Seamless Pipe

The main seamless tube manufacturing processes came into being toward the end of the nineteenth century. As patent and proprietary rights expired, the various parallel developments initially pursued became less distinct and their individual forming stages were merged into new processes. 

Seamless Pipe

Source : http://www.bemafotra.com/fr/wp-content/uploads/2014/01/Welded-Carbon-Round-Steel-Pipes-ERW-pipes-Welded-Round-Tubes.jpg

Today, the state of the art has developed to the point where preference is given to the following modern high-performance processes:

• The continuous mandrel rolling process and the push bench process in the size range from approx. 21 to 178 mm outside diameter.
• The multi-stand plug mill (MPM) with controlled (constrained) floating mandrel bar and the plug mill process in the size range from approx. 140 to 406 mm outside diameter.
• The cross roll piercing and pilger rolling process in the size range from approx. 250 to 660 mm outside diameter.

 Manufacturing Process

Mandrel Mill Process

In the Mandrel Mill Process, a solid round (billet) is used. It is heated in a rotary hearth heating furnace and then pierced by a piercer. The pierced billet or hollow shell is rolled by a mandrel mill to reduce the outside diameter and wall thickness which forms a multiple length mother tube. The mother tube is reheated and further reduced to specified dimensions by the stretch reducer. The tube is then cooled, cut, straightened and subjected to finishing and inspection processes befor shipment.

Mandrel Mill Process

Source : http://www.wermac.org/pipes/pipemaking.html

Mannesmann Plug Mill Process

In the Plug Mill Process, a solid round (billet) is used. It is uniformly heated in the rotary hearth heating furnace and then pierced by a Mannesmann piercer. The pierced billet or hollow shell is rollreduced in outside diameter and wall thickness. The rolled tube simultaneously burnished inside and outside by a reeling machine. The reeled tube is then sized by a sizing mill to the specified dimensions. From this step the tube goes through the straightener. This process completes the hot working of the tube. The tube (referred to as a mother tube) after finishing and inspection, becomes a finished product.

Mannesmann Plug Mill Process

Source : http://www.wermac.org/pipes/pipemaking.html

Tolerances 

The wall thickness tolerance of 12.5 % for hot rolled seamless pipes is specified fundamentally in ASTM A999 or EN ISO 1127 T2. However, wall thickness differences caused by the manufacturing procedure may lead to a possible eccentricity, that is, to a deviation from symmetry (Diagram 2). Normally the tolerance for wall thicknesses of welded pipes is defined in ASTM A999 or EN ISO 1127 T3. The evenness of the steel plate or coil thickness ensures that the wall thickness tolerance remains constant across the entire pipe body and much better than the required ± 10 %. This means there cannot be any eccentricity. Particularly for orbital welding or subsequent welding processes on building sites, a constant wall thickness and thus the exclusion of any eccentricities is a crucial criterion.

The wall thickness tolerance

Source : http://www.butting.com/fileadmin/daten/redakteure/Download/EN/Prospekte_EN/BUTTING_Seamless_or_welded_pipes.pdf

Corrosion Resistance

The pipes welded on the basis of the valid calculations (AD-data sheet 2000 / ANSI B 31.3 / ASME VIII) are of exactly the same quality as seamless pipes, providing a 100 % weld check has been performed. With the production of longitudinally welded pipes, carefully selected welding procedures are used, combined with the state-of-the-art testing technologies (e. g. digital X-ray inspection). In the process, the corrosion resistance in the weld area is kept constant by using higher alloyed welding additives, i. e. at least at the level of the base material. The assessment of the interior pressure calculation for seamless pipes is 100 %. This can also be ensured with welded pipes when combined with a complete weld check (welding factor v = 1.0). As a result of this reliability of the production process, the longitudinal seam in the welded pipes does not constitute a weak point. Circumferential welding with both seamless and longitudinally welded pipes must therefore be performed to a high-quality level and must take account of the specific parameters.

References :
http://www.wermac.org/pipes/pipemaking.html

http://www.butting.com/fileadmin/daten/redakteure/Download/EN/Prospekte_EN/BUTTING_Seamless_or_welded_pipes.pdf

Dega Damara Aditramulyadi

Student ID : 15512046

Course      : KL4220 Subsea Pipeline

Lecturer   : Prof. Ir. Ricky Lukman Tawekal, MSE, Ph. D.

                  Eko Charnius Ilman, ST, MT

Ocean Engineering Program, Institut Teknologi Bandung

http://www.ocean.itb.ac.id/en/