Induction Bend Radius for Pipeline with Pigging Requirement
Induction Bend Radius for Pipeline with Pigging Requirement
(OP)
Hi everyone.
This is one simple question but was challenged, hope I can get support herein.
For pipeline induction bend, we usually use 3d (12” above) or 5d (less than 12”) as governing for curvature radius, it actually can facilitate the pigging during erection and operation. I believe such practice must be followed in most engineering design firm.
However, when we review one of pipeline design in which around 2km pipeline are set on jetty and trestle, 1.5d induction bend is provided for the 14” line due to restricted jetty spacing as explained. We were going to advise a higher curvature radius, e.g. 3d, as mandatory comment to be incorporated, unfortunately the stakeholder doesn’t like to revise his design and wonder which code the “3d” curvature radius was specified in.
Honestly speaking, I didn’t find code basis from ASME or API, even in design manual that I own. Can anybody herein guide me for code support? Or was I really wrong that 1.5d can be applied for pipeline with pigging requirement?
Thanks.
This is one simple question but was challenged, hope I can get support herein.
For pipeline induction bend, we usually use 3d (12” above) or 5d (less than 12”) as governing for curvature radius, it actually can facilitate the pigging during erection and operation. I believe such practice must be followed in most engineering design firm.
However, when we review one of pipeline design in which around 2km pipeline are set on jetty and trestle, 1.5d induction bend is provided for the 14” line due to restricted jetty spacing as explained. We were going to advise a higher curvature radius, e.g. 3d, as mandatory comment to be incorporated, unfortunately the stakeholder doesn’t like to revise his design and wonder which code the “3d” curvature radius was specified in.
Honestly speaking, I didn’t find code basis from ASME or API, even in design manual that I own. Can anybody herein guide me for code support? Or was I really wrong that 1.5d can be applied for pipeline with pigging requirement?
Thanks.





RE: Induction Bend Radius for Pipeline with Pigging Requirement
RE: Induction Bend Radius for Pipeline with Pigging Requirement
The first ILI tool I ever saw (1991) was limited to 60D bends. That has improved every year since, and 1.5D tools are mainstream today. Anyone who can't do a fabricated (1.5D) fitting can't compete anymore. I don't think that is really a current issue.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Induction Bend Radius for Pipeline with Pigging Requirement
You have two excellent responses there which I would echo.
1.5D bends are really long radius elbows and not induction bends. You need to make sure they make the ID the same as the pipe in case they use a lower grade material. The only other thing I would say is that you would need to avoid multiple elbows within 3-4m so that the inspection pig ( if this feature is required) does not transverse more than one bend at a time, especially if any second bend is out of plane, i.e. one horizontal 90 followed by a vertical 90.
The key issue is usually risk - the tighter you make the bend the higher the potential for a stuck pig, especially if someone inserts a non flexible or shaft pig.
A pipeline which is mainly or all above ground on a jetty is able to be inspected from the outside so the requirement for internal inspection tools is reduced.
It might be a good idea to use 3D bends where possible as a compromise.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Induction Bend Radius for Pipeline with Pigging Requirement