Allowable Nozzle Loads for PE Tanks

Question

Allowable Nozzle Loads for PE Tanks

nikolastrojman (Industrial)

(OP)

27 Sep 24 15:34

Hi!

Does anyone have experience with allowable nozzle loads of tanks made of plastic i.e. polyethylene?
I'm trying to find any reference in literature, standards, and norms that could put me on the right track.

I need to do a stress analysis for a couple of DN100 stainless steel pipes connected to PE tank nozzles and input that the allowable bending moment is 30Nm and the torsion moment 200Nm.

The problem is this 30Nm of allowable bending moment which I think is very difficult to satisfy. The question is how to properly model this steel/PE nozzle interface in the first place i.e. this plastic nozzle is not stiff as in the case of steel tanks.

Any help would be appreciated.

RVAmeche (Mechanical) · Answer 1 · 2024-09-27 17:27:21

I would think for a PE tank you'd want to have hoses or something near the connections to minimize loads and not deform the tank.

LittleInch (Petroleum) · Answer 2 · 2024-09-27 17:34:40

It won't be very high, but you could have a decent amount of flexibility so just anchor the stainless line 500mm in front of the nozzle and don't worry any more about the tank.

If you really want to model from the anchor ( I wouldn't bother myself), just make sure you allow the nozzle to move by say 0.5mm without force and the analysis will show very low loads.

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bimr (Civil/Environmental) · Answer 3 · 2024-09-28 06:16:52

Assume zero for the allowable nozzle loads of tanks made of plastic i.e. polyethylene.

LI, that would be a mistake. You will end up with the piping rupturing the plastic tank. Plastic tanks are flexible and tend to "squat" as the tanks are filled and retract as the tank is emptied.

Because of this tank material flexibility, plastic tanks should be designed with flexible piping between the piping anchor and the tank.

The manufacturer's of plastic tanks recommend flexible piping in their installation instructions.

Flexmaster® Flexible Tank Connector

Link

Link

LittleInch (Petroleum) · Answer 4 · 2024-09-28 06:30:53

Fair enough.

A lot depends on your tank but flexibility is the key for sure

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

EngrPaper (Mechanical) · Answer 5 · 2024-10-02 14:02:57

The only PE tank I installed had installation literature similar to the picture above. Hoses for pretty much all connections were required with omega or u-loops. And from chatting with the folks who did the installation, even the nozzles themselves with no connected piping were quite leaky due to the bulkhead fittings.

NW_Wash_Eng (Mechanical) · Answer 6 · 2024-10-03 15:06:58

I have to agree with all posts above. I have purchased PE tanks from multiple vendors and all of them have required a flex connector/hose at the sidewall flanges. They really are not designed to handle any sort of load at their connection points. However, I do believe it is the sidewalls that require the most attention. I have had vendor approval to not use a flex connector on a flange connected to the domed head of a tank, but that was a pretty small line and it took some proper supporting to get them to be okay with it. I bet if you reached out to the tank manufacturer they will have some literature on best practices for installation and connections for your specific tank.

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Allowable Nozzle Loads for PE Tanks