AutoClave Leak

General Composites Discussions Equipment Talk
#1

Dear Fellows,

I am facing a problem in vacuum leakage during the cure cycle in Autoclave. We check and assure the vacuum bag is leak proof before the start of curing cycle. But every cycle parts , contain the back filled nitrogen in form of balloon in the vacuum bag. We dnt know what is the reason why it happens? we took some actions to Remove this problem which are the following,
1- we buy new vacuum hose from AirTech USA Brand silicon coated.
2 - Change the Male and female connector With Airtech brand AQD500
3 - check the vacuum system for eakage. No leakage found

but the problem is still there

My question is
1- is that this can occur due to the expansion( at 280C, 7 bar , 550 mmHG Vac) of couplers and they get clearance and let in N2 to the system ?

Please give me some expert advice how to troubleshoot or what can be the cause/remedy.
If you need any information please let me know.

Waiting For your Reply

Best Regards
iqbal

#2

Hello,
do you use a correct kind of sealant tape and bagging film? What kind of temperature and pressure ramp do you use? What kind of moulds do you use?

Kind regards Dominik

#3

Did you also check the vacuum system for leakage at 280C? If possible, rig one of these to your vacuum system (outside the autoclave)

http://catalogue.airtech.lu/product.php?product_id=404&lang=EN

Than at least you can see if there are leaks. test with an emty mould.

Can you specify the exact materials that you use (bagging materials) Are they all 280C compliant?

Getting things to work at that temperature can sometimes be tough.

#4

It is possible that your hose system might have different expansion rates and start a leak. For those temps, try a compression fitting hose system, not a quick-disconnect. They might have compression washers as well.

#5

Dear All,

Thanks for your feed back.  The bagging film and sealant is also purchased from  Airtec  USA . Its my mistake temperature is 180C instead of 280C (sorry for mistake ).  Mold is Invar steel , and ramp rate is 2C/ min. cooling rate is 3C/m  and stabilization time is 180 min  at 180C.

Waiting for your further expert advice

Best Regards
Iqbal

#6

I had similar problems and discovered that the o-rings in the connectors were not made in Viton, so that after a few cycles they didn’t seal anymore.