HDPE Pressure Vessel
HDPE Pressure Vessel
(OP)
I am designing a pressure vessel composed entirely of polyethylene (HDPE). The main problem in designing this vessel is that the Sec VIII of ASME code seems to deal primarily with steel, when polymers are discussed they usually FRP.
Do I use the safety factors for steel vessels for my wall thickness calculations?
In section UG-34 there is an equation for a flat unstayed head, this equation has a “C” factor that is attributed to the joint used to attach the cap to the shell. Is this “C’” factor related to “E” (Joint Efficiency used in UG-27) of the cylindrical shell? If not how do I calculate the wall thickness of the shell with respect to the attachment of the cap?
TIA,
Michael
Do I use the safety factors for steel vessels for my wall thickness calculations?
In section UG-34 there is an equation for a flat unstayed head, this equation has a “C” factor that is attributed to the joint used to attach the cap to the shell. Is this “C’” factor related to “E” (Joint Efficiency used in UG-27) of the cylindrical shell? If not how do I calculate the wall thickness of the shell with respect to the attachment of the cap?
TIA,
Michael





RE: HDPE Pressure Vessel
I've never calculated plastic vessels, but suppose that the bases for allowable stresses are not the same as for metals. B31.3 has also allowable stresses for PE.
prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design
RE: HDPE Pressure Vessel
Regards,
Gunnar
RE: HDPE Pressure Vessel
I looked into B31.3 but it still seems as though this type of code doesn't fit our product. Our design temp and press are 200 degrees C and 60 psi. The product is to be cylindrical, 2" dia. and 6" length. I am looking into injection molding both the shell and the end caps and then hot plate welding them together. Originally I had designated threads but the joint efficiency required the wall thickness to be quite large, thus making the OD greater than 2". Would you specify this as a pipe or a pressure vessel?
Sorry to be asking so many questions but my boss is on leave for a death in the family so I don't really know where to start.
Michael
RE: HDPE Pressure Vessel
All this is from memory from some time ago. So if I am talking rubbish, I apologise. I have not kept up-to-date with HDPE pipes.
Kiran
RE: HDPE Pressure Vessel
Thanks,
Michael
RE: HDPE Pressure Vessel
You should clarify once for all the design data, as the answer will heavily depend on them.
Suggest that this object could be similar in size, thickness and fabrication methods to the gas buried pipelines normally used for distribution in urban areas.
Anyway we don't want to solve school problems on this site, so please go on with your own forces.
prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design
RE: HDPE Pressure Vessel
This is not a school problem. I am working on a new product that is undergoing revision and testing. Check out http://www.liqui-cel.com/
There just seems to be a gray area in the code with respect to pressure vessels constructed of non-reinforced plastics. And the design data is not set in stone because the idea is still being fleshed out, hence the extremely large temperature value.
Michael
RE: HDPE Pressure Vessel
Michael- For a good primer take a look at the Harrington Plastics Engineering Handbook. http://harringtonplastics.com/techpgs/handbook.htm
As others have stated, be careful with temperature.
Verify the liqui-cel.com address - it didn't work for me.
jt
RE: HDPE Pressure Vessel
Thanks so much,
Michael
http://www.liqui-cel.com
There were extra spaces in the last link.
RE: HDPE Pressure Vessel
http://www2.beuth.de/index.php3?rub=10%20Datenbanken&tar=/sixcms/list.php3%3Fpage%3Ddatenbanken
you will find that the temperature you have given will not be economical to build using solid HDPE - i would suggest a dual laminate (as described in mandatory appendix M-12 of the ASME RTP-1).
be very careful of the forming procedures, weld efficiencies, and welder qualifications. if you are not familiar with the design and construction of this type of equipment you should refer to those that are.
we, Viatec, inc. www.viatec.com, are a manufacturer of such equipment and are very familiar with the design requirements. we are also active in the ASME RTP-1, AWS, and ASME B31 committees for this type of equipment.
RE: HDPE Pressure Vessel
This may have been made clear in the previous posts but the maximum recommended service temperature for HDPE pressure pipe is 140 F with a derating factor of 0.5.