March 18, 2013

PLANNING with Mr. Pankaj A. Shah

AIA Engineering has 5 plants in India: Bangalore, Changodar (Moraiya), Nagpur, DFPL Trichy, and Odhav Storage houses are available in the foundries for fast moving materials/supplies such as grinding balls. M1 or Moraiya plant 1 or Unit 7 is the biggest foundry with a capacity of 90,000 TPA The current limiting factor in our production is that our plant capacity is not meeting the required capacity of

our customers especially with the big balls (i.e. 80/90/100/125/140mm) We are currently producing or manufacturing Grinding Media, Tube Mill liners, Mining liners, and Vertical Mill

parts. There are 4 foundries in Odhav:

1. Unit 1 produces 60mm to 140mm grinding balls and Tube Mill liners total capacity of 850MT/month interchangeable total capacity meaning the foundry can produce 500MT of GM + 350MT of TM liners or any other combination that totals to 850MT

2. Unit 12 manufactures Tube Mil liners and Mining liners total capacity of 1400MT/month almost a 50-50 capacity production per part (i.e. 50% TM, 50% ML)

3. Unit 5 manufactures Sintercast inserts,Quarry parts, and Ball ring segments for Raymond Mills in Coal Power Plants total capacity of 375 400MT/month

4. Unit 6 same as Unit 5 but with a capacity of 275 300MT/month

5. Unit 13 manufactures VSMS parts and Mining liners total capacity of 1500MT/month 50% VSMS, 50% Mining liners

Changodar / M1 plant / Unit 7 has a current capacity of 7,500MT/month for grinding media only but has expansion works for phase4 (horizontal line) which is meant for bigger balls and will have a capacity of 5,000MT/month at full operation.

expansion is expected to be fully operational on December 2013. manufactures only grinding media with sizes ranging from 15mm to 80mm.

Wellcast in Bangalore located at 1500km from Ahmedabad total capacity of 3,200MT/month for 60mm to 125mm grinding balls. nearest port is Chennai

DFPL Trichy, Tuticorin total capacity of 800MT/month for 60mm to 125mm grinding balls

Nagpur manufactures centrifugally cast rolls or Raymond rolls which is used together with Ball Ring Segments (BRS) total capacity of 700MT/month

If client wants to have its order in 1 lot only, it will be assigned with 1 plant but if client approves of several lotsthen planning can divide the order to 2-3 plants (e.g. smaller balls shall go to one plant while the bigger balls shall go to another plant. worst case scenario would be the client wanting the order in 1 lot (1 B/L) but no plant can accommodate the volume so planning will then distribute the order to 2 plants wherein the smaller volume shall be transported to the plant that handles the bigger volume so as to save on transportation

costs. NOTES: 1. Always try to convince the customer to have their order on several lots so that it could provide more flexibility for planning. However, worst case we can go with single lot.

2. If there is an inquiry, always ask planning on how long the delivery period will be which will be dependent on the volume or quantity of the order.

The range in delivery date (FOB/CFR/CIF) in our offer is dependent on the following:1. To allow flexibility in production technically clear order might be received several days after the offer was made and during this time the plants may already be full.2. Size/Volume of the order as well as the grades being ordered.

Standard delivery time are as follows:1. Grinding Media

big balls (i.e. VT18): ~ 6 weeks small balls (i.e. VH12): ~ 4 weeks

2. Tube mill liners new order: 11 13 weeks spare order: could be faster

3. Mining liners old/repeat order: 8 weeks new order: 10 weeks

4. VSMS old pattern: 14 weeks new pattern: 21 weeks NOTE: VSMS parts need 2-stage machining that's why it takes a longer time to produce (e.g.

Fettling)

DRAWING OFFICE with HKB and Jignesh Raval

PDP or Preliminary Design Proposal is a basic requirement for a new order. It primarily covers the scope and full detail of the order. It must be submitted with drawings (detailed drawings if possible) to provide complete information of order.

Grindingchamber

Classifyingchamber

Outlet trunionInlet trunion

LCD/middle diaphragm

Process flow in the Drawing Office

Technically complete order

Drawing Office generates GA drawings

Pattern shop accepts drawing from Drawing Office

Validation of Casting dimensions

Proceed to manufacturing

March 19, 2013

VM Plant

There are 4 furnaces in the VM Plant: 2 MT, 6MT, 6MT, 15MT wherein the 15MT furnace serves as theholding furnace for large quantity castings.

Process flow in the VM Plant

Order from Planning

Quality Control gives required composition

Melting mixes and makes desired alloy/grade

Pouring of liquid metal to preheated crucible

Pouring of liquid metal to Sand Moulds (Sand Casting)

Heat treatment to achieve desired microstructure (martensitic)

Quenching by air or by oil

Machining / Fettling

Final delivery

VM plant only caters to VSMS and some mining liner requirements.

Quality Control with Pramod P. Jain and R. Basu

Martensitic structure is the hardest microstructure and can achieve up to 68 HRC depending on its carboncontent. The higher the carbon content, the harder the martensite.

Bainite structure can achieve similar hardness as martensite but not up to 68 HRC. However, it is tougherthan martensite but is less corrosion-resistant due to lesser carbides.

Retained austenite is believed to be maintained at 10% - 20% and is a function of carbon content. It is alsobelieved to help in corrosion-resistance.

Martensite could also be tempered to achieve better toughness but hardness will naturally decrease.

NO BAKE Sand system: without baking and involves chemically bonded sand (sand + resin + hardener)

Green Sand Casting: has moisture involved. there are a number of testings involved to control the sand's moisture and prevent moisture-related defects in the castings such as voids, sand compactibility, green compression strength, sandpermeability, and loss of ignition properties. involves the re-use of sand with clay so there is a need to recalculate the amount of freshbentonite (clay) the aim is to achieve good internal soundness which means that there should be no shrinkage

this is attained by brute force method with the pattern at low and high temperatures.

for the liners, annealing is done prior to fettling or grinding. Annealing further improves the grain size andmakes it finer.

an almost homogeneous structure is achieved by exposing the casting (all castings except grinding balls) toaustenitizing temperature which will allow the previosuly heterogeneous microstructure to re-organize andhomogenize.

for grinding balls, a homogenizing treatment is done by exposing the balls (select grades only) to atemperature of 670 770 degC for about 8 hours.

better for impact and abrasion

QC demands 100% inspection of all liners using gauges.

Grinding media are only heat treated in a continuous furnace

Main functions of QC are as follows: analysis of hardness from surface to core; work-hardening phenomenonanalysis; OES analysis from melt samples during and prior to pouring

Always ask about customer feedback whether it is good or bad. For good performance a report with datawould suffice but if it is bad, ball/liner samples would be better together with a report.

As per AIA standard there is a +/- 3mm tolerance for grinding media.

RISER

Illustration 1: Sample of a horizontal casting of grinding media

Illustration 2: (left) Sample of casting mould for big grinding balls (60mm & above). (right) Sample of casting mould for small grinding balls (50mm & below). Both promote directional solidification.

March 20, 2013

Pattern Shop with M.Z. Vaghela

Typical process flow in the pattern shop:

Estimation of Inquiries from Technical Services / Planning

Drawing Office

Pattern Shop

Order Evaluation

Determine pattern nos. (either new or old)

Release for pattern making

Matering or Pattern Designing

Pattern Making

Pattern mounting on the Match Plates

Providing of Gating and Rising systems

Preparation of Bulk Production Card (BPC)

Release of pattern along with BPC for sampling

Foundry makes 1 sample casting

Inspection of sample by QC and Pattern Shop

Good or with minor repairs Bad(no re-sample)

repair works

Release pattern for bulk production

re-sample

Storage of the pattern after production

To take out the mould from the pattern, a tapered edge is designed to allow smooth release of the mould.

Overview of AG and SAG mills with Mr. Richard Drouin, Mr. Sanjiv Mehta, and Mr. Kanendra Dave

grates are normally Chrome-Moly alloys

AG mills can have High-Chrome material (due to low impact) while SAG mills can have Chrome-Moly (more impact resistant).

High-chrome cannot sustain a point impact or a localized impact as opposed to Chrome-Moly

always watch for the mechanism on how the mill is being fed (manipulator)

Feed Head Liner (FHL) and Discharge Head Liner (DHL) are high wear areas

initially, a company can go with a High-Low shell configuration due to the weight-based aspect of operating cost.

to keep shutdown as short as possible, 1 of 2 (in a set) liners will be changed. This also keeps the operation or production at a more stable condition (process-wise).

typically at the DHL, grate plates last for 3-5 months while for the FHL it can last up to 7-8 months, while the blind plates can last for a year all are dependent on the operating conditions.

Questions to ask to client: 1. What do you want the machine to do?

2. If a client asks a grate design with lifters, ask why because normally a grate without a lifter has half of the life of one with a lifter

3. How many castings are we going to install?

the lesser the castings, the better (in production standpoint) since installation time will be shorter

4. What are the areas along or across the pulp lifter? if there is an area that is smaller it may create a vortex which results in higher wear of the grates.

SAG Mill case studies the size of the FHL is pretty much limited by the size of the machine that will be used in the

installation; it would be good to know the dimensions of the machine's clamp/hook/lifting mechanism

Vega has employed the use of Y-shaped rubber backing material to facilitate in faster liner removal

insist on using long bolts (may cost more) to allow faster dismantling because Chrome-Moly yields/flows and closes the bolt hole thus making it difficult to remove

with rubber liners there is savings on power consumption but the effective volume goes down and fineness of grind suffers.

March 21, 2013

RWL or Unit 12 with Engr. J. P. Basu

Unit 12 caters to Sintercast inserts, tubemill parts (liners, grates, plates), quarry parts, and mining parts (liners, grates)

Sintercast is made by another company and is only manufactured into inserts by enveloping the sintercast with high chrome metal

3 Main Customers are Mining, Cement, and Power industries

Unit capacity is 1000-1200 MT/month with diffferent specifications

This unit employs 2-stage rejection:1st rejection foundry rejection (physical inspection)2nd rejection after heat treatment during fettling work total of 5% rejection is the limit for this unit

houses 2 melting furnaces 1 MW (2-2.5 MT) and 1.8 MW (3.5-4 MT)

has a remote laboratory for chemical composition tests using OES and a Carbon-Sulfur analyzer

conducts sand analysis using sieve analysis (mesh size distribution), acidity test, and clay content analysis

Process Flow Chart for Unit 12:

GCFW or Unit 5 with Mr. Yogesh K. Sharma

Sintercast inserts (ceramic material) are transferred to Unit 13 for the manufacturing of segmented rollers.

Ball Ring segments are made for Raymond Mills which are used in Thermal Plants.

Flow chart is similar to that of RWL minus the CO2 system.

The unit's capacity is 350 375MT per month of castings.

Ceramic cake (sintercast) is supplied by another company and then Unit 5 converts it into Sintercast Inserts by pouring metal wherein the sintercast gets enveloped with the metal.

Unit 5 started as the Grey Cast Iron Company and this is where Mr. BKS started his metal industry business. Since then, he expanded and converted the company into AIA Engineering.

This unit utilizes 2 cores resin-coated sand and CO2 sand (curing agent is used together with the sodium silicate and sand mixture).

4 Mould and Core Making Processes1. Green Sand uses river sand and has retained moisture2. No Bake uses wash sand and could be made two-part, three-part, etc.3. CO2 uses either wash sand or river sand together with sodium silicate and then with Carbon Dioxide to initiate a reaction with the sodium silicate which then acts as the bond of the mould.4. Resin-coated shell core process

March 22, 2013

Heat Treatment Plant or Unit 2 with Mr. Mahesh N. Shah

this unit handles heat treatment of Tube Mill liners, BRS, and some small mining liners.

oil-quenching and air-quenching is done depending on the hardness requirement as well as the preference of the client with how they want the ball finished (with or without oil).

however, if hardness could not be reached with oil-quenching and client does not want oil in their balls, oil-quenching could be done to reach the hardness and then a subsequent de-oiling process (e.g. shot blasting) is done to remove the oil from the balls.

choice of oil-quenching or air-quenching also depends on the end application.

prior to heat treatment, annealing is done to all tube mill liners but not for VRM parts. Moreover, some grades are subjected to tempering or stress-relieving so as to achieve a specific toughness and prevent premature breakage.

this facility can handle 1000MT per month wherein each of the 7 furnaces can handle up to 10MT depending on the material to be annealed.

a penetrating liquid (pink or white) is used to check if there are cracks on the castings.

castings are either packed in wood boxes or metal boxes.

marked balls are also heat treated in this unit and dependng on its grade, it is either air-quenched or oil-quenched.

materials except for Marked Balls are air-quenched with blowers on the top as shown below:

batch-type furnaces are used for tempering or stress-relieving and also for annealing

pusher-furnaces or continuous furnaces are used in tandem with oil-quenching. a special oil is used for oil-quenching the biggest oil tank being used has a capacity of 16,000 liters

schematic of the oil-tank:

Process flow for Unit 2:

As cast casting

Annealing (Batch)

Quenching

Air-quenching Oil-quenching (Hardness of 50+ HRC)

Tempering / Stress Relieving (batch)

Packing

Fabrication Shop with Mr. Dipak Naik

Airport Ring assembly, Level Control Diaphragm and Outlet structures are being fabricated by vendors (machine shops) that AIA has contracted.

depending upon the market situation, the contracts are revised every 2-3 years.

All fasteners and hardware to be used for the fitment of diaphragm grates are also being contracted by AIA and is re-packed in Unit 315 prior to shipment to clients.

the Fabrication shop basically does production planning of the raw materials. The main responsibiities of the Fab shop are painting, packing, inspection, and dispatching.

no manufacturing is involved here

there is a total of 9 vendors for fabrication and 5 vendors for fasteners/hardware

packing work is also being done by contractors

the raw material used in the fabrication of ARs and LCD structures is a special MS called Selma steel which isa high-tensile steel

fasteners are tested upon delivery by suppliers at Unit 315 wherein the rejected fastener samples are being rejected together with the whole supply lot.

DP test and threading will be checked and also the cleanliness of fasteners. accepted fasteners will then be tested for hardness, tensile strength (% elongation), and chemical

composition. for small bolts, the hardness should be within 23-32 HRC while for big bolts it should be within 28-32 HRC.

if client wants high tensile bolts, hardness will not be tested since they are inversely proportional.

all fasteners are segregated and classified as per customer specifications

the threads of bolts is sealed with a lubricant to prevent corrosion during shipment and storage the seal should only be removed when the bolt is about to be removed

March 23, 2013

M1 or Moraiya 1 Plant in Changodar with PBR

grinding media with sizes of 15-90mm is being manufactured in this facility can make standard and special grades of balls for both 1st and 2nd chambers

air-quenching and oil-quenching are done on grinding media depending on the grade tempering may also be done depending on the grade

no fettling is done with the grinding media

there is an on-going expansion with a capacity of 4,000MT per month for 60-125mm grinding balls

the temperature range for grinding media heat treatment is at 850 1030 degC and then oil-quenching is done at a temperature range of 150 160 degC.

has 8 batch-type furnaces for ball sizes up to 90mm and 5 heat treatment furnaces (pusher-type) wherein the balls are either air-quenched or oil-quenched

this plant has a remote laboratory for chemical composition analysis (using an OES) and also a small tubling mill for ball testing

has an automated vertical casting machine which has a sand pouring mechanism and a compacting mechanism that allows AIA to cast small balls quickly

FURNACE

OIL

HOPPER W/ VIBRATING SCREEN

CONVEYOR

M2 or Moraiya 2 Plant or Fabrication shop with Mr. NA Patel

handles the machining of VSMS part for Loesche, Polysius, Atox, MPS, and Back Cock mills

there is a total of 9 working Vertical Boring Machines with sizes ranging from 1.4m to 6.1m in diameter to cater to the different mill sizes of the clients

prior to shipment, 100% inspection is done by the QC department to ensure that the castings concur to the specifications or requirements set by the customers

there is a max allowable crack of about 20mm before any liner/roller is rejected

for table liners, the liners are set or arranged accordingly to simulate its position inside the mill. This procedure allows AIA to prevent fitment problems at the customer end

packing of rollers and liners is done with wooden boxes or as per customer specifications

March 25, 2013

Tube Mill training with Mr. Jignesh Joshi

there are 3 kinds of diaphragms: middle, discharge, and pre-heating pre-heating diaphragm only has lifters and no shell liners

cylindrical lifters can be rotated about its axis which helps to control the level of cement in the 1st compartmentof the cement mills

proper material level means that it is the same level with the balls. If there is no proper material level, power consumption and wear may increase

2 Varieties of LCD: (1) standard; (2) optimized for Standard LCDs the thickness of the grates is 50mm +5mm and uses long bolts that fastens

through the grates and back plates; has 7% Cr; WEAKNESS: longer maintenance and higher labor for Optimized LCDs the thickness of the grates is 70mm +5mm and have more sectors; uses sholter

bolts for fastening of each grate and plate; STRENGTH: shorter maintenance and lower labor

STANDARD LCD AND GRATES

OPTIMIZED LCD AND GRATES

Cylindrical lifters

Head Liners standard thickness of 85mm usually with 11% Cr alloy if the client wants a different design, estimation will be done and based on the weight the alloy is

determined.

Shell Liners

lifting non-lifting how much lifting is needed? types: depend on hardness standard class std. sol'n for classification types: thin class increases chamber volume step & wave (11%Cr, 1-1.5%C) deep wave class high wear application double wave (7%Cr, 0.3-0.5%C) conveying class for high moisture application plain step (11%Cr) other design Universal Vega Liner (T13)

Lift computations:

Lift = L = H h Life = 0.6 x L

Lift = L = H h (max); L = H h' (min)

**For Double Wave design aggressive design for hard material; has uniform wear on the surface if the thickness of the liner above the keyhole is at 15mm, the liner needs to be replaced must be used with a minimum of 28% ball level

**For Plain design normally this design is not recommended because grooving is generated

**For UVL lightweight with per plate weight of 24kg

A: H = 80mm; h = 60mmB: H = 100mm; h = 60mmC: H = 120mm; h = 60mm

could be arranged differently depending on the nature of the feed: A-B-A-B A-C-A-C A-B-A-C A-A-A-A

Parameters to be considered: Feed granuometry: check for D80 (80% passing size)

if D80 is 12-15 = coarse if D80 is 10 = fine

Bond's Work Index or Vega Index ask if the circuit includes a pre-crusher or not*NOTE: as per AIA, if C is the only alloying element, if the C is below 2% it is regarded as a steel and above this it is regarded as an iron.

Generally, the shell is drilled according to DIN standards and if the shell holes do not match the liner design, normally AIA goes with semi-boltless configuration where the bolted liners are positioned at 90deg away from each other.

Take note that the inlet opening dictates the ball level inside the mill.

2nd Chamber classification of balls is the main function of 2nd chamber liners normally fed with balls of sizes 17mm 50mm where ideally the bigger sized balls are nearer the LCD balls in the 2nd chamber have higher hardness (not tempered) while the balls in the 1st chamber are tempered balls.

there is about 20% Retained Austenite in the 2nd chamber while there is 6% Retained Austenite in the 1st chamber (spalling results from volumetric expansion if RA goes beyond 6%)

Critical Speed of Mills speed at which the grinding balls tend to stick to the periphery of the mill; at 100% Critical speed, the centrifugal force is higher than the gravitational energy of the ball*NOTE: engineer should always check for the rotation of the mill (looking from the feed end) and decide

on the layout of the liners

Norms for critical speed:

mill normal range< 3m 68 72 %

3 4 m 72 74 % 4 5 m 74 78 %

> 5m > 78 %

Vcr=42.3/ (D ) ; for 100% Critical speedwhere D = internal mill diameter

actual speed can be measured with a stopwatch and measure the time it takes 25 revolutions (repeat three times)

%Vcr= (Va /Vcr )100 ; where Va = actual measured velocity

N1Z1=N 2Z2

N2=(N1Z1 )/Z2 ; where N1 = shaft speed N2 = girth gear speed Z1 = # of teeth of the pinion Z2 = # of teeth of the girth gear

*NOTE: all above mentioned data are available with the client

Volume Filling

Deff=Di(2t L ) ; where tL = liner thickness Di = inner diameter Deff = effective diameter

if the head wall is tapered, there are two chamber lengths: effective length (similarly, the liner length) average length (FHL to LCD)

check the empty height, h, three times and then take the average (always take measurements at the center of the mill)

the optimum filling level for the 1st chamber is 28 30% (of 60mm 90mm balls)

%VL=112 .5(125( hDeff )) for mill inspection or audit, it is important to look for the following: dt, h, Deff, effective length, ball condition, and ball sizes

for the 2ns chamber, a classification test may be done wherein at every 1m interval, collect the balls inside a 500mm diameter sampling area (at the center of the mill) using strong bags. The approximate weight of the collected balls would be 3 4 kgs. to get the average piece weight of the collected ball samples, do the following: (1) weigh the balls (per interval); (2) divide the total weight (per interval) by the number of samples; (3) plot theaverage piece weights and if there is a decreasing trend then the classification of the balls is good.

ave . pieceweight=W 1N1

,W 2N2

,W 3N 3

,. .. ,W nN n

collect also the historical data of the parts such as: who are the suppliers of the parts? What is the metallurgy of the supply? When was the supply installed? How many hours has the mill been running? What was the lifetime guarantee that was given? For balls, when was the last ballsorting (re-grading) done normally, it is done yearly?

the standard slot sizes are as follows:discharge grates = 8mm; grate plate = 6mm

For the 2nd chamber, the rule is that the smallest ball should be twice as big as the discharge slot size (approx. 17mm). On the other hand, the smallest or minimum size in the 1st chamber should be 60mm since 50mm balls pose breakage due to its higher hardness and lower toughness.

Ball Mill Specific Power Consumption (SPC)

SPC= kWofdrivemotormilloutput

SPC= kWht

For SPC computation, collect monthly data of the company for the past 5 months and generate a plot.If the fineness is increasing, the SPC will also be increasing; for a PPC (Pozzolan) feed with 3600 Blaine, the SPC will also increase; fr PSC, SPC will also be increasing.

Formulas for SPC computations:

1. For the 1st chamber,

SPC1=0 .0806Deff3 .014Leff, 1p1J(1 .361.25 )N

1.27

where p1 = density of the charge = ~4.5 t/m3 J = volume loading N = mill speed, rpm Leff,1= effective chamber length

2. For the 2nd chamber,

SPC2=0 .0806Deff3.014Leff, 2p2J(1.361.25 )N

1.27

where p2 = density of the charge = ~4.65 t/m3 J = volume loading N = mill speed, rpm Leff,2 = effective chamber length

*NOTE: Normally, the LCD is placed at 1/3 the total length of the mill; Always ensure that the effective chamber length ( Leff,1, Leff,2) is at the optimum.

to actual power consumption of the mill, go to the MCC and check the Energy Meter Reading for every hour interval.

Crash Stop Audits

Open-Circuit Mill

Vair = < 1m/s; at the end of the 1st chamber there should be 1% retention, R, of size 2.5mm

Closed-Circuit Mill

Vair = 1.2 1.5 m/s; at the end of the 1st chamber there should be 5% retention, R, of size 2.5mm

Circulating Load, CL, is normally at 200-300%

CL= (CA )(AB ) ; where C = classifier product; A = classifier feed; B = Classifier reject

*NOTE: screens cannot be used as Final classifiers but only as primary classifiers. the ventilation fan provides both ventilation and suction inside the mill. in the above diagram, hot air with dust goes into the baghouse fiters and then goes out as dust-free gas onto the ventilation fan. The dust will be put back to the bucket elevator and then to the classifier. measurement of the air velocity is done at the clean air duct (between the baghouse and the fan), using a pitot tube and a u-tube manometer.

take samples from the classifier feed, product, and rejects for analysis and check for 90, 45, and Blaine.

Blaine is defined as the surface area of the sample over its weight

Blaine= surfaceareaweightofsample

Blaine= cm2

gm

Blaine apparatus measures the time it takes for the air to displace the water to a certain level, h, and then correlates it to a Blaine number. The finer the sand, the higher is its corresponding Blaine number.

We can also check for

the classifier efficiency in a Closed-circuit mill system which is normally at 70% for 3rd generation classifiers:

ClassifierEff .=C ( AB )A (CB )

100

Check also for the method of crash-stop that the company is utilizing. This may either be triggered by stopping a ventilation fan or by turning off the MCC or others.

What to inspect during crash-stop? material level (is it lacking, optimum, or very high?) conduct chamber sampling (for cement): for every 1.5m interval at 3-4 inches deep for the 1st chamber; for every 1m interval at 2-3 inches deep for the 2nd chamber.

*NOTE: be sure to sweep the fines off of the sampling area's surface conduct sieve analysis or particle size analysis: 16/12/10/8/6/3/2/1mm for the 1st chamber; 5/2/1mm/ 90/45/Blaine for the 2nd chamber check for liner grooves and the lifter height check for nibs (uncrushed particles) in the 1st chamber

if crushing is not effective, nibs can be found in the diaphragm or nearit. This means that the 1st chamber liners need to be improved, hence, ball charge data coming from the customer should be gathered. Ball data charge calculation:

Ave . Ballweight= TotalweightofballsTotalno .ofballs

if the crushing is ineffective, the immediate action is to increase the average piece weight of the balls.

Alternatively, the piece weight of the ball can be calculated as follows:

W ball=Dball

3

250,grams

when the lift has lost 60% of its original thickness, recommend for a liner replacement.

Life=0 .6L ; loss in lift

for the 2nd chamber, the basis of replacement is the classification test (plot) andthe sample sieve analysis (plot)

Clinker is the main ingredient of cement: C2S (Alite), C3S (Belite), C4AF (Aluminum Ferrite), and C3F (Ferrite)

Alite and Belite have effects on grindability while Aluminum ferrite andFerrite has negligible effect Hence, check for the amount of C2S/C3S in the feed and also the litre weight (weight of 1 litre of clinker). The ideal litre weight is 1150-1200

Ball size # balls per MT # balls90mm = ______ MT x 343 = _________80mm = ______ MT x 488 = _________70mm = ______ MT x 728 = _________60mm = ______ MT x 1157 = _________

Total weight Total # balls

Equilibrium ball charging means that all sizes of the balls are equal in number (not in weight). This allows for the estimation of the make-up charge by considering that the wear and tear is thesame for all the ball sizes. Please take NOTE that make-up is composed of bigger sized balls only (i.e. 90/80mm).

If the ball charge is already at the optimum, adjust the cylindrical ball lifters of the LCD to achieve the target retention in the 1st chamber.

1st Chamber Inspection Checklist

1. FHL thickness2. # of rows of FHL3. Measurement of the trunion opening diameter, dt4. Measurement of the chamber effective length, Leff5. Measurement of the empty height, hemp (check in 3 places)6. Measurement of the effective diameter, Deff (ensure that liners are 180deg apart)

e.g. count from the 1st liner to the 16th liner for a mill 3.2m with a step & wave design7. Measurement of the lifting height of the liner

if liner has a double wave design, use an ultrasonic thickness gauge or check the liner in the manhole or check for liner-to-liner diameter, Da

if Da = Do + 90mm, recommend for liner replacement; Do is original liner-to-liner diameter

8. # of sectors in the diaphragm Check for diaphragm choking

9. Measure the slot sizes (6mm-10mm)

10. Measure the plate thickness if the plate has lost 60% of its thickness, recommend for replacement

11. Measure the central screen diameter12. Calculate the Volume Loading based on what is bigger between the trunion opening diameter or the

central screen. (base on the bigger diameter)

2nd Chamber Inspection Checklist

1. # of rows in the back plates2. thickness of the back plates3. measure the effective diameter4. measure the effective length5. measure the empty height6. do classification test (if necessary) especially if guaranteed life has been reached7. comment about liner condition8. # of sectors of the outer diaphragm9. check for choking10. measure the slot sizes (should be around 8mm 12mm)11. measure the discharge (outlet) plate thickness12. measure outlet central screen diameter

when the design of the central screen is too small and less porous, recommend for a re-design13. calculate for the volume loading

Vega Standard Grades (Alloys)

For 1st Chamber Grinding media: Vegatough18 (standard grade)For 2nd Chamber Grinding media: Vegahard12 (standard grade)For FHL: Vegaline112 (standard grade)For Step & Wave liners: Vegaline112For Double Wave design: Vegaline107For UVL design: Vegaline313For Grate plates: Vegaline107 (standard grade), Vegaline112 (optimized), and C01For Back plates: Vegaline112For Standard Classifying design: Vegaline212For Outlet Diaphragm grates: Vegaline112

Alternative Grades for Specific Applications

For 1st Chamber Grinding media: VegaPlus (tempered)For 2nd Chamber Grinding media: Vegahard Special (tempered)For FHL: should not be proposed without discussion;

Vegaline107 designed with a lifter; long and thin ( 1%, production will decrease since the moisture will promote coating and blinding and also decreases the liner life.

March 26, 2013

Training at the Drawing Office with Mr. Bharat Suthar

the Drawing Office handles the GA Drawings, Mill drawings, and also the Trunion drawings GA drawings are meant for understanding the drilling pattern, manhole position, size, and type

for a new requirement wherein there are no engineers available to get the measurements, we can compare the new requirement with a similar mill.

PDP is prepared by the Planning department based on the information gathered by the Technical Services Engineer, hence, it is the technical background of the requirement.

the Drawing office uses Solidworks which is a 3D Modeling software. It helps the engineer to better understand how the requirement would fit inside the mill.

2D drawings such as the GA drawings are still produced using AutoCAD.

If an engineer gets deputed in a plant and has the opportunity to get measurements from the mill, the engineer needs to measure 3-4 times and get the minimum reading.

Also, if possible, get the liner drawing of the bolted liners/row especially if the current supply is not from Vega. This should be counter-checked with the GA drawing.

If the existing middle diaphragm is not from Vega and Vega is supplying the shell liners, it is imperative to get the measurement from the LCD to the bolthole of the bolted liner adjacent to the diaphragm. Get 3-4 measurements and always take the maximum measurement.

For manhole covers, normally Vega gives 15deg tapered sides for ease of dismantling and installation. If a client requires for a change in manhole cover design (from square edged to tapered) take note that the manhole liners and the side liners should also be changed. If a client wants to change the manhole cover from outside opening to inside opening, Vega should offer manhole cover and its surrounding liners. If a client wants to change the manhole cover from inside opening to outside opening, Vega should offer the manhole cover, surrounding liners, and shell modification. Hence, Vega will need the existing manhole drawings with complete dimensions.

As a standard, engineers should mention in the report that we are looking from the inlet end or the feed end.

When the GA drawing has a ? it is imperative that the engineer should gather the said data/dimension and immediately send back to Drawing Office.

All Vega diaphragm supplies come with filler bars since this would allow for ease in dismantling and installation.

If Vega is offering for a diaphragm supply (Vega LCD, Vega outlet), we should also offer the side liner rows since their could be fitment problems with other supplies.

For shell liners, ensure that there is no axial gap in the circumferential rows by putting circular wedges/shims. This may not be at an equal interval from each other but rather it should be put where the gap is present.

To lock the circular wedges, weld it to the locking wedges (longhitudinal). If in case during the inspection that the wedges are sticking out, hammer it back to position.

It is very important to specify everything for new orders. Indicate whether the company has changed its name just like the case of Fortune Cement which is now LRI-Batangas. It is also critical to mention the mill number.

When making a follow-up on a current order, please make sure to give the OA# because this will enable the Drawing Office to trace back all previous supplies given to the customer.

March 28, 2013

Training for VRM with Mr. Rajesh G. Modi

A wooden or metallic template marked with 10 equal points is used to monitor the wear of rollers and table liners.

To determine the amount of wear in the roller, measure the gap between the template and the roller (as seen above). Make 3 readings at each point and get the average wear depth.

Then, determine the surface area of the roller and then compute for the weight loss of the roller in grams:

wt. loss of roller=surface areawear depthdensity of steelwhere density of steel = 7.85 g/cm3

Next, gather the tonnage ground and then compute for the wear rate of the roller:

wear rate of roller= weight losstonnage ground

Coal has the tendency to move very slowly due to high coefficient of friction (~0.11). This corresponds to higher mill rpm. As per design, the dam ring height is quite high.

if the wear at the dam ring side (of the roller) reaches 45 50mm or when the thickness of the roller reaches 40% of its original thickness, we recommend for replacement.

The Raw mix has faster movement than coal due to lesser coefficient of friction (~0.09). This corresponds to alower mill rpm and lower dam ring.

if the thickness of the roller reaches 40% of its original thickness, we recommend for replacement.

A Dovetail pin is used to lock the table liner segments in place and prevent the table from moving or slipping.

To measure the wear of the table liners we first use a level scale to determine if the table liners are parallel to the ground (if not parallel, uneven wear is most likely to occur). Then use a template and then measure the gap from the template. To compute for the wear rate, proceed with the same computation as the rollers.

Roller supplies depend on the mill manufacturer:Atox: segmentedPfeiffer: segmented or monoPolysius: segmented or monoLoesche: always monoUBE: always monoFLS: always mono

For segmented rollers there is a 35-40% ceramic inserts while for mono rollers we can only give in high chrome.

Table liners are always segmented (for ease of maintenance).

When a new client gives a RFQ, look for the following:1. Pattern of wear2. Current supplier3. Alloy type of previous supply4. Maximum wear of depth5. Operational parameters such as tonnage, mill output, and power consumption6. Cement feed characteristics like quartz content, size of feed, moisture content, and bond index

As per OEM, most castings can be used up to 40% of the casting's thickness, hence, when we supply we onlygive 40% ceramic or 65mm thick ceramic (whichever is lower).

if client wants higher wear depth (>65mm) we can offer 10,000 operating hours or 65mm wear depth at 2.5 g/ton.

For Mono rollers, our solution is inserted sintercast with a maximum thickness of 22% of the roller thickness. gives improvement of 1.6 to 2 times the non-Vega supply.

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VRM Inspection Checklist

1. Feed characteristics2. Grinding elements (same as with the RFQ)3. Dam ring height and design4. Nozzle ring opening area and design5. Classifier condition6. Reject chamber condition

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Converse to the tube mill concept of having the mill running at a % of the mill's critical speed, VRM's need thecentrifugal force to be slightly higher than the frictional force and consequently higher than the critical speed.

Raw mill = 1.4 1.5 times the critical speed Coal mill = 1.9 2 times the critical speed Clinker = 1.2 1.3 times the critical speed