API 5L Steel Line Pipe Length Tolerance Designation

As we know API 5L steel pipe covers seamless and welded steel pipe. When buyer purchase steel pipe, the length range shall be stated in the contract.

API 5L pipe length definition

In API 5L standard spec, the steel line pipe shall be delivered in accordance with the random length and approximate length in the order contract.
In API 5L specification 9.11.3.3 specified the tolerance for the the pipe length as belowed:
a. Unless other lengths agreed, (Length with less tolerances), random lengths shall be applied as the table 12.
b. Approximate lengths shall be delivered within a tolerance of +/-500 mm (+/-20 inch).
The common random length of API 5L steel line pipe is designated at 6 m, 8 m, 9 m, 10 m and 12 m. The length also can be customized according to specific requirements.

The tolerances for random length pipe shall be as below table (API SPEC 5L Table 12).

Is it easy to comply the pipe length tolerance

For the welded pipe the raw material is steel coils or steel plates, so it is easy to comply longer length with big diameter. But for seamless steel line pipe, raw material is steel round bar and manufactured by hot rolled processes, so the pipe length is limited by the raw material round bar and how big diameters line pipe required. If required longer length (more than 12 meters or 40 ft) with big diameters (specially OD more than 20” or 508 mm), it is difficult to comply with seamless.

How to handle seamless steel pipe with longer length and big diameters

Normally for Chinese seamless steel pipe manufacturer the maximum original diameter produced by hot rolled process is 16” 406 mm, few manufacturers are capable of produce maximum 18” seamless steel pipe, Octal could supply maximum 20” 508 mm original seamless steel line pipe by hot rolled process.

For the seamless steel line pipe outer diameters more than 508 mm, it shall be manufactured by hot expanding processes. (Octal supply seamless steel pipe maximum to 1200 mm).

Hot expanding process for seamless steel pipe

Hot expanding process is an after-treatment for the original hot rolled seamless steel pipe, it is the process to enlarge the pipe diameters by hot expanding. During the hot expanding process, the heater (normally the heat ring) makes the heat to the pipe body, by the help of the different Dia of hydraulic lever inside the pipe move through the pipe internal, the diameters will be expanded as required size.