Swedish standard

Technical center

The internal pressures are calculated by using the following formula:

Where:

P	Internal pressure (Mpa) (* 10 => bar)
t_min	Minimum wall thickness (mm)
S	Allowable stress (S = R_p0.2/1.5) (MPa)
OD	Nominal outside diameter (mm)
ID	Inside diameter (OD-2×t_min) (mm)
m	Coefficient depending on the quota OD/ID m = 1 for OD/ID <= 1.6 m = 0.25×OD/ID+0.6 for 1.6 < OD/ID <= 2.0

Attention: The pressures on these pages are given only as guidance. Dimensioning of piping systems also depends on other factors like external forces, thermal stresses, dead weight etc. Furthermore the design must be made according to regulations from local authorities and approved accordingly. For tubes in pressure vessels and boilers it is important to consider standards like TKN (Tryckkärlsnormer) 1987 and PSN (Pannsvetsnormer).

Allowed maximum wall thickness and outer diameter:
8 mm	10 mm	20 mm	24 mm	OD max.	mm
3RE60	3R12 3R60™ 3R65 8R30/6R35 8R40 8R70/5R75 Sanicro^® 28	2RK65™ SAF 2304^® SAF 2507^®	SAF 2205™	Sanicro^® 28 SAF 2304^® SAF 2205™ SAF 2507^®	260 260 260 273

**Proof strength R_p0.2 (MPa)**
Sandvik	SS	20°C	100°C	150°C	200°C	250°C	300°C	350°C	400°C
3R12^*1)	2352	190	149	134	125	118	112	107	103
3R60™^*2)	2353	210	167	152	141	132	126	122	118
3R65^*3)	2348	210	167	152	141	132	126	122	118
6R35^*4)	2337	210	174	160	150	143	137	133	129
8R40^*5)	2338	220	181	167	158	150	145	140	136
5R75^*6)	2350	220	187	176	168	161	156	152	148
2RK65™^*7)	2562	220	175	165	155	145	135	130	125
Sanicro^® 28^*8)	2584	220	175	165	155	145	135	130	125
3RE60™^*9)	2376	450	370	345	330	325	320
SAF 2304^®^*10)	2327	400	315	290	275	265	255
SAF 2205™^*11)	2377	450	360	335	310	295
SAF 2507^®^*12)	2328	550	480	445	420	405

(1 MPa = 10 bar)
*1) RN 78. t<=10mm
*2) RN 78. t<=10mm
*3) RN 78. t<=10mm
*4) RN 78. t<=10mm
*5) RN 78. t<=10mm
*6) RN 78. t<=10mm
*7) RN 78. t<=20mm
*8) NGS 1608, March 1990. OD <= 260mm, t<=10mm.
*9) NGS 1604, Sept.1983. t<= 8mm. Tmax 300°C
*10) NGS 1607, March 1992. OD <= 260mm, t<=20mm. Tmax 300°C
*11) NSG 1606, Nov 1998. OD <= 260mm, t<=24mm. Tmax 280°C. Rp0.2 is 290 MPa at 280°C, for not welded constructions
*12) NGS 1609, March 1998. OD <= 273mm, t<=20mm. Tmax 250°C