ISO 15500-20:2015 provides specific requirements and tests applicable to the rigid fuel line in carbon steel, intended for use on the types of motor vehicles, as defined in ISO 3833, with a service pressure for natural gas as a fuel of 20 MPa (200 bar) settled at 15 ?C.
ISO 15500 is intended to be applied to vehicles using natural gas which comply with requirements established in ISO 15403‑1 (mono-fuel, bi-fuel, or dual-fuel applications). This part of ISO 15500 does not apply to the following:
a) liquefied natural gas (LNG) fuel system components located upstream of, and including, the vaporizer;
b) fuel containers;
c) stationary gas engines;
d) container mounting hardware;
e) electronic fuel management;
f) refuelling receptacles.
NOTE All references to pressure in this part of ISO 15500 are considered gauge pressures unless otherwise specified.[1]

[1] 1 bar = 100 kPa = 0,1 MPa.