Pressure testing


#1

I've been looking for a (relatively) inexpensive way to do some pressure testing. A local resource suggested buying a 5 gallon pressurized paint pot, which seems like a good idea, but prices start at close to $300 (http://www.amazon.com/California-Air-Tools-365B-Pressure/dp/B008FQEC6Y).

If there is anyone in the Boston area who wants to share ideas or costs for this?

-- Sean


#2

Reviving an old post - but did anyone every try this? It appears to be a very safe way to do some pressure testing but I wanted to know if anyone had actual experience?

Thanks


#3

I haven’t tried using one of these paint pressure vessels although like that they have a large opening. I have been using an old pool filter housing that I got of the side of the road and pressurising it using the water pressure out of my hose (60 psi). Pool filters typically come with a bleed valve at the top allowing you to remove all air, significantly reducing any safety risks.


#4

I have been doing serious pressure testing of cable feedthroughs but i wouldn’t have though it was overly cheap as I’m at a university and have access to a custom RIG that i can simulate 2.5km (250 bar). Its essentially a piston that you wind back to draw water in then wind in to apply pressure. William is right make sure there is no air in the device and if you are simulating high pressure ensure that the thing is properly secured with bolts and again on high pressure place something like sand bags over the bolts as they can snap and are basically bullets.


#5

I thought I’d add a comment to show the importance of pressure testing. I happened to be doing final testing on the cable penetrators on my main hull last night and ended up with a catastrophic failure. Very disappointing but am happy nothing of value was inside. Upon inspection I found a washer from one of the penetrators sticking out into o-ring groove, which would have resulted in a point load on the tube.


#6

To what depth was that ?


#7

I rather hoped the paint vessels would be pretty safe, given the environment and purpose they usually live in. I’d intended to fill it as full as possible with water, so limiting the amount of air inside, but I’d not though to see if one could be modified to be pressurized using water from the mains.


#8

@Teaguey the test pressure was around 60psi or equivalent to approx 40m. In theory the tube should be able to go deeper, although that’s the maximum pressure my mains water supply gets to. Having said that I am launching from the shore and don’t have anywhere that deep near me


#9

I see what failed the tubes hermiticity or the feedthroughs?


#10

The tube itself failed under the pressure. This was most likely due to a washer sticking out resulting in a point load as well as poor quality acrylic tube.

The cable penetrators (or feedthroughs) are fine. For these I have drilled out the centre of 316 stainless bolts and then epoxy the cables in using marine epoxy. To seal the bolt against the end cap (which is an acetal disc) I use a silicone gasket sealant designed for water pumps. This way if I really want to I can remove a cable.

I have 2 sealed vessels in my ROV design using the same methods and materials. The other tube handled the pressure fine.


#11

Ah ok, i am about to test some penetrators like that which are pre-made by blue robotics https://www.bluerobotics.com/store/parts/penetrator-10-25-a/ I’m planning to test to 1km and if they hold 1.5 then 2.


#12

Yeah those BR penetrators look really good. That’s where I got inspiration from for my stainless bolts.

1km is a whole other level! Good luck. If you can post your results that would be awesome. What are you using for your main hull. You must have pretty thick acrylic or steel.


#13

Well the deepROV I’m going to be making will be thick aluminium/ or possibly stainless i think, I’ve not designed it yet.
I will post what i can when its all said and done!
The testing is done in a custom rig that has a brass plug sat in an aluminium chamber