Detect Crack in a Gearbox Casing

What makes it certain there is a crack? Of what consequence is this crack?

Correction: the gearbox now contains only 750 liters of oil...

Hahahahahahaha!

That is a huge gear box. With gear oil having a nominal density of 890 kg/m^3 that comes to just over 660 kg of just gear oil. Any case designed to hold this much mass will not likely have a difficult to find hairline crack suddenly appear. My first guess is that this oil on the floor is from an overfill or surplus spill not noticed at the last servicing. My next guess is that a gasket or seal is weeping. You might find that an insect or other vermin has plugged the vent hole. The very last thing I would investigate is a hairline crack in the case.

If a hairline crack is still believed to be the problem then any machine with this much oil in the crankcase is an expensive machine. X-ray or gamma ray inspection may be well worth the expense.

we found oil on floor. that makes us certain that there is a small crack..

How much oil? Over what period of time? How about posting a photo of the suspected area of the casing?

Summary of information so far:

• There is a suspected leak from a gearbox containing ordinarily 850l of oil. The casing is of unknown size and of unknown materials. The leak is small and exhibits as a small tiddle on the floor. The gearbox has been removed and drained, and no-one knows how to find the leak, yet alone fix it. There is no information about what this gearbox does, its place in the scheme of things, what make it is, whether the manufacturer has been approached by telephone for recommendations, whether there is a cold spare available, or anything else, really.

Is there any chance of some pertinent information becoming available to readers within the next month-to-six-weeks or so?

Would it matter if this thing took a couple of years to get back up-and-running?

Is there a dipstick on this gearbox? How is the oil level changing with time?

'Is there a dipstick on this gearbox?'

.

I suspect there is at least one, though I can't say with any certainly how likely it is to be on the gearbox or even in the vicinity.

Usually automotive gearboxes do not have them. You fill the box through a plug until it runnith over.

Certainly seems like most automotive gear boxes have a dipstick in near vicinity (typically just aft of the steering wheel).

In my experience, automatic boxes have dipsticks but manual ones do not.

Oil leaks slowly. When gear box ready for installation then after 6-7 hours found oil leak. and its minute.

Please respond to the question on consequence. For example, if this gearbox is in use 24/7 and cannot be stopped, then topping-up the gearbox until either a shutdown or a failure occurs is about the only way forward. If it can be stopped, drained and cleaned, then any number of methods of non-destructive testing become available. The one to choose and the repair technique then become a simple matter of economics.

right now its in workshop for repairing. kindly advise for the test & how to repair?

Kindly state the material of construction, the size of the crack and its location relative to other structures. This information is absent from the original and subsequent posts - is it being withheld because it is "irrelevant", or something? WhereTF is the leak?

material: Cast Iron

Size: We don't know where crack is?

To find crack is over issue.

thank you sir. But, casing thickness is of 6 cms, will it work....

Try it and see.

<unsubscribes>

thank you sir...

I could hear the door slam from here. LOL!

Probably. Can you put a fluorescent material in the oil, then use a black light to determine the leak location. Maybe Magneflux, but I know little about it. Are you sure the leak is a crack, or could it be a bad seal? How do you plan to fix it? Maybe epoxy worked into any crack? Maybe welding, but that might require heating the whole gearbox and then slow cooling to avoid cracking beside the repair.

Magnaflux works on engine blocks should work on cast iron gear box casting.

Clean the outside of the gearbox thoroughly and assign someone of adequate intelligence to OBSERVE it until the point of the leak can be found.

I suggest that the observer not be you.

After the origin of the leak is found, commission someone of adequate skill who can replace the leaking seal, or clean and braze the crack in the gearbox, after all oil is removed.

Once again, I suggest that this repair not be attempted by you.

lyn-

Perhaps you and others may agree with me---

As I skim through these answers I spend more time on the simpler ones that I do the complicated and expensive ones. Not trying to be critical but the cost I estimate for some may be more expensive than replacing the gear box with a new one. The ones I seem to spend the most time on are those that appear to have the highest probability of actually working. These also seem to be the least expensive solutions.

I am reminded of an old mechanic, who once worked for me who could fix almost anything but a broken heart. His philosophy was---

KISS ----> KEEP IT SIMPLE STUPID

He sure saved me more money, kept the equipment running which kept the products going out the door. He did more for the operation than 5 engineers with twice the salary could do with their slide rules, pocket calculators or multitude of reference books could. His only deficiency was that he had an extreme lack of tact when dealing with engineers. I think he only liked me, an engineer, because I used a ratchet wrench as a paper weight in my "IN" mail tray on my desk.

Good Luck, Old Salt

Did somebody ask for an expensive solution? I'll offer an expensive solution. Thoroughly clean the inside of the gear box and then seal it with just one port for a vacuum pump with a helium leak detector. Apply a very small stream of Helium from a tank and a small diameter hose. Helium will find tiny cracks you never dreamed were there.

redfred-

I'll raise you one. Want the cheapest solution? Here is a real cheap one and probably the most used one in the history of gearboxes.

Tools: rag; flashlight; 4" woman's make-up mirror and a cheap magnifying glass

Procedure: 1) Wipe surface clean with the rag. 2) operate gearbox. 3) look at gear box exterior for leak(s). 4) utilize flashlight if ambient light is not bright enough. 5) for areas that are out of reach or have restricted clearances also use the mirror to look at surfaces. 6) If leak can not still be found repeat with the magnifying glass.

Environmental statement-- Rag can also be used to clean up any spilled coffee or other potential pollutants.

A really old method from a really old guy. Also a real cheap method from a really cheap guy (my wife doesn't give me a cost of living adjustment in my allowance). This procedure is about the only thing older than me.

Good Luck, Old Salt

I do understand your point that one can easily spend more money trying to identify a problem than it is worth. The only thing cheaper than telling the guy to look for a leak is to tell the guy not to look for the leak. Just coat the entire gear box with a sealant.

I think he only liked me, an engineer, because I used a ratchet wrench as a paper weight in my "IN" mail tray on my desk.

Therefore, using some shop-related paper weight may help!

Lehman57-

Yes, it did help. The only problem with it was people were always borrowing it to fix something and never bringing it back. After that I used an old broken welding stinger so that people weren't as interested in it. Despite that someone also took it. Finally found that a 2" butt weld flange would last. It had a large cut in the neck so it wasn't easily useable. I guess no one wanted to take it because of the extra work.

Good Luck, Old Salt

"A partially trained money"

Don't you mean, "monkey"?

Yes I caught that too.

Unfortunately after the 10+ minute wait for the system to accept my post it wouldn't let me go back and fix it.

"What-the-heck" ... gonna post this SIMPLY to see whether 'Yashit' actually provides any "Updates"
(as he promises in his Post #63).

I'd give another "GA" to your post, save one little nitpick: If he is to add positive pressure in order to encourage/exacerbate the leak, WHY BOTHER with "flush-and-fill"? Simply top-it-off, strategically place a few observers and 'puff-away'.

I'd have to agree with lyn, though, in that the OP does seem to be underqualified to attempt anything here.

My ACTUAL "bittersweet input" to THIS 'Gearbox_thread' is posted at (Post#18) at THIS thread (about 1/2 way down that post, for those who DARE to venture therein) [Look below *Ref's* there]...!

{{ Once again , as at the bottom of my comment HERE ... Kudos to PW, for at least prompting in Post#10 above : _{^{"Please give the forum some information to work with!"}} }}

Strip the motor apart, clean well and spray liquid penetrant on the inside and developer on the outside.

Motor, what motor???

We have zero useful information from OP who wants to be led by the hand to fix a problem they can't even define.

This is BS, the OP is less than helpful...................................

,

<UNSUBSCRIBES,,,,,SLAMS DOOR ON WAY OUT, WHILE MUTTERING TO SELF ABOUT INCOMPETENT FOOLS>

Sorry, Gearbox. I was thinking about a motor problem when i posted, Senior moment.

I have read through most of the suggestion and some are pretty good. I will add one more that in this circumstance might have saved you a bunch of work and a lot of guessing. There are several dies that can be added to the oils. I have used process in the past to find these types of issues without all of the drama. I would suggest talking to your lubrication supplier and they can help with this. I also would encourage you to hire someone whom has experience in these matters.

Running a gear box with a leak such as described is not much of an issue. In most cases the crack (if it is a crack) may seal by its self once the unit gets to operating temperature.

Dear Mr. YashitSwami,

Magnetic Particle Test, Eddy Current Test, Die Penetration Test should help to find out the crack. Ultrasonic Test also will help but if any curvature is there, it may mislead.

Pl. post the information, how you have found out.?

DHAYANANDHAN.S

Thank you sir, there are curvatures at the corners, so, we are going with die penetration.

If the DEA detects crack in your gearbox, that will be even worse trouble.

http://en.wikipedia.org/wiki/Dye_penetrant_inspection

When I worked at general dynamics,the inspection process was as follows, if you have an idea where it is sprinkle metal dust around the area,then they used horseshoe shaped magnets. When they put the magnet on the area ,the dust particles stuck to the crack forming a easy to see line. I'm not sure if that application is possible ,but there must be something along that line of testing for your gearbox crack ( suspected) good luck.

Some oils will fluoresce when exposed to UV (black) light. Can you cover the gearcase to block off outside light, then illuminate the case with a UV light to see if you can detect the source of the oil leak - it would help to clean the case with a solvent first. As others have suggested it may be necessary to aid a dye to the oil to make it detectable.

thanks for the suggestion, I'l surely consider.

Are you sure it is of cast iron? Some times bigger GB are made of fabrication, then it could be weld joint leak...

yes, it is cast iron body.

That will work or clean the box properly, wash with duco thinners, dry. Spray paint with dark red aerosol, let it dry and spray with white duco over the red..just a thin layer.

The red in the crack will show thru the white paint. This can be done to determine if an expensive gear is sound too.

I totally agree with Yesyen on this matter. I spent many years fabricating large HV Transformers and each vessel was tested for leaks by coating all the seams in a white chalk liquid (developer) which dried as a chalk smear. We then filled the vessel up with paraffin and the leak showed as a pink bleed in the chalk. Sometimes we added some of the red dye into the paraffin to enhance the process. Then mark the leak on the gearbox, drain and repair.

yesyen-

Understandable as to how you find the crack but what about the kerosene? How do you drain it and effectively rinse it out of the gear box? If this is not done completely, the first oil fill-up will become diluted by the kerosene and not work as it should. Also will it damage the seals or bearings?

How will the kerosene be disposed of? It can't be burned in a diesel engine or a boiler because any fine sand, gear powders or chips will clog the filters and/or the nozzles/injectors. Proper disposal of it will be at least $10.00/gal in drum quantities.

The detection is fine but what about the clean up and disposal.

Good Luck, Old Salt

If kerosene is difficult substance to handle in your place, I'm sorry for suggesting it. In many countries kerosene is still a convent and relatively a cost effective solvent compared to Trichloroethylene. At times we use kerosene for clearing the components and give final rinse with Trichloroethylene, if bone dry surface is required. In that way, kerosene finds some sundry usage in work shop.

Yes, with gears and other components in position, filling the gear box with such solvent is not advisable. After testing and draining the kerosene, then rinsing with lube oil would still may not ensure 'no trace of kerosene'. I intent to suggest this, if only the gear box in stripped off condition and case is free to take a fill.

Hi, you can either dye pen or MPI the gearbox to find the crack.

Good luck.

Simple way to test hair line crack is lime test - clean surface and apply lime solution

Second one dyepenetration test - pink colour spray is available in market - clean surface and spray it - let it dry crack will be visible

Third one is ultrasonic test - bit costly

Thanks anil...

Hello Suresh thanks for your reply, we are going for D.P. test and we have planned to fill crack with steel weld putty.

Hi Yashit, Good to hear that. Please let us know the results for benefit of all people here.

Check this out: http://cr4.globalspec.com/thread/86287 its about "Leakage Detection Using UV Lamp"

There are two part spray-on metal crack detectors. I have used them with good results.

Just Google "spray-on metal crack detectors"

Are you sure it is a crack?

1. Check the real amount of oil required.

Consider that the amounts of oil, specially in cases of cast body, use to be only orientative. Refer always to some level indication. (Dipstick, sightglass, LT... etc).

Those can be located in the gearbox or in some auxiliary tank attached.

Gearboxes of this size use to have some lubrication circuit, and the oil mentioned in the name/data plate may refer only to the oil required for the gearbox, ignoring the amount needed for the pipes and pumps of the lubrication unit. Even if they have been supplied together by the same manufacturer. (I know it by experience).

In some models (i.e: some model of Flender/Siemens) the level of oil must be adjusted with the oil pump running. Not stopped. If this in not considered, the unit can be erroneously overfilled, leading to overflood by some breather or joint.

2. Breathers.

Breathers are installed?. Without breather, and due to the pressure generated by the expanding air as temperature increase, it can produce a leak by some seal till the pressure stabilises and leak stops, leaving a low level of oil with no further leakage.

This will occur most likely during a cold start, when the oil heats up.

3. Internal piping of the gearbox.

Check the internal piping of the gearbox. Are open all the valves and pipes that should be open? Are pressures in those pipes as they should be?. Is oil able to go to all the places it must go, in the required conditions of pressure and flow?

4.Crack.

In case of crack with leakage of oil, that you can see on the floor, even with small amount, a good cleaning, newspapers and Gorilla tape or similar should allow to zeroin quite accurate and rapidly (hours). Because your oil will be at least VG 320, It should leave a good track.

4.1 Once the crack is detected.

Do not focus only in the crack, but the origin of the crack.

4.1.1. If the issue can be clearly defined as manufacturing defect (most commonly some welded seam in case of welded construction) you have had a good day.

Check materials and procedures (you or your supplier have them, we don´t) and apply them.

4.1.2. Defective assembly.

Get all alignment and installation protocols and cross check with manufacturer specifications. Do the values found match? If so, verify all of them again before reassembly (baseplate geometry and level) and during the assembly (input or output misalignments, excessive or irregular torques in the couplings or fixation).

5. Information Exchange.

Can you give some data of the manufacturer, model, assembly, use?

I have had several cases of cracks detected in gearboxes of this size, and I would not mind to exchange some information (within NDA limits) about it.

6. Please give a feedback about the findings. This would make many people to feel that the efforts put here are meaningful, encouraging to help others.

Salu2 cordiales,

Abel.

...Would add to Abel's very thorough method;

-Add an oil pan underneath the gearbox. This will help you for small spills , never mind the reasons for it....

I am thankful to you for your detailed reply.

This gear box is more than 80 years old, no one knows anything about it.

casing is of cast iron, and after maintenance we found oil leakage, so, it seems a case of mishandling of gear while assembling.

No internal piping in the gear box.

Now, i am worried about origin of crack, as we find crack we are going to fill steel weld in it. its a two part metal paste, which is as hard as steel.

As we get results i'll definetly update them all.

And I am again thankful to you for educating.

Best Regards,

Y. Swami

If the gearbox is still under any warranty, turn around and send it back to whomever manufactured it as faulty. In such matters, always blame everyone but yourself.

Or have the manufacturer representative come and do the inspection, and recommend a path forward.

"how to detect crack in a gear box casing. having a huge gear box, which stores 850 litres of oil, unfortunately there is a crack in casing. unable to figure out where crack is?

Is there any way to find out?"

If the case is ferro magnetic, Wet Flouresecent Magnetic Particle (WFMT) examination;

Whether or not ferro magnetic, Die Penetrant Testing (PT) (slower than WFMT, several step process);

As already pointed out by someone, Radiographic Testing is an option, but difficult and expensive (and gear box would most likely have to be drained and opened).

A quicker and less expensive option is Ultrasonic Testing, either Shear Wave or Phased Array. Phased Array would be quicker, but a bit more expensive than Shear Wave. Either would be less expensive than RT.

Bang for your buck wise, your best options are probably either WFMT or PT.

Dan W.

any axis forces being applied to the gear box?