[rahtreelimbs]

I understand that you need to stop drill a crack to prevent the crack from spreading
My question is two fold.....how do you identify the exact end of the crack and should you weld up the hole when welding the crack?

[Otto Nobedder]

I have the advantage of dye-penetrant, but,

You can simply select points beyond the crack. Center-punch them, drill them with a 1/8" bit, the hit them with a counter-sink so you have a beveled opening. Grind/slit the crack the same way, and weld it like any other open-root weld.

Or, as I often do, grind out the crack to near it's bottom with a 1/4" grinding disk, and finish through with a 1/8" disk. If you pay attention, your grind will extend past the crack into undamaged metal, and you can, again, weld as any other open root.

Steve S

[Rick_H]

I have the advantage of dye-penetrant, but,

You can simply select points beyond the crack. Center-punch them, drill them with a 1/8" bit, the hit them with a counter-sink so you have a beveled opening. Grind/slit the crack the same way, and weld it like any other open-root weld.

Or, as I often do, grind out the crack to near it's bottom with a 1/4" grinding disk, and finish through with a 1/8" disk. If you pay attention, your grind will extend past the crack into undamaged metal, and you can, again, weld as any other open root.

Steve S

Near identical to the process I use, works every time.

[Braehill]

It doesn't always work, but you can put the piece in water up to about half it's thickness and heat it up until it starts to boil the water and the steam will push water up through the crack as it cools revealing it's outline. That's not practical for some things but it works on smaller parts that can expand to open the crack. Bigger items that are constrained will sometimes seal up the crack with expansion.

Len

[weldin mike 27]

If its steel it will have a natural magnetic field that can be harnessed by sprinkling grinding dust on to the area, It isnt strong and not as accurate as proper magnetic particle tests but it will show a bit.

Mick

[jroark]

I've heard of drilling aluminum to stop cracks but is it necessary to drill steel or does grinding it out work the same? I've ground cracks in steel to undamaged metal and it seemed to work fine.

[Poland308]

I think either way will work on steel. But if you can't grind all the way through the steel then it would be a good idea to drill it.

[Otto Nobedder]

Frankly, I prefer to grind it all the way out. It works as well, though makes more weld.

If the intent is to weld a patch piece over the top, then a stop-drill with no further action will suffice, though I'd use a drill dia. at least the material thickness.

I should have included this in my first reply, but over the last several weeks I've been a bit of a "one trick pony" doing vacuum repairs, where I can't just throw a doubler over it and call it good.

Steve S

[ex framie]

Yeah, but its a hell of a trick.
Thats the issue when you become "competant" all the SJ's migrate your way.
Nice to be appreciated eh.

[Otto Nobedder]

Yeah, but its a hell of a trick.
Thats the issue when you become "competant" all the SJ's migrate your way.
Nice to be appreciated eh.

"SJ" 's? S#!tty jobs?

Yes, it's great to be appreciated (and paid in kind).

Today, the boss hosted a salesman for a company that makes Helium leak detectors like I use, and included me in the meeting. He showed the fellow pictures of my latest find, the one I recently posted, explained CSS in great detail, and went on to tell the fellow, in front of me, that I was the best at this of anyone he's known in his 42-ish years in the business, and he'd done the work himself.

Take this for what it's worth... There's MAYBE 50 people in the U.S. who do specifically what I do. Being among the best of 50 is like being Valedictorian for a small town high-school in the middle of nowhere.

It still made me feel good.

Steve S

[LtBadd]

Yeah, but its a hell of a trick.
Thats the issue when you become "competant" all the SJ's migrate your way.
Nice to be appreciated eh.

"SJ" 's? S#!tty jobs?

Yes, it's great to be appreciated (and paid in kind).

Today, the boss hosted a salesman for a company that makes Helium leak detectors like I use, and included me in the meeting. He showed the fellow pictures of my latest find, the one I recently posted, explained CSS in great detail, and went on to tell the fellow, in front of me, that I was the best at this of anyone he's known in his 42-ish years in the business, and he'd done the work himself.

Take this for what it's worth... There's MAYBE 50 people in the U.S. who do specifically what I do. Being among the best of 50 is like being Valedictorian for a small town high-school in the middle of nowhere.

It still made me feel good.

Steve S

You earned it, so you deserved it! Congrats Steve.

I used an old analog Alcatel 120 unit that was as fussy as an old woman, not too bad really. The company we used for parts and repair told me that if it ever goes then that's it, no more repair parts available. Sure would have been nice to use a new digital unit.

[Coldman]

Hey Steve,
just on that topic, do you use ultrasonic leak detection to help you zone in on micro-leaks?
Vic

[Poland308]

One of the guys I work with got to use a ultrasonic detector that was a loner from a factory rep and he's just been raving about. I hope he can convince the shop to buy a couple.

[Otto Nobedder]

Hey Steve,
just on that topic, do you use ultrasonic leak detection to help you zone in on micro-leaks?
Vic

No, we don't do any UT, but that's a hell of an idea. I'd never thought of it in a diagnostic context before... Always as post-weld confirmation.

I'll explore the possibilities. It could speed up leak location significantly, if it will tolerate the peculiars of my most common leak mode.

Steve S

[Coldman]

Steve,
Micro-leak detection in refrigeration systems can be a tedious task and I use several techniques to assist. Sometimes I need to employ all methods to find pesky leaks.
Ultra sonic leak detection is an important method that I use frequently and in the USA would be really cheap - a no brainer.
I use the Amprobe UD300 http://www.amprobe.com/amprobe/auen/env ... ?pid=73435

The theory is that gas escaping a micro leak is at very high velocity due to the venturi effect and therefore emits ultrasonic sound. The gas velocity is less than the speed of sound so the ultrasonic emission is still detectable for vacuum leaks where gas is rushing into a pipe or vessel in reverse of a pressure leak. I test with pressure and vacuum, because sometimes a leak will seal in pressure but open up in vacuum and visa versa. I think it would be ideal for your situation.

The unit is a small hand held device withe ear phones attached and various level of sensitivity and two nozzle attachments, the first being a mini "radar" type dish collector that picks up ultrasonic leaks in the general area and from some distance (like across the road if you want it to. You will want to shut down your shop air compressor system unless you want find and fix them leaks too!). I use this first to establish if there are any leaks and approximate location. The second nozzle is just a short tube that will only detect sound at the tube entry for precise location finding.

You would still need to use your existing methods to get a visual but the amprobe would certainly cut down time getting to within an inch of the leak.

I've used it walking under a long pipe rack 20ft in the air to find leaks in pipes and valve glands etc. Works a treat. Great for automotive work. I've found that some (not all) fluro lights emit ultrasonic sound that set it off and I have to turn out the lights and go by flash light. You will learn to cuss a little more because people across the shop scrunching plastic or scratching their moose nuckle gives interference.

Check it out and see what you think.
Coo-eee!

[Otto Nobedder]

I've had some small successes with "acoustic" sensing with a mechanic's stethoscope. However, that requires a leak many thousands of times larger in magnitude than I typically am searching for.

True UT, looking for reflections in the metal itself, holds promise.

Steve S

[Coldman]

With the UD300 I can find micro-leaks of 3 grams per year refrigerant loss. I know I have these kinds of leaks if I can't pull a system vacuum below 100 microns which I like to do if I can to really test a system out or if I leave a vacuum pump running overnight and its not down to 70 microns the next day.

[Otto Nobedder]

With the UD300 I can find micro-leaks of 3 grams per year refrigerant loss. I know I have these kinds of leaks if I can't pull a system vacuum below 100 microns which I like to do if I can to really test a system out or if I leave a vacuum pump running overnight and its not down to 70 microns the next day.

Interesting. I'll have to investigate that. With vacuum vessels, the gas (air) is "escaping" in the other direction, into the vessel, but it may still make a detectable noise. However, it's not "apples to apples" to your description of refrigeration systems. The amount of leak I'm usually hunting is rarely detectable by vacuum-level. I found a major (by our standards) leak in a vessel that held at 3 microns for two weeks without the pump on it. I once calculated a typical leak rate of (if I recall... I'm not calculating it again today) 2.5E - 09 Atm-cc/sec helium (2.5 nanoliters per second) would take 12 years, 8 months, and change to leak 1 cubic centimeter of helium at standard temperature and pressure. That post is here somewhere with the actual numbers (may be 2.7? I've slept since then).

However, reflective UT, basically Ultrsonic SONAR, has some potential to help me find these cracks once I know they exist and roughly where.

You all have my curiosity up, and I'll be doing some research.

Steve S

[Poland308]

I do know you can't UT anything cast. The process of casting makes it inaccurate they can't get constant reading because the inconsistent density and voids.

[BLURAT]

Hello Members,

I have been busy with work and just logged in to catch up on my WT&T fix. From day one, this fine site has been the cream of the crop. I'm still amazed, but not suprised. The quality of people associated with this gem, from Jody at the top, to all of his elves (moderators) is just outstanding. You all are so extremely well versed, experienced and HUMBLE. It's an absolute blessing to be even a miniscule part of this.

The topic at hand here, drilling out the end of a Crack prior to repair, is as old as time. You all managed to take it to a NASA level discussion on procedural possibilities. That's the beauty of the knowledge base of all the fine, humble people here.

Steve's suggestion on countersinking
The holes is brilliant. I just wrote that down in fact. The others tips are no less brilliant. From my first visit here, Steve has been an obvious Fort Knox of knowledge and in the trenches experience. ..all tempered with extreme humility, tact, and humor. Your employer is most certainly blessed Sir....as is the public who unknowingly benefit from the safe movement of volatile products over the open road in your trailers. I don't mean to ramble on, but these are my thoughts on an early Sunday morning.

Don't change a thing here...and you all are most appreciated by me.....I ALWAYS learn something new here every day.

Be Safe All,

Shawn

[weldin mike 27]

Nawwww. Thanks a lot.

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