Removing a Stuck Coupling

Hello, Sparkstation.

the hub is keyed but not threaded nor tapered. the frozen hub is on a motor that drives a draft fan.

i am going to try cooling as suggested.

( can you notice my caps are off?)

thank you.

The main thing is...take your time! Don't try to pull it off by hurrying along. As you've heard, use lots of penetrating oil, and also, don't beat it to death. Use your pullers smoothly and steadily, and if it doesn't come off the first time, let it stand, and try again later. If you do this, you'll get it off eventually.

I have seen pulleys/gears that have stood for decades that were eventually removed by the puller/oil/heat method. One time took three weeks on and off, but it did come off with minor damage.

Patience is the key.

PB Blaster!!

will help break apart almost anything.

Sorry - wrote my reply before seeing your response.

Hey Sparky,

After 30 years in the business , I could not have come up with a more comprehensive answer than yours. !!!!!

Had an exact same problem once , and even though the manual said interfrence fit, the hub was actually screwed !!!!! direction of rotation is important since it dictates the type of threads (LH or RH).

Only other suggestion is when using liquid penetrant to free up the sized components, you may need a product such as Kroil .

Works fine for me. Said to be the most penetrative oil in the market.

hey hi there

its my third day & i have tried to removed the hub by heating n pulling for

pulling i have made a puller with 20mm thick plate even though its getting bend

i have given 400 bar pressure with hydraullic jack too

now only i have to try by cooling the shaft by N2....

A laast i made it in the fourth day busing big nozzle torch by heating evenly

& raising the pressure of hydraulllic pressure at 310Bar...

I do not have any magic suggestions except that heat is usually the most successful.

I assume that you are talking about a keyed parallel shaft to coupling hub fit?

If so, clean everything, use lots of penetrating oil, attach and tension your very good quality puller, heat the coupling on one side only until it is seriously hot (only you know how hot that can be, I do not know anything about material or duty or the machine), give the coupling a number of good healthy cracks with something that will not damage it too much. Hope for the best and then let cool, add penetrating oil and try again heating on a different side of the coupling. I prefer to use a C shaped backing plate and a strong-back with a couple of M16 stud bars to pull on rather than most commercial legged pullers.

Cut it off a long the keyway. Right angle grinder with cut off wheel works well. At the keyway you can get all the way thru with out damaging the motor shaft Once thru the one side it may relieve it enough that a puller will take it off. Small chisel as a wedge in the cut will open the bore to add some relief.

hello, ozzb.

Truth is i want to re-use the hub so, i am going to attempt cooling the shaft and heating the hub then applying the puller as earlier suggested by 'Sparkstation". I will only use your suggestion if my attempt of smooth removal fails.

Thank you.

I think you will find your problem is the key. if it is half moon type try getting a sharp chisel or appropriate screwdriver UNDER the lip and prising up Or use a drift to tap down on the key and break it loose in the slot. Make sure there aren't any locking grub screws securing the key in place, they can be hidden under surface grime.

If you do use heat, heat a line along the keyway. I would try not to heat it as the heat can damage the coupling, particularly the tooth hardening.

try using a Hydraulic puller. They are far more effective than regular ones in these situations.

"if it is half moon type try getting a sharp chisel or appropriate screwdriver UNDER the lip and prising up Or use a drift to tap down on the key and break it loose in the slot."

An appropriate screwdriver does not exist for this or any other striking, bending or prying application and if you were to go this route it probably would have little effect on a 100mm shaft application anyhow. And you may be explaining to someone how you got a foreign object wedged in the keyway and broken off thus causing you to destroy the hub in order to remove it.

And Mr. Burns won't be happy...

There are specific screwdrivers made for just such work. They are quite different in construction to a normal screwdriver, normally having the shaft running all the way through the handle, terminating in a metal top. the shaft steel is also different, having far more spring and the tip is chip resistant. Obviously you can't use them in electical applications. Stanley is one manufacturer however you won't find them in kits or the local hardware as they are a specialist tool.

Do all the above, but most important keep tension on the puller whilst you are doing it, hitting the protected shaft and/or hub will often break the surface welding.

Do not use a hammer as you may cause damage to any bearings on the same shaft, unless of course your aim is to replace the bearings in the first place. Then tighten up the puller hard and give it a few sharp hits with a hammer, sometimes this will start the ball rolling (so to speak!).

If you cannot see a keyway (look for a slot either in the hub or the shaft, use a mirror to check between motor and pulley), it is most probably threaded. The direction of the thread will be so that the hub/thread tightens when the motor is loaded by the fan....turn it in the opposite direction to loosen.

I am of the same mind as you Andy, I have had a lot of pulley and gear hubs that have been solidly stuck such as this. After applying a bit of heat, I find that when I have the right puller on, a sharp strike to the puller center shaft will definately get the hub moving.

This is of course after many foul expletives, and usually followed by a victory dance.

Perfectly put!!

You remind me strongly of my own experiences in the RN......its still a good memory!!! (inspite of the swearing till it was off!!)

That "sharp" tap with the hammer on the end of the puller was a great help.....and did not damage anything either.

Following on from Tims comments on heating. Traditionally boilermakers "heat and shrink" by heating an area and pouring water on it, be careful not to shrink the coupling and make matters worse.

It sounds to me that you may not be heating the coupling hot enough or you may be heating the shaft while you are heating the coupling. Also try and select a puller that is way stiffer than you think is needed because if it flexes it won't work as well. One thing you may try is to use a hydraulic type puller, heat the coupling all around to a dull red color, mount the puller and once you have a applied the force start to "ping" the coupling with a hammer. Many times I have seen the vibration from a hammer strike (or several) will cause the coupling to release. Also you may need move the puller around the coupling several times so that the force is applied to several different locations. If the coupling moves a little and freezes up again you may need to re-heat it during the process.

pipewelder

I had a coupling one time, that was rusted and the outer surface was covered with a layer of build up that was hiding 2 holes that had recessed allen set screws.After cleaning out the holes and loosening the set screws,it came right off. Skipper

If you can get the shaft out put it into a hydraulic press and push it out. Heat and cooling will all help too. You could mount the shaft vertically between two large wooden blocks and hammer it out with a sledge hammer protected by hardwood or copper dolly.

It has to do with obtaining max temperature differential between coupling hub and shaft.

You need an hydraulic puller (or press if space allows) (50 to 100 tonnes)fully preloaded. Then, if bare shaft section is available pack this section with dry ice and let soak to lowest temperature. When that has been accomplished you have to heat the coupling hub with the largest torch available. Try to apply an impact hammer in the shaft direction on top of the hydraulic ram. Monitor temperature differentials (shaft & hub) with infrared thermometer and make sure hub heat does not flow into shaft section. You really have only seconds to accomplish this after the heat is applied. Remeber that steel expansion rate is about 6 mils/inch dia/100 degree F>

Best wishes, Rene Vanderspek, Toronto, Canada

PATIENCE!

If there is one thing I have learned it is that you are not in control in these situations. I have had some luck in the harder ones by applying heat with the hottest torch available Sometimes a Mapp torch, sometimes oxy-acetylene. Keep steady tension on with the puller. Sharp raps with a steel hammer in a non critical area. The idea is not to bend, or distort the flange, but to start vibrations. Try cooling with penetrating oil. My favorite is PB blaster as noted before. I would try to rap the flange in line with the length of shaft. Another effective method to use is to shock the play out of the mechanical gear puller. As you tighten the threaded shaft into the puller, all the play in the puller threads are forced in the direction away from the shaft. Take the 4 pound or larger hammer, and drive the puller's threaded shaft into the shaft. Again. Again. Now re-tighten the threaded shaft again. Repeat as needed. Remember the first thought PATIENCE. Good luck.