Document b5RNxnLQBvrEXNd17XZEpBYy
August 30, I960.
'r. Ji'Jtchrraftt
Subjects Becoven V.'llio*; *raperetion of Acbestos Fil^re
LvUUlas Cws;*:lucted during 1938 indicated that the efficiency c:' t:j. luj.ov.'Hi willow in the preparation of different Chrysotlle i*;-t :r:!. vrrlt;4.- coni-idercfcly, anti in dependent on both the fiber
i - * t.i. tl;. fib-ir uo*. ran. Since we s.i*u currently using six hr^i*i i:n ia tne willow at Plant 1, and an average of 18 hairpins. In the willows tt our pipe plants, the attached study was undertf-h.;n to I'ctonoins the effect of different numbers of hslrplnc i:; t-h prupwration of various Chrysotile and Blue fibers as a ; onaiblc E.?an& of increasing their relative strength.
Tho results of this study indicate that the use of 32 hair pins instead of the present lo is the cost economical for the preparation of pipe fibers, and that the use of 48 hairpins in stead of the present six is the sost econoxical for willow pre parations at Plant 1. Based on the improved relative strengths obtained with Increased preparation, a saving of approximately $200,000 per year would be realised in pipe manufacture, and a a.-r/ing of approximately $32,000 per year would be realised in the operation of No. 4 Machine, Plant 1, Although this Increased preparation would, to some degree, decrease filterabllity and increase water retention, changes in these characteristics should not drastically effeot machine operation.
In addition to the savings from more efficient preparation, there are indications that our fibers, on the average, have been upgraded over the past several years. As a result of this up grading, an additional deorease In raw material ooat of approx imately f100,000 per year would be realized in pipe manufacture, and approximately $11,000 per year in the operation of No. 4 Machine, Plant 1.
JAK/rodt
CTD000924
Subject: Denov&n Willow Preparation of Asbestos Fibers
Project 4.1.L J. A. Halone
Studies conducted during 1958 Indioated that the efficiency of the Denov&n willow in the preparation of different ChryBotile fibers varies considerably, and is dependent on both the fiber grade and the fiber souroe. In particular it was noted that the preparation of Caasi&r AK with lB hairpins Increased the relative etrength by only four per cant* while the sore preparation in creased the relative strength of Casslnr AC and C&G 3 by cn average of 16 per cent* and the relative strength of Bell 4x and C&G 5 by an average of 24 per cent. Since we are currently using six pins in the willow at Plant lf 18 pins in the willows at Plants 8 and 9* and 21 pins in the willow at Plant 6 (see Appendix I}* it ap peared desirable to Investigate the effect of different numbers of hairpins in the preparation of various Chrysotlle and Blue fibers as a possible means of increasing their relative strength.
In this study of willow preparations* Caaaiar fiber (grades. AC* AK* and AX)* C&O fiber (grades 3 4* and 5) Bell fiber (grades 4k and 6d)* and Blue fiber (BT/AC and NC-300) were chosen for test as being representative of the principal asbestos producing areas from which we are currently purchasing. All fibers were evaluated for relative strength* water retention characteristics* filterability* length distribution* dust content* surface area* and buoy anoy in the as reoelved state* and after preparation in the Denovan willow with 12* 24* and 48 hairpins (see Appendix II on test pro cedures). The results obtained are listed in Tables I and II* and are shown graphically in Figures 1 through 30. All preparations were carried out at the standard willow speed of 1230 revolutions per minute and a feed rate of approximately 2000 pounds per hour* using standard hairpins (see Note* Appendix I) whloh had been con ditioned in regular production for approximately 120 hours.
As indicated in Figures 1* 2* 3# and 10* the Casslar fibers and NC-300 Blue respond similarly to willow preparation in that the relative strength increases rapidly up to about 24 hairpins* reaohes its maximum at about 30 hairpins* and thereafter decreases. Reference to Figures 4 through 9 indicates that for the C&O and Bell fibers and for BT/AC Blue* the relative strength increases rapidly up to about 12 hairpins* and thereafter continues to in
crease gradually up to 48 hairpins.
In terms of fiber filterabllity and water retention char acteristics* the following chsngas oocur in the hairpin ranges indicated:
CTD000925
-2-
Chrysotlle Fibers Blue Fibers
Chrysotlle Fibers Blue Fibers
-Average Decrease In Fiber Fllterablllty
__
0 to 12 pins 12 fco 24 plna 24 to 36~plna 36 uo~48 plna
15 2 5
12
Average Increase In Per Cent Water Held after Filtration 0 to 12 pins 12 to 24 pins 24 to^36 pins 3b to 4B plna
12 4 11
32
Chrysotlle Fibers Blue Fibers
Average Inorease In Per Cent Water Held after Pressing '0 to 5.2 pins 12 to 24 pins 24 to 36 pins 36 to"48 pins
2u00
6 13 5
Note* rero hairpins - fiber as received
Tterough the entire range of preparation, there is a continual reduction in the length of all fibers, as indicated by the Clark Fraction 1 weight per cent and the dust content, although only in the case of the Blue fibers, and possibly the C&Q 4 and Bell 4K, is the change in dust content truly significant (see Figures 11 through 20). Through the entire range of preparation, there is -- also a continual Inorease in the openness of all fibers, as indi cated by the surface area and the buoyancy (see Figures 21 through
30).
A oost analysis of the relative strength results for pipe fibers, based on the i960 allocations (see Appendices III through
V), indicates that under the conditions of the present study, op timum operation of the Denovan willow is obtained on the average
with about 35 hairpins (see Figure 31)> A cost analysis based on the preliminary 1961 requirements also indicates that optimum oper ation is obtained with about 35 hairplnB. In actual production,
the use of 32 hairpins, with eight in each stage, would be the most practioal, and would give essentially the same results as those ob
tained with 35* Disregarding the effect of sluggers and hairpin arrangement, a saving in raw material cost of approximately $200,000 per year would result from the use of 32 hairpins instead of the
present average of about 18. Further, an additional deorease in
raw material oost of approximately $100,000 per year would result from the revised relative strength values obtained in the present
study.
Although the use of 32 hairpins would, to some degree, deorease filterabillty and increase water retention, changes in these char acteristics are on the average at a minimum in the 18 to 32 pin range,
and should not drastloally affeot machine operation. In this regard, it is recommended that the number of hairpins in the Denovan willows be increased stepwise, by first going to 24 (with six in each stage),
and then 32 (with eight in each stage), so that the plants oan be
come aocustooed to any changes in machine operation which
CTD000926
? 7 ; '* -r. It-
J i i'
-.1 that the willow r.-t;-ges *U Plants i
." 9 --rt3 ii J1 j5 f c~ a K^x.Vrit of mix plr-s,. Find tpnt cnly the
nillov' atago4 at Plant 8 are drilled fox* 12. it Is recomaervlad that
proceed at cnce to obtain stages a idler to th&^e at
Mant 8, to that advantage can be taken, at the earliest possible
date,. of the higher relative strength values obtained with inareaee: *
/leer prop ration. The Engineering Pepartrent has c&'tlruxted that
stage?? ?irj.lur to thofco at- Plant 8 can be pur-h.s.sed for about $530
per rv.13 r end that the cc^t rf installation would ho ah cut ?00 tc
$33S per dll.
A rrri cr.al vsii? cf tV tv'lcdve vtrorgrh. r.er.xlts for Bell 4lf :::' Eul' b3r. ' ncn ii50 Ujogc rf tb.e=r fibers
in /.pas, Linveches, Shc-r?:.*?,oxtr'f ned Jivnc^ent-Oir 6X r.t Flint 1 `*'0 App: r_J.'c.' 117. t*-.- c?:"" V`f in L*h.r.wr> gr /pr.;.cdly in Fig vr 3r-c
A:? inaic~tcd,. r: raving ir rar rert erici e-c.ai- ef ^ppr-orir.-vt eJy $16r per yc-at; wo.-sii ronult irca, the- ve cf 24 fcairplr.'i ins tec 2 cf the
present cix,' sdLlle parish of Approxisately $32.COO per yep- would recult freis tlie use of 48 t-=irpin3. Further,, sn additional decrease in rav iciterial cost cf approzirately $11,-,C0? per yeur would result rror; the revised relative strength valuoi? obtains 3 for Pell 4K end
Bell 6D in the present ittody.
Although the use cf 24 tc 48 hairpins would, to boos degree, o'ecresce filter-ability cni increase water retention,, chafes in
these characteristics should net drastically affeot xaebine oper ation. In this regard, it i recoEsended that the nunVer of hair pins in the Plant 1 willow be increased Ptepwise, by first going to 24, and then increasing the ir.rr.ser to 32 , 40. and finally 48, so that the plant can becc accustomed tc any changeb In ttachine oper
ation which Bight oocur.
It should be emphasized that the present cost analyses ere baaed, in the case of pipe fibers, on the I960 allocations and. In the case of No. 4 Rschine, Plant 1, on the anticipated I960 usage of Bell 4k and Bell 6r> in Apac, Linabeetoe, Sheetflextos, and Monobestos 6x. f.s the availability of certain fibers ohanges, ao alto will the msafetn' of
hairpins for cptiaaxa willow operation. In conclusion, it should b> especially emphasised that each additional hairpin In the l8 to 32 pin range represents an average saving in pipe Ranufeeture of about 14.000 per year, and that each additional hairpin in the six to 48 pli. raiuve represents an average saving in the operation of No. 4 Kachlnc, Plan? 2 of about $800 pex* year.
CTD000927
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CTD000928
In d ica te d .
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number o f
the
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CTD000930
CTD000931
CTD000932
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CTD000934
CTD000935
CTD000936
CTD000937
CTD000938
CTD000939
CTD000940
CTDOOO941
Zfira
CTD000942
CTD000943
CTD000944
CTD000945
CTD000946
CTD000947
qTDOOOQ*8
CTD000949
onn CTD000950
CTD000951
CTD000952
CTD000953
CTD000954
CTD000955
CTD000956
Appendix I Denovan Willow Pin Arrangements Plant 1 (6 pins total)
Three hairpins In the second and fourth stages. Plant 6 (21 pins total)
Three sluggers in the first stage, six hairpins in each of the three lower stages. Plant 8 (18 pins total) Six hairpins in each of the three lower stages. Plant 9 (18 pins total} Three sluggers in the first stage, three hairpins in the second stage, six hairpins in each of the two lower stages. Note: Hairpins constructed of 1 x 5/8 x 26 inch bar bent uni
formly to 3/4 inch radius. Sluggers constructed of 1 x 2 x 13$ inch bar drilled with one inch hole 12 inches from end.
CTD000957
Appendix II
A. C. P. A. Evaluation
In this evaluation, 150 gran test cakes containing 51 per cent cement, 34 per oent pulverised silica, end 15 per cent fiber are prepared by mixing the dry materials with a specified amount of water, under controlled conditions, and filtering the result ing slurry In a Buchner funnel. The time from vacuum application to the point where the water seal between cake and funnel Is broken (as indicated by a deorease In the filtering vacuum) is taken as the filtering time. The filtered weight Is determined, the cake pressed at 500 pounds per square Inch, and the pressed weight re corded. The samples are then cured for a minimum of 16 hours, under controlled humidity conditions, and are finally autoclaved for 20 hours, using saturated steas. After curing, the cakes are dried to constant weight and then tested In flexure. Proa the average breaking load, the reinforcing characteristics of the fiber being evaluated, relative to standard C&O 3 as 100, are determined and expressed as relative strength.
(a) Relative Strength
The relative strength has Its application In effective ness of furnish calculations- These calculations can best be Illustrated by the following examples
The relative strength of a blend containing 100 pounds of Casslar AC (relative strength 110), 500 pounds of C&O 4 (relative strength 80}, and 400 pounds of NC-300 Blue (relative strength 70) 1st
In a furnish containing 16.0 per oent of this blend, the effectiveness of furnish would bet
(79.0) (16.0) - 1264
Recent studies have Indioated that the relative strength values obtained by the A.C.P.A. method are aocur&te to within plus or minus four strength units.
(b) Filtering Time
Since the end of filtration Is taken to the point at whioh a decrease in the filtering vacuum oocurs (caused by loss of the water seal around the oake edge ^ end is not based on the time required to remove a specified amount of water, it is dependent not only on the rate at which water Is removed from the asbestos-cement slurry.
CTD000958
2- -
but also on the water retention properties of the fiber used. Consequently, without the per cent vrst-rr rBh^lnir.7 after filtration, the filtering tic* has no cffinito meaning.
(c) Filtered Weight
The filtered weight. In tense of the per cent water held after filtration, indicates the wa^-er retention properties of the fiber used. This value perlite an estimate of the moisture content of the wet machine film after passage over the vacuum box.
(d) Pressed Weight
The pressed weight, in terc3 of the per cnt water keia after pressing, is an indication of the reciatarae- to water removal under pressure. The value la a guide at to the moisture content of the rolled product in wot machine operation and as to the moisture content of pressed sheets.
Clark Classifier
The Clark classifier consists of a semicircular tub divided into four main ccxpartmrnta, in each of which is a circular screen driven by a geared motor. The rir. cf ench screen consist 7- of t brass strip which forms a seal by rotating between the slit ecoec of a piece of soft rcfefcsr tubing counted cn the inside of the tub. By means of e constant head box, water Is passed thru tne clari fier at a specified rate. In each ccrrpartSMTtt the inccuir*g wateis directed to the befctosi of the tub by neene of a weir and baffle. The consequent action of the water serves to keep the fiber? frcm settling and to present them regularly to the rotating screens. To further minimize the effect of settling, each co^artnert is equipped with a water nozzle which provides additional agitation.
In operation, discs containing 1/h inch and 1/8 Inch circular perforations and screens of 3 and 100 mesh are employed, with dup licate runs being made on five gram samples, After olssDiflection, the individual fractions are collected and the weight per cent^ der.erJsinedj, with the dust [-100 E.e3h material; beirjg'Vbtalned by dif ference. Since the Clark apparatus classifies according re 1e.ns':h,, with the longer fiberB being held in the first cczrpartSLsntp In gen eral, the higher the Fraction 1 weight percent, the ierger the fiber.
Although the Clark olaseifier results are reported to the closest 0.1 per cent, differences of less than two per cent caivnot be considered truly significant.
CTD000959
Fiber mteraMllty
In the fiber filterability test., 30 grans of fiber are stirred with 500 milliliters of tfater and the resulting slurry is poured into e standard sieve (a 4-1/2 inch, 50 leeah sieve is used for three and four-* grade fibers and Blue; an eight inch, 60 saeah sieve iff used for five, six, and seven grade fibers)* Water is then added in rpr-y form until a definite liquid height is reached, and the rrar.':>er cf seccuio is determined for a epeoified volume cf water tc pass thru the asbestos: mat. Using the 60 seeh. rieve as & basis, thr fiber tlj v-er-r.bilivy is calcul ated aa the ratio of the- filtering tirefur- :i Cv7 3 t-c the filtering time for the .Clear bring rvrluuitc '. c::prr r:r.oa : u a peu cr::':^gr- TMa flbnr f f lterabilifcy fig.v.z
of tire piolcup rate on the i;et machine cylinder-: .1fce7.1M.livy figurer- indicating a flower
-A* .. * o. t.
u >v
The apparatus on-ployed for the detervsination of surface erea (ppecific eorface} is a Rigden. air permeability eyot-ea cf the type usee by TcB;At in the evaluation of textile fibers* Basically,
the rnerat-ion depends on the recistance to air flow offered by a
fiber - with this resistance increasing with openness and dv*3t ecntc-nf ana decreasing with length* Jr this rereact , whan interpreting surface area .data, the specific surface of a fiber relative to its oper;r.as3 re-:st be considered in the light cf both the dust content and the length*
Buoyancy
In the buoyancy test, which is run in duplicate, one gran of fiber la mixed Kith 250 milliliters of water in a stoppered graduate by oscillating 40 complete times in one minute. The fiber is then allowed to settle undisturbed for one hour at the end of which tine the voluma of the fiber column is read in milliliters. Although no general correlations have been established, this buoyancy figure, for an individual fiber, is a reasonable indication of the degree of preparation. In general, the higher the buoyancy, the more highly prepared the fiber.
As an aid tc the use of data obtained from the foregoing teste, the following discussion of fiber characteristics, with reference to their effect on product quality and machine operation in the various manufacturing processes, is Inoludeds
Asbestos-Cement Pipe
In the selection of fibers for use in the manufacture of asbestos-cement pipe, the relative strength, average length, and dust contend, and the filtration and water retention characteristics
CTD000960
ci I->3.- :'Icrvr. are of' p; ir/vy 5r -perLianna, It- i.a necessary to x?r.o s..
cf-cotSvr.r- or cf furaiar. which
aset the cpe-cified utrengti
reS'.iire:r"Rt Sjw>.3 :'fr 3r desirable* for wot efrength, to have e long
fiber- end ::itd a lew fast content. Tut-veer* fro?, the point of view
of production rate and pipv formation,, it J s also desirable to use
fast filtering fibers c? low water rctenMop.. in t-hiit regard, ex-
per-ienae bas inilcafr a that the presence cf Slue filer allows for
vr*c: ure of r.igb^r rc-Ilpp precEturcs in the sroiafasture of asbe-sGea-
(x::;vt pip-- v?5 theufr air. coatarn: or deferring fchs pip.;. curing tr.ild-
..
A.: - La ,r\ ?/-:a fi< :.? t c-.~ !>.<: a!- * c-;f: ent ecrtrt/.bjro
.It
a~ i-r? -engv-o ;-.r buih t.i vc i cz:' rascU iv^vea', iv .haalA r.
nc.vc-d. thr.v r/a-h fiber. : hate- high. w-awer jvt-ont'.oriS exa' Coni to c5.c-
ervaj.s. p;:p- C-cn.r.1 c;-1.. LiUr.r.'.if ,
iifugc hi ffily epevse-:- fit-erc aistr
r.criu'Ait'nf' vovarc'r prvJuo* atrc:rthr such fiVrrw filter clowly,
crave. big-?, vav-.c.r retort ion.?... r:i p.1po frond to decrease pipr densltia
Shin^.len and Flat- Sheets
In frhr- selection. of fibers lor use in the- iraftufaofcure cf
shingles ana flat obects, the relative stnrngfri.ir atersge length, 3su-. dust car teat, ani the filtration .ur:$ water retention character
istics of tho fiber*; are. of primary Importsneer It. is necessary t-c
use an eff oofcitP.nsaB cf fiirrcirh tSiiob will set? the specified strength r-erv.ireronos., and it in dsair-a'rle r,o have, a loag fiber end and a lor dust content; r so as to sinislse cracking in the wet and finished
abatese Further, fror the point of view of production rate, it ie alee desirable to use fast filtering fibers of lew water retention. In the case of veneer fumiEhees however . the use of short* highly opened fibare is preferable* since such fibers give a box1 uniforra appearance to pressed surfaces.
Corrugated
In the selection cf fibers for use in the nanufacture of cor
rugated, the relative strength, average length, dust content, and water retention characteristics of the fibers are of primary ibportance. It is necessary to use on effectiveness of furnish which will meet the specified strength requirements, and it is desirable to have a long fiber end, a low dust content, and a relatively high water retention in the unforced sheet so that cracking does not occur during the foraaing operation.
Monobestos
In the selection of fibers for use in the manufacture of Honobestos, the average length and dust content, and the filtra-
CTD000961
-5-
tion and water retention characteristics of the fibers are of pri mary importance. Fast filtering fibers of low water retention not only increase production rates, but also minimize warpage by giving more uniform sheet densities. Further, although increased length and decreased dust content contribute towards high water retention, they do tend to increase filtration rates and to minimize oracklng by providing more strength in the wet and semicured etates.
Asbestos Paper
In the selection of fibers for use in the manufacture of asbestos paper, the average length, dust content, and openness of the fibers are of primary importance. In general, the longer the fibers and the lower the dust content, the greater the tensile, tear, and bursting strengths and the more flexible the paper. Fur ther, although an increase in openness appears to have a negligible effect on tear strength and flexibility, it does Increase the tensile and bursting strengths. It should be noted, however, that increased openness as well as Increased dust content and decreased length, con tribute towards poor filtration rates, low porosity, and poor ab sorption characteristics.
Millboard
In the selection of fibers for use in the manufacture of KI11board, the fiber reinforcement and openness, and the filtration and water retention characteristics are of primary importance. It- is necessary to use a furnish uhloh will meet the specified strength requirements, and it is desirable, from the point of view of pro duction rate and sheet formation, to use fast filtering fibers of low water retention. Although increased openness contributes to wards better fiber reinforcement, it also decreases filtration rates, increases water retention, and tends to decrease sheet density.
Sheet Packing
In the selection of fibers for use in the manufacture of sheet packing, the average length, dust content, and openness of the fibers are of primary importance. In general, the longer and more open the fibers, and the lower the dust content, the greater the tensile strength. It should be noted, however, that with this Increase in tensile strength, there is also a tenaenoy to decrease sheet density.
CTD000962
Appendix IXI
Allocation of Fiber for Pipe Manufacture - i960
Ca33iar AC
972 tons
Cassl&r AK
3756 tons
Cascl&r AX
1776 tone
C&O 3
1572 tons
c&a 4
2412 tons
C:C S>
2316 tons
E'i'/AC Blue
750 tens
HC-30O Blue
2850 tons
Qrlqualand Blue
600 tone
Note1 Blue fiber tonnage based on i960 contracts.
Anticipated Usage of Fiber &r No. 4 Kaenine,. Plant 1 - i960
Bell 4K
462 tons
Bell 6D
920 tons
Bell 7D
462 tons
Bell 7M
612 tons
Notes Anticipated usage based on Apao, Linabeotos, Sheetflextos, and Konobestcs 6X.
CTD000963
Appendix IV
Following are the relative strengths obtained for the fibers evaluated in the present study, together with the relative strengths currently being used for these fibers;
Fiber
Current
Relative Strength (Figures 1 through 10)
Relative
Strength 6 pins 12 pins 18 pins 24 pins 30 pins 36 ping 42 plns48g
Casslar AC
122
Casslar AK
100
Casslar AX
86
C&O 3
105
c&o 4
75
C&O 3
56
Bell 4K
76
Bell 6D
42
BT/AC
101
NC-~0 A/c - 3oo 62
-- ----- ---- ---- -- --- --
77 83 47 48 ---- -- --
110 117 121 121 120 lit 101 108 113 113 109 10*
87 87 86 85 84 ** 106 107 1C8 109 111 11*
80 8l 81 82 82 8; 57 58 59 60 61 6: 85 87 89 91 94 9 48 49 50 51 52 5 103 105 107 109 111 11 70 72 72 72 72 7
Note; (1) Current relative strength for Bell 6D based on as received fiber! current relative strength for C&S 3 and ST/AC Blue b&Bed on preparation with three sluggers and 18 hairpins} current relative strength for all other fibers based on preparation with 18 hairpins.
(2) Increase in relative strength of Bell 69 willowed with six hairpins results from current relative strength being based
on as received fiber.
Increase in relative strength of Bell 4k willowed with id hairpins results from improved fiber quality. Bell 4k Is now less erudy and has a higher percentage of long end than in the past, thus
increasing its relative strength.
Change in relative strengths of other fibers willowed with 18 hairpins results from differences in fiber quality. In par ticular, Casslar AC is now more erudy and has a lower percentage of long end than in the past, thus decreasing its relative strength; C&O 4 is less erudy and hap a lower dust content, thus increasing it's relative strength! KC-^OQ Blue is lass erudy, thus Increasing
its relative strength.
CTD000964
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CTD000965
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CTD000966