3/8" Bulkhead Through Polycarb Lid?

[Mmj120789]

I was in the process of getting my new chamber setup and was wondering if it is OK to run a 3/8" male to 1/4" female npt bulkhead through polycarbonate?

 

[Graywolf]

That will work if the bulk head fitting is long enough to reach. Depending on pot diameter, you may need a fairly long one, to compensate for the lid thickness required to address deflection under vacuum. Here is an article dealing with the lid thickness issue:

https://skunkpharmresearch.com/diy-vacuum-purging-chamber/

 

[Mmj120789]

Thanks man I appreciate you replying to my posts. Seems like you try to help anyone on here in need.
Have a great day thanks for the advice. The other day you mentioned the 12" x 12" 1/2" polycarbonate was not thick enough for my 5 quart pressure cooker vessel .....?
ttps://skunkpharmresearch.com/diy-vacuum-purging-chamber/[/QUOTE]

 

[Graywolf]

Thanks for the good thoughts!

Not necessarily, what diameter is a 5 qt pot? Just passing on the math, because 3/8" would be far to thin for a 12" diameter pot.

8-2-13

The question arose regarding the suitability of a 2″ Polycarbonate plate lid on a 20″ pot, so I thought that I would share the answer and the math with you:

In summary, it looks to me like a 2″ Polycarbonate or a 2″ Acrylic plate would work. Stress at the extreme fiber at 450 psi, is a small fraction of the 9,500 psi ultimate tensile strength.

Deflection would only be about .004″, so high cyclic fatigue shouldn’t be an issue.

Calculating stress at the extreme fiber and deflection of Polycarbonate vacuum chamber lids lids

The formulas for calculating stress at the extreme fiber and deflection for a simply supported flat circular plate from the Thirteenth addition of the Machinery Handbook are as follows:

1.0 Assume:

S= 0.39W

t2

d= 0.221 W R2

Et3

Where:

S = Stress at the extreme fiber

T= Ultimate Tensile of Polycarbonate =9,500 psi

p= Pressure in psi = 14.7 psia atmospheric pressure

W= Total load on plate= p X area = 4618 lbs

t= Plate thickness= 2″

d= Deflection

R= Radius of plate= 1/2Diameter = 10″

E= Modulus of elasticity = 375,000 psi

D= Diameter of pot= 20″

Mechanical properties taken from: http://www.boedeker.com/polyc_p.htm

2.0 Therefore:

d= 0.221 X 4618 lbs X 100 = .034″ deflection on a 2″ plate

375,000 psi X 8

s= 0.39 X 4618 lbs = 450 psi

 

[Mmj120789]

The outer diameter of the vessel is 9 3/4" I.D. of
8 3/4" with a depth of 5" I suppose I'd rather use a smaller vessel than buy another sheet of PC tbh though because I'm not going to be running more than 14 g of oil at a time..I just already have the 5 quart pressure cooker laying around. Thank you again for the help...also while I have you...side note .opinion on vac pump ?? 2 stage 4cfm pump I'm looking at on eBay for right under 100$
The jb eliminator fell through so I'm ordering one from eBay any sugg?

• Voltage: 110V/60Hz

• Power:240W

• Flow Rate: 4 CFM

• Ultimate Vacuum: 0.3 Pa

• RPM: 3400

• Power: 1/3 HP

• Oil Capacity: 350 ML

• Overall Dimension: 12.5"X 4.7"X 9.4"

• Weight: About 18.9 Lbs

• Material: Aluminum

Package Includes:

• 1x 4CFM 2 Stage Vacuum Pump

 

[Mmj120789]

Palsun (lexan) polycarb sheet is 12" x 12" x 0.45" thick the press. Cooker wall thickness is close to 4/10" thick

 

[Mmj120789]

Palsun (lexan) polycarb sheet is 12" x 12" x 0.45" thick being Conservative and the pressure Cooker wall thickness is about 3/16"thick

 

[Graywolf]

You will have excessive deflection under vacuum and ostensibly eventual failure from high cyclic fatigue, using 0.45" Polycarbonate on a 12" pot.

 

[Mmj120789]

You will have excessive deflection under vacuum and ostensibly eventual failure from high cyclic fatigue, using 0.45" Polycarbonate on a 12" pot.[/QU

Thanks for the info. Since I will not be running that much could I get by without visibility inside my chamber? What would you recommend on minimum thickness of the poly carb? For the pressyre cooker 12" pot

 

[Mmj120789]

The outer diameter of the pot is less than that sorry od is < 9.5"