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Tulysan Nec Limited, Chennai.
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Safety Tips For Salica Ramming Mass
A really good monolithic lining requires extraordinary care by the manufacturer, in selection, purity and grading of raw materials, uniformity of mixing and careful packing.

Maintaining this quality to achieve a perfect wet or dry lining requires equal care from you, the user , from the moment any ramming mass reaches your factory until the first metal is poured.

At Stores
Maintain sufficient inventory so that quality lining materials are available at all times.
Before you receive the ramming mass, set aside a clean permanently dry area in the stores , away from coal dust , cement boric acid , furnace additives etc, Which are harmful to the lining life, if they accidentally spill on the ramming mass bags and get into the lining. Sweep thoroughly and lay down some wooden supports to keep bags away from damp floor.
When unloading the ramming mass first dust off the load in the truck. Make sure that the unloader does not use ANY HOOKS: keep spare gunny bags and plastic liners ready to re-bag torn bags. If possible, use compressed air to blow off wood splinters etc from each bag before stacking. Then cover the stack carefully with a sound tarpaulin or heavy plastic. Use on a first-in first-out basis, keeping newspaper or a marker between different lots. Keep supplies from different suppliers in different stacks, as they may require different levels of binder and the melting shop should be sure what it is getting. This is very essential for effective follow-up of lining complaints if they arise.

Open one or two bags fully without damaging plastic liner.
Check visually that grain size, colour and appearance are similar to earlier lots from that supplier. Watch out for organic impurities or mica (mirror – like flakes) or felspar (white or pink grains with flattish facets having a pearly vitreous shine). These will lower the sintering temperature and refractoriness of the lining. Use a magnet to spot – check for iron particles.
Plunge your arm into the bag. The mass should not feel damp. If it is, or if bags are wet onthe outside, consult melting shop about drying procedure , in advance , before ramming.
Close plastic bag tightly and re-stitch outer bag without tearing the liner.
If a sample is to be drawn for laboratory inspection. IT MUST BE A REPRESENTATIVE SAMPLE. Empty an ENTIRE BAG on a clean plastic sheet and proceed by the “QUARTERING”: divide the heap of ramming mass into equal quarters. Take two diagonally opposite quarters of the manufacture, then and provide this heap into quarters again. Repeat this six to seven times till you get a sample, small enough to send to the lab in an airtight package.

Test for Moisture, if the sample is wet or that which has arrived during the monsoon. Dry mixes should have not more than 2% moisture . On drying before mixing and ramming, the moisture should be reduced to below 0.5%.

Test for Bulk Density, the most important property affecting the lining life. Fill, say.300 gm well – mixed ramming –mass (without binder) in to a 200 ml glass measuring cylinder. Loose Bulk Density (weight / volume) will be around 1.7 gm/cc or the silica or 2 – 2.7 gm/cc for dry basic masses.

In a sieve Analysis , the Absolute Values of the sieve analysis are Not Important .Any number of different gradings in which smaller grains fill the spaces between larger grains , can all give a good dense – packing mass, which is the min requirement.

If you wish check the sieve analysis of a properly quartered sample on, say 0.6 mm (30mesh)and 0.1 mm (150 mesh )screens . Keep a record and look for idle variations 20% of the previous average, of the same supplier, or for excessive coarse (more than 5% oversize particulars by weight ) Furnaces up to 8 should give 0-4 mm or 5 mm dia particles. Larger furnaces can have 0-7 mm grain size mixes.

The best possible test for a doubtful or new supplier’s product is to use one or two bags from a new lot for ramming the top or spout of a furnace lined with earlier proven material , or for the last patching in a campaign. That way , if any problem shows up in use , you will have adequate stocks of the earlier suppliers and enough time to find a solution.

At The Mixing Area
Sweep, dust and clean the floor, weigh-scale , drying and mixing trays or mixer etc. before you send for the material, from the stores. If using charcoal for pre-heating the ramming mix arrange the bed and then get the rest of it well out of the way.

Dust off each bag again, at the entrance before taking it in. Bags may have dropped to the ground en-route , or stores personnel may have been away when the material was collected.

Keep a dustbin handy to collect pieces of cut string after the bags are opened , or they may end up in the lining.

Premixed Monolithics
Basic ramming mixes can usually be used as supplied. Suppliers , like us , supply silica ramming mixes on request premixed with a standardized quantity (1.5%) of boric acid binder , or to order as requested by large customers. This ensures great uniformity of mixing, but it must be stored in perfectly dry conditions. Also no other ramming mass without boric acid should be stocked , lest, workers add extra binder by mistake to the premixed monolithc.

Dry Mixing
Plain silica ramming masses need addition of commercial grade boric acid powder in the melting shop before use. A minimum of 0.8% is usual at very high temperatures (e.g steel melting) and a maximum of 2% boric acid for cast iron or non-ferrous melts. Purer ramming mixes need slightly (0.1% to 0.2%) more binder than impure mixes.

Boron oxide is sometimes used instead of boric acid for faster sintering cycles. But since only half as much is needed, uniform mixing becomes twice as critical.

As far as possible, use the same percentage binders through lining to avoid confusion and possible error. If lumpy, sieve the boric acid through a 1 mm screen before weighing and keep the weighed lots in closed plastic bags.

Plan to mix between 50kg and 250 kg ramming mix at the time, depending on the furnace size and mixer or mixing – tray capacity. This means a boric acid package of between 500 gm and 5 kg weighing accuracy should be 5 % so use suitably small scales and check for zero – error before you start weighing. (Keep suitable check – weight handy for frequent use).

Weigh the ramming mass bags before use. To keep out dust while emptying into the drying tray fold the inner plastic liner down over the outer woven bag like a folded sock. Remove outer gunny before shaking the inner bag empty. Emptying through a 12 mm(1/2”) screen will remove string or paper bits etc.

NEVER USE PART OF A BAG – you may leave behind either coarse or fines segregated in transit and get a non-uniform lining. Material in the drying tray should form a 30 – 60 mm layer for convenient drying and mixing.

De-magnetize the material in the tray (after leveling and picking out visible impurities) by taking with a one-foot strip of wood with several ordinary magnets fixed to it. Remove what you can in 3-4 rakings.

Only Irion particles above 1-2 mm can cause erosion pockets in linings. Fine iron dust is difficult to remove and generally harmless, but if excessive it will increase the fluidity of the binder and hence the thickness of the hard – sintered that zone, leading eventually to a shortened lining life.

USE SEPARATE TRAYS for heating/drying and for mixing. Heat the drying tray with gas if available. When using oil burners or charcoal, beware of spillages that can contaminate the ramming mass, bags or containers.

Aim for drying temperatures of 70° C if binder is premixed otherwise 110° C or so.

Stir ramming mass occasionally while heating. If it is noticeably damp (power sticking to your dry palm after holding a fistful) it will require a couple of hours for proper drying our. If drying is insufficient, the steam formed on sintering will open up cracks – forming passages in the lining.

Then transfer it to a cooling try before mixing ( in that same tray or in a mixer)

Cool the ramming mass till you can count to ten with your palm pressed against its surface. Demagnetize and heat a second batch while the first is cooling. Boric acid loses it first molecule of water 80° C. if boric acid is added while the ramming mass is too ho, it will melt to form little globule and cannot be distributed uniformly. This may show up as pinhole defects in the lining surface.

Make a PREMIX with the boric acid by doubling and redoubling. In a basin mix thoroughly by hand the required boric acid with an equal quantity (say 1 kg ) of dried ramming mass. To this mix, add an equal quantity (2kg ) of ramming mass and mix again by hand. Repeat once or twice more (e.g. 1+1=2, + 2 =4 + 4 = 8 kg of premix). This uniformly diluted lot may then be mixed with the remainder of the batch, preferably by doubling and as above, or by sprinkling the premix on the rest of the batch and turning or raking. DO NOT SPRINKLE UNDILUTED BORIC ACID for mixing- its volume is too small for uniformity.

Even if a mechanical mixer is used, add the boric acid in a diluted premix as above for more uniform distribution.

CHECK YOUR MIXING PERCENTAGE for uniformity once in two months, or whenever a new workman is doing the mixing or for the first five linings in the case of new users as follows:

Add robin blue or dhobi’s ultramarine (50 gm per bag) to each batch, in the same way as you added the boric acid premix and mix the batch as described above. Mixing in uniform when the whole batch has attained a uniform colour. It is quite harmless to the lining.

For mechanical mixing, check the performance of the equipment periodically as above. Add Robin Blue in exactly the same way that boric acid PREMIX is added, and along with it.

After emptying the mixer ,look for blind corners or pockets where the colour may not have reached and take corrective action.

Check lining density by recording the weight of contents on containers, if the mixed batch is stored rather than used directly. Store in clean well covered containers and use with in 12- 15 hours. Remember that boric acid is hygroscopic and can pick up moisture. Condensation (dew) overnight can drip into layers. Keep with minimum surface exposed. Cover the closed containers with tarpaulins if stored near furnace area.

More Ramming
The condition of the furnace can seriously affect the performance at a newly installed lining. So :
Tighten all nuts, Bolts and joints to minimize furnace vibration during operation. This will prevent segregation of particles, and resultant pockets in the partly- sintered lining.
If backing bricks are replaced or repaired, allow the fresh grouting –mortar to dry well as a dry ramming mix is to be in contact with it.
If coils have been changed , make sure they are perfectly concentric with the former to be used. Otherwise linings will be thinner on one side than the other, with resultant faster wear.
The coil grout surface should be absolutely level and uniform. Any uneven projections will interfere with free upward expansion/contraction of the sintered lining in use , and may cause horizontal cracks.
Check and pressure – test cooling water and coils to avoid blockage or leakage. Descale and treat water regularly. Efficient cooling behind the lining gives a good temperature gradient that prevents run- through and interior erosion.
Place a TALL SCREEN between the ramming area (new shell and mixing area ) adjacent furnaces or ladles, to prevent sparks flying into the lining unnoticed. These sparks of metal can cause run throughs once the lining is in use.

Sweep and clean the working area thoroughly , starting with hoist rails, which often drop dirt into the furnace while lowering the former etc.

Record Keeping
Prepare complete works Instruments for all aspects of lining. Namely mixing placing ramming, sintering , patching breakout and especially for furnace operation, i.e. routine melting practice , including proportions and specification or descriptions of materials charged.

Make sure these works Instruments are always accessible to operating staff and workers.

Keep them up-to-date. Once some experimental change becomes permanent revise the works instructions with a paragraph number new page, and reasons for the change.

Review at least twice a year : Have all concerned personnel read through the instructions and invite comments or revisions. Make this a formal event or it will never get done. 9 this is well worth doing in all foundry departments.

For a routine record – keeping of furnace performance, GRAPHS are far more informative and meaningful than numbers in a log.

Plot curves of current Drawn by a particular furnace shell vs the Number of Heats for instance. Once you have a half – dozen curves, trace them all on to one tracing paper and draw one smooth common curve through them. This will be your own personal average or Target Curve based on your own particular operating conditions and practice.

Draw this onto a graph paper and cyclostyle it for daily use. While the furnace is in an operation plot, your current readings every 5 or 1 heats alongside the Target Curve for comparison. Deviations and potential deviation show up very clearly on a graph rather than as mass of numbers, and immediate corrective action is possible.

Similarly collect date and plot graphs regularly for different Process/ variables Like.
   Lining    Life    Vs
  Hours per Heat  
   Lining    Life    Vs
  Average Hours per Heat  
   Lining    Life    Vs
  Average Heats per Month  
   Lining    Life    Vs
  Heal Level  
   Lining    Life    Vs
  Boric Acid Percentage  
   Lining    Life    Vs
  Coke / Carburizer Quality  
   Lining    Life    Vs
  Metal Composition  
   Lining    Life    Vs
  Tapping Temperature  
Over a period of time , these will highlight the correct way of doing things

Also keep a running Graph of process efficiencies, plotted after every campaign, such as :
Kg Metal Melted per Kg Ramming Mass / Refractory consumed
Kg Metal Melted per Unit of Energy Consumed.
These Graphs are more useful than coasting figures, such as Value of metal melted per Rupee of Energy consumed, since these prices may fluctuate.

Such graphs will enable you to establish norms for different process variables understand your particular operation more thoroughly and aim for real improvements in process efficiencies which will ultimately improve your market strength.

Strive for a pleasant consistent and systematic working climate in the plant. It will not only make everyone happier, but will really give longer lining life and cheaper metal at spout then conditions in which everyone is constantly “ fire fighting “ coping with crises handling emergencies under pressure to keep up with constantly changing demand or disorganized habits in the casting – shop or quality and supply of charge. This requires uncontrolled, on the spot changes in melting practices, and predictable lining life is hard to achieve under these conditions.

So plan organize and relax as you tap out your profits.

The information stated is based on the best laboratory and literature data and is not a warranty or a guarantee, nor violation of any patent. it is presented for consideration and verification only and is not to be used for specification purposes.
  copyright @ 2006
Sudha Meltchems, India.