Chemical Engineering December 2019 - 44

Cover Story
TABLE 6. SYSTEM PRESSURES AND TEMPERATURES FOR CLASS 600 PIPING
SYSTEM (GROUP 1.1 MATERIALS [1])
Design temperature,
°C
200
Design pressure,
bar / MPa
65 / 6.5
*Note: as per applicable design code
TABLE 7. CALCULATION FORM FOR WORKED EXAMPLE
Nominal flange
diameter
W(P+F+M)
2πGP (G/4 + 2bm)
W(PT)
πGPT (G/4 + 2bm)
W(GS)
πbGy
Wbolt
T = K D W/1,000
Target torque
LTF = 1.01 + (D/C)
Wbolt × LTF
HPA of selected tool
Tool pressure
*Note: Hydratight tool reference number AJ4
TABLE 8. COMPARISON OF CALCULATION VERSUS TABLE 1 OF REF. 3
Flange
identification
Flange: NB 150
(NPS 6 in.)
Flange: NB 300
(NPS 12 in.)
Bolt size Target torque
of example,
Nm
1 in. -
UNC
1¼ in. -
8UN
278
602
Associated
bolt stress,
MPa
154
158
Target torque of
Table 1 of Ref.
3, Nm
677.9
1423.6
Associated bolt
stress, MPa
345
345
Author
Walther Stikvoort (Address: Wagnerlaan 37,
9402 SH Assen, the Netherlands; Email:
stikvoort@ziggo.nl) is a renowed principal
mechanical & structural integrity consultant
who has spent about 50 years in the design
and design verification of pressure vessels
and piping to recognized key design codes
and also has significant experience in fitness-for-service
engineering critical assessment
(ECA) according to common FFS proceTABLE
9. THE PROBABLE BOLT STRESS, σBOLT, DEVELOPED MANUALLY, AS CITED IN
THREE CODES
Source
Bolt size: 1 in.- UNC
Bolt size: 1¼ in. - 8UN
42
ASME BPVC VIII
Div.1; Appendix S
σbolt = 310 MPa
σbolt = 277 MPa
EN 13445-3Annex
G
Rules for pressure vessels
(RfPV); D 0701
σbolt = 198 MPa σbolt = 268 MPa
σbolt = 177 MPa σbolt = 240 MPa
dures. He has demonstrated his expertise in several key roles,
such as expertise holder static equipment engineering (Authority
Level TA-1) at NAM (a joint venture of Shell and ExxonMobil) (18
years) and as manager mechanical engineering at Kellogg Continental
(15 years). Stikvoort worked for NRG as a senior consultant
asset integrity (7 years) and for GLT PLUS (Jacobs) as a principal
consultant mechanical integrity (6 years). He developed numerous
engineering standards and practices focused on improving asset
integrity and involved in the development and lecturing of training
courses and seminars for the pressure equipment community. He
is the author and co-author of various papers and articles published
in recognized international journals, engineering textbooks
and technical magazines. Stikvoort graduated from the Higher Institute
of Technology (The Hague, the Netherlands) where he studied
mechanical engineering.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
DECEMBER 2019
NB 150 (NPS 6 in.) NB 300 (NPS
12 in.)
657,193 N
545,470 N
296,503 N
657,193/12 =
54,766 N
0.2× 25.4 ×
54,766 /1,000
278 Nm
1,894,776 N
1,572,664 N
646,226 N
1,894,776/20 =
94,739 N
0.2 × 31.75 ×
94,739/1,000
602 Nm
Not applicable
1.01 + (41.275/196.3) = 1.22
175,603 x 1.22 = 214,282 N
3,674 mm2 (*)
58.32 MPa = 583.2 bars
NB 500 (NPS 20 in.)
Hydrostatic test
pressure, bar /
MPa *
107.9 / 10.79
Rated pressure
at 200°C, bar /
MPa [1]
87.6 / 8.76
Rated pressure
at 38°C, bar /
MPa [1]
102.1 / 10.21
ample, whereas for the values according to
Ref. 3, use is made of a generic situation
where a target pre-stress of 345 MPa (approximately
50% yield strength of bolt material)
is taken as the starting point.
Another very
important
item
in
bolt4,214,464
N
3,498,005 N
1,119,147 N
4,214,464/24 = 175,603 N
ing design is the question of whether the
necessary bolt stress is actually realized,
and what special means of tightening, if
any, must be employed. Most joints are
tightened manually by ordinary wrenching,
and it is advantageous to have designs
that require no more than this. Some
pitfalls must be avoided, however. The
probable bolt stress developed manually,
when using standard wrenches, is cited
in a number of recognized codes and in
the specialized literature. An overview is
found in Table 9. There one can see that
there is a considerable spread in probable
bolt stresses for the bolt dimensions from
the example. The calculated bolt stresses
of 154 MPa (for the 1 in. bolt size used
in the NB 150 flange) and 158 MPa (for
the 1 ¼ in. bolt size used in the NB 300
flange), are significantly lower than those
that can be achieved by means of simple
conventional manual tightening tools (for
instance, wrenches).
n
Edited by Gerald Ondrey
References
1. ASME B16.5 - 2017; Pipe Flanges and Flanged Fittings NPS 1⁄2
Through NPS 24.
2. ASME BPVC VIII Div.1- 2017; Appendix 2.
3. ASME PCC-1- 2013; Appendix K.
4. ASME B 16.20 - 2012; Metallic Gaskets for Pipe Flanges Ring-Joint,
Spiral-Wound, and Jacketed.
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