. 2023 Dec 19;16(1):2. doi: 10.3390/polym16010002

Table 15.

The calculation expressions, according to [100,106,107].

ASME RTP-1 3A-310 [24]	ISO 14692 [18]
$P_{a} = \frac{K \cdot \frac{E_{r}}{F} \cdot \frac{D_{o}}{L} \cdot {(\frac{t}{D_{o}})}^{25}}{1 - 0.45 \cdot {(\frac{t}{D_{o}})}^{0.5}}$ $E_{r} = \sqrt{E_{a} \cdot E_{h}}$ $K = 4 - 0.75 \cdot \frac{E_{r}}{1000000}$	$P_{c} = 20 E_{h} {(\frac{t}{D})}^{3}$ $P_{a l l o w a b l e} = \frac{P_{c}}{3}$

P_a—allowable external pressure; E_a—axial tensile modulus; E_h—hoop tensile modulus; F—design factor = 5.0; D_o—outside diameter; L—design length of vessel section (if this were applied to piping, it would normally be the distance between stiffener rings, if used, or between hangers, with 360° contact, or between secondary overlays and other external stiffeners); t—nominal wall thickness; P_c—buckling collapse pressure (bar); E_h—hoop modulus (MPa); E_r—resultant modulus(MPa); D—mean pipe diameter (mm); P_allowable—allowable external pressure (bar).