Minimum thickness of 3 layer polyethylene coating
DIN 30670 – Polyethylene coatings for steel pipes and fittings
Nominal size of pipe | Minimum thickness of normal coating, in mm |
| Up to DN100 | 1.8 |
Over DN100 up to DN250 | 2.0 |
| Over DN250 up to below DN500 | 2.2 |
From DN500 up to below DN800 | 2.5 |
| From DN800 | 3.0 |
The minimum coating thickness shall be 0.7mm greater where coatings will be subjected to particularly high mechanical stress.
Along any 1 m length of pipe, the coating thickness may be up to 10% less than the minimum required, provided the thinner area does not cover more than 5 cm2
ISO 21809-1 Petroleum and natural gas industries – External coating for buried or submerged pipelines used in pipeline transportation systems – Part 1: Polyolefin coating (3-layer PE and 3-layer PP)
Coating classes and design temperature ranges
Coating class | A | B | C a |
| Top layer material | LDPE | MDPE/HDPE | PP |
Design temperature ranges (℃) | -20 to +60 | -40 to +80 | -20 to +110 |
a Installation and transportation at temperature below 0 ℃ can cause mechanical damage
Minimum total coating thickness
Pm Kg/m | Total coating thickness a | ||||||||
Class A1 b | Class A2 c | Class A3 d | Class B1 b | Class B2 c | Class B3 d | Class C1 b | Class C2 c | Class C3 d | |
| Pm ≤15 | 1.8 | 2.1 | 2.6 | 1.3 | 1.8 | 2.3 | 1.3 | 1.7 | 2.1 |
15＜ Pm ≤50 | 2.0 | 2.4 | 3.0 | 1.5 | 2.1 | 2.7 | 1.5 | 1.9 | 2.4 |
50＜Pm ≤130 | 2.4 | 2.8 | 3.5 | 1.8 | 2.5 | 3.1 | 1.8 | 2.3 | 2.8 |
| 130＜Pm ≤ 300 | 2.6 | 3.2 | 3.9 | 2.2 | 2.8 | 3.5 | 2.2 | 2.5 | 3.2 |
300 ＜Pm | 3.2 | 3.8 | 4.7 | 2.5 | 3.3 | 4.2 | 2.5 | 3.0 | 3.8 |
a The required total coating thickness may be reduced by a maximum of 10 % on the weld seam for SAW welded pipes.
b Class 1 is for light duty （onshore sandy soil）
c Class 2 is for moderate duty （clay soils, absence of backfill）
d Class 3 is for heavy duty （rocky soil or offshore）
