Pressure Test Plugs in Machined Aluminum Housing

[jimbod20]

I have a machined aluminum 6061 housing I need to pressure test for leaks and want recommendations/guidance to seal open external ports. Pressure test is governed by customer specifications. Pressure test is 75 psid with air in water for 10 minutes.

We machine cores/passages to make all internal fluid path connections, then install threaded plugs with epoxy adhesive in four of the machined passages to seal external holes. The housing is fully machined prior to pressure test. A fully machined housing has a large amount of time invested.

I have two holes on the external surface of the housing .315 inches in diameter I need to plug or seal for pressure test. The finished machined housing results in machined features immediately adjacent to where the machined holes exit the surface of the housing which then make a face seal type arrangement difficult. I'm hoping I can find expandable plugs I can insert into the two holes that will ensure a safe leak tight seal for pressure test without marking or damaging the inside surface of the holes. The customer will visually inspect and marks are justification for workmanship rejections.

I have searched the internet and do find expandable type plugs that are similar to what I'm looking for. I'm hoping to find experience based feedback via this message thread.

 

[LittleInch]

Do you have a drawing or photo of these holes?

How thick is the housing where these plugs are?

What sort of access is available for the plugs?

How would the connection be made in the finished article / connection?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[btrueblood]

What does your customer use to seal this opening, and can you ask them for a spare one?

 

[jimbod20]

Hello,

LittleInch
I can't (shouldn't) provide pictures or a drawing. Access to the two .315 inch diameter holes is wide open. The length of both machined holes is approximately 2 inches. There is a large wall thickness surrounding both machined passages. I do have 'other' small/local machined features on the surface in close proximity to the holes which makes a face seal difficult.

btrueblood
The two flow passages in question are a customer interface. Both provide a fluid connection interface at the next assembly level. There is a custom o-ring groove far beyond both holes that seals the interface from the exterior environment (ie no external leaks). Both holes are low pressure and seal via a flat surface interface. I can't isolate for pressure test, therefore, they need to be plugged for the pressure test process. Pressure test is to ensure the integrity of threaded glued plugs.


Any experience/concerns/recommendations using expandable rubber plugs this small with air pressure at ~75 psig? I am trying to find out if I can buy expandable type rubber plugs this small.

 

[LittleInch]

O so you have a 2" long hole 8mm diam??

Try someone like this and they might do you a "special", but best to at least draw a little sketch of the hole you want plugged with dimensions.

https://www.huntingdonfusion.com/index.php/en/products-list/38-mechanical-pipe-plugs-and-stoppers

they have a US office

Also try searching for laboratory equipment.

these guys go down to 12mm

https://www.par-group.co.uk/general-consumables/pipe-stoppers/

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[btrueblood]

Can you slip a couple of .314 diameter rods, with o-ring grooves on their cylindrical surfaces, down the holes to effect a seal? Each rod would have a resultant 6 lbs. or so of force, you could hold them in place by hand if necessary, or rig a clamping device to keep them in position.

 

[btrueblood]

You don't say how big these housings are, but regardless: we do dunk tests at 70 psid all the time, on production products. We build fixture(s) that hold the products, and attachments that plug requisite orifices that are customer interfaces, usually with an o-ring face or cylindrical gland seal. The parts and plugs are held in place with toggle clamps and the whole fixture is arranged so that the part can be picked up and dunked into a test tank, and when needed, rotated to ensure visual access to any possible leak source. Y'all just need a big enough frame to do the same thing to whatever your housing is, and a big enough tank to dunk it in.

Oh, and design a dust cover for the tank when not in use. And provide a bottom drain so that when it gets gunky you can clean it out easily.

 

[jimbod20]

Hello,

Thanks for the input LittleInch and btrueblood. I believe we have similar thoughts and ideas.

I'm hoping I can buy something off the shelf, however, we have other similar products we manufacture and pressure test (air and water) and I have designed and fabricated a variety of o-ring plug and face seal fittings as required for production pressure test.

I'm going to buy a couple of the following mcmaster catalog expandable plugs for the two 0.315 inch diameter holes. I think they will work fine. The machined 0.315 inch diameter cores have no physical access constraints, therefore, I don't anticipate complexities. I will most likely design and install a test plug setup shield which covers the plugs. The pressure test tank will be enclosed.

https://www.mcmaster.com/2552K52

I'm going to buy a similar larger expandable plug and see if I can modify to fit a larger third (.5691 inch diameter) hole I also need to plug for pressure test.

https://www.mcmaster.com/2552K54

This plug will be a little more complicated. The diameter is a nonstandard size and I need the overall length of the plug to fit into a .8 inch long slot which then provides for the plug to slip into the .5691 inch diameter hole.

I'm sure I can figure out how to make the pressure test setup work. If you have thoughts/recommendations/ideas, please let me know.

Thanks again.

 

[btrueblood]

Attach a wire or cable to retain those plugs when (not if) they blow out because they get worn, or somebody forgot to tighten the wing nut before applying pressure. If I was going to revamp our pressure tester today, I would put a lockout on the air supply until the product is immersed, just in cause somebody forgot to install a retaining ring or etc.

 

[jimbod20]

Thank you.

Worn plugs over time. The failure to properly install and secure the plugs. I'm thinking I could replace the wing nut with a hex nut and establish an installed torque for pressure test. Air source lockout (I have this setup on a low air pressure test setup today). A lockout to prevent adjusting the air pressure once set. A mechanical cover or shield over the plugs. etc. I'm thinking about a simple, robust test setup and safety.

I appreciate the notes and feedback