bolt spacing and loading design for without flanges

[pavvpk]

Hello,

Could somebody point me to right direction on which code (ASME SEC VIII Div 1 / PD5500) to follow to calculate bolt spacing and loads for a low internal pressure housing with no flanges.

This is a cylindrical tube with flat plates on both sides.
Material: Clear Acrylic
Load type: internal pressure

I would like to know which code to follow and validate loading. Please take a look at attached file showing this tube details.

Thanks,
pkpavv.

 

[desertfox]

Hi

To my knowledge plastic materials are not covered by either standard and because plastics behave differently to metals it's hard to predict what occurs in your situation, for example if you are tapping into the plastic then the weak part is the plastic threads if you are using steel screws, is any temperature involved and or what environment is this component subjected to.

Now all that said you could consider the flat ends to be simply supported round the edges and subject to a uniform pressure and try to establish stress and deflection.
The cylinder you could consider it to be a thick walled vessel and use Lamb's equations.
The above would be a starting point.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[pavvpk]

thank you for the response. At this point material of the housing is not critical.We can also use Aluminum housing with acrylic front and back ports for this project and also we are planning to test different materials.This product doesn't involve any certification requirements but I want to follow a recommended code standard as a starting point.

In this process, I want to read and learn these standard codes. If could point out correct code, then it would make learning process quick.

1. my primary question here is which of these codes((ASME SEC VIII Div 1 / PD5500) layout seal and fastener design for a flat end cylindrical pressure housing.
2. If we choose to use rectangular box geometry (with aluminum), which code is better to follow?

thank you,
pkpavv

 

[desertfox]

Hi

To answer your question directly I would use PD5500, however I believe you will run into problems with some of the dimensions and geometry of the components and required ratio's.
This will apply equally to the ASME.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[chicopee]

There are design manuals for plastics one of which if I recalled properly was published by Noryl.

 

[JStephen]

The codes anticipate certain types of construction, and if you're doing something different, they may not cover the situation at all.
Note also that the ASME code has exemptions for small vessels, etc., so if it is not required to comply with ASME, it's simpler not to.

 

[racookpe1978]

Back to the original questions you have not answered:
What pressure do you consider "low pressure"?
What temperature?
What fluid? (We think air, not a hazardous liquid, right?)
What hazard or what result if it
(1) leaks a little?
(2) leaks a lot?
(3) bends under pressure? (How much bending is "too much"?)
(4) blows completely off?

Are you making a test or single-use fixture for your company?
Or are you making tens of thousands for commercial sale?

 

[racookpe1978]

At this point material of the housing is not critical.We can also use Aluminum housing with acrylic front and back ports for this project and also we are planning to test different materials.

Thinking about that description, I'd recommend an alumimum body (tank wall) but size each end not for the internal stress (pipe hoop stress) that you expect, but for the product diameter (sets ID of tube) + groove wall + gasket groove width + groove wall-to-bolt hole + bolt hole circle )bolt thread OD + outside bolt hole thread margin (as needed for strength of the tapped threads = OD of the tube.

Almost guarrantteed: Your combination of the mechanical features (O-ring groove, + 2x O-ring groove walls, 2x thread wall thickness, thread diameter) will be greater than the internal pressure hoop stress minimum wall thickness. And you MUST have the mechanical features right to seal both ends with ANY kind of plastic flat plate.

Set your plastic flat plate thickness.
Add on the outside of each plastic plate a metal ring fitting over the plastic to clamp the Al tube to the O-ring to the flat plastic cover plate to the clamping plate ring to the studs coming out the tapped holes.
Your will avoid cracking the plastic since the stress is more even all the way around, and the O-ring will be better (more evenly compressed into the smooth machined groove in the Al tube. The Al tube tapped holes are not as strong as steel PV tapped holes, but you claim this is a low pressure job. Also, the Al tube can be tapped much closer and with much more success than a plastic wall tube.