes MDMT?
All of these components are also 100% X-rayed and subjected to PWHT (requested by the customer and not by the code), so we think that, in case the previously calculated MDMT was not low enough, we could have taken advantage of the 17°C reduction provided by UCS-68(c), in addition to the reductions of Figure UCS-66.1M, right?
We are designing two heat exchangers with a required MDMT of -45°C.
The first of these is a BJU where all the main components subjected to pressure (shell barrel, body flanges, tubesheet, exchanger tubes, nozzles pipe, bolts and nuts) are made of materials that fall under paragraph UCS-66(g) which states:
"(g) Materials produced and impact tested in accordance
with the requirements of the specifications listed
in Figure UG-84.1 (Figure UG-84.1M), General Note (c),
are exempt from impact testing by the rules of this Division
at minimum design metal temperatures not more
than 5°F (3°C) colder".
Figure UG-84.1M), General Note (c) states:
"Material produced and impact tested in accordance with SA-320, SA-333, SA-334, SA-350, SA-352, SA-420, impact tested SA/AS 1548 (L
impact designations), SA-437, SA-540 (except for materials produced under Table 2, Note 4 in SA-540), and SA-765 do not have to satisfy
these energy values. See UCS-66(g)."
The only components that do not fall under this definition are the reinforcing pads of nozzles and lifting lugs and the wear plates of support saddles, which are in SA 516 Gr. 70 Normalised, which in any case do not exceed 13 mm, so we fall into the -48°C section of Figure UCS-66M (Curve D).
1) Is it correct to say that, considering only the above, we are not in impact test condition for this exchanger, both for materials and welding procedures, because the welding materials were also ordered with the impact test at -50°C?
2) If the materials are mentioned in the General Notes (c) of Figure UG-84.1M, is it correct not to assign a curve to each right material, but only to exempt the impact test by referring to the note "Exempted for UCS-66(G)"? And in the case of SA 516 Gr. 70 exempting with the note "Exempted for UCS-66(a) Figure UCS-66M"?
3) In the drawing datasheet under 'Material Impact Test' is it correct to write 'NO' referring to the notes above, or should we write 'YES' because the materials we are using are impact tested anyway, regardless of UCS-66?
4) The SA 516 Gr. 70 was ordered with impact test at -46°C, also mentioned in the material certificate, does this not exclude the need to enter Figure UCS-66M? Logically if we order a material that has already been tested (even if not required by the material specification in ASME II) at a lower temperature than the required MDMT we should benefit in some way also in the Mechanical Calculation Report, so we think, please correct us if incorrect.
The other heat exchanger is a BXU and like the first is made of low-temperature materials, except for the channel where the barrel and elliptical head are made of SA 516 Gr. 70 with a thickness of 24 mm (the flange is made of SA 765 Gr. II):
Governing thickness per UCS-66(a)(1)(-a)(-1) is 24 mm --> SA 516 Gr. 70 Normalised (Curve D) --> MDMT Figure UCS-66M is -36 °C (above requested MDMT of -45°C), but with PWHT we can consider a -17°C reduction in calculated MDMT ---> MDMT adjusted per UCS-68(c) is -53 °C --> Impact Test Exemption per UCS-68(c).
Can we state in the Mechanical Calculation Report and in drawing the Impact Test is exempted per UCS-68(c) or we have to consider only UCS-66?
Tubes of the bundle are in SB 163 N08825 (welded to weld overlay part in Inconel 625 of tubesheet in SA 765 Gr. II), how can we calculate the tubes MDMT?
All of these components are also 100% X-rayed and subjected to PWHT (requested by the customer and not by the code), so we think that, in case the previously calculated MDMT was not low enough, we could have taken advantage of the 17°C reduction provided by UCS-68(c), in addition to the reductions of Figure UCS-66.1M, right?