The principal ductile iron pipes and fittings dimensions and tolerances are standardized:
– nominal wall thickness (pipes and fittings)
– nominal cement mortar lining thickness (pipes)
– pipe length
– pipe external barrel diameter.
Ductile iron nominal thickness
For DN 60 to 300, nominal thickness of the ductile iron is the one for class 40, C40, defined by EN 545.
For DN 350 to 600, NATURAL pipes are class 30, C30.
For DN>700, the nominal thickness of the ductile iron for pipes and fittings is calculated as a function of the DN.
For a given DN, the external diameter of a pipe must be identical, whatever the wall thickness class or pressure.
Tolerances for iron thickness
Tolerances are given depending on the device, pipes or fittings, and DN in the table opposite, which gives the tolerance less (for the calculation of the minimum thickness.)
Standards EN 545 and ISO 2531 do not stipulate an upper limit.
This thickness complies with EN 545 and ISO 2531.
|Type of piece||Nominal wall thickness|
|Tolerance in mm|
and class 30
|≤ 5.0||– 1.3|
|> 5.0||– (1.3 + 0.001 DN)|
|≤ 6.0||– 1.3|
|> 6.0||– (1.3 + 0.001 DN)|
|Fittings||≤ 7.0||– 2.3|
|> 7.0||– (2.3 + 0.001 DN)|
Pipe cement mortar lining thickness
|60 to 300||4.0||– 1.5|
|350 to 600||5.0||– 2.0|
|700 to 1200||6.0||– 2.5|
|1400 to 2000||9.0||– 3.0|
Pipe working length
The pipe working length is used for linear calculations. It is the length of the pipe excluding the socket. Socket pipes have the following working lengths:
|DN||Pipe working length|
|STANDARD EXPRESS||UNIVERSAL and PAMLOCK|
The tolerance for these lengths is ± 30 mm.
The percentage of pipes delivered with a shorter working length must not exceed 10 % of the total number for each diameter of socket and spigot pipes supplied (Standards EN 545).
To calculate the number of pipes needed to build a pipeline of given length, it is necessary to increase the working length of each pipe gap which must be reserved in the back of fitting after assembling the joint.
Laid length = working length + gap
Barrel external diameter
The external diameter of the spigot end of socket pipes is indicated in the corresponding product sheets.
External diameter tolerances
The tolerances for pipe external diameters comply with EN 545 and ISO 2531 joint.
For DN ≤ 300: the pipe barrel external diameter measured with a circumference tape must be such that at least two thirds of the pipe length from the spigot end can be used for assembly when the pipe has to be cut on site.
For DN > 300, this rule also applies to a percentage of the pipes agreed between the manufacturer and the purchaser.
Ovality of pipe and fitting spigot ends must:
– remain within the OD tolerance limit for DN 60 to 200;
– not exceed 1 % for DN 250 to 600 or 2 % for DN > 600 (EN 545).
A procedure exists to correct ovality.
Recommendation : When cutting a pipe, it is recommended you use a circumference tape to first check the outside diameter of the area where the pipe is to be cut.
Barrel internal diameter
The pipe internal diameter, expressed in millimetres, corresponds to the DN number (nominal diameter).
Standard EN 545 authorizes the following tolerances:
– DN 60 to 1000: – 10 mm.
– DN 1100 to 2000: – 0.01 DN.
For BLUTOP pipes, the DN/OD indicates the external diameter.