hydro pressure testing

[BrokenBiker]

just watched colin furze's latest vid about hydroforming steel using a pressure washer.

now ages ago I wanted to weld up a tank that needed to hold 35 bar, however I had no safe way of testing it to prove it safe so didn't bother doing it. cant actually remember what it was for now.

so, I have a pressure washer, and a few regulators and all the plumbing gubbings. am I correct in thinking that even at a pressure of like 100 bar, if the vessel being tested splits, you get no more than a jet of water out of the split, and then the pressure is released and no big bang and bits of steel shrapnel flying left right and centre as you would with pneumatic pressure testing?

 

[Welderpaul]

We use one of these. Goes up to 50 bar. Just fill it with water and pump it up. You will either see a weep if its got a leak or it just won't pressurise. Water won't suddenly 'let go' like air will. Safest way of pressure testing.

 

[Paul.]

Why risk damaging your pressure washer?. you need a hydrostatic test pump, 30 bar one here. http://www.screwfix.com/p/rothenber...ping - Tools&gclid=CLXmybWBgsACFULmwgodsb8A5g

 

[BrokenBiker]

so if it gets to say 40 bar and then a weld fails, the water will just leak out safely? like the sound of that. I looked into units similar to that but the price was a bit steep, and I only wanted it for the one job so just gave up in the end. the job couldn't have been important as I cant remember what it was for

 

[BrokenBiker]

Why risk damaging your pressure washer?. you need a hydrostatic test pump, 30 bar one here. http://www.screwfix.com/p/rothenberger-rp30-pressure-testing-pump/83797?kpid=83797&cm_mmc=Google-_-Product Listing Ads-_-Sales Tracking-_-sales tracking url&kpid=83797&cm_mmc=Google-_-Shopping - Tools-_-Shopping - Tools&gclid=CLXmybWBgsACFULmwgodsb8A5g

because my pressure washer only costs 28 quid, the price of that unit is the reason I never bought one

 

[Welderpaul]

It probably won't get to 40 bar if there is a dodgy weld. It's a safe bet the water will show as weeps on corners stop/starts.
The water will come out with a bit of force if it suddenly went but the worst that will happen is that you get wet.
Can't see a pressure washer working.

 

[brightspark]

what pressure does it run at . i can turn mine down quite low or to full power. i dont think it would do a tank any favours just letting it have it full blast after u have filled it with water 1st

 

[PTvor]

They test aqualung cylinders by pressurising them with water, not air, for the very reason that should they fail, air under pressure expands and can drive shrapnel about at high speed, but water doesn't. They also immerse them in water as well to help contain any bits.

Jets of high pressure water can be lethal, as was found in submarines which were depth charged and had seams split.

Personally, I wouldn't mess about with a makeshift arrangement based on a pressure washer.

 

[BrokenBiker]

what pressure does it run at . i can turn mine down quite low or to full power. i dont think it would do a tank any favours just letting it have it full blast after u have filled it with water 1st

not sure what pressure it runs at, but its not adjustable, however I have a regulator that would let me increase slowly.

It probably won't get to 40 bar if there is a dodgy weld. It's a safe bet the water will show as weeps on corners stop/starts.

The water will come out with a bit of force if it suddenly went but the worst that will happen is that you get wet.
Can't see a pressure washer working.

 

[Rig Pig]

Most pressure washers are capable of 2000 - 3000 psi at dead head, may bit a bit lively for a 30 bar test!

 

[hotrodder]

They test aqualung cylinders by pressurising them with water, not air, for the very reason that should they fail, air under pressure expands and can drive shrapnel about at high speed, but water doesn't. They also immerse them in water as well to help contain any bits.

I think the immersion in water deal is mostly about measuring expansion of the pressure vessel for example it might be hydroed at 1.5 X working pressure and to pass it has contain that pressure for some length of time without it's volume changing more than 1% or whatever

I don't think a pressure washer would work very either, hydroforming is very different in that you want the part to yield and change shape. Proper hydrostatic pumps can be hired if it's not gonna get enough use to justify the ££. Either that or make friends with a plumber...

 

[PTvor]

I think the immersion in water deal is mostly about measuring expansion of the pressure vessel for example it might be hydroed at 1.5 X working pressure and to pass it has contain that pressure for some length of time without it's volume changing more than 1% or whatever

I don't think a pressure washer would work very either, hydroforming is very different in that you want the part to yield and change shape. Proper hydrostatic pumps can be hired if it's not gonna get enough use to justify the ££. Either that or make friends with a plumber...

My information came from a diving magazine years back, so your information might be better than mine.

It occurs that these manual hydrostatic testers have a small piston, not the continuous pressure put out by a pressure washer, so if there's a split there's a small piston's worth of high pressure water and no chance of a continuous jet.

I must admit that this is one where I wimp out. I just don't think 100 bar pressure, which is at the low end for a pressure washer, is a fit subject for experiments in the shed.

 

[Sidewinder]

I actually have the RP30 we use it for our plumbing tests, works great, once you have filled the system with water.

 

[hotrodder]

Liquids are effectively incommpressible, as long as there's no air in the system not a lot happens if anything lets go as already said. I've have had bungs let go suddenly before when hydroing things, makes you jump and the floor gets wet but that's it. Found a vid of a catastrophic failure at 6000psi / 413 bar...

I've got a nasty scar on my right knee from a bicycle rim of all things... talking a tiny volume and only 100psi but when the rim let go it was FAR more spectacular than that vid, peeled apart like a banana and gashed me in the process

 

[Robotstar5]

Most pressure washers are capable of 2000 - 3000 psi at dead head, may bit a bit lively for a 30 bar test!

You should see the ones we have in the paintshop for cleaning baked on paint off the skids that carry the bodyshells through the ovens, they run about 900bar! and have to have someone holding a "dead mans handle" outside the cleaning booth for safety

 

[PTvor]

Liquids are effectively incommpressible, as long as there's no air in the system not a lot happens if anything lets go as already said. I've have had bungs let go suddenly before when hydroing things, makes you jump and the floor gets wet but that's it. Found a vid of a catastrophic failure at 6000psi / 413 bar...

Yes, but there obviously wasn't anything behind that capable of delivering a decent flow rate at continuous high pressure, which is what you'd expect with a high pressure hydrostatic testing system and not what you'd get with a pressure washer.

I worked at a place years back where a contractor was killed by a high pressure water jet from a huge pressure washer.

 

[Wedg1e]

We've used a hired pump unit to test pipelines, no drama when things split or come apart, had wet feet a few times though

A mate of mine runs a local dive shop and pressure-tests scuba tanks; it's something to do with the tank stretching causing the water it's immersed in to be displaced... more than a very small value and the tank fails (and gets a big hole drilled through the side so it can't be used).

 

[Robotstar5]

... more than a very small value and the tank fails (and gets a big hole drilled through the side so it can't be used).

Surprised no one's been on here asking to have a scuba tank they got cheap repaired

 

[brightspark]

Surprised no one's been on here asking to have a scuba tank they got cheap repaired

dont tempt fate new ideas crop up all the time