Internal vs External Restrained Ductile Iron Pipes joints.

I would like ​to know the ​advantages and ​disadvantages ​of using ​internally ​restrained ​ductile iron ​pipe ​joints compared ​to the ​externally ​restrained ​ductile iron ​pipe joints in any #Pipelines  project. ​  ​

What are the ​maintenance ​disadvantages ​of both these ​approaches? ​  ​

How difficult ​is it to ​dismantle both ​types of these ​joints? ​

Please share ​your experience ​with both ​internally and ​externally ​restrained ​ductile iron ​pipes.  ​
Which do you ​think give ​better results? ​

Taxonomy

• Pipe Supplier
• Technology
• Infrastructure
• Sewer Networks
• M S Pipeline Construction
• Pipeline Installation & Maintenance
• Pipelines
• Infrastructure
• Water
• Pipelines
• Pipes and Pipelines

4 Answers

1. Thanks Visakha Rajput for her answer.

   We have revised the chapter about restrained joints in our Ductile iron Ductile Iron Pipe Systems Manual. If you choose the link to EADIPS - E-book Chapter 9 you will get examples of different restrained socket joints.

   Christoph

2. You may want to read some relevant documents on Restrained socket joints and their uses here.

3. I agree with what Marta indicated. Just add that in the case of internal joints it will not be possible to resist axial tensile forces.
   Also, in the case of external joints, the material of the screws is critical. In Valladolid (Spain) we have many problems with zinc chromated (non-stainless) corrosion screws in less than 15 years.

4. Hi Vithana,

    To decide which joints to use (external or internal) you must first confirm the pipeline pressure. Then, another factor you have the diameter, because the avaiability of one or another solution depends on these 2 factors. A few years ago you only had internal restrainedjoints for smaller diameters, nowadays you have also internal restrained joints for bigger diameters (I believe untill 600 mm at least). The internal restrained joints are much more easier to install. For the external ones you have to weld the pipe at the bottom, and it gives more logistical problems. Neither the internal or external are easy to dimantle because you can't consider it as dismantling joints. If we are talking of automatic joints, it's almost impossible to dismantle. The mechanic joints, with externally fittings (but not restrained) you can dismantle if you wish in the future (but technically it isn't the best option.

   To repair a ductile iron pipe there are several options, as for examplo the HERMETICA fittings produced in Spain.

   Kind regards,

   Marta Dutschmann Gomes