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Ask the Kiln Doctor Your Question

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Friday, April 16. 2010

Ask the Kiln Doctor Your Question

To submit your question, just click on the "Comments" link below. Then fill out the Comment form to leave your question. Posted by pete laskie in ASK THE KILN DOCTOR at 05:22 | Comments (201) | Trackbacks (0) TrackbacksTrackback specific URI for this entry No Trackbacks CommentsDisplay comments as (Linear | Threaded) after shimming pads 3/16" on tyre closest to the feed end our kiln.the feed tube started dragging the spiral plates inside of the kiln , how much did this raise the end of the kiln by adding these shims #1 Mike Wilcoxen on 2010-06-04 10:37 (Reply)

The kiln shell will be raised by the thickness of the shim (X) at the support pier. How that translates at the feed end of the shell requires knowing the distance to the next tire (L) and the distance to the feed end (L2). Amount raised at the feed end = (L + L2)/L x X. Even this is approximate as shell sag has not been taken into account but likely close enough. #1.1 Walter Gebhart on 2010-06-29 13:29 (Reply) Please help me with the formula which calculates the shimming pads (loosen pads)for the kiln tyre. #1.2 HongMinh on 2011-01-11 23:20 (Reply)

A new entry "Calculating Cold Gap" shows the formulas. #1.2.1 Walter Gebhart on 2011-01-12 06:11 (Reply)

where is the proper setting for limit switches on thrust rolls. we have a low and high alarm and just beyond these we have a low/low and a high/high witch trip out the kiln drive #2 Randy Scott on 2010-06-05 06:01 (Reply)

Before giving possible answers to this question can you tell us if this kiln is fitted with a hydraulic thrust mechanism or are both thrust rollers fixed?

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#2.1 Walter Gebhart on 2010-06-30 08:30 (Reply) pls l need some technical point for white metal bearing scraping for blue matching contact between bearing and shaft #2.1.1 farid on 2011-06-20 23:23 (Reply)

If needed scrape each side of the bearing three times, once from near bottom all the way to the top, secondly from mid way to the top and finally the last third to the top. At the bottom the shaft should have contact with the sleeve for no more than 1/7th of half circle ~ about 25 degrees. The finished sleeve should have a smooth gradually thinning contour up each side. After assembly the total clearance between shaft and top of the bearing shell should be no less than 0.002"/inch shaft diameter. #2.1.1.1 Walter Gebhart on 2011-07-07 14:46 (Reply)

sir kiln rated capacity 250tph, main drive rated capacity 520kw normal running current 650 -750 amps. But current frequently varying from 650-1100 amps sometimes 2000 amps also.can i get the solution. what are the factors affecting this. #3 jayamurugan on 2010-06-10 07:03 (Reply)

You do not metion what process this kiln is. Let us assume its a cement kiln. This type of process is prone to building a coating on top of the refractory lining. Mostly this coating is not uniform around the circumference. This produces an imbalance, which causes the motor to load up as the eccentric weight is driven to the top (hi amperage draw on the motor) and then it actually assists the motor on the way down (minimum amperage draw on the motor). This phenomenon is transient because it follows the changes in coating formation. If this swing in motors amps is constant and does not change significantly over time (a few weeks or so) then the imbalance may be due to permanent damage to the kiln shell such as a significant bend in the shell. There are other possibilities as well. #3.1 Walter Gebhart on 2010-06-30 09:18 (Reply)

Dear Sir, We found problem today evening(12-06-2010)at Girth gear and Pinion Contact. At one particular position jerking is occuring when Girth gear mesh with Pinion. Load is gradually incresing and decreasing(160-280). #4 Nagaraja.C on 2010-06-12 05:27 (Reply)

Please determine where the gear splice joints are in relation to the pinion when this jerking action happens. #4.1 Walter Gebhart on 2010-06-30 09:27 (Reply) dear sir cement kiln having 1100 tpd capacity in shutdown period machined roller replacd at pier-1 (towards discharge end) in running replaced roller downhill side roller thrust bolts are cutting many times.kiln was floating upwards and downwards but roller axial thrust always uphill side and kiln taking more ams (trip)and tyre having concave shape so the roller contacting area was less and taken lead wire test this roller taking load and down hill side bearing 90 deg temperature details of tyre & roller old rooler diamer =1180 tyre diameter =3550 center distannce=1186 new roller diameter =1152 shim added new roller = 13mm kiln trip many times please give good seggestion thanking you sir y.suresh naidu #4.2 y.sureshnaidu on 2010-07-27 19:00 (Reply)

Clearly a good roller alignment is necessary. #4.2.1 Walter Gebhart on 2010-08-28 11:47 (Reply)

Re: Kiln Rotational speed v's throughput Hello kiln doctor My question is more process orientated however I am hoping there are some rule of thumb design theories that may be known to you. We have a kiln that is operating at around 60% of it's design max speed. Recently the flow through the kiln has been unstable, and we are getting surges which affect process quality. I have been asked to look at whether the kiln rotational speed is sufficient to provide steady flow through the kiln at these new tonnages. My logic says if the kiln is run faster it will allow more material to run through it steadily, however we have run the same speed for 12 years and are hesitant to change lest we encounter any difficulties with the drives. Can you offer any assistance? Regards Andy Holben #5 Andy on 2010-06-17 21:20 (Reply)

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Without knowing the process (which we as a mechanical services company will always know too little about) only some generic comments are offered. The relationship between kiln speed, slope, length, diameter, and natural angle of repose of the material is usually calculated using the US Bureau of Mines retention time formula; T = (1.77x L x (A)^0.5)/(P x D x N) Where A = the natural angle of repose of the material in degrees P = slope of the kiln in degrees D = the inside diameter of the kiln in feet L = length of the kiln shell in feet N = rotation speed in revolutions per minute T = retention time in minutes Calculate twice; once with the feed material characteristics and again with product characteristics and average the two. When internal lifters are present, as is typical with dryers, the time is usually increased 50% When you say you get surges, this could be a result of the material properties (natural angle of repose) changing at some points in the kiln. Adding more feed only will change the bed depth but not retention time and that will affect heat transfer and efficiency. Changing feed plus speed proportionately keeps a constant bed depth but reduces residence time requiring a higher firing rate and so on. #5.1 Walter Gebhart on 2010-06-30 09:45 (Reply)

I want to know the safety features for the kiln in power failure crash stop. What effect [does this have on] the kiln? #6 sumeit sharma on 2010-06-22 04:22 (Reply)

Hot kilns that stop rotating risk permanent shell warping. The result is often referred to as bent shell, a dog leg, a crank and so on. When severe, the damage can be permanent. The safety features to prevent this is an independent auxiliary drive usually a gas or diesel driven engine and in tropical climates putting the kiln under roof to prevent the double effect of a torrential downpour in conjunction with a power failure. #6.1 Walter Gebhart on 2010-06-30 11:28 (Reply) how much the tolreances are there for the kiln girtg gear Axial & radial run out? Axial run out tolerance: 0.001 inches per foot of gear pitch diameter. Radial run out tolerance: 0.0015 inches per foot of gear pitch diameter. WG #6.2 sumeit sharma on 2010-07-01 02:55 (Reply)

In our kiln the roller bearings are [spherical] roller bearings. They are frequently damaged. We want to change it to bronze half bearing bushing. RPM of the kiln is 5. What precaution should we take? Regards Usman #7 Usman on 2010-06-25 11:10 (Reply)

Spherical roller bearings fitted on kiln trunnions (support rollers) are extremely difficult to align. Consequently failures are more frequent than sleeve or bronze bushing type bearings. Occasionally the spherical roller bearings are abandoned for that reason. This is a very expensive solution. There is a way around the problem. Our recently developed Thrust Monitor System electronically monitors roller alignment to make sure it is 100% correct. Adding this system assures the full B10 life is reached for every bearing. The Thrust Monitor system can be retrofitted to any bearing size or style in one or two days. Subsequently roller alignment can be perfectly tuned to operating speeds, loads and temperature. All this at small fraction of the price to change, rollers, bearings and support bases, which would be required to switch from sphericals to bushings. #7.1 Walter Gebhart on 2010-06-30 11:45 (Reply)

Dear sir, For your information our kiln girth gear module 25 and nos. of teeth 196, i would like to know that is it necessary that the girth gear joint bolt is pre-heated in oil bath upto 120 degree centigrate before tightening the bolt in hot kiln girth gear joint. bolt is HT and M39 x 180 mm long . what is the correct steps to fit bolt in kiln girth gear joints, please suggested me. thanks, sunil kumar cement manufacturing company ltd. lumshnong meghalaya, india. contact no. +91 9862009412. #8 sunil kumar on 2010-07-06 05:04 (Reply)

There are procedures, where the bolt is heated to certain temperature, which stresses the bolt to pre-determined stress when cooling down. This procedure should be used only if the gear is designed for it. Otherwise it is always a good idea to have the bolts at the same temperature with the gear. Normally this is not a problem, but if the gear is hot and the bolts are cool, they should be warmed up before assembly. #8.1 Walter Gebhart on 2010-08-30 15:40 (Reply)

my cement kiln is 6.2 m dia & 92 m length.having 2 thrust rollers with hydraulic drive. what should be the average floating in mm of the kiln when up or down. and also we are often facing in support roller bearing ( bronze metal)temperature increases & sometimes the temp shoots high leaving with smoke & sometimes oil temp high. why this




support roller bearing temperatures are high when the kiln is running normal. pl. reply #9 shaktivel murugan on 2010-07-10 12:16 (Reply)

The amount of kiln float will be no more than the difference in width of the pinion and gear. The gear will move from one edge of the pnion to other but must never overhange the pinion either on the uphill or downhill side. High bearing temperatures are caused by high thrust loads (bad alignment); can also be caused by a damaged shaft due to oil contamination or by oil of insufficient viscosity. #9.1 Walter Gebhart on 2010-08-28 11:35 (Reply)

We have a 3 tire kiln, which is less than 6months old with the following dimensions. Kiln Shell OD = 5030mm (including pad plates) Kiln Tire ID = 5040mm Temp of Shell at Support 1 & 3 = 200 to 250 0C Temp of Tire = 125 to 150 0C Measured creep = between 5 to 11mm (average 8mm) Measured air gap = between 3 to 6mm (average 5mm) Temp of Shell at Support 2 = 280 to 300 0C Temp of Tire = 170 to 180 0C Measured creep = between 0.5 to 0.8mm (average 0.7mm) Measured air gap = between 1 to 2mm We would request you to kindly advice me on how to calculate and adjust the shims in all tires in order to avoid seizure of the tire and also for safe operation of the kiln. I need your immediate advice with suggestions and some reference study material or documents. Can you also give me guide lines as how much cold gap to be maintained in all tires. #10 C.S.Lakshmi Narayana on 2010-07-19 06:45 (Reply)

The standard hot gap at each tire is measured in terms of tire migration (creep) per shell revolution. The normal range is 6 to 12mm. The correction formula would be by creep reduction. e.g. the creep is 40mm and needs to be reduced to 6mm. 40-6=36mm reduction is needed. Therefore the gap needs to be reduced by 36/PI = 11.5mm since this involves two chair plates, each must be made thicker (shim plates added) by 11.5/2 = 5.7mm. In case the creep is less than 6mm some safety margine is lost. Heating the tire is one solution. Tis would mean enclosing the tire similar to a gear guard housing and lining it with infrared heaters. An extreme measure but it has been done before. Otherwise keeping a close watch and not letting the creep stop completely is all you can do. #10.1 Walter Gebhart on 2010-08-28 12:08 (Reply)

How to measure the migration of the kiln & what is the standard value of migration a kiln should be maintened #11 Ramesh Eshwaran on 2010-07-21 04:07 (Reply)

The question is not clear; is it kiln up hill to down hill travel? In which case that would be the difference between the pinion width and the gear width. Is it tire migration? In which case it would be 6 to 12mm in the hot operating condition. #11.1 Walter Gebhart on 2010-08-28 11:38 (Reply)

Dear Sir, Our Kiln is 4.11 dia & 64 mts long .The thickness of chair plate is 22 mm. Kindly let me know the standard air gap to be maintened betweeen the shell & tyre & the formula deciding the sir gap. Our Kiln is 4.11dia & 64 mts long .The thickness of chair plate is 22 mm #12 Ramesh Eshwaran on 2010-07-23 23:24 (Reply)

The standard hot gap at each tire is measured in terms of tire migration (creep) per shell revolution. The normal range is 6 to 12mm. The correction formula would be by creep reduction. e.g. the creep is 40mm and needs to be reduced to 6mm. 40-6=36mm reduction is needed. Therefore the gap needs to be reduced by 36/PI = 11.5mm since this involves two chair plates, each must be made thicker (shim plates added) by 11.5/2 = 5.7mm. #12.1 Walter Gebhart on 2010-08-28 11:45 (Reply)

Dear Sir, We have Polysius cement kiln 5600 TPD, the thrust device pressure is varying from 40 bars to 80 and the thrust device move too and fro by 1mm in each revolution of kiln. This is a newly erected kiln and last time it was running with constant pressure at the hydraulic thrust device. Regards. #13 Shams alam banagsh on 2010-08-03 04:29 (Reply)

This phenomenon is usually attributed to an uneven shell temperature caused by uneven coating in the kiln near the thrust tire. This caues the the shell to bend and results in additional axial run out of the tire causing the thrust cycles. This symptom will come and go as the coating changes. #13.1 Walter Gebhart on 2010-08-28 11:52 (Reply)

Our Kiln tyre material Short specification is GS-20 Mn 5. So what does GS stands for? #14 Nagaraja.C on 2010-08-10 04:50 (Reply)

GS is cast steel. The others are percentages of other alloys. #14.1 Walter Gebhart on 2010-08-30 15:38 (Reply)

Inspection of our #2 Tire recently led to a snapping sound that is coming from the tire itself. It is always in the same location. Tire itself is thrusting down and inspection reveals nothing. the retaining ring I thought may be biting as the sound always comes from the top of the kiln. Any suggestions? #15 Keith Post on 2010-08-20 13:28 (Reply)




Possibly a filler bar is being bent by the tire migration and then when it reaches near the top the tire looses grip on it (due to the running gap at the top of the shell) and it snaps back. Try lubricating the bore of the tire with a mixture of powdered graphite mixed in water with some soap (emulsifier) and that may relieve the symptom. #15.1 Walter Gebhart on 2010-08-28 12:01 (Reply)

I have a kiln the design drawing shows zero gap between the Chair plates and the tyre. Because of the creep that is taking place, the gap between the Chair plates and the Tyre within a short time of operation. If left unattended the gap can increase upto 5-6 mm. My question in this instance where the thermal expansion of the kiln is not a consideration, why should I not stop the creep by mechanical means. Note I am querying the stoppage of one degree of freedom that is the rotation of tyre on the axis of the kiln, but not stopping the flexing of the tyre on the Y axis (vertical). Please comment. #16 Daniel Massie on 2010-08-29 23:51 (Reply)

When there is no reason to have a creeping tire (typically when the temperature difference between tire and shell is less than 100Cº) then zero creep means no wear and tear, less on-going maintenance over the long haul; a desirable situation. The problem is once a tire does creep there is no easy way to stop it. Welding is not recommended. The best retrofit that can usually be done is tightly shimmed filler bars. Wedge systems usually break free. The best design is with the tire shrunk fit directly on the shell. #16.1 Walter Gebhart on 2010-08-30 15:25 (Reply)

ASSUMING THAT KILN IS PERFECTLY OK,IF ANY ROLLER STOPS AS TYRE GETS OFF (SAME ROLLER WAS MOVING NORMALLY EARLIER & ROLLERS NOT DISTURBED),DOES THIS PHENOMENON HAVE ANY RELATIONSHIP WITH SHELL TEMP PROFILE/KILN PROCESS PARAMETER? PL EXPLAIN CONSIDERING SPONGE IRON KILN,4 PIERS,4.3 M ID,80 M LONG. #17 nandu on 2010-08-30 13:10 (Reply)

When a kiln tyre lifts off a roller and the roller stops turning this is a direct result of the kiln shell bending due to a significant imbalance of the shell temperature one side to other in the vicinity of the tire. Typically the cause of such shell temperature profile imbalance is a buildup of material inside the shell that acts as an insulating layer. When such build up or coating inside the shell is not uniform around the circumference the external shell temperature can vary widely thereby bending the shell. Most times this is a transitory condition that rights itself. This phenomenon may also cause a mechanical imbalance on the kiln rotation, which can be seen as a pronounced load cycle on the kiln motor amperage draw. The power swings on the motor(s) will be in phase with the kiln rotational frequency. #17.1 Walter Gebhart on 2010-08-30 15:36 (Reply)

Is there any worked out example or a formula that I can use to establish the force that is causing the creep? Thanks. #18 Daniel Massie on 2010-08-30 19:59 (Reply)

The force that is creating creep is simply the rotating shell. Since the shell diameter under the ring is smaller than the bore of the ring, the shell completes its rotation sooner than the ring. The difference is what we call creep. #18.1 Walter Gebhart on 2010-08-31 13:16 (Reply)

In the Tech papter refer http://www.kiln.com/technical/tech_papers_display.php?Rotating-kiln-tyres-lubricating-between-the-tyre-and-shell-1; section 'What is creep and why is it necessary?' there is a reference to splined tyre support designs. Since I am in the process of replacing a tyre in one of the drum (granulator), I would like to consider this design as an option. Can someone assist to locate where this design is available. Thanks #19 Daniel Massie on 2010-08-31 17:33 (Reply)

Migrating or tyres that creep (they slowly revolve around the shell about 1/2" per turn) is an economical means of protecting refractory in a direct fired operation. If there is no refractory in the vessel to protect then why put up with the associated wear-and-tear and the on going maintenance that’s required with migrating tyres? A splined tyre is a means of locking the tire from rotation around the shell but still leaving room for the differential thermal expansion between shell and tire. Splined tyres also dramatically reduce shell flexing, again a desirable feature that improves refractory performance and increases service life. It is a very expensive design (available from Polysius, F.L. Smidth and others). For vessels like granulators that have no refractory or more generally speaking, vessels whose difference in shell to tire temperature does not exceed 200Fº migrating tyres are not recommended. Tyres on such vessels are best shrunk fit directly to the shell without the use of the intermediate support chairs or filler bars. #19.1 Walter Gebhart on 2010-09-01 06:01 (Reply)

Dear Sir, We have a Three support FLS kiln of 3800 TPD. We have a hydraulic thrust device an in the circuit of the HTD (Hydraulic thrust device) accumulator with prcharging pressure of 30 bars. My question is, how much axial / thrust load should come on thrust device if it is mechanical and if it is hydraulic. Is 10 bar as a normal operating pressure on hydraulic thrust device for 3800TPD does make sense that it is taking the required load. What should be the minimum pressure and % load on hydraulic thrust device. Whether mechanical balance and process parameters come in the role for this . #20 Sanjay Sharma on 2010-09-02 06:44 (Reply) in our kiln support roller uphill side bearing ,roller spin slightly more than downhill side what does means tell me the thrust of roller? #21 sandeep on 2010-09-08 06:14 (Reply)

Your question is ambiguous. Please restate and elaborate clearly.




#21.1 Walter Gebhart on 2010-10-29 09:08 (Reply) PLEASE PROVIDE THE DETAILS TO FIND OUT KILN INCLINATION FOR RUNNING AND IN STANDSTILL CONDITION. #22 Nagaraja.C on 2010-09-20 23:30 (Reply)

A full alignment survey needs to be done to establish this accurately. Otherwise just measure the slope of any base. #22.1 Walter Gebhart on 2010-10-29 09:07 (Reply)

What are the daily check list for the kiln? #23 shakil (Homepage) on 2010-10-06 03:48 (Reply) During planned UT inspection, a crack was discovered at a shaft of a support roller of a two-support a cement kiln (FLS Rotax type). The crack dimensions are approx. 50mm X 50mm and the shaft diameter is 650 mm at this section (the first contact point of the roller bore with the shaft). The rotary kiln is in operation from 2003, overall condition is very good, without any significant problems. What are the prospects for the development of this crack and what can you advice for the next steps? As this is a two-support kiln, is there any danger for the rotary kiln to skip over the support stations in case of a shaft total failure?!!! #24 Dimitris Delavogias on 2010-10-08 04:55 (Reply)

On the face of this limited information this sounds like an extremely serious problem. Suggest that the roller be replaced immediately. Shafts fail routinely and with a two support kiln the resulting damage will be unpdredictable and potentially catastrophic. #24.1 Walter Gebhart on 2010-10-29 08:36 (Reply)

I have started to notice blue-purple lines on my tyre at the hot end of my kiln, but the temperature of the tyre is about 91 deg.C . The Kiln is used for alumina and the area is dusty sometimes. I was thinking of a loading problem but the bearing temperatures are ok. What is causing these lines? #25 Adrian on 2010-10-08 18:50 (Reply)

Blue- violet colors are due to surface heat changing the reflectivity of the surface. This is common with freshly machined steel surfaces. #25.1 Walter Gebhart on 2010-10-29 08:18 (Reply)

Dear Sirs; my qustion is , is their any bad side effect from the industrial water inside pipe line if i stopped the plant more than one month without working , the water circulation will stop too , so if the plant completely stopped for more than one month , may we face mechanical problems from the water due to this stoppage ? and id their is expected problems how we can solve this problems or how we can clean the lines again after working the plant #26 Adel Onsi on 2010-10-17 01:22 (Reply)

What kind of plant are you talking about? Where is it located? #26.1 Walter Gebhart on 2010-10-29 08:11 (Reply)

it is CEMENT plant , it is located at EGYPT #26.1.1 Adel Onsi on 2010-11-03 23:51 (Reply)

To be safe why not just blow out the water using compressed air. Some condensation will still probably occur but at least that water will be pure and not be acidic. #26.1.1.1 Walter Gebhart on 2010-11-13 14:26 (Reply)

thank you so much #26.1.1.1.1 Adel Onsi on 2010-11-24 00:57 (Reply)

To be safe why not just blow out the water using compressed air. Some condensation will still probably occur but at least that water will be pure and not be acidic. #26.2 Walter Gebhart on 2010-11-13 14:24 (Reply)

Dear Sirs, Regarding : Cracked Roller We were contacted by a bearing manaufacturer to do a expansion heating job on a new cast roller, they instructed us to heat up the roller to ±290°C and hold for ±8hours, they would then measure the ID of the roller and if expanded enough insert the shaft (stored in dry ice)into the roller. We raised the roller at a rate of 65°C p/h and held it at 290°C for about 8 hrs. When they wanted to measure the ID they noticed the presence of cracking on the inside bore of the roller. They are now trying to blame us for the cracking based on the fact that we had heaters on the outsie of the roller and none on the inside. Couild you please help me with the following; 1. Would this roller have had to undergone heat treatment in the manufacturing process (normalizing). 2. would the absence of heaters on the inside bore cause any problems. Eagerly awaiting your reply, Kind Regards, John Dickinson #27 John Dickinson on 2010-10-24 23:34 (Reply)

We only deal with fordged rollers unless the roller is very large. What is the diameter and width of this roller? Who manufactured it? Only they would know if it was heat treated. When we shrink fit rollers on to a shaft we leave the shaft at ambient (20C) and heat the roller in an oven to abot 300 -350C for about 12 hours. We have no experience with "heaters" applied directly to a roller. #27.1 Walter Gebhart on 2010-10-29 08:08 (Reply)




Why prejacking pump is not used in kiln? with Technical calculation. #28 Zahir khira on 2010-10-26 07:06 (Reply) Please provide physical and chemical properties of easy bar for lubrication of kiln tyres. #29 ak on 2010-10-28 04:48 (Reply)

Please contact [email protected] #29.1 Walter Gebhart on 2010-10-29 07:49 (Reply)

Please define what a "prejacking pump"? #29.1.1 Walter Gebhart on 2010-10-29 07:53 (Reply)

in my plant kiln torque problem, all parameter are normal , so please give solution on kiln torque increses #30 vaibhav on 2010-10-28 07:55 (Reply) There is not enough information given to provide an answer. First the entire weight of the operating kiln and its slope is needed. E.g. 1000 tons at 3% slope. Then the theoretical load on the thrust roller would be 30 tons. Now add some safety factor for misaligned rollers, tire wobble, shell bends, things like that. Say this is 100%. So now the load is 60T on the thrust roller. Next you need to know the diameter of the hydraulic thrust rams (total piston area), which will allow you to calculate the expected pressure. Why not just ask the OEM? #31 Walter Gebhart on 2010-10-29 07:09 (Reply) Please describe in detail what you mean by "kiln torque problem"? #32 Walter Gebhart on 2010-10-29 07:43 (Reply) hi dears I have a question about supporting rollers.what is the reason of roller scabing.in fact why fall a lot of soft scabing pieces from roller surface when kiln is running hot thanks alot #33 hadi on 2010-10-31 00:05 (Reply)

This is a simple case of bad roller alignment. Find the neutral point and move no more than about 0.5mm on one bearing for skew if needed. #33.1 Walter Gebhart on 2010-11-13 14:14 (Reply) This is a simple matter of bad roller alignment. Move the roller to the neutral point and if needed move one bearing no more than about 0.5mm for positive skew. #33.2 Walter Gebhart on 2010-11-13 14:17 (Reply)

dear sir what are the reasons of differet temp. on the width or the tyre and what is the permisbble temp. differences on the kiln tyre's width? with best regard #34 Ali shahsavar on 2010-11-07 03:33 (Reply)

The heat in the tyre comes from the shell. Therefore the shell is hotter on one side of the tyre compared to the other. There is no danger to the tyre no matter what the temperature difference is. #34.1 Walter Gebhart on 2010-11-13 14:30 (Reply)

The other day, I was preheating a cement kiln after a refractory job. the kiln was clear of all internal coating. I had to abort the heatup due to extenuating circumstances and I was asked by my operator, what should be the rotation schedule. There was no material in the kiln so I had advised him that no "barring" was required. After a few minutes, I realized that I was wrong in my advice to the operator. This only highlighted some ignorance of procedures to protect the kiln during this strange situation. Can you give me from first principles the procedures and the reasoning behind some of the standard procedures explaining the mechanical stresses that the kiln shell would be experiencing during kiln heat up and cooling. #35 Alonzo Ramsaran on 2010-11-07 19:20 (Reply)

Volumes can be written on this topic. I can just give a few pointers in this forum. Of first concern is the refractory by avoiding rapid changes in temperature (thermal shock). Temperature increases and decreases should never exceed 50?C per hour preferably lower than that say 20 to 30?C. This is based on kiln exit gas temperatures. During heat up tire migration should not reduce to zero, if it does the heat up is too aggressive. On cool down reduce the draft fan to a minimum that just keeps the feed end of the kiln from going to positive pressure. Stopping a hot kiln for more than 10 minutes risks warping the shell, this could be irreversible. Barring, incremental rotation every 10 minutes or so, avoids that risk. The hot kiln could be stopped indefinitely if the temperature could be locked in by stopping the draft completely. Unfortunately few kilns have that facility, e.g. inlet and outlet shut off dampers. Barring intervals are increased until the shell temperature drops below 150?C at which point the kiln can be completely stopped. #35.1 Walter Gebhart on 2010-11-13 14:50 (Reply)

Why is the temperature differential so important to consider when taking creep. I understand that the temperature differential between the tyre and the shell should not exceed 180oC. What is the reasoning for this. #36 Alonzo Ramsaran on 2010-11-08 09:47 (Reply)

It’s not so much a matter of temperature difference but the understanding that residual creep is a safety margin. The maximum allowable temperature difference will vary for each tyre depending on its mass, width to thickness proportions and location on the kiln. When the difference is high enough that the tyre stops creeping the safety margin is lost and a further increase in shell temperature risks crushing refractory and permanently necking the shell. 6 to 12 mm residual creep at operating temperatures is considered ideal. #36.1 Walter Gebhart on 2010-11-13 15:02 (Reply)

Dear Sir What`s the meaning of teeth profile correction . and why could we found that`s term at large gears . Are there any precautions that must be observed when dealing with such gears .




Regards Ali #37 Ali Awad (Homepage) on 2010-11-15 08:19 (Reply)

Teeth profile correction, if minor, could mean using a paste type lubricant that fills in small pits. It could also mean a running-in compound that polishes newly machined gear teeth. It could also mean recutting of the gear. #37.1 Walter Gebhart on 2010-11-15 09:58 (Reply)

Dear Sir Profile correction i just asked meant a differant addendum gears , a large one at pinion , and small at githe . regards #38 Ali (Homepage) on 2010-11-15 10:58 (Reply)

Sounds like a mismatched pinion was installed. The pinion would have to have the outside diameter machined to reduce the addendum. #38.1 Walter Gebhart on 2010-11-16 18:54 (Reply)

Dear Sir. I Wasn't meaning mismatching gears in contact but i meant a spur gears with corrected profile and that terms pointing to The distance between the pitch line of the rack and the rolling line is called corrected profile DM . The corrected profile is positive when the pitch line of the rack is above the cutting pitch circle of the gear. In the opposite case there is minus correction. For example :- for standers gears addendum equal the module . For corrected profile gears the addendum equal module + DM . So i need to re send my question if you don`t mind ,,Are there any precautions that must be observed when dealing with such gears .. Regards #38.1.1 Ali (Homepage) on 2010-11-25 09:28 (Reply)

Your terminology is still confusing. Pitch lines commonly scribed into both sides of both gear and pinion and are tangent when the pinion is correctly aligned to the gear for both spur gears and helical gears. #38.1.1.1 Walter Gebhart on 2010-12-07 14:13 (Reply)

In my application the temperatures are under 100 deg C. Creep is causing wear and increasing the gap between the tyre and chair plate. To overcome this issue, there are cases where the chair plates have been welded to the tyre. This did not solve the problem because the weld sheared off which I believe would be due to flexing of the tyre that takes place during its rotational cycle with the load in the drum. Correct me if I am wrong. After fair bit of thinking, I am reaching a conclusion that if the thermal growth to close the gap between the tyre and the chair plate is not an issue, than the tyre should be part of the drum. Correct me if I am wrong on account as well. In old machinery where the tyre is free to creep and where the growth of the drum due to heat is not an issue, the tyre should be stopped from creeping. I am thinking in terms of degree of freedom of the the tyre. Axial degree of freedom is stopped by stop blocks. Vertical freedom of movement (90 deg to axis of drum) downward is stopped by chair plates, upward is left free. Third degree of freedom, side ways (90 deg to axis)is similar to vertical axis, the fourth being rotational which causes the creep and subsequently wear. To stop this rotational freedom of movement, I am thinking of f a bracket to clamp on the tyre from underside. This bracket would rest against the stop blocks of the tyre. The contact surface would be lubricated to allow free movement of the tyre in horizontal and vertical axis. Any comments For or Against this conclusion. Daniel #39 Stopping the Creep on 2010-11-15 21:37 (Reply)

You are correct on most counts except clamping the tyre may not work just like welding did not work. The clamps will likely rip away. Just as a by-the-way; when the temperature difference between the shell and the tyre is under 100?C the original construction should be to have the tyres shrunk fit onto the shell. Shrinking as a retrofit, although not impossible may not be practical. The best approach would be to install new chair plates as tightly as possible. With a little heat the shell expansion should lock up the tyre, which is what you want. Some creep when heating up and cooling down will of course still be there, which will eventually cause wear again. At that point repeat the process. Short of getting a shrink fit (replacing a section of shell with a new shrunk on tyre) that will be the most cost effective approach. #39.1 Walter Gebhart on 2010-11-16 19:18 (Reply)

Walter, My thoughts are that the welding did not work because the forces in the direction (90 deg to axis) were higher than the tensile strength of the weld. My thoughts are that under shear (Shear force being the force that causes the creep)was too high for the weld. Slippage of the clamp is expected,hence I was planning to install 4 clamps. I thought of giving this a try instead of




denting the side of the tyre to locate the the clamping bots? Understanding that all the turning force is taken by the girth gear and pinion assembly, what is the value of the force that causes the creep. Assume Speed reducer and 200 kW motor drive and 200 Tonne weight in the drum. Can you assist in establishing the force that is between the tyre and the trunnion causing the creep. Thanks, Daniel #40 Daniel Massie on 2010-11-16 21:21 (Reply)

Any mechanical "clamps" no matter how many you put on are likely to give up sooner or later. Any meaningful calculation of the forces involved would be near impossible. The primary mover is the gear, which turns the shell. The shell then drags the tire around. The tire being larger in diameter than the tops of the chairs doesn't quite make a full turn when the shell does. This difference, the difference in their circumferences, we see as creep. So the first force is simply the power drawn by the motor. How much of that power is transferred to any one tire? Next is the weight of the kiln. The reaction at any given pier is actually calculated, which allows optimum pier location and sizing tires, rollers bearings, plate thickness etc. That weight can be transferred to a single clamp since the shell moves up and down wrt to the tire as seen when you compare their relative positions at the top and bottom. How do assure that all the clamps take their proportionate load? Polysius and later FLS have successfully designed such a system that is called The Splined Tire and the Tangential Support respectively. Then the most elusive force of all is the fact that the shell and tire flex as they turn. This will be the principle cause of weld failure. The force on the weld is one thing and likely not enough to fail it but the force reverses with every turn of the shell. Since the shell and tire do not move as one (which they would do when the tire is shrunk on) they flex independently. So there you have it; a force that drives the tire and a reversing force due to gravity that independently flexes between shell and tire. #40.1 Walter Gebhart on 2010-11-22 06:59 (Reply)

H1! Walter, Could you please explain 1. What is Tangential Support design? 2. When the tyre flexes, the force reverses, but the direction is still towards the centre or away from the centre of the drum. Am I right in saying that? If yes than I would state that the clamp face that is leaning against a stopper mounted on the shell of the drum would have a sliding motion. Am I right in saying that? Thanks, Daniel #41 Daniel Massie on 2010-11-22 22:30 (Reply)

I have put a picture of a tangential supported tire on the blog page. Also posted is the original design patented by Polysius in 1969. The illustration is an extract from the patent. As far as your second point is concerned; both tire and shell flex. At the bottom the shell pushes down and mostly fits flush with the tire. At the top in the case of a migrating tire, the shell moves down away from the tire, creating the gap at the top. So, if we look at the tire and shell’s relative movement they come in contact and separate once each revolution as well as move circumferentially one with respect to the other. Also, they do not rotate as true eccentric circles; it’s more of an oval path for both. This results in an assembly where it is very difficult to mechanically stop creep. The splined design effectively uses a key between each chair pad such that the shell is suspended (or tangentially supported) at 3 o’clock and 9 o’clock so there is almost as much gap at the bottom as there is at the top. Gravity (shell flex aka ovality) still has an effect so the upper gap will still be larger. #41.1 Walter Gebhart on 2010-11-23 11:43 (Reply)

In the tangential support design, it appears that lugs are bolted on to the sides of the tire. Each lug having two say M20 bolts. If I were to develop the concept to further my desire to stop the creep, I could rest this lug against a circular pin welded onto the shell. This would give a line contact. The lug would slide over the pin at the contact line. The issue now would be sheering off the pin from the shell. This can be overcome by many lugs, as is the case in the tangential support design. What do you think? #41.1.1 Daniel Massie on 2010-11-24 18:03 (Reply)

In the tangential design the "bolts" actually go right through the tyre. I suspect that any clamping device on the tyre will slip no matter how many are put on. Walter G #41.1.1.1 Walter Gebhart on 2010-12-07 13:49 (Reply)

What is meant by girth gear and pinion module? #42 Suresh (Homepage) on 2010-11-25 03:04 (Reply)

"Module" is the unit of size that indicates how big or small a gear is. It is the ratio of the reference diameter of the gear divided by the number of teeth. http://www.khkgears.co.jp/en/gear_technology/pdf/module.pdf #42.1 Walter Gebhart on 2010-12-07 13:55 (Reply)

We are facing a prolem of the kiln RPM frequently,sometimes reducing and stopped automatically.Ist pair thrust roller dimensions 9mm difference on diameter.Balancing by shim.What to do?




#43 Jatin Chandra Dadhara (Homepage) on 2010-11-25 10:28 (Reply) The question is not well understood. Do you mean the kiln stops rotating because the motor stalls due to high loading? If so your support rollers are badly aligned. Walter #43.1 Walter Gebhart on 2010-12-07 13:25 (Reply)

Dear Sir, I want to ask that in finding Retention time of kiln in cement manufacturing there is a factor "11.2" I want to ask that how and from where it comes. thanks alot waiting eagerly for the answer Regards Kamran #44 Kamran Zafar on 2010-11-28 14:39 (Reply)

The US Bureau of Mines retention time formula; T = (1.77x L x (A)^0.5)/(P x D x N) Where A = the natural angle of repose of the material in degrees P = slope of the kiln in degrees D = the inside diameter of the kiln in feet L = length of the kiln shell in feet N = rotation speed in revolutions per minute T = retention time in minutes I am not sure where the "11.2" comes from. #44.1 Walter Gebhart on 2010-12-07 14:22 (Reply)

Dear Sir, Daer sir we have a small rotary kiln burning waste materials. We are in a shut down period and have removed the feed end webco seal for renewal. The seal run surface has become very hard and began to delaminate from the main shell. (6mm thick approx) Can you advise if this is a seperate material from the main shell. Photo can be supplied for more information #45 Alan Campbell on 2010-11-29 06:20 (Reply)

A photo would certainly help. Webbco seals usually run on a wrapper plate that protects the shell. Is it perhaps the wrapper that is separating from the shell? #45.1 Walter Gebhart on 2010-12-08 07:55 (Reply)

Hi Walter, How can I know that the kiln roller is at its neutral position before I start re-alignment? #46 adam hohyes on 2010-12-05 02:48 (Reply)

The first step in any roller adjustment should be to float the roller through its neutral position and go from there. Provided the roller is fitted with a sleeve bearing it has an axial float of about 6 to 12mm. Adjust so that the roller moves axially from the current position (normally it should sit downhill for positive thrust) in small increments of about 0.01mm. Wait about 1/2 hour between moves (waiting time depends on kiln speed). When, with the last move, the roller shifts axially you know you have crossed the neutral point within the magnitude of the last move. Carefully observe all the roller's bearing temperatures through this process. #46.1 Walter Gebhart on 2010-12-08 08:08 (Reply)

dear sir last week i was taken kiln axial pressure readings as below. 1.kiln 1st pier right hand side roller(view from kiln out let end) moved 1 mm up hill to down hill axial pressure- 150bar feed-260 Tph thrust position- -0.4 rpm- 4.5 time- 10.35 am bearing dia400x480 2.kiln 1st pier left hand side roller(view from kiln out let end) moved 1 mm down hill to up hill axial pressure- 170bar feed-270 Tph thrust position- -1.9 rpm- 4.2 time- 11.15 am bearing dia400x480 3.kiln 2nd pier right hand side roller(view from kiln out let end) moved 1 mm down hill to up hill axial pressure- 470bar feed-275 Tph thrust position- -2.5 rpm- 4.2 time- 11.55 am bearing dia500x600




4.kiln 2nd pier left hand side roller(view from kiln out let end) moved 4 mm down hill to up hill axial pressure- 430bar feed-285 Tph thrust position- -2.7 rpm- 4.0 time- 12.35 pm bearing dia500x600 5.kiln 3rd pier right hand side roller(view from kiln out let end) moved 8 mm down hill to up hill axial pressure- 100bar feed-240 Tph thrust position- -2.6 rpm- 3.9 time- 9.45 am bearing dia400x480 6.kiln 3rd pier right hand side roller(view from kiln out let end) moved 8 mm up hill to down hill axial pressure- 100bar feed-220 Tph thrust position- -1.7 rpm- 3.6 time- 9.00 am bearing dia400x480 why axial pressure is more? what it indicates? which parameters i have to check? is there any relation b/w graphite lubrication of roller and tyre? #47 ramaraju on 2010-12-20 00:13 (Reply)

Please clarify; "moved 8 mm up hill to down hill " what has moved - the roller? why did it move? "thrust position- -1.7" how is this measured; from what reference is this measured? #47.1 Walter Gebhart on 2010-12-23 07:28 (Reply)

these readings are kiln axial pressure readings ( moved 8 mm up hill to down hill) means the gap b/w bearing thrust collar to roller shaft thrust ring is 8mm, roller shaft thrust ring moved 8mm down side. ("thrust position- -1.7") means when i was taking pressure readings at that time kiln hydraulic thrust position is - 1.7 #47.1.1 ramaraju on 2010-12-24 02:25 (Reply)

your original questions: why axial pressure is more? Axial pressure on the support rollers varies with roller skew (alignment), degree of tyre wobble (axial run-out) and with hydraulic thrust roller system pressure. what it indicates? If pressures are not equal it means the rollers are not optimally aligned. Additionally the pressure will vary during each shell rotation proportional to the tyre's axial run-out. The hydraulic thrust system will also affect the axial pressure. To align the rollers correctly and to balance axial thrust or neutralize the rollers the hydraulic thrust system should be shut off for at least 12 hours before measurements/adjustments are made. which parameters i have to check? Floating the rollers (with the hydraulic system turned off) to within 0.1mm of neutral would be ideal. is there any relation b/w graphite lubrication of roller and tyre? Graphite block lubrication helps reduce wear on the rolling surfaces if roller skew is not perfect. #47.1.1.1 Walter Gebhart on 2010-12-25 09:03 (Reply)

i m working in a iron ore pellet plant.i want to know "how kiln support roller alignment is done" #48 satish on 2010-12-22 00:21 (Reply)

Do the support rollers use spherical roller bearings or are they sleeve journal bearings? #48.1 Walter Gebhart on 2010-12-23 07:23 (Reply)

Dear Sir Our kiln is a 3 pier, 3.8 m dia and 56m length with fixed tyre (i.e.the toothed tyre) please advise for the following: 1-Although we having fixed ring which ovality is supposed to be limited why does the chair pad wellds crack in pier 1 (outlet)?




2-Although the maximum runout of kiln shell is 1 inch and maximum temperature different is 130 why does the tyre 2 (middle) lifts from the left roller? could it be possible with tyre fixing? 3-Why does the tyre 2 (middle) goes off from only one of the rollers (left one)and not the other? 4-As a matter of principle, what are the plus/minus points of fixed tyre system compared to loose tyre support? #49 m.j.yaghoot on 2010-12-22 04:53 (Reply)

1) Chair pad welds will crack due to excessive loading/stress. This may not be directly related to excessive ovality. 2) the tyre lifting off the rollers has nothing to do with the method of tyre fixing. It is the result of a bend in the shell usually a temporary condition caused by uneven clinker coating. 3) Asymetrical lift-off could be due to roller misalignment or loading. Is it the upturning side or downturning side where the roller lifts off? 4) The splined or tangential support system of a tyre is primarily employed to reduce the ovality (the amount the shell flexes during rotation) of large diameterkiln shells. Reductions are typically 4:1 compared to the conventional migrating tyre with the same shell diameter. This should translate into much longer refractory life. A secondary advantage is reduced maintenance since wear due to tyre migration has been eliminated. Disadvantages are a high capital cost and costlier repair costs when such are required. #49.1 Walter Gebhart on 2010-12-23 07:34 (Reply)

it is downturning side where the roller lifts off . #49.1.1 m.j.yaghoot on 2010-12-26 06:13 (Reply)

I suggest the possibility that the added weight of the material load inside the kiln on the upturning side is keeping the tyre in contact with the roller, whereas on the downturning side, the less loaded side, allows the bend in the shell to lift the tyre away from the roller. This may be a transient condition which could correct itself over time. #49.1.1.1 Walter Gebhart on 2010-12-26 10:51 (Reply)

why Floting Tyre. what is that PI which u mention in method of reducing thr Tyre Creep. please answer my quation Thanking you PRABHU GOUDA U #50 Prabhu Gouda U on 2010-12-29 02:24 (Reply)

A floating tire allows for differential thermal expansion between shell and tire to protect the refractory from being crushed. PI = 3.14…. #50.1 Walter Gebhart on 2011-01-03 09:39 (Reply)

kindly describe the loading pattern of spherical roller of support roller bearings #51 manoj on 2011-01-08 22:09 (Reply)

The question is very vague, please elaborate. Is there a particular problem you are trying to solve? #51.1 Walter Gebhart on 2011-01-10 06:54 (Reply)

i wanna ask every body, our kiln has 79 m length and 3m of diameter. it's supported by three tyre. the case is in tyre number 2. i found an abnormal sound in bearing number 2. can you explain to me what th problem is ?? thanx before.... #52 blackstrezz on 2011-01-10 19:06 (Reply)

What is the quality of the sound? Is it clicking, snapping or sqealing? #52.1 Walter Gebhart on 2011-01-11 00:23 (Reply)

respected sir, I ravi belwal executive engineer at hari machine ltd. we are having a problem that the support roller, that are manufacture is of low hardness (round 180 bhn)what remedies should be taken to bring it to 280-300 bhn,the change in properties( chem,mech.) does not much consider to the party plz advice sir as they are 12 in no. worth nearly 1 crore. #53 Ravi belwal on 2011-01-19 02:48 (Reply)

If these are large kiln rollers, they can be sleeved with harder material sleeves. Small rollers (for us the limit is 36”) can be flame hardened, but it needs to be done right not to leave any soft spots. This would be surface hardened only. Sleeves would be through hardened. #53.1 Walter Gebhart on 2011-01-19 19:00 (Reply)

kiln shell crack observed just below tyre.one plate of 1.5m*1.5m fixed over the crack area inside the kiln and welded.Thereafter refractory casting is being done.This means, to cover up the shell crack,1.5*1.5m plate is now in between cracked shell and refractory casting.There is a gap of about 20mm between two plates for shell deformation. Question is:- (1)what will be the effect of trapped air in between the two shells. (2)should the gap between the shells be filled up by refractory material. #54 m.s.vas on 2011-01-26 04:12 (Reply)

Shell cracks, especially under a tyre, cannot be successfully repaired using such patch plates. The crack must be repaired directly in the plate that is cracked. Repairs must be made from both sides, which means moving the tyre to gain access. If the shell plate is more than 20 years old we recommend replacing the whole section of shell under the tyre going at least 300mm past the circumferential weld at each side of the tyre uphill and downhill. #54.1 Walter Gebhart on 2011-01-26 11:08 (Reply)




What is the calculation for taper shim. How to make taper shims. #55 suman kumar neogi on 2011-01-26 08:55 (Reply)

Tapered shims are made by using Blanchard grinding where the shim plate is magnetically held for grinding. The thinnest edge is normally kept to a minimum of 3mm. The angle of the taper depends on the required correction to the slope, so the thickest edge of the opposite shim will depend on the width of each housing and the distance between housings. Shims must be the full length and width of each bearing housing footprint. Great caution must be exercised to not comprimise fitted keys between housings and bases as the housings will be raised when shims are introduced. #55.1 Walter Gebhart on 2011-01-26 11:16 (Reply)

dear sir , i have 3.95 dia x 61 mtr length kiln. kiln float(thrust) setting is -5 to +5 . what is the kiln floating(up & down) time frequency ? is there any chance increase kiln float setting? #56 ramaraju on 2011-02-05 06:35 (Reply)

Please provide the units for -5 to +5. #56.1 Walter Gebhart on 2011-02-10 15:38 (Reply)

Hello there, I would like to ask your opinion on the merit of installing a roof cover over a rotary kiln in a tropical climate where heavy sudden downpour is expected. We are installing a kiln in such a location and there is a debate between the Operation & Maintenance and construction folks. The construction folks are saying that the heavy rain; whenever it happens, will not create a thermal stress to the shell and such no problem with the refractory should be expected as a result. The Operation and Maintenance guys seem to think otherwise. The shell surface temperature will be around 150 deg C. Anyone can comment? Thanks #57 Khairul Jais on 2011-02-09 01:52 (Reply)

There is a risk if there is no auxiliary drive installed. When a severe storm arises with heavy rain there is also a good possibility of electrical disturbance and power failures. No danger to the kiln and refractory exists even during heavy downpours as long as the kiln continues to rotate. The worst case scenario with no cover is during a heavy downpour a power failure occurs and the kiln stops rotating. In that case the risk for refractory failure and severe bending of the kiln shell along its length is very high. Such bends may be irreversible. Naturally the auxiliary drive must have its own independent power supply, typically a gas or diesel engine that is routinely started (weekly) to assure 100% availability. If one is installed and reliable then kiln covers (which are comparatively expensive) are optional. #57.1 Walter Gebhart on 2011-02-10 15:34 (Reply)

Dear Sir, Either it is better to lubricate the kiln supporting roller during light-up after a long shut down of the kiln or not. Because as per my perception it will elongate with temperature at the same time two dry metal surfaces will rub against each other, specially when rotation kept stopped during light up. #58 shams Alam on 2011-02-19 03:59 (Reply)

Yes it is required to lubricate, this should not be an option. When the kiln is standing, oil drains out of the bearing. Then when it is started there is a short moment of metal to metal contact, some bearing material is lost and the bearing becomes slightly damaged. They say if the kiln is never stopped the bearings would last forever. Unfortunately nothing is forever. The procedure should be to drain 1 litre of oil from the bearing and pour it back onto the distribution tray about 10 minutes before starting kiln rotation. #58.1 Walter Gebhart on 2011-02-20 06:13 (Reply)

Sir, Some time we feel high vibration at gith gear ( this come once in rotation ) and some time there is no vibration at gith gear ? Please ansawar and oblige #59 Mustamer Khan on 2011-03-02 22:36 (Reply)

This is excessive radial run-out due to transient thermal bends in the kiln shell. Move all the rollers on the pinion side of the kiln closer to the center of the kiln until the vibrations stops. #59.1 Walter Gebhart on 2011-03-21 05:09 (Reply)

Dear sir I would like to know the quality of new generation of kiln supporting roller bearings (kind of main metal)in F.L.S or Polysius kilns . with best regards #60 Ali keighobadi on 2011-03-07 23:27 (Reply)

You should ask F.L.S. and Ploysius. We are not their spokesmen. They do not inform us of what materials they use in their designs. #60.1 Walter Gebhart on 2011-03-21 05:11 (Reply)

hi sir i want to know how to calculate air gape of tires at the time of kiln running #61 kalyan chakravarthi on 2011-03-17 23:05 (Reply)

Take the measured creep (tyre migration) for one revolution and divide by PI (3.14....) #61.1 Walter Gebhart on 2011-03-21 05:12 (Reply)

Which is a better modern kiln 2-support or 3-support and why? #62 G V Rama Krishna on 2011-03-26 04:02 (Reply)

Assuming the production capacities are the same choose the one with the lower cost.




#62.1 Walter Gebhart on 2011-04-07 14:01 (Reply) hi sir we have 3mtr dia and 46.3 length kiln in our cement manufacturing industry and our production was 1600 TPD.The kiln was 3 pier KILN.please TELL ME ABOUT kiln Thermal expansion and what is the formula of thermal expansion calculation and our kiln thermal load was 2.5G.cal/HR/M^2 #63 kalyan chakravarthi (Homepage) on 2011-04-04 23:23 (Reply)

Expansion = Length x change in temperature x coefficient of expansion E = LxTxC E and L will be the same units C ~ 6.8x10-6 for mild steel when T is in Fahrenheit degrees C ~ 12x10-6 for mild steel when T is in Centigrade degrees C values shown are approximate since C is itself a function of temperature. Usually the whole length of the kiln is divided into a number of sections with each assigned an average external shell temperature and a corresponding coefficient of expansion. These are then summed to get the overall change in length. For example from 20 ºC ambient; 10 meters @ 300ºC expands 10x(300-20)x12.5 x10-6 = 0.035 meters 10 meters @ 150 ºC expands 10x(150-20)x 11.8 x10-6 = 0.015 meters Total expansion: 50mm #63.1 Walter Gebhart on 2011-04-07 14:40 (Reply)

hi sir our kiln lengthis 45mtrs,Dia 3.0 mtr ,change in temparature was 320-120 and i want to know our kiln thermal expansion please explain me Thanking you sir, Regards, T.Kalyan chakravarthi #63.1.1 kalyan chakravarthi (Homepage) on 2011-04-13 23:00 (Reply)

The method for calculation is given above. #63.1.1.1 Anonymous on 2011-04-21 09:42 (Reply)

Dear sir, our kiln had mechanical thrust rollers at our site. Our problem is KILN was continuously floating at the top only by using graphite powder or raw mill powder we are changing the kiln position in to bottom even though also kiln was not floating at bottom more than 30mnts in our observation we found that our KILN had downhill tendency in our experience mechanical thrust we should have uphill tendency is it correct or not please give me your precious recommendations and further proceedings proceedings thanking you sir, With regards, T.Kalyan Chakravarthi. #64 kalyan chakravarthi (Homepage) on 2011-04-04 23:36 (Reply)

Putting abrasive material on the rollers and tyres (such as raw meal) is destructive and should not be done. Your kiln needs to have the rollers properly aligned and skewed to control the kiln position. #64.1 Walter Gebhart on 2011-04-08 09:31 (Reply)

Dear Sir, We have three tyre Polysius kiln with Diameter 5 m. We got zero migration of tyre 3 toward out let. We check the air gap physically but physically there was zero air gap all around the kiln as well. No considerable crank was observed. In cold condition the air gap was about 18 mm. At the time of zero air gap the average shell temperature was about 300 C and the temperature of the tyre was about 100 C. If we consider the coefficient of thermal expansion as 0.000012 m/mC so still there should be an air gap of 7 to 8 mm. But why we got zero air gap/zero migration it is out of my understanding, Please help us in this regard to understand the problem. Best regards. #65 Shams Alam on 2011-04-13 09:24 (Reply)

Simply stated your measured temperatures are not accurate. You can only measure surface temperatures. There is a heat gradient through both the shell and the tyre. Clearly the average internal temperatures are much higher or more specifically the internal difference in shell to tyre temperature must be higher than you are measuring. #65.1 Walter Gebhart on 2011-04-21 09:05 (Reply)

Dear sir, my question is , our formula for calculating retention time is 11.4*L/(Speed*Diameter*Slope) I have been told to find out how that formula comes about #66 cosmas (Homepage) on 2011-04-13 15:26 (Reply)

The US Bureau of Mines retention time formula; T = (1.77x L x (A)^0.5)/(P x D x N) Where A = the natural angle of repose of the material in degrees P = slope of the kiln in degrees D = the inside diameter of the kiln in feet L = length of the kiln shell in feet N = rotation speed in revolutions per minute T = retention time in minutes




#66.1 Walter Gebhart on 2011-04-21 09:21 (Reply) Dear Sir, I want to know how we will calculate primary air input quantity for kiln as per kiln dia,length and kiln feed tonnege per hour please tell me the formulaFor example our KILN dIA3.0Mtrs,Length 45Mtrs and kiln feed input 110tons per hour and day production was 1600tons please give me the clarification thanking you sir, best regards, T.Kalyan chakravarthi #67 kalyan chakravarthi (Homepage) on 2011-04-13 23:22 (Reply)

Primary air is the function of the burner design and the firing rate. You must get this information from the burner supplier. Kiln or calciner burners vary greatly with respect to internal design and fuel type e.g. coal, oil, natural gas or alternative fuels. There is no formula. Each burner is designed for specific applications. Typically primary air is between 5 to 15% of stochiometric air. Usually when the secondary air is preheated by the process a lower primary air yields better fuel consumption/ton product. #67.1 W Gebhart (Homepage) on 2011-04-21 09:53 (Reply)

hello i would like to ask how to measure kiln migration and the refrence for measurement taken. thkx #68 abebe alemayehu on 2011-04-15 04:12 (Reply)

see "measuring creep" on the kiln doctor blog main page #68.1 Walter Gebhart on 2011-04-28 19:03 (Reply)

Dear Sir, We are having the cement kiln which was supplied by the FLS (4.32 dia X 67 meter lG) and its age is 02 years. And in this kiln at discharge pier both rollers and tyre having a non significant pitting marks. We don’t having any following defects in the kiln • There is no significant crank on the kiln (mech/thermal) • Axis of the kiln is absolutely straight. • Contact between roller and tyre is 90 -95 % • We are not using any oil/water on the rolling surfaces • Axial run out of the tyre is within the limit. • Hertz pressure is also within the limit. Please inform us what could be possible reasons for the cause. Regards, G Krishna #69 Kumar on 2011-04-22 05:02 (Reply)

With out seeing these "non significant pittings" it is impossible to comment. Send pictures to [email protected] #69.1 Walter Gebhart on 2011-04-28 18:59 (Reply)

Sir, Is it a new trend to have all three Tire/Support rollers of same sizes in 3 pier kiln ? If so can you pls. give the rerefrence. Regards Rao #70 Rao on 2011-05-02 01:26 (Reply) R/S, I am narendra kumar, working in sponge iron plant at ( GUJ) in INDIA. my question is that my kiln is working in upward motion .means when we run the kiln its tendency to go upward side & in rainy days or just in rain it does slip at support rollers. due to this we stopped the kiln .so please tell me the reason behind this. REGARDS, narendra kumar. #71 narendra poonia on 2011-05-03 12:03 (Reply)

The support rollers are not correctly aligned. #71.1 Walter Gebhart on 2011-05-26 19:36 (Reply)

dear sir we we have FLS kiln of lenght 75 mtrs and diameter 4.75 capacity 8100 tpd. problem: hunting in HTD system pressure between 10 bar to 35 bar in every revolution of kiln and HTD position vary between 3 to 4 mm when hunting observed. on observating that out of tyre total contact surface circumference, 11% circumference surface not came in contact with




roller surfcae and a gap is observed of 1mm appox in every revolution. Both supporting roller thrust is between allowable limit that is between 40 bar to 160 bar. our HTD has been replaced with new one and after that surface grinding of tyre and thrust roller have been already done. please give me reason of HTD system pressure hunting and its solution??? #72 BALWANT SINGH RAWAT on 2011-05-07 00:47 (Reply)

The cyclical pressure is due to tyre wobble [axial run-out]. This is likely due to temporary thermal bends in the shell or possibly incorrect tyre installtion or permanent shell damage that has bent the shell. #72.1 Walter Gebhart on 2011-05-26 19:40 (Reply)

How can I determine the required wheel width to support a rotary kiln at the tire? I know the tire and wheel hardness, speed, normal force. I can calculate Hertzian stress easily enough, but what is the allowable stress? #73 Bob Bartlett (Homepage) on 2011-05-15 18:29 (Reply)

Hertz surface pressure < 58,000 - 62,000 psi = 400 - 428 MPa depending on application ( speed, etc. ). Generally the tire width is increased until the max allowable Hertz pressure is satisfied. There are other options. #73.1 Walter Gebhart on 2011-05-26 20:14 (Reply)

Our Dry cement kiln dia is 3 mtr and length is 48 mtr. There is no coating/ring formation inside the kiln but kiln main motor load is running on higher side after last shutdown. Earlier it was 100 to 150 amp in normal while now it is around 250 to 400 amp with same filling level. Please suggest possible reason and solution. #74 V. K. Sharma on 2011-05-22 20:52 (Reply)

List all the work and changes done to the kiln during the shutdown. Review each carefully to determin if any could have added weight or incresed friction. #74.1 Walter Gebhart on 2011-05-26 20:20 (Reply)

i want to know the equations the calculating the kiln migration, to impelement it on our system #75 Morad Makram on 2011-05-23 05:40 (Reply)

If you are referring to the tyre migration around the shell; this is a measured value not a calculated one. #75.1 Walter Gebhart on 2011-05-26 20:22 (Reply)

Dear sir, I've 2 questions 1.What's the oil test method to detrmine the thrust of a kiln support roller having spherical roller bearings. 2.we have a kiln having 04 support piers. if i give 10mm shim below each support roller bearing plummer block then by what height the kiln axis will be lifted. #76 manoj kumar sahoo on 2011-05-29 00:25 (Reply)

1. I think this is likely the" slip test". A shot of WD40 across the face of the roller; as it goes through the pinch point will cause a knock in the bearings when skew is present. 2. 10mm #76.1 Walter Gebhart on 2011-05-30 06:37 (Reply)

pls inform me about the recommanded temp. for white metal bearings which useing in kiln suppoting roller with mineral( shell omala 680) and syntetic(mobil SHC639) oil #77 farid on 2011-06-03 03:53 (Reply)

We cannot comment about specific oils or brands. The maximum allowable temperature is based on what the oil can tolerate. That means how hot can the oil get before it looses its viscosity and metal to metal contact results. In general mineral oils must stay below about 90C. Some synthetics can go much higher up to about 230C. For kiln rollers the oil viscosity is typically between 1700 to 2000 SSU @38C unless the kiln manufacturer has made other recommendations. The final selection of lubricant must take seasonal changes into account as well. #77.1 Walter Gebhart on 2011-06-16 15:36 (Reply)

Hello Sir,i am facing a problem in kiln which i am not able to figure out.ours is a 2500 tpd cement kiln with 3 tire and roller support.its normal torque is 500amps.but recently the torque curve is following a cris-cross sine-cos curve.amps intially 150amps den 200,300,400,500, and den again 400,300,200 and this goes on and on.i have noticed this time interval is 22 full rpm.full rpm of our kiln is 4.4 and also thrusters are fitted.coating is a minor problem here. #78 gyandweep on 2011-06-07 05:35 (Reply)

Are your thrusters hydraulically driven. If so please check the cycle time. #78.1 Walter Gebhart on 2011-06-20 20:51 (Reply)

I would like to ask your opinion on the following: Due to uneven coating in the Kiln we have a large difference of the temeperature around the Kiln shell at base 2. This is creating a thermal crank of the shell with a result the tire to be partially lifted of the supporting roller at every revolution of the Kiln. Also in every revolution the shaft of the roller is pushed and floads back and forward from one thrust colllar to the other creating a strange noise.We are very concerned of the high stresses on the rollers and shafts.This started initially at base 2 but now the same pattern is happening at all bases and rollers.How can we reduce the thermal crank effect without having to stop the kiln. Thank you very much #79 Christoforos Nicolaides on 2011-06-07 12:01 (Reply) Dear Sir My Name is Kalyan I want to know about Girth gear presuure angle, how we will calculate it and how it works please give the answer Thanking you sir #80 T.Kalyan chakravarthi (Homepage) on 2011-06-08 23:12 (Reply)




I regret we are not gear designers or manufacturers. I suggest you consult a machinery handbook. #80.1 Walter Gebhart on 2011-06-20 20:46 (Reply)

What could be the posiible reasons for girth gear joint bolt failure when root gap is within acceptable limit. #81 suman neogi on 2011-06-09 07:04 (Reply)

Possible reasons; Excessive axial run out, bolts are not of the correct material, bolts do not have the correct diameter, bolts are not torqued correctly. #81.1 Walter Gebhart on 2011-06-20 20:42 (Reply)

Kindly confirm me the mimimam gap requirement in-between kiln shell and top face of thrust roller. #82 selvakumar on 2011-06-13 00:21 (Reply)

The thrust roller must never come in contact with anything on the kiln. The distance is therefore a matter of safety. I would suggest anything less than 50mm can be potentially dangerous. The thrust roller(s), if incorrectly positioned on the upturning side of the kiln centerline can be drawn up and hit the kiln or the tire stop blocks with catastrophic results. Thrust rollers must always be off set about 5mm towards the down turning side of the kiln centerline. #82.1 Walter Gebhart on 2011-06-16 15:49 (Reply)

Assuming that this is just a temporary bend the only correction possible is to get the coating in the kiln more even. This is a process/operational problem. Uneven coating is mostly attributed to thermal shocks or at least thermal variations. When the process is stable the temperature profile will also be stable and an even coating builds. This is only one possibility there are others also process related. When the process is straightened out so will be the kiln. #83 Walter Gebhart on 2011-06-16 15:57 (Reply) kindly confirm me that what is the limitation of sim plate provided to reduce the creep or hot gap #84 selvakumar on 2011-06-23 03:43 (Reply)

After shimming, in the cold condition, the original cold clearance must be restored. Each tire will have a different cold clearance. These are usually given on the kiln General Arrangement drawings. #84.1 Walter Gebhart on 2011-07-07 14:49 (Reply)

Could you please to inform me what will be happened if the splash plate in preheater cyclone was worn out #85 Mohamed Saeed on 2011-06-26 04:04 (Reply)

You will loose thermal efficiency of that cyclone. #85.1 Walter Gebhart on 2011-07-07 14:50 (Reply)

Dear Sir, My question is why the kiln will have the thermal expansion towards down hill side from the inlet tyre, why it cant be towards inlet side. plz inform me. #86 kumar on 2011-07-01 23:57 (Reply)

The kiln expansion anchor point is the thrust tire. From the thrust tire to feed end expansion will be to the feed end. From the thrust tire to the discharge end expansion will be to the discharge end. #86.1 Walter Gebhart on 2011-07-07 14:53 (Reply)

In our plant the bearings of supporting rollers of kiln are spherical roller type. This is a Chinese plant. Originally it was designed for 2 rpm speed. Later on in 2006 it was upgraded from 1000 to 1900 tons/day and the speed increased from 2rpm to 4.8 without any changes in the lubrication and bearing system. The problem is that bearing fails frequently causing heavy production loss. To overcome this problem we want to replace these bearings with Bronze half sleeve bush bearing with housing which we already have arranged from JAVEDAN CEMENT, POLYSIOUS PLANT that was also designed for 2 rpm. In this connection we want to know your views whether it is feasible or not. If it is possible you are then requested to please ask your representative in Pakistan to send a technical team to survey the plant regarding the above job and quote for the same. #87 Mohammad Usman on 2011-07-08 06:45 (Reply)

Changing to sleeve type bearings is likely your only option. The rollers and support bases will also have to be changed. The shafts will be a larger diameter with sleeve bearings. The sleeve bearings need to be of the type with an internal spherical seat so that the brass liner can align itself to the shaft. The bearings should also have bolts holding it to the base. Polysius do make bearing housings within which the sleeve is fixed and which have no hold down bolts. At 4.8 rpm this latter design will be no better than your sphericals. #87.1 Walter Gebhart on 2011-07-11 07:20 (Reply)

Sir, The bearing of polysius plant is bolted with the housing like Fuller plant of Javedan cement on which you have worked during erection & commisioning. The lubrication system is of bucket type. Is it enough or needs extra lubrication ? Please let us know. #87.1.1 Mohammad Usman on 2011-07-13 21:01 (Reply)

How did you know I worked in the Javedan plant? If the bucket wheel oiling system was designed for 2 rpm it must be modified to work at 4.8. The angle of the buckets must be increased so that the oil does not overshoot the tray. I have no experience with such a dramatic change of speed in this respect so I do not know what the new angle should be. You could ask Polysius or F.L.Smidt otherwise you may have to build a test stand to find out what the best angle is. The best solution is to add an electric lubrication pump that circulates the oil, which can filter and cool the oil at the same time. A small pump station at each bearing would start circulating the oil prior to every start of the kiln thereby dramatically improving the life of the bearings. Most of the bearing damage occurs on start up because the oiling wheel has to make ½ a turn before any oil is delivered to the shaft. #87.1.1.1 Walter Gebhart on 2011-07-14 14:27 (Reply)

Kiln Doctor, we have a 60ft by 6ft rotary kiln used for reactivating carbon. A contractor was removing old refactory by blasting and ripped a tear in the side of the kiln about in the middle. This is 1/4 inch plate. The tear was put back into postion and




welded in place. I don't think this will hold up. I want them to make better repairs before the new refactory is put back in. How should damage like this be repaired? #88 John Peters on 2011-07-12 08:25 (Reply)

The only satisfactory repair would be to replace the damaged section of the shell. Shells are made in "cans" about 8 feet long. These cans are welded together circumferentially to make up the needed length of shell. When replacing a section the cuts should be at least 6” away from an existing circumferential weld. Plus the location of the cut line should be no less than ½ a can away from the next circumferential seam on the remaining shell. In other words with the repaired section in place you do not want two circumferential seams less than ½ a can apart. #88.1 Walter Gebhart on 2011-07-14 14:09 (Reply)

IN OUR CEMENT PLANT WE FIND FREQUENT RUNNING OF THUSTER PUMP IN KILN AND WE HAVE CHANGED THE FLOW CONTROL VALVE IN BOTH RETURN AND PUMPING BY NEW ONE BUT STILL THERE IS NO IMPROVEMENT IN THUSTER PUMP RUNNING IS SAME AS BEFORE THE CHANGING THE PREVIOUS VALVE.WE ARE NOT ABLE TO INCREASE THE OFF TIME OF THUSTER TIME (APPROX. 4 HOURS) THUSTER PUMP RUNNING TIME ON TIME:20 MINS OFF TIME:5 MINS #89 varathu on 2011-07-21 04:30 (Reply)

Your support rollers are out of alignment. They must be set closer to their neutral skew positions in order to allow your hydraulic thrust system to function correctly. #89.1 Walter Gebhart on 2011-07-24 19:18 (Reply)

what could be the possible causes of kiln amps fluctuation. The kiln is a twin drive sponge iron kiln. Amps variation is upto 200 amps for both master and slave. But at any instant of time the amps variation between master and slave is within 50 amps. - Uneven coating formation is not so significant in the kiln. #90 suman kumar neogi on 2011-07-21 04:40 (Reply)

There could be a couple of issues or a combination of them causing an amp cycle. Typically it is an imbalance in the kiln weight such as a build up of material, a coatiing for example on the refractory which is not uniform around the circumference. It may also be a bend in the kiln shell, which also acts like an imbalance. Such a bend may be temporary, thermally induced again by uneven coating or it may be permanent shell damage caused by a refractory failure. #90.1 Walter Gebhart on 2011-07-24 19:25 (Reply)

Dear Dr. Kiln, Do you have any knowledge about low emissivity coatings or paint applied to the hot zone of the kiln? The goal would be to keep the temperature inside the kiln the same while reducing the amount of fuel burnt. Are there any adverse effects of doing this? Are there any modifications to the kiln that would have to be done before applying a coating? #91 Michael Kyle on 2011-07-22 11:31 (Reply)

Lowering the radiant heat loss of the shell, which can be as much as 6% of the system heat input by using a low emissivity coating is an age old endeavor. The problem is the cost of applying and maintaintaning such a coating. Technology is always changing. The kiln shell is a tough environment. We are not aware of any coating that survives for any length of time and whose appplication and maintenence cost doesn't outstrip the savings in fuel efficiency. Simply evaluating such savings after an application requires an agreed upon bench mark. All such measurements are frought with uncertainty. Consequently we are not aware of any coating that has been successful. #91.1 Walter Gebhart on 2011-07-24 19:48 (Reply)

Dear kiln doctor, In sponge iron pkant,we are facing hot spot problems ,which occurs nearly either uphill or downhill side of tyre.4 months ago, we faced this problem downhill side of outlet tyre ( near about 2.5 m from tyre centre) and now its started to occur at downhill side of tyre no 3 from outlet end. Pl give me the solutions to relieve from this problem as this problem causes to stop the kiln frequenly. Give solutions, what should we take preventive and any remedial actions? #92 siva nandy on 2011-08-01 11:40 (Reply)

Just reporting hot spots and their locations is insufficient information to suggest remedial actions. The action required is more in-depth investigation. Hot spots means localized refractory failure. A complete history of refractory installation needs to be reviewed. What type of refractory is failing? Is it only one type or are several types involved? How long has the refractory been in service at the hot spot? Are the failed areas previous sites of failure and/or repair? Try to narrow down the variables. Failures can generally result from inappropriate type of refractory for the location, bad installation or operational problems such as thermal shock due to rapid changes in firing rates, rapid start ups/cool down. By narrowing down these general variables further sub classifications can be investigated. #92.1 Walter Gebhart on 2011-08-06 18:09 (Reply)

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