New Ball Mill

Maybe this will help, http://www.abymc.com/Articles/Submitted/Ballmill.html.

That's a bunch of crap. Your friend better get some spare parts too. The supplier probably won't be in business long, if that's the way they do things.

Hi Kramarat

many thanks I will read and get back to you...he did not order the unit....read it...mill a bit larger like 13tons...

another question if I may...

we need bolts to mount it and wil need to get them made..will we be able to use EN9....?

best

Ferreiro

Sorry, not my area of expertise. I agree with nick name. If you can supply pictures, make, model # and any other pertinent information, someone here will probably be able to help you out.

Bolts to mount what?

It all depends on stress usually the major bolts used in ours are (rather studs since these are tensioned and not tightened) 12.9 grade HT condition with rolled threads (not cut)

UD15

Can you send a sketch and give information about gears. Better make some pictures to help understanding your problem.

Alignment tolerances depend on pitch and gear dimension so that without any input no real help can be given.

Hi Nick Name...thanks

do you know how to post pictures...I did take photo's best Ferreiro

In the command bar you will see in 7th position from left to right the pictogram of a camera depress it and follow the indications. Use ONLY .jpg or .jpeg format and we will see the results.

Nick

Hi nick name,

I uploaded some pictures of the mill...are they not up....

I will check again..

Best

Ferreiro

Hi Ferreiro,

Thanks for the pictures. The mill is just a little fellow! Nevertheless, it is a key piece of equipment in the comminution circuit. If the mill goes down, so does the entire plant

Are you sure that you wish to risk this on information that you get via the internet? It's like giving your mother an apendectomy while listening to a doctor describe the procedure over the telephone. Without adequate experience, you and your friend are taking a huge risk. Think about it.

Is it a wet mill or dry mill? Horizontal?

If it is dry horizontal, may be we will be able to give some guidance however it will finally boil down to the supplier since our mills (a bit larger than your friends - the weight without balls in 3 figures) are likely to be much more complex. And the simplest part in that is the gear alignment.

Our's is girth gear driven by pinion- with reducer gear box, as is likely to be yours.

After the ball mill is correctly mounted on the bearings, first mount the girth gear. Center it properly , ensure (in case the gear is split) the parting planes are correctly matched and the pitch gap is maintained. In ours it is ensured at gear cutting stage, but then again who knows what your supplier has done.

Align the pinion to the gears. Ensure the uniform contact across (centered between Drive saide and non drive side of the flanks) and also he specified back lash (this should be available punched on the girth gear and pinion both)

The backlash also is to be checked on the two edges ( Drive end and non drive end ) by feeler gauge/ lead wire and must be equal.

Then align the Reducer to the driving shaft and then the motor to the reducers,

BTW: where on earth are you and from where you managed to buy it where the supplier does not take the responsibility of commissioning his equipment? Even my washing machine was commissioned by the service rep of IFB.

UD15

Thanks for the help...Tanzania near Lake Victoria....Product comes from China....

best

Ferreiro

OK My comment stands. The mill is a simplified and smaller version of our mills (not so complex).

BTW: which bolts you meant that you wanted to be made locally? girth gear mounting? For ours as I mentioned those are 12.9 grade and stretched at the recommended value (40T) for you depending on the bolt size it might have to be stretched. Foundation are normal J bolts. Liner bolts are already visible so there is nothing to talk about them.

UD15

Hi Guest and all that have assisted so far...

Mounting of the mill to the concrete plymth...No J bolts in the area.....

what bolt...8.8 10.9 or 12.9 high tensile strength should be used..the information is just M36...

the torque setting of the bolts that hold the gear to the mill....I will see the bolts in the morning saturday when I return to site...If I check the size that will give me an idea...and perhaps I can ask for more help again...

once again thanks to all that have been so helpful.

When on the site count the teeth for the gears (pinion and crown), outside diameters and width. Do you know the rpm of the motor (it is not clear on the picture) and the nominal power (130kW ?)? If it is possible measure the span over Z1=0.15*Z where Z is teeth number for each gear. Round the result. For instance if the gear has 14 teeth then Z1= 2.1 take the value over 2 teeth and over 3 teeth. This will allow to determine the pitch (or module) and estimate the best the different maximal possible errors in alignment.

What kind of tool have you for the bolt tightening ? The torques have to be in the range of 4000 Nm.

What Mr. Bolt Integrity wrote is very true so that you should use the best your equipment. If you make a sketch of the bolt (free length under nut) and parts it keeps together (thickness) it is possible to give you some indications how to tighten. It would be a lot better if you could use stretching if you have the access to the technology (the money to pay for it) or at least have a possibility to measure the clamping force if you only can assembly by torque. Such an equipment is not too expensive (in the range of $ 3000) and is worth the money.

Ferreiro,

I'd suggest that you source 10.9 bolts for the application. I'd further suggest that you ensure that they're not brought in from China; Often, regardless of what's stamped on the head, one really doesn't know which grade one is getting. I've seen too many horror stories because of this.

If you can provide some additional dimensional data, we can provide you with the required preload and elongation. We'll base this on 90% yield. This is typical for mill bolting. The data required are:

• bolt length - from the bottom to the top of the head (!)
• shell flange width
• head flange width
• Girth Gear width
• washer width

Although it will be utterly misleading, we can also provide you with a target torque figure along with the estimated K Factor used in the calculation. Although many "experts" claim to be, we're not prescient sooth sayers: Just as nobody else can, we can't predict the degree of friction that you might encounter at each fastener in each hole. If the as-is K Factor is inconsistent with the actual and you don't adjust your applied torque accordingly, you may run into serious issues.

Oops: Typo!

"If the as-is K Factor is inconsistent with the actual and you don't adjust your applied torque accordingly, you may run into serious issues"

should read:

"If the estimated K Factor is inconsistent with the actual and you don't adjust your applied torque accordingly, you may run into serious issues"

On the concrete base, a steel base (sole plate must be grouted ) This sole plate (at least for us) is leveled, J bolt stretched and then the special high compressive concrete mix is poured.

This helps in further alignment of the two trunnions of the mill.

For this case M36 Bolts for foundation may be safely 8.8 grade since the power is not high only 132KW drive

(Just for comparison our's are 2.5MW+

Where the Drive pinion bearing housings have M52, 10.9 Grade 4 bolts each ie total 8 bolts)

Shell supporting (Main bearing housings) are mounted by 6 bolts M52 - 10.9 Grade each side)

Both bolts are stretched and nut tightened.

The Girth gear coupling bolts already mentioned in previous post.

For your capacity If I scale down even 8.8 may be more than enough. Though exact calculations will need total stress analysis.

BTW:

1. Try to stretch the bolts rather than torque.

2. Put some thread lubricants (Molykote 1000 or some other) to assist in future dismantling. It is what we always recommend to our customers.

UD15

A bit of semantics but, all bolts are stretched when they're suitably tightened. It doesn't matter if this done by torquing or, by axial tensioning. If the bolt hasn't stretched, the bolt is not tight. Remember: A bolt is merely a "spring"

The amount that a bolt stretches is directly proportional to it's load. Since the design engineer knows how much load the fastener must hold to ensure joint integrity, he also knows how much the bolt will stretch at that load. Reputable mill OEMs provide elongation values for each size of fastener on each joint application.

*Unfortunately, opportunistic low-price pirate manufacturers following a five-year plan who have no real engineering department but who merely copy existing designs (and thus cannot provide technical support - sound familiar?) will not be able to provide this information to you. At best, they'll have somebody look at a table of bolt sizes vs material and provide you with a "torque" value .

Interestingly, you can torque-tighten a bolt but not achieve stretch . This happens when, during the tightening process, one encounters more resistance than anticipated. As indicated above, the design engineer knows how much load the bolt needs to carry. In the field, however, most millwrights have no clue as to what to do with this figure. Thus, the engineer uses this value to come up with a torque figure. This is not a straight conversion! The designer must guess at the level of friction that might be encountered during the tightening process. If the guess is incorrect, the bolt may end up being either too loose or even too tight - even though the "correct" torque was applied (with a calibrated torque wrench, even!)!

Unless you wish to base the reliability/availability of critical process equipment on a guess or a hope or a wish or a prayer, any bolt torque value should only be considered as a "target".

HI Nick name..

main gear has 72 teeth. width 250mm.while the pinion has 20..with 265 gear hieght 46mm..the electric motor is a 132 kw....or around there as the electrician is still to confirm..The gear box has no details...so I am hoping to start the motor to check the speed of the pinion gear...the main gear is to turn at 28rpm or there about

I will be on site in the morning to check what tools they have..like torque rench..I will take photo's and draw the bolts that are on the main gear

I am unable to find a straight edge so I am going to see what I can use to align the two gears..I have looked for lead string to put between the two gears and might have to make it ..any ideas..

I am taking my laptop with so I will upload the info asap when I get to site..

Once again thank you ALL for the assistance..

It would be good if you could provide above dimensions for all bolts/studs and indicate where they placed (position and numbers), it will help to give you a correct answer.

Hi nick name...

mail gear still not fitted...

have bolt will measure for sizes....

have sizes for materials of mill...

best

Flegelo

This joint has three structural components. As indicated in my previous message, you'll also need to provide the width of the girth gear (at the spotface) as well as the individual widths of the head and shell flanges.

"I am unable to find a straight edge so I am going to see what I can use to align the two gears"

This is scary. Very, very scary.

Ferreiro, with all due respect, if you're unable to find a basic straight edge, you are woefully out of your element.

Up to now, you've asked about aligning the GG to the pinion. Question: Have you even thought about aligning the gear box to the mill yet? This should be your first concern. Only once those two are properly aligned and set should you be thinking about aligning the GG. There is a big difference between the two. Time to find a tight-wire, plumb, transit and alignment formulae.

Although well premature, if you don't have leads you can easily substitute non flux core soldering wire.

This is very serious indeed. And, it's also something which we're routinely involved in.

• What size is the mill?
  
• Trunnion-mounted?
  
• Shell mounted?
  
• How many shell sections?
  
• How many head sections?
• How many Girth Gear sections?

Bolting: Although the liner bolts can accept the inaccuries of "torque" (which in fact they should if the intent is to only tighten them with impact wrenches), the structrual bolts cannot. The preloads must very precise otherwise you risk throwing bolts, leaking slurry, eroding flanges, breaking gear teeth and having the entire works come grinding down to a complete stop (did you notice the pun?!).

Competent OEMs (which this one seems not to be) will not provide warranty coverage of their mills if these critical joints are simply torque-tightened. In this regard, here's a link describing a common occurance and how it was avoided:

• SAG Mill Girth Gear Replacement

We've got alignment procedures for large mills. You can have them at your risk if you'd like.

Hi BoltIntegrity..

Many thanks...

I have photo's that I have taken..prior to the fitting of the gear...

I just have to see how to load the photo's...

I am getting great assistance here..and I will get all the information so I can give you a better picture of the unit.

Best

Ferreiro