welcome back friends in the previous lecture

we have studied about different moulding sand properties we have seen how these properties

are going to affect the final quality of the casting so it is important for a foundry men

to control these moulding sand properties thats why in this lecture let us see how to

test the moulding sand properties so this lecture is moulding sand testing these are

the important moulding sand tests one is the moisture content test another one is the clay

content test next one the grain fineness test next one the permeability test next one the

compatibility test finally the strength tests and among the strength test there are four

one is the green compression strength green shear strength dry compression strength and

finally the hardness now let us see these tests one by one first

let us see the moisture content test how to determine the moisture content in a moulding

sand in the beginning we have seen that the moulding sand should contain moisture from

two to five percent how to know whether it the moisture is between two to five percent

if the moisture is below two percent what can happen they may not be enough for what

say binding or if the moisture content is more than five percent then what happens excessive

of steam and hot gases will be produced and because of that there will be blow holes and

pin holes on the surface of the casting so the moisture content should be optimum so

how to measure the moisture content in the moulding sand so this moisture content can

be measured using an infrared heater so we can see here this is an infrared heater and

yes uh here we can place the sand spaceman so when you keep this what say container with

the sand the green sand inside this ah infrared heater may be after few minutes the moisture

will be dried out then we can find out the moisture content so this is the ah procedure

place twenty to fifty grams of uh prepared green sand the pan and heat it in an infrared

uh woven for about two to three minutes then what happens the moisture in the moulding

sand is evaporated so initially we have weighed it may be it may be say about twenty two or

fifty grams of the sand now the moulding sand is taken out from the pan and it is weighed

again the percentage of the moisture can be calculated from the difference in the weights

the percent of the moisture is equal to w one minus w two multiplied by hundred whole

divided by hundred what is this w one and w two w one is the weight of the sand

before drying before we kept inside the infrared woven and what is w two it is the weight of

the sand after drying difference of these weights multiplied by hundred whole divided

by initial weight of the sand gives the moisture content so this is the old and traditional

method of finding the moisture in the green sand recently a new techniques have been develop

that is the rapid moisture teller so this is the the new technique develop right so

if the process of the infrared woven it to takes ah what say we need initially we need

to weigh the sand then we have to put it inside the woven and heat it about two to three minutes

again take it out and again weigh and we have to make some calculation

that way it takes about ten minutes totally whereas this rapid moisture teller tells us

within a minute how so this is a small equipment so when calcium carbide comes in contact with

the moisture acetylene gas is generated so this is well known to us now this principle

is used in the rapid moisture teller now what we will do a weighed quantity of sand sample

is mixed with a fine fixed quantity of calcium carbide reagent and the whole mixture is thoroughly

shaken in a vessel in which pressure gauge is fixed now ah we are what say making me

calcium carbide react with the moisture of the green sand and accordingly acetylene gas

is produced now what is the amount of acetylene gas produced it depends upon the moisture

content of the moulding sand now the acetylene gas produced develops pressure

the instrument indicates moisture on the pressure gauge so this pressure gauge is calibrated

so right so accordingly we can know the percentage moisture in the moulding sand so this takes

very less time thats why it is known as the rapid moisture teller

next let us see the clay content test so it is very important for us to control the clay

in the green sand again so when we are talking about the clay ah yes initially we will be

mixing the clay or it is also known as the binder and uh remember among this clay or

the binder the most important binder is the bentonite now ah in the previous lecture we

have seen that as we keep pouring the molten metal into the mould as we keep reusing the

sand again and again what happens part of the clay or the part of the binder

which is close to the mould wall will be heated above five hundred degree centigrade once

it is heated above five hundred degree centigrade it loses all its properties binding properties

it cannot create cohesion anymore between the neighbouring sand grains but physically

it is present so now we need to what say distinguish between the ah what say actual clay or the

active clay or the total clay now let us see how to measure clay contest so clay content

means there are two terms is it the total clay which is um what say ah some of the active

clay and the dead clay or there is the another test ah in which we only measure the active

clay first let us see how to measure the total clay content right so this is the what say

an ah instrument used for the total clay content right

so this is the equipment now this is used ah what we do is we what say mix the sand

in a container with water and uh we stir it using this equipment so this is the way separate

fifty grams of dry moulding sand and transfer to wash bottle right next one add four seventy

five cc of distilled water plus twenty five cc of three percent naoh sodium hydroxide

now hesitate this mixture for about ten minutes with the help of the sand stirrer this this

is the sand stirrer next one fill the wash bottle with water up to the marker after the

sand has settled right siphon out the water from the wash bottle now after we stir some

time right remember we have mix the sodium hydroxide

what does this uh sodium hydroxide do it separates the clay particles from the sand grains and

sees that it ensures that the clay is settle down sorry clay will be floating and the sandal

will be settle down now while the clay is still what say mixed with the water will be

siphon it out using a siphon now what is there inside the bottle only the water not the water

only the ah fine and clear clean sand base sand is there clay has already been siphoned

out now this sand is to be dried out remember in the beginning we have taken fifty grams

of the sand next one now the percentage of the clay content can be calculated as follows

right percentage of the clay content is equal to w one minus w two into hundred whole divided

by w one where w one is the weight of the sand before

the test and w two is the weight of the sand after the test but remember this is the test

for finding out the total clay content but for us total clay impo ah what say content

is not so important but what is the active clay because part of the clay becomes the

dead clay so what is the active clay so for that we need to conduct another test so this

is the clay content to test for the finding out the active clay the test which we have

conducted previously is to ah that is the test for finding or the total clay whereas

the this test we will be using for finding or the active clay right so here we use the

methylene blue what is this mrthylene blue solution

it is a what say ah heterocyclic aromatic chemical compound with the molecular formula

c sixteen h eighteen n three scl so this is the a chemical um formula of the methylene

blue now methylene blue is a potent cationic dye now ah how to proceed how to conduct this

test so we have to use an apparatus right so this is the apparatus used for the methylene

blue test in which we will be finding out the ah active clay content steps in methylene

blue test first one what we have to do is we have to calibrate the methylene with the

clay system so this methylene blue solution reacts with the active clay so ah as long

as the active clay is present right so this methylene blue will be reacting and we cant

see any methylene blue and its effects now what is happening is ah is uh what say

we will be calibrating say for this much of what say active clay this much of methylene

blue will be required for reaction for this much of clay this much of methylene blue is

required so this way what they uh with prior experiments we have to calibrate the methylene

clay system next one in the second step so the first part is the calibration second part

is the take five grams of the sand in a stainless steel container and fifty ml of two percent

tetra sodium pyrophosphate solution via pipette disperse sand particles using an ultrasonic

accessory right so slowly fill the vessel with the methylene blue from the burette and

stir the system now we have what say ah mixture of the sand

and the tetra sodium pyrophosphate right now what is happening is we are dropping methylene

blue drop by drop now remember in this sand what say the active clay is there but we are

slowly dropping the methylene blue solution as we keep dropping the methylene blue solution

the active clay readily reacts with the methylene blue solution and sees that methylene blue

has no effect this process will continue so how to know that the clay content is exhausted

methylene blue is dominating using a glass rod remove a single drop of the liquid and

place it on a filter paper watch for the formation of a blue green halo

around the central spot so this is the indication that the active clay is exhausted and methylene

blue is dominating we have to take a what say glass rod and remove single drop of the

liquid and place it on a filter paper if the what say active clay is exhausted then there

is little excess amount of methylene blue and [meca/because] because of that when you

place the drop on the filter paper there will be a blue green halo means thats an indication

that the active clay content is exhausted then we have to stop uh what say drop in the

methylene blue solution right so if we dont see the what say blue green halo increase

the addition of the methylene blue drop by drop till blue green halo appears

once of this blue green halo appears we have to stop dropping the methylene blue solution

now we have already calibrated between the methylene blue solution and the clay content

now how much methylene blue is what say consumed so that we have to find out from the burette

now from that calculate the amount of from the burette calculate the amount of the methylene

blue consumed and based on the consumption of the methylene blue using the calibration

factor determine clay content of the sand remember that methylene blue doesnt react

with the dead clay it reacts only with the active clay so that is how we can find out

the active clay in the green sand next one let us see ah among the moulding sand properties

let us learn how to find out the grain fineness test

so for finding out the grain fineness test there will be what say sieve shaker will be

there so the equipment looks like this there will be different sieves will be there and

here we can see different sieves are there right so there will be ah for each sieve there

will be a mesh will be there in one mesh there will be coarser what say holes will be there

in some other meshes medium holes will be there and in some other meshes fine holes

will be there so initially at the top the coarser [mess/mesh] mesh will be there you

can see this one is the coarser mesh below that say the mesh me having the little smaller

holes will be there below that likewise there will be mo what say more what say ah what

say sieves will be there and all these will be arranged one over another

at the bottom there will be a pan and here we can see when all these what say sieves

are arranged together it looks like this and this is known as the sieve shaker this is

known as the sieve shaker now how to find out the grain fineness number this remember

first of all what is this grain fineness number this grain fineness number tells us how big

the sand grains are or how small the sand grains are if the grain fineness number is

very high means the sand grains are very fine sand grains on the other hand if the grain

fineness number is very small it indicates that the sand grains are very coarser sand

grains now this is the way place the sample of dry sand after removing the clay in the

upper sieve generally a people place fifty grams or hundred

grams place the sample of the dry sand remember it is dry sand and free from the clay next

one yes uh we put it in the here we open this lid and here we places that to dry sand fifty

grams or hundred grams next vibrate the sieve shaker for a definite period yes this can

be vibrated there will be a vibrating system will be there we can set it to the for vibrating

ten minutes five minutes or fifteen minutes and uh this whole structure will be vibrating

now what happens the sand which we have placed inside slowly it will be coming down and if

they ah remember and this sand may contains different what say grain sizes right maybe

few sand particles or coarser few sand particles are finer and few sand particles are of medium

size and accordingly the finest particles will reach

the bottom pan whereas the medium sized sand particles will be collected somewhere in the

between in between whereas the coarser particles will be remained in the upper sieves so that

is how the sand will be distributed in different sieves now where now we stop vibrating this

sieve shaker weigh the amount of sand retained on each sieve means we have stop it and we

have to to remove separate all these sieves and carefully collect the sands that are collected

in each and every sieve and we how to very precisely we have to vary sands in all these

pans then compute the percentage of distribution of the grains so this is the data sheet for

the sieve analysis right so here we can see each sieve has been given a specific number

right so what is the sand ah initially we have dropped

right and the percentage we have to enter here next one is this is the cumulative percentage

and say for each uh what say sieve there will be a multiplier will be there now after that

there will be a product product of a and b means uh percentage collection of the sand

in each sieve multiplied by the ah what say this multiplayer product right ah this is

the product a into b now grain fineness number it is indicated by gfn is equal to sum of

products means these are the products these are the products sum of the products divided

by sum of the percentage weights of the sands retains what are these percentage weights

and here we can see these are the percentage weights and if we add up these here we get

the sum of the percentage weights means sum of these products divided by sum of these

percentage weights gives us the grain fineness number that is how we can find out the grain

fineness number grain fineness number is indicated by or simply is known as the gfn now let us

take a problem a sample of fifty grams of moulding sand was sieved through a sieve shaker

the quantities of sands collected in different sieves were recorded determine afs grain fineness

number of the said sand and what are the quantities of the sands collected in different sieves

so these are the quantities of the sands remember the different sieves are assigned the different

numbers the first sieve is assigned the number six

the second sieve is assigned number twelve third sieve twenty fourth sieve thirty fifth

sieve forty sixth sieve fifty seventh sieve seventy eighth sieve hundred ninth sieve one

forty tenth sieve two hundred eleventh sieve two hundred and seventy and the finally the

pan will be there so totally including the pan there will be twelve sieves will be there

of course pan cannot be considered as the sieve with excluding the pan there will be

eleven sieves will be there now in these sieves so these are the sands collected in the right

in the first i think first four sieves there was no sand was corrected next one in the

war say ah uh forty is excessive means the ah sieve with the number fourteen point two

grams were collected similarly in the sieve with number fifty point

six five grams were collected similarly in the sieve with number seventy one point two

grams were collected similarly in the sieve with the number hundred two point two five

grams are collected and in the sieve with number one forty eight point five five grams

are collected in the sieve with number two hundred eleven point zero five grams are collected

and with the last sieve with the number two seventy ten point nine grams are collected

and finally in the pan nine point three grams are collected and these are the total we can

see forty for point one grams are retained or collected right and there will be a loss

will be there there will be a toss because say ah some sand grains will be trapped between

the meshes and when we separate the meshes and we when we what t say ah take them out

some sand particles are tapped and they wont come out that is how though we have what say

taken fifty grams and finally if we add up all the sands which we take from different

sieves it will be less than fifty grams now this is the given data so this is these are

the right ah afs sieve numbers these are these are all and this is the these are the sand

what say amounts collected in different grain what say sieves and in the first four sieves

no sand is collected and these are the sands collected in different sieves now this is

the percentage of the sand retained now what is the amount of sand that we have taken we

have taken fifty grams of sand now what is the ah in fifty grams of the sand

so this is the amount of sand contained point two grams and if you want the percentage it

will be point four grams and ah uh here in the sieve with the number fifty point six

five grams are were retained now what is the percentage one point three similarly here

it is two point four and here it is four point five and here it is seventeen point one twenty

two point one right twenty one point eight and eighteen point six and this is the sum

of the what say ah amounts of the sands retained in different sieves that the percentage uh

what say of the retained sands here now ah here we can see an important curve curve that

is the multiplier for each sieve there is a particular multiplication factor right

for the first sieve the multiplication factor is three for the second sieve ah means with

the sieve number twelve the multiplication is factor is five and for the third sieve

the multiplication factor is ten and for the fourth sieve the multiplication factor is

twenty right for the see what say sieve with uh number forty the multiplication is thirty

for the sieve with number fifty the multiplication factor is forty and for the sieve seventy

the multiplication factor is fifty for the sieve hundred the multiplication factor is

seventy for one forty sieve the multiplication factor is hundred for two hundred sieve the

multiplication factor is one forty for two seventy sieve the multiplication factor is

two hundred and for the pan the multiplication factor is three hundred and

it is easy to remember these multiplication factors for example i will show you see here

we can see it this is the multiplication factor multiplication factor ah say uh for example

you consider this sieve with two seventy what is its multiplication factor two hundred that

two hundred is the previous sieve number you see this is the previous sieve number similarly

for two hundred mesh sieve the multiplication factor is one forty but you see what is this

one forty this one forty is the sieve number of the previous sieve number you see similarly

for one forty sieve the multiplication factor is hundred and what is that hundred it is

the sieve number all right ah the sieve ah the previous sieve number you see like this

likewise it is easy to remember these multiplication factors now in the last column we are finding

out the product a into b where a is the percentage of the sand retained

in each sieve b is the multiplication factor which is assigned for what say each and every

sieve now here we are making product a into b now the total the sum of the product is

fifteen thousand two hundred and forty three the sum of the percentages of sands retained

is eighty eight point two now we will find out the grain fineness number grain fineness

number is equal to sum of products divided by sum of percentage weights of sands retained

what is the sum of products sum of products is this much fifteen thousand to forty three

and what say sum of percentage of the sands retained is eighty eight point two so yes

now we have substituted those values in this formula

now we are getting grain fineness number is equal to one seventy two point eight or it

is approximately equal to one seventy three afs so the afs grain fineness number four

theses sand is one seventy three so this is the way to find out the ah what say grain

fineness number of the moulding sand so remember this uh what say what say number seems to

be little high generally in most of the sand foundries the grain fineness number right

of the sand casting industries it will be between say say fifty to seventy so that is

the normal what say grain fineness number of those sands and here the grain fineness

number is hundred and seventy means this is very fine sand

on the other hand if the number happens to be very low below fifty or below forty then

its a very coarse sand whereas this one is a very fine sand so that is all that is the

interpretation of the grain fineness number next one let us see the permeability test

we have seen that what is permeability permeability is the ability of the moulding sand to enable

hot gases to pass through the neighbouring sand grains and finally to the atmosphere

because when we pour the molten metal the moisture in the moulding sand readily reacts

with the molten metal and forms steam and hot gases these stream and hot gases will

be escaping through the ah gaps between the neighbouring sand particles and finally they

leave the mould so a good moulding sand should have this property of the permeability

if the permeability is not adequate what happens the gases thus produced will be accommodated

inside the mould and finally they lead to the gas and blow defects blow holes defects

now how to know whether our sand has the required permeability or not so we have to determine

so how we will determine this permeability the quantity of the air that will pass through

a standard specimen of the sand at a particular pressure condition is called the permeability

of the sand means we will make a sand specimen may be generally it is two inches diameter

and two inches height and generally about say ah two thousand cc of uh air will be made

to pass a at a particular pressure but whether two hundred cc will pass right or not uh we

have to see so that is how we used to measure the permeability so for that purpose ah we

use the sand rammer right so this is the specimen tube its a cylindrical

tube and inside this is what say specimen tube we placed the sand for placing the sand

effectively we place the tube here take this tube and put it here so this is the filler

accessory and through this of funnel we what say drop the ah what say green sand and the

grain sand green sand will be dropping inside this specimen tube and now we place this specimen

tube here so this the sand rammer so this sand rammer has a hammer you can see and this

is the hammer and this is the what say hand uh spindle we can rotate this spindle like

this and every time when you rotate this hammer will go and suddenly will fall again if we

rotate it will go and it suddenly it falls so when we place this what say sand specimen

here and with the sand inside that and yes now you rotate the what say that spindle the

hammer goes up and falls down and the sand will be compacted generally people give three

to five rams now the sand will be compacted inside the specimen tube right now we now

to take this specimen tube with the compacted sand inside to the permeability meter so this

is the permeability meter or the permeability ah test apparatus now how to measure the what

say permeability using this permeability apparatus now ah previously we have filled what say

moulding sand in this specimen tube we have to bring this placement tube and we have to

place it here we can see here there is a what say whoop ring here we have to place it and

here we can see there is a jar there is a jar and there will be water in it and with

this what say what say handle ah or a this lid can be raised

up then what happens air will be going inside now when you release it slowly the air will

be coming out and it will be passing through this tube and finally it will pass through

the sand specimen so this is the ah what say ah what says permeability apparatus right

what are the components it has an inverted bell jar which floats in a water so this is

the inverted bell jar now it right specimen tube for holding these sands specimen right

so here we place the specimen tube and finally there is a manometer for measuring the air

pressure and here we can see there is a manometer what are the steps involved two hundred cc

volume of air held in the bell jar and it is forced to pass through the sand specimen

at this time air entering the specimen is equal to the air escaped through the specimen

take the pressure reading of the ma manometer right note the time required for the two hundred

cc of air to escape through the specimen now permeability can be measured like this permeability

number is equal to vh divided by apt where v is the volume of the air h is the height

of the specimen in centimeters a is the area of the cross sectional area of the specimen

that is the space centimeters next one p is the air pressure grams per square centimeter

next one t is the time taken by the air to pass through the sand specimen and this is

expressed in seconds now let us take a problem determine the permeability of a afs standard

what say specimen of five point zero eight centimeters means two inches diameter and

five point zero eight centimeters means two inches height the air drum was raised to take

two thousand right centimeter cubic centimeters of air into it the whole air was then allowed

to escape through the sand specimen at a pressure of ten grams per or centimeter square meter

this is square in a span of fifteen seconds now ah how to calculate the permeability first

of all this is the formula for the permeability permeability number vh by apt where v is the

volume of the air in cc h is the height of the specimen in centimeters a is the cross

sectional area of the specimen square centimeters and p is the air pressure next one t is the

time taken by the specimen to pass through ah time taken by the air to pass through the

specimen and it is experienced in seconds that way v is equal to two thousands centimeter

cube cubic centimeters next one h is is the height of the specimen that is five point

zero eight centimeters a is the cross sectional area of the specimen that is twenty point

two six eight square centimeters p is the air pressure that is ten grams per square

centimeter next one t is the time that is the fifteen seconds now we have the formula

so this is the [fo/formula] formula for the permeability vh by apt let us substitute these

values in this formula when we substitute and simplified the permeability becomes two

hundred and five so this is the permeability of the sand so we have seen how to measure

the permeability of the sand moulding sand next one let us see the compatibility test

so we have covered moisture content test clay content test grain fineness test permeability

test and now let us see the compatibility test

what is this compactibility the compactibility indicates the water tempering degree of the

green sand moulding then how to measure it compactibility is the percentage decrease

in height of a loose mass of sand under the influence of a controlled compaction we take

the what say loose sand and we make a controlled compaction then what is the reduction in height

percentage reduction in height that is the compactibility so this is the compactibility

scale accessories right mounted on the sand rammer sometime back we have seen the sand

rammer right so to measure the compactibility this is the compactibility accessory which

is fitted on the sand rammer now we can see here since these are the we can see here three

ah specimens are there specimen tubes and this is the moulding sand this is also the

moulding sand and this is also the moulding sand

and all the three specimens are given same compaction may be they they are given three

what say rams but see the reduction is this much in this case the in this case in the

second case the reduction is this much in the third case the reductionism this much

means the third sample has the highest compactibility and this is how the compactibility varies

with the clay content now testing procedure how to measure the compactibility position

a specimen tube and pedestal cup on the tube filler beneath the funnel outlet next one

pass the sand to be tested through the screen until the specimen tube is filled so fill

this specimen with the moulding sand loosely dont compact to yourself right next one stickle

the what say sand level with the top of the tube if there is any excess sand that one

we have to stickle next one remove the specimen tube and place in position on the sand rammer

now we have to take this specimen tube after placing sand inside and we have to put

it under the sand rammer now this is the sand rammer and this is the specimen tube and the

specimen tube and we have to place it here and right so this is the what say oh we can

with that we can rotate and we here we can see this is the hammer and it goes suddenly

it falls goes suddenly it falls now when we place the specimen tube with sand and uh we

can give rams generally lower the plunger and gently on to the sand and ram three blows

three rams have to be given then what happens this is the accessory to measure the what

say ah this compactibility now this accessory will be fitted here will be fitted here now

when we give the three rams certainly there will be reduction in the height of the sand

if it has got a good compactibility there will be more reduction and if it has a poor

compactibility there will be less reduction accordingly read the percentage conpactibility

by the position of the top of the plunger shaft on the scale so here we can see how

much reduction is there accordingly from that we can see the percentage reduction also so

that is how we can find out the compactibility of this moulding sand finally let us see the

strength tests under the strength tests we have the green compression strength and we

have the green shear strength we have dry compression strength and finally we have the

hardness so let us see how to measure the green compression strength for measuring the

green compression strength also we have to prepare the sand specimen in the same way

yes uh this is the sand what say tube specimen tube and in this we have to place the moulding

sand now we have to ah what say give the blows

or we have to make the give the rams generally three rams or five rams now right so the this

is used for the ah what say filling easily means what say the specimen tube is kept here

and uh through this way we put the moulding sand we place the moulding sand so the moulding

sand is easily placed in to the it is easily placed in to the tube now there is a universal

sand strength machine is there you can see this is the universal sand strength ah what

say machine now we we have to prepare the sand specimen yes this is the tube and in

the in to that we have to place the moulding sand and using the rammer and we have to make

the rams and the sand will be compacted and here we can see the what say specimen separator

so using that ah we can separate the sand specimen from the tube and this sand specimen

we have to kept keep here so these are the here we can see there is a pendulum is there

right this pendulum here we can see is a small wheel is there and when we rotate this wheel

what happens the pendulums slowly goes up and here there is a graduation is there and

here there is a scale and for uh what say green uh what say compression strength there

will be one scale will be there green shear strength there will be another scale will

be there similarly for dry compression strength and dry shear strength there will be another

two more scales will be there totally there will be four scales will be there here

now we are measuring the green compressions strength for measuring the green compression

strength right we have to put this specimen at the bottom at the bottom and these what

say specimen holders will be plane holders plane holders right between these plane holders

we place this specimen and when we rotate this pendulum as it goes up the weight of

the pendulum falls on the sand specimen at one stage this specimen breaks and a magnet

will be ah what say carried along with the pendulum somewhere here a magnet will be there

so as the pendulum is going up it goes they magnet goes along with that the moment the

sand specimen breaks there the what say magnet will be what say arrested and uh of course

the pendulum comes back because the specimen is broken now ah where the what say magnet

is arrested the that is the what say green compression strength next one using the same

what say ah what say sand ah universal sand strength machine

we can also measure the green shear strength right so this is the here we use the specimen

pads used for the shear strength so here the specimen pads are different from the specimen

pads that are used for measuring the green ah compression strength in the case of the

um measuring the green compression strength the specimen pads are plane they are plane

here they have a ah projection here he this is one pad and there is a projection here

and this is the other pad and here also there is a projection and in between we place the

sand specimen and yes uh we place it on the ah what say universal ah what say sand strength

machine what happens as the machine what say pendulum is going up what happens previously

compression force was falling on the specimen now because of the what say pads the nature

of the pads now a shear force will be acting on the specimen again same thing you keep

rotating this ah right pendulum pendulum will be going up at one stage they there will be

shear will be maximum and the specimen will be broken and uh the magnet will be carried

along with the pendulum at one place it will be arrested where it is arrested and now we

have to refer to the scale which is meant for measuring the green compression strength

right there ah note down that uh reading that is the green compression strength now same

uh same way we can also find out the dry compression right so ah for measuring the dry ah dry compression

strength yes uh ah yes at the bottom for uh this is the position for placing the or for

finding out the green shear strength and green compression strength

when we want to measure dry compression strength and dry shear strength we have to place the

specimen here at the top and the same thing the pendulum will be there and we have to

rotate the pendulum will be raised up as it is raised up the load will be falling on the

sand specimen but one uh thing is here more load will be falling on the sand specimen

same thing if we want to find out the dry compression strength yes uh keep rotating

that at one stage the specimen fails and now we have to refer to that scale which is meant

for measuring the dry compression strength from that scale and from where the magnet

has stopped that is the reading of the dry compression strength similarly if we want

to measure the dry shear strength now we have to change the pads for measuring the dry compression

strength and uh what say green compression strength the pads will be plane for measuring

the dry shear strength and for measuring the green shear strength

the pads will have what say projections on both the sides so because of the projections

your shear will be induced now here we have to use the second ah set of the pads though

which are meant for measuring the shear strength yes the dry specimen will be here and keep

rotating the pendulum at once stage they will fail now we have to refer to the scale which

is meant for uh ah measuring the dry shear strength where the magnet has stopped that

indicates the dry shear strength of the specimen finally this is the ah determination of the

mould hardness so ah right for measuring the hardness so this is the what say small device

this is known as the hardness tester now ah right it is what say uh there is a scale is

graduated inside the dial now here we can see there is a small what say ah projection

is there so this uh actually is pushed when we want

to ah find out the hardness hardness indicates the resistance of the mould to plastic deformation

due to evolution of the gases it also indicates the resistance against erosion due to flow

of melt so that is the hardness now what we do we prepare the sand specimen and above

the sand specimen we take this hardness tester and press it and here is the knob and the

knob will be little pushed up because of done that what say the dial gauge here it will

be rotating how much it is rotating accordingly we can know the hardness of the moulding sand

not only what say what say specimen even on the final mould we can find out the hardness

in a similar way just to take this hardness tester and press it on the mould and we can

know the reading friends ah in this uh what say lecture we

have seen the ah different methods to find out the properties of the ah moulding sand

right not the properties how to conduct the ah what say different tests and we have learnt

how to measure the moisture content test right and we ha under the moisture content is the

traditional method we have learnt and the rapid moisture teller method also we have

learnt next we have seen to ah what is the method to find out the clay content the active

clay and the total clay both the methods we have seen for finding out the ah what say

active clay there is a method called the methylene blue test so that we have learnt next one

we have seen how to measure the grain fineness number right

so the grain fineness number indicates the size of the sand particles if the grain fineness

number is very low the sand particles are very coarser on the other hand if the grain

fineness is very high the sand particles are very fine particles so how to they measure

this grain fineness number we have learned next one permeability permeability means ability

of the moulding sand to allow hot gases to pass through the sand system so this is very

important so we have seen how to measure the permeability next one what is this compactibility

right percentage reduction when a what say it is rammed or a compaction is made so we

have seen how to measure the compactibility under under the ah strength tests we have

seen how to measure the green compression strength and how to measure the green shear

strength and how to measure the dry compression strength and finally the hardness so with

this we are closing the what say moulding sand testing we will meet in the next lecture

thank you

## 6 Comments

## Sreenivas MD

Thank you sir,

here you are not explained about return sand and sand temperature.

## Ningappa HM

Sir,

I want books for green sand testing.

Please give me your mail id

Or mobile number

This is my no 9008707888

## Mathivanan K

sir thank you ,for the sand test show demonstration.

## Mathivanan K

sir thank you ,for the sand test show demonstration.

## YATIN BANSAL

Sir. How to prepare naoh solution. Kindly explain. Thank you.

## Sangamureddi Kishore Naidu

Can we use this for gate lectures?