size of bolts in a hydraulic cylinder

[brents]

hello,

i have an aluminum cylinder with an aluminum flange screwed into the end with (8) 1/4-20 bolts with a thread engagement of .375" for each bolt...

the bore of the cylinder is 2.625" and the input pressure will be 10,000 psi..

my question is:

are the 1/4-20 tapped holes in the 6061 alum cylinder strong enough to withstand the 10,000 psi?

i am trying to figure out if my thread engagement is way to shallow...

any help would be appreciated.

thanks,
brent

 

[hydtools]

That bore will apply 54,119 lbs force on the cap, 6,765 lbs per capscrew. Grade 8 capscrews are rate to 4,770 lbs tensile strength and hex socket head capscrews are rated to 5,725 lbs tensile strength. The capscrews/bolts are overloaded. No need to worry about the aluminum thread, the bolts will fail first.
I'd recommend you upsize to at least 5/16 or up to 3/8. Engage 1.5 to 2 diameters.

Ted

 

[unclesyd]

Can you come back with picture or drawing of the cylinder components. 10,000 psig is pretty high pressure and has to be treated with respect.

hydtools.
Do you think that there is screwed head glad and he using jackbolts?

http://www.crconline.com/Components/catalog.html

 

[hydtools]

unclesyd, agree a picture would help.

Jackbolts? Could be. Then the 1/4-20 screw strength would have no relation to the service load. Just the gland removal force. I took the description of screwed into the end with 1/4-20 screws to mean the flange is attached to the cylinder with the screws.

brents, more information?

Ted

 

[brents]

thanks for the replies...

i scrapped the 1/4-20 bolt idea, and I took the advice of going to 5/16-18 screws instead..

i tested the cylinder and it blew the seal at 8000 psi..

the seal was fine, the problem was the wall thickness where the bolts were..it blew the wall out everywhere the screws were.

the design is a bolt hole circle for the flange. the alum cylinder is 3.5" x 2.625" which is a .438" wall thickness..not bad except for the 5/16-18 holes left too thin of a wall...

i have redesigned the cylinder using 3.5" od x 2.250" ID, which now will give me plenty of wall thickness. i will still use the 5/16-18 screws which will be overkill, but thats ok by me...

my original design was just a little too powerful for what it was going to be used for..

i obviously wasn't thinking too great when i originally designed this...

this should work now,

thanks,
brent