Elbow sizing for foam pigs
Elbow sizing for foam pigs
(OP)
I have to pig a 24 inch crude line with a foam pig and I am unable to decide what size 90 deg elbow to use .
Should I choose 90 deg elbow of radius 1.5 D or 3D. I would also appreciate if you can refer me to a standard that has associated information about it as well.
Regards,
Ashwani Chandra
Should I choose 90 deg elbow of radius 1.5 D or 3D. I would also appreciate if you can refer me to a standard that has associated information about it as well.
Regards,
Ashwani Chandra





RE: Elbow sizing for foam pigs
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Elbow sizing for foam pigs
RE: Elbow sizing for foam pigs
Also, try using the internet for searching.
PigsUnlimited.com
The Art of Pigging
PipelineEngineering.com
TDwilliamnson.com
Contact suppliers to see what they carry.
Your situation ( current and future ) will determine the elbow radius you use. Standard long radius elbows have a 1.5D radius and are OK for only short, soft pigs. At http://www.hackneyladish.com/DimensionData-pr1.asp... are listed 3D elbows, but they may be rare. Induction bends are the way to go for larger radius bends and straight sections on both ends sure do make it easier in the field.
RE: Elbow sizing for foam pigs
RE: Elbow sizing for foam pigs
RE: Elbow sizing for foam pigs
Once again thanks for showing me the right path.
Regards,
Ashwani Chandra
RE: Elbow sizing for foam pigs
Whilst you can find pigs that can traverse 1.5D bends, you seriously limit the supply, the risk of blockage or jamming is much higher and you effectively loose the ability to intelligently pig your line in the future. Don't forget that many pigs find it difficult to traverse elbows which are very close to each other or in different planes.
I've seen many
For anything that calls itself a pipeline (what code are you designing to?), as opposed to piping, and/or is buried at any point, you would be well advised to use at least 3D bends (not 1.5 D elbows) and preferably 5D or higher. You need to consider possible changes in operation , maintenance clearing and internal inspection over the next 25-30 years and how much difference these handful of bends (you give us no data on length and no of bends) are compared to the significant difficulties of pigging with 1.5D bends.
Quite frankly the cost of the bends as opposed to elbows is so low as to be insignificant when spread over the life of the pipeline, but would make it much easier to pig due to any currently unknown requirement in the future.
don't forget to use barred tees on branches > 0.3D of your main pipe.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Elbow sizing for foam pigs
One example. A client purchased a field and found that the trunk lines were 8 inch Sched 5 and should be rated at 300 psig. My client was running the system at 560 psig (thank goodness for safety margins). The most cost effective fix was to pull a poly liner through the entire system. The liner could be pulled around a 3D bend, but not a 1.5D bend. Cutting out the 1.5D fittings and replacing them with 6D bends cost more than the liner.
David Simpson, PE
MuleShoe Engineering
Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat
RE: Elbow sizing for foam pigs
you must get smarter than the software you're using.
RE: Elbow sizing for foam pigs
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: Elbow sizing for foam pigs
During my research I came across many journals and articles which asserted more on using the same thumb rule ratio to be less than 1.5 for pig length to diameter. I double checked all the product line of TD williamson for scraper pigs dimension that most of their pigs had this minimum threshold for their corresponding line size.
I do realize that 1.5 D is a close dimension to work with assuming any hydrate formation that might cause the pig to stuck but this a close to 200 ft of line inside the facility being used for surge line , so only active during surge events.
TD williamson doesn't pay for cutting pipe surely but its surely provides technical support and we have requested that on our previous projects .
40 D cold bends are not at all possible as we have a limited real estate and also need to effectively design ur piping for allowing traffic patterns in and out of the station. For pipeline scope they would surely apply but not for onshore facilities.
The design for the 1.5 D is requested by my client as they don't want to overkill the design for a surge line despite our recommendation for a larger radius bends. So my job is to make sure I can envision things which would meet the client's demand without hampering operations , which would not have been possible if I didn't get to discuss with you guys.
RE: Elbow sizing for foam pigs
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: Elbow sizing for foam pigs
Its weird to know that more than a 100 year old practice doesn't have a standard written for correctly sizing the pigs. A google search is effective if one knows what exactly he is looking for, which proportionally reduces search time .
Shooting an arrow and painting a bullseye around it doesn't necessarily serve the purpose , facts need to be proven and with that minimum size control ratio of 1.5 for the pig the pieces started to fell in piece. The beauty lies in understanding the essence of an engineering principle and implementing it to respective conditions with its associated variable factors , a protocol that every novice should learn to follow and every experienced should try to remember.
RE: Elbow sizing for foam pigs
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: Elbow sizing for foam pigs
Take the time and read back through your posts and the replies starting from the top and work out when it was exactly that you told us that you were looking at 60 odd metres of pipe inside a plant and not 60km of pipeline buried in the ground. You would have had a rather different response and I can't for the life of me understand why you want to pig this line.
BTW the 100 years was (at least) the combined experience years of the guys answering your questions, not 100 years of operation.
It may come as a surprise to you to discover that not everything in pipeline engineering is written down in a standard or code, but that's because there are simply too many variables to cover all the angles.
Interestingly enough I had a close look at the pigs listed in your previous attachment and the smallest ones are in fact > 1.5 L/D ratio. How this helps with deciding what size elbow to use is not clear, but at 24" you could use 1.5D, but as said before why you would ever contemplate this is much more difficult to understand....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Elbow sizing for foam pigs