best way of finding/defining a crack in a steel hydraulic pipe

[marcusthehat]

The nominal 15mm OD pipe from the pump to the valve block, is cracked somewhere near a bend, "pissing" oil upwards, but only when at maximium pressure (i.e. when the PRV is working)
I had thought I had "near-enough" found the leak location, but v hard to properly see while "in-situ", and I figured that the crack would become visible after buffing up prior to brazing.
NOPE, no crack to be seen, so I got the whole proximate area brazed, but on re-fitting it is still leaking.
How do I best pinpoint the leak location?
cheers
mth
P.S.
I refrained from using the point of my finger to pin-point the leak.

 

[milkloss]

A piece of cardboard is good

 

[njneer]

To be honest if you have brazed it and not managed to seal it you would be as well with a new one .
However if that not an option , buff off all the braze , cap one end and Pipe up a hose with a probe on the other end and plug it into a spool on another tractor or handler and pressurise it to pinpoint .
Uncap the pipe and heat the cracked area to burn off any oil then braze it again.

 

[Tommy]

Could you wrap tape round it? The oil will/should tear the tape on the hole if it's fairly thin

 

[Hayboy]

Assuming you have it removed if you can clean the outside of the pipe then dust with lime/flour and pressurise. Should see a damp patch at the crack.

 

[marcusthehat]

Thanks all, I did carefully "sweel", as near as possible a single layer of electricans tape around the whole area prior to refitting, on the basis that if it was still leaking, hopefully the high pressure jet of oil would leave a telltale split in the tape.
I am leaving the pipe in-situ until Mon morning, I will then see if this tape-tactic worked.
Be bugger to make up fittings to pressurise, with a big banjo bolt at one end and an "O" ring sealed flange at the other, I will price up a replacment Monday regardless, if punitively expensive, splicing in a short length of megaflex hose may be a workable alternative.
PS
I
presume "in the trade" some sort of crack finding dye technology exists?
cheers again
mth
yup!
the technology exists
see link
https://www.rocol.com/products/crack-detection-dye-penetrant

 

[phillipe]

@Gator

 

[Hayboy]

The trade would use dye penetrant followed by developer, fairly simple process and used for exactly what your trying to do. Trouble is unless you know someone in the trade it could be quite expensive to get someone out to find the crack. If you where local I would be happy to have a go.

 

[Mursal]

The trade dye in the first instance here, would be seal one end and fill the pipe with diesel?
Consider also that its not that pipe, but another leak?

 

[Rust]

Not with your hand !

 

[Mur Huwcun]

If you clean all the paint off first before brazing you should be able to see the crack opening up when you're warming up the area with the torch.

 

[Yale]

View attachment 512880

Not with your hand !

Fork.....

 

[ACEngineering]

If its on a striaght bit cut the bit out and fit a compression fitting and if needed a new bit of tube to rejoin.

 

[Cowabunga]

I've used fountain pen ink on the cleaned exterior pipe surface to good effect before now. It finds the crack and highlights it as a fine dark line.

 

[brynseiri]

End of your tongue

 

[Farmer mk1]

If you clean it with something strong and make sure it's all gone, then get a small blow torch and heat the pipe up slightly, not so it's hot but just warm the oil will come out of any cracks with slight heat. Just don't get it glowing or anything like that lol

 

[milkloss]

[QUOTE="Hayboy, post: 3791462, member: 1628]then dust with lime/flour and pressurise. Should see a damp patch at the crack.[/QUOTE]

There's a 'your mum's so fat' joke in there somewhere

 

[Dukes Fit]

You're best to use masking tape as it will tear easier with less chance travelling than vinyl tape.

If you want a detection spray try Rocol dye/penetrant paired with Rocol Developer spray.

 

[Kiwi Pete]

Lick and stick these on yer pipe.
I had a similar issue in my steering column, between @Mur Huwcun and a few rollie papers I tracked it down, oil leaves good evidence on ricepaper

 

[marcusthehat]

Last suggestion prob the best, that and masking tape rather than vinyl tape, thanks all.
Ah larn sommat knew every day!
mth