MECHANICAL DAMAGE TO CORN IN A PNEUMATIC CONVEYING SYST].

Transcription

1 MECANICAL DAMAGE T RN IN A PNEUMATIC NVEYING SYST]. by CANG J 00 CUNG B.S. Seul Natinal University, 195*7 M.S. Seul Natinal University, 1959 A MASTER'S TESIS submitted in partial fulfillment f the requirements fr the degree MASTER F SCIENCE Department f Agriultural Engineering KANSAS STATE UNIVERSITY Manhattan, Kansas 1969 Apprved byi Majr Prfess

2 IS ii TABLE F NTENTS intrdutin 1 bjetives... 2 PAGE literature review k experimental methd 9 equipment' 9 materials 15 experimental design 20 PRCEDURE " 23 SYSTEM ANALYSIS 25 ANALYSIS F GRAIN DAMAGE 3 STATISTICAL ANALYSIS 36 RESULTS F STATISTICAL ANALYSIS k DISCUSSIN F RESULTS ' kj NCLUSIN. 52 REMMENDATIN 55 ACKNWLEDGEMENT 56 BIBLIGRAPY 5? APPENDICES 60

3 113 LIST F TABLES Table PAGE I. Classifiatin and distributin f test rn arding t size and/r shape * a. Sme physial and mehanial prperties f test rn arding t size and/r shape b. Mehanial damages t eah lassified rn befre handling.in pneumati nveyr Levels f experimental variables The stati pressures fr varius rtameter readings with feeder sealed and unsealed The average air velities in the nveyr pipe rreted fr temperature and pressure The average rn speed and feeding rate in the pneumati nveyr... 35?. Mehanial damage f large medium flat yellw rn at 12 perent misture ntent... 6l 8. Mehanial damage f large medium flat yellw rn at 20 perent misture ntent Mehanial damage f rund yellw rn at 12 perent misture ntent Mehanial damage f rund yellw rn at 20 perent misture ntent... 6f II. Mehanial damage f small small flat yellw rn at 12 perent misture ntent Mehanial damage f small small flat yellw rn at 20 perent misture ntent Analysis f variane, 12^ misture, (small rak.), Analysis f variane, 20/2 misture, (small rak) Analysis f variane based n the brken data with 12;' misture ntent Analysis f variane based n the brken data fr 20'^ misture rn.,

4 iv PAGE 17. Analysis f variane fr dkage data (12$ misture ntent) Analysis f variane fr dkage data {2.0% misture) Analysis f variane fr devaluatin number (12 perent misture ntent) Analysis f variane fr devaluatin number (20 perent misture ntent) 81

5 LIST F PLATES Plate PAGE 1«Phtgraph f pneumati nveying system used in the experiment, Shemati diagram f pneumati nveying system.. 1*+ 3. Plt f rtameter reading versus stati pressure measured t estimate air lss thrugh air-lk feeder 28 b. Average air velity in the nveying pipe f nveying system 33 Figure LIST F FIGURES 1. Plt f devaluatin number f ttal damage versus dkage Relatin between the brken and dkage fr every mbinatin f treatment 8^ 3. Damage rate with respet t nveying length versus nveying length fr 'fur air velities, 85 k* Plt f relatinship between damage rate with respet t air velity and air velity,, Small raks t rund shape at different air velities «. 87 n 6. Small raks small small (flat) size rn at different air velities Small raks t large medium (flat) size rn at different air velities The brken damage t rund-shaped rn at different air velities 90 9a The brken damage t large medium (flat) size rn at different air velities The brken damage t small small flat size rn at different air velities Dkage f rund shape rn versus nveying length fr different" air velities 93

6 12. Dkage f small small (flat) size rn versus nveying length fr different air velities, Dkage f large medium (flat) size rn versus nveying length fr different air velities., ^. Devaluatin number f ttal damage t large medium (flat) rn versus nveying length fr different air velities Devaluatin number f ttal damage fr small small (flat) size rn versus nveying length fr different air velities Devaluatin number f ttal damage t rund shape rn versus nveying length fr different air velities. vi PAGE * Devaluatin number f ttal damage t small small (flat) rn versus nveying air velity fr different nveying lengths Devaluatin number f ttal damage fr rund shape rn versus air velity fr different nveying lengths Devaluatin number f ttal damage t large medium (flat) size rn versus nveying air velity fr different nveying lengths

7 . INTRDUCTIN arvesting by field shelling, artifiial drying, and mehanial handling f rn n the way frm prduer t nsumer, haraterize the mdern methds in a rn harvesting-handling system. All these presses have been harged with ausing damage t grain. arvesting mahinery may be respnsible fr mst f the mehanial damage, and nsiderable effrt has been devted t imprve the design f mbine mpnents and mbine peratin in rder t minimize damage t rn during harvest,, wever, sme rn is damaged during elevating, thrwing, and pneumati nveying (30) During reent years, freign buyers have been inreasingly ritial and nerned regarding the pr quality f U. S. grains and seeds. Muh ritiism f the pr quality is attributed t the substantial amunt f brken kernels reprted t be present when reeived by freign buyers. The estimated average f rn sreenings leaned ut befre the grains get t the nsumer is ver three perent. These sreenings are wrth less than whle rn. The pneumati nveyr has several advantages ver the mehanial nveyr fr transprting grains; nsequently, it is used in marketing hannels. Cmpliated prblems are invlved in grain handling, sine grain prperties suh as dryness, brittleness, texture, struture, and resiliene must be taken int nsideratin t keep the breakage t a minimum during

8 handling peratins. Mst f the investigatins in the grain nveying field were t btain fundamental knwledge f the flw mehanism neessary fr prper design, seletin, and speifiatin in rder t imprve perfrmane. Limited, infrmatin n grain damage during pneumati nveying has been reprted fr explaining the relatin between the extent f damage espeially in nnetin with seed viability and variables pertinent t the pneumati system. Realizatin was bserved in the imprtane f intrduing a new nept f grain damage that inludes damage in terms f nt nly seed viability but als any lss f ver all grain quality nt limited t a speifi use. This investigatin has attempted t determine the mehanial damage aused by pneumati nveying. It has lassified the damage int several ategries and has studied the effets f grain prperties and peratin nditins f the system n the extent f eah damage mpnent. BJECTIVES The bjetives f this investigatin were t study the nature and. extent f mehanial damage t rn made by pneumati nveying. Mre speifially, (1) T btain mparative data f mehanial damage aused by several perating nditins f the pneumati nveyr. (2) T investigate the effet f rn kernel size and/r

9 shape and misture ntent n the extent f mehanial damage fr varius perating nditins. (3) T study the damage dne by repeated runs with the same grain and perating nditins.

10 LITERATURE REVIEW Transprting grains by pneumati nveyrs is nt a new field f develpment. Wrk by. Gasterstadt (12) prbably started the referenes nerning pneumati nveyrs in mdern engineering literature. e related pressure drps assiated with flws f air and air-slid mixture thrugh wheat and granular slids. is investigatin shwed linear relatinship between the pressure drp and air-slid rati. Beause f the imprtane frm the standpint f designing a system the pressure drp in the nveying pipe was studied by numerus investigatrs suh as Segler (25) f ariu and Mlstad (13) t Crane and Carletn (8), Mihell (21), Vgt and White (26), and Crnish and Charity (6). They used different apprahes, either theretially r empirially, t rrelate stati pressure in the nveying pipe as a funtin f imprtant fatrs suh as material nveyed, pipe length and diameter, grain lad, grain and air velity and system arrangement. N ne presented a sund, rrelatin whih enmpassed all the fatrs fr prediting pressure drps. In nveying agrnmi seeds, the grain velity is imprtant nt nly in getting flatatin t mve but als in aviding severe impat urring at high velity. Many reent papers have fused attentin n the study f partile velity. Dallavalle (9) summarized and disussed the results f terminal partile velity determined by varius investigatrs. e presented equatins fr vertial and hrizntal terminal velity based n his experiments. Fr mixtures f partiles

11 f irregular shapes and varying densities, Fley (11) prpsed t use the terminal velity f partiles as a measure f partile harateristis rather than using alulated fititius partile sizes based n Stkes lav/. Eilanski (3) investigated the terminal velities f varius seed grains, the range f whih was 17.9 feet per send fr alfalfa t ^4.3 feet per send fr sybeans. endersn (15) suggested that in vertial transprt f material the air rate wuld be that required t supprt material, r flatatin velity, f the granular material, plus the nveying rate f abut 50 feet per send. Aid en (1) remmended nveying air velity ranges fr varius agrnmi seeds, but gave n nsideratin t mehanial damage assiated with air velity. Segler (25) shwed that the rati f grain velity and nveying air velity was nstant fr wheat and in hrizntal nveying it was higher than that in vertial nveying. is data indiated that grain velity was abut 36 perent f air velity fr hrizntal nveying and 27 perent fr vertial nveying. Cramp and Priestly (7) used the same methd but btained smewhat higher values fr grain speed-up t nearly 50 perent f air velity. Casters tad t (12) was the first t pint ut the urene f damage t grain when it is nveyed with t high air velity. wever, he made n speial investigatins n this aspet. Segler (25) arried ut extensive wrk t investigate the varius fatrs invlved in grain nveyane that might have an influene n the degree and extent f the damage. A mst ritial fatr in determining whether r nt damage will

12 ur was the nveying air velity. is wrk with peas shwed that the inidene f damage rse prprtinately with the ube f air velity in its range between k$ and 95 feet per send. Misture ntent f grain was shwn t be an equally ritial fatr. Fr peas, the breakage was 0.1 perent with 17.1 perent misture ntent, but was 11.1 perent with 1'j.k perent misture ntent. Experiments with wheat at three different misture ntents shwed that whereas there was little evidene f damage t wheat at 15 2 perent misture ntent even at an air velity f 130 feet per send, damp wheat (22.6% m..) and dry (10.3/ m..) were badly damaged at this speed. Segler (25) als pinted ut the influene f material input n grain damage. The damage inreases as the input dereases. It was assumed, that the denser stream f material at the greater inputs ats in sme way as a ushin against the pipe wall, r perhaps that the individual grains llide with the wall less frequently r less steeply at the greater inputs. Segler als assumed that the pipe diameter wuld affet the grain damage and tested his thery n peas, with nveying pipes having l.s and 10.8 inhes diameter, but idential in lengbh and arrangement. is results shwed, that grains were damaged mre in the smaller pipe than in the larger ne, but the extent f the damage was very small either way and nt signifiant fr pratial purpses. There were several investigatins made t determine the effet f the pneumati nveyr n seed viability. Ktzer (20) investigated the extent f viability lss due t varius

13 7 perating nditins f pneumati nveyrs. e tested srghum seed, barley, rn and ats fr three different nveying systems, the apprximate nveying apaity f ^-850 t S500 punds per hur, velity range between and ^?00 feet per minute, and the misture range between 11 t 12 perent. is experiments shwed that the nveyr had n signifiant effet n viability f barley, rn and ats (when germinated at ptimum nditins) immediately after nveying r after a 9-mnth strage perid. Crn nveyed five times in the hrizntalelbw system and planted in ld sil had lwer seedling emergene than nnnveyed rn samples r than rn nveyed ne time r three times. Mehanial injuries aused by the nveyr beame evident in srghum and rn nly after a strage perid r when seed was subjeted t adverse grwing nditins. Pearsn and Srensn (23) studied minimum air velity fr nveying and air velity in whih damage t germinatin f srghum grain urs. They als investigated the influene f misture ntent n establishing safe range f air velity. Different methds f grain damage evaluatin have been made fr different demands. When grain is used fi stk feed, damage t germinatin r hipped grains is innsequential, 'with seed m it is f urse imprtant that germinatin nt be impaired, and breakage be avided. T determine seed viability in nnetin with pneumati nveying, the standard germinatin and ld sil emergene tests were used (20), Segler (25) used Luff's ammnia predure t investigate husk damage f barley fr malting purpse. Varius ther methds suh as fat aidity,

14 8 glutami aid dearbxylase, and triphenyl fetrzllum hlride are available t detet physilgial hange (5)«The present ffiial methd fr determining damage invlves individual analyses by visual bservatin fr varius types f damaged kernels. This methd is t tedius and time nsuming and human judgment plays t imprtant a part 5n the final results. The sieving methd (27), that has been standardized as the U.S. ffiial Grain Standard, shws sme brken kernels and freign material but nt all the damaged kernels. As yet, a definite methd appliable t varius damages f different grains has nt been established. Thus, investigatins are being nduted at Kansas State University (5) and elsewhere t find ne r mre prperties whih will serve as a damage index and t develp a methd r devie t determine quantitatively the perentage f sund grain in a sample s that the need fr individual analyses fr different types f damaged kernels an be eliminated. Sine nly limited data n grain damage assiated with handling equipment and varius types f nveyrs are available, investigatins n this aspet are urgently needed fr develping methds and devies t minimize grain damages.

15 9 EXPERIMENTAL METD A. Equipment The pneumati nveying system used, fr the experimental wrk nsisted f air blwer, air-lk feeder, nveying pipe, ylne separatr, pwer unit, and varius metering and pressure guages. This may be lassified as the lw-vlume, medium pressure system. Phtgraphs f the pneumati nveying system and the shemati diagram f the mpnent arrangement are shwn in Figures 1 and 2. A psitive displaement air blwer was used fr supp3.ying air int the system. The blwer was speified t have a apaity f delivering air at the maximum pressure f 10 p.s.i.g, ntinuusly, r 12 p.s.i.g. intermittently at the maximum temperature f 350 F. The air intake filter was nneted t the blwer t prevent pssible airbrne impurities frm entering the system and t subdue the nise generated by the blwer. The amunt f air intake uld be regulated by hanging blwer speed. The pressure relief valve was installed diretly after the blwer t prevent verlading. The inlet air temperature and pressure were measured, befre air passed thrugh the rtameter in rder that vlumetri flw rate f air uld be evaluated fr different air temperatures. The rtameter, was alibrated, at 100 F and 2 p.s.i.g. pressure t measure 180 ubi feet f air flw per minute at the 100 perent reading. The rtary drp-thrugh air lk feeder was used t intrdue

16 10 Plate 1 Phtgraph f Pnuymatl Cnveying System used in the Experiment.

17

18 12 grain int the system, thus, ensuring n exessive amunts f air lss frm the system, A surge hpper was plaed n tp f the air lk feeder; the amunt f grain fed was metered by the irular ne f if ie fitted in the hpper. A standard manifld fr the drp-thrugh air lk nneted the air delivery and the grain transprt line. * Ttal length f the transprt line between the feeder and ylne separatr was 200 feet. The first and last prtins f straight vertial lines were transparent pipe lines, thrugh whih the passing material uld be seen. These were 'aryli resin tubes, eah being 6 feet 2 inhes lng and having an inside diameter f 1.9 inhes. The remaining transprt line was 1.9 inh I.D. aluminum pipe. The line ntained 15 elbws, f whih 14 were 90 degrees with 24-inh radius f urvature, and. the ther, 4-5 degrees with the same radius. Their length was equivalent t 4-5 feet 6 inhes. The pressure drps in the transprt line uld be measured thrugh pressure taps lated at varius setins f the line. It was fund later that nly tw taps, FT 1 and PT 2, as shwn in Plate II, were neessary t arry ut the purpse f the experiment. The stati pressure f these tw psitins was rerded by the spiral element type pressure rerder.

19 13 Plate II Shemati Diagram f Pneumati Cnveying System Length f nveying linei 200 Diameter f nveying pipei 1.9" ID Straight prtim Vertial ' 6" hrizntal - 132' Number f elbws i 1^(90-2VR), 1(^5 Equivalent lenghti k5 9 6 n - 2^"R)

20 r: «^ -' u r en 3 X' < 14 V. 13 CM \ a 0) 4J ed IJ 5-i T3 i l 0) <U 0) u U ^ a) **s a) a ex - E a 1 t a<-< a 3 U C CX, s a j ^ M u <y l» U a W r~t **- J-l k< f-1 «* 0) 4J S

21 J B. Materials Yellw rn harvested in 196? and 1968 was used in this investigatin t evaluate the mehanial damage aused by the pneumati nveyr. Shelled rn f IS- 6? was taken frm the hilled strage test bin after 150 days f refrigerated air treatment at the grain temperature f 35-^0 F. The misture ntent f the grain when tal en frm the bin was within the range f ^ wet basis. Shelled m f 1968 was als taken frm the hilled strage test bin after k weeks f treatment at the same temperature range. The misture ntent f the rn was arund 20^. Shelled rn generally is mpsed f varius kernel sizes and shapes, and its distributin may differ nsiderably arding t the grwing histry and variety f grain. Beause f prevailing differenes in mehanial and aerdynami prperties f grain, distributin harateristis were nsidered t be signifiant in pneumati nveying. By use f a rn grader, the rn was first srted int eight unifrm shapes and sizes 1 small medium flat, small sm.all flat, large flat, large medium flat, large rund, medium rund, large kernel, and residue. Perent weight fratin belnging t eah lass is shwn in Table 1. Sme f the physial prperties f the lassified grain were measured and are shwn in Table 2. Residue (#8) was mpsed f raked rn and freign material. Large kernels (#7) were an extremely small fratin, less than ne perent, f the whle. Therefre, amng the ther six mpnents, large medium (#5)i small small flat (#2), the mixture f large rund and medium

22 16 p d U d g -p t p < fl P 3,0 P T3 Tl 3 P. eti C s w P f 05 \ T <M ti Cj Q) N 0) d Eh ^-v P 0) «fi a u^ n 03 2 r -3" N TJ & n^j a CM CA 00 t-!k "Us V ft ~ - - «- - P ^_ Mh a nw nn tn- b «^ ^-=i =*s h In «d R * N F P1 ~ ** ** P i 2 n ^ l] C^-3" CM ^r^ =*te 5) R ^ - VA ^ 0) mk Fh S * CN- 5N- N N A ft P P P IA b0- d VA f^ CM ^*fe "D J- ^CN- U~\0Q d <m CM v ^ a? 0\ VT'.CM V 4-t^n ^ -jft ^A P 3" ^3- hp -3- M3 J- CA =fe ^ d U^^A -CA d! h # * t-3 ^ IA 00 CA ± ft CJ CM v P t C 0\0 <^r-\ CA f VA ^AMS N =%!?h 3 3" d 3" s Jh U^VAV N ^? 1-1 A ft ****** P CM P ^-v -3- N =tfe d d d R n CM n e h ^^ en <i-i Fh ^ ^ CM V CM CM CM + ft *n P h e 3- C NV 3 -P CM V CM *A r-l r! d -h d **fe T3 1 Jh 00 N CM V^\U-N. Cm la ft b C P d CJ n CJ * C C -P P, MNn M r-l d Ci-i C 1! C P P 4^ 4^ P b w 0-^ C^ 3) 0) d v Eh Eh vflfn - T! n N Q 1 aj r-l

23 i * 17 p -P <«-. P U P Ph 0) P- ed 55 XI h 05 J3\ Xi 05 d N S r*i 05 -P f S C x: * p< p r-i CU E as 05 <M r 05 e CM 2 x; \ C"\. ^ T3 3 CM C^ -3- N Sfe ^; fn N B MtI-P \D -3- ^ ^. ITN, fn X! Si CM ^ N ^ ';- N S i-3 6 <*- 00 n CS- - CM bqp 00 3 G5 CM n. -3" 1 Sljj 05 1 t^l <m 1 n N r n b r-i =} CM r 3 n ^ CM C.5 J f CM n u Cv. r r 0-4J \D -3- CM CM CM N u^ ^^ B r 03 C-. N n ** **** S _j- -3- r 3 -p 00-3" r - 05 CM n r-. 05 T3 r CM CM CM 1 ^ g C^ 1 & 1 v r r\ a. r * ^-v r * * h fa XJ -C?s, ^» -P P P b b r ^ i l -P»^» 0^ -^ a p C3 a r u e Gj C in U r?-i P M p ^ ^ bi Cm -W P ^ P '-^p - 00 t- ^ 5 ta T-i?-l ai -h 05 n r-i & Q rl 5 a 0$ P s P- B e 1 P P U-N. i 0^ ^ P'feS. 05 ^ -v 'V.^ E- 0) e e m m M f-i CM U n 3 br P<w P^ ^ S» ' C P 05, r-l r C 'm «^ ' V P CM V\ <«-. 'm Cm 0) ^ 3 3 r 05 aj 05 ffl b3 t 05 r r g <: < * a. *

24 i «18 h a E C\i 00 v ^ n ^ ^-' * «n - C ^-x «^ t CJ? r-q «*-^ 'D y fi j d x: - CM N ^~- ^ ^ n ^ M!4 *-* -3- CM P <*-< P tf E E CQ ^ M : 3 T) *-* u^ U-N N CM *-n ^ <M &0 P~\ \? W 05 S r~ ^ 03 x, E 3 3 "C ""^ U^ V 00 ass. ^ v ^ C\2» r-u -d" \ -P *» ^ ** t C\J P3 fac ~ 03 p C X as d S ID 05 h Jh t.=* v, P - P-\ ft C5 3 E h ^ S C^, ^ ^ h P 3 C -P C3 M 03 E ^ P, <u E «M S - X 3 b,q tx1 VT n 3 ^s V VPi U CM S3 «^^ «t CM CM f < 3 1, q I CC 1 Eh K t CS -l E m 3 S & N r-l N a P \ 03 T) 03 - U -D t -C E 3 flf 1 E -P s5 t X ; E ^^» ^~» d -P -P.h d a ) f aj 03 N P h CVl r-l ^ - G< «M _, ^^ «^ ' C/l

25 1 9 rund (#3i #6) the prprtin being 4 t 6 were seletee t be tested in the pneumati nveyr system. Shelled rn kernels belnging t these three lasses were f distint shapes and/r sizes, Furthermre, the majrity f rn samples, abut 80/a, fell int these lasses. In this manner, a unifrm sample in size and/r shape was btained. During harvesting and handling, rn kernels were damaged. Damages t the riginal samples fr three lasses seleted were evaluated and are shwn in Table 2.b.

26 20 C. Experimental Design Fur variables were studied t amplish the bjetives f this investigatin! air velity, number f repeated runs, misture ntent, and size and/r shape f grain. Levels f eah variable studied are summarized in Table 3«Even thugh the air velities were designed as abve, it might nt be easy r nvenient t btain suh desired velities fr all experiments, beause sme hanges f temperature and. air pressure in the system wuld ause the hange in air velity. As a nvenient way, therefre, the apprpriate rtameter readings rrespnding t the desired air velities, whih are shwn in parentheses in Table 3 were used t regulate air flw rate. The estimatin f atual air velities used fr eah treatment was btained by using the equatin f ntinuity with rretins due t pressure and temperature variatins. The air velities s btained are shwn later alng with ther experimental results. The number f repeated runs, 1, k, and 8 times in the design, are equivalent t the ttal nveyed length f 200, 800, and 1600 feet, respetively. The seletin f tw misture levels, ne fr dry and ne fr wet rn, was based n the assumptin that shelled, rn, having the apprximate misture ntents designated, uld be enuntered frequently in pratial pneumati handling. Fr the experimental desin, "fatrial" design was used in whih fur levels f air velity, three levels f the repeated run, three levels f size and/r shape, and tw levels f misture ntent were invlved. Therefre, there were 72(^x3x3x2)

27 ?J Table 3» Levels f Experimental Variable: Levels Variables 4 Air velity (fpm) (rtameter reading) ^ (65%) 6300 (75$)?600 (92$) N. f repeated runs Size and/r shape Misture ntent 1(200') M800') small small large medium flat (#2) flat (#5) dry rn wet rn (abut 12$) (abut 20$) 8(1600') Rund (raisture f #3 & #6) 1/ Apprximate values

28 2: treatment mbinatins fr eah repliatin. Tw repliatins were made fr eah treatment mbinatin.

29 9'- 3 D, Predure Seven punds f sampled rn, prepared as explained in (B), were used initially fr eah test run. The grain's feeding head abve the rifie was maintained fairly nstant t assure a unifrm harge int the system. As grain was intrdued int the system, the pressure and temperature were raised while the rtameter readings were lwered. The degrees f hange depended upn the system's peratinal nditins f air and grain feeding rates. T btain infrmatin neessary in defining the peratinal nditins fr a given run, the air pressure, air temperature, and rtameter readings were rerded befre and after intrduing grain int the system. A sample divider was used t evaluate damage f nearly 300 grams f grain treated in the pneumati system. The remainder f the rn sample was put thrugh a dkage tester whih separated all ther matter remaining n the sieve after sreening. The prtin that passed thrugh the dkage tester sreens was weighed and alng with the ttal weight was used t evaluate perent f dkage. The same predure was fllwed fr every mbinatin f predetermined levels f fur variables investigated i air velity, misture ntent, size and/r shape, and the repeated runs. The mehanial damage was lassified int three ategries brken damage, large raks, and small raks. The standard fr these lassifiatins was established arbitrarily and defined as fllws i brken damage any kernel that was hipped r brken

30 24 large raks raks extending thrugh the whle kernel small raks -any mark f skin damage ther than the large raks T failitate the damage evaluatin, rn was first treated with green dye s that any hip r rak in the kernel uld be seen easily. The dye-test.was an effetive visual aid in distin-" guishing the damaged kernel frm the sund ne. Sund kernels and thse lassified by the dye-test were weighed and the perentage f eah lass f damage was alulated. T estimate the grain velity in the nveying pipe, a series f nveying tests were arried ut. A- stp wath was used t measure the time required fr the frnt mass f mving grain t pass frm the upper setin f the first transparent line t the upper setin f the last transparent line. Befre the end f this test the time required fr the last mass f mving grain t appear in the same setins f the transparent line was measured als. Sine the distane between these tw setins was knwn, the average velity uld be btained by dividing the knwn length f pipe by time required. In this investigatin, the feeding rate was regulated by an rifie; thus, nly the time required fr a given amunt f the sample t enter the air lk needed t be measured in rder t btain the feeding rate.

31 25 SYSTEM ANALYSIS Air velity in the nveying pipe was knwn t be imprtant and uld beme the mst imprtant fatr In nnetin with mehanial damage f grain nveyed. Beause f leakage thrugh the air lk feeder, turbulene f stream line due t bends alng the pipe line, and velity variatin in axial diretin f pipe, it may nt be easy always t estimate aurately the air velity fr a given air input int the system. Based n measurements and sme priniples f fluid mehanis, hwever, the average air velity in the dut an be alulated apprximately. As mentined earlier, the air flw rates in the pneumati nveyr system were measured and regulated by rtameter readings. Sine the rtameter is lated between the blwer and air lk feeder, air lss thrugh the feeder must be estimated first, T estimate the air lss, the stati pressures frm tw different psitins n the pipe line were rerded fr varius rates f air flw with eah air lk feeder sealed and unsealed-. The pressure taps were lated befre and after the feeder as zfi-m in Plate II. The ralatinships between the rtameter readings and the stati pressures with feeder bth sealed and unsealed were shwn in Table k. It was fund that the ratameter reading was diretly prprtinal t the square rt f stati pressure as shwn in Plate III. The regressin analyses were perfrmed t relate these variables t give

32 26 y Table 4. The stati pressures, psig, fr varius rtameter readings with feeder sealed and. unsealed Rtameter i reading 100 i With i 4.42 feeder sealed 1 j "withut f eeder sealed p i. P * 2 J 1 P \ 1 P t i i 85 i 80 i 75 i t t : i t» t 65 i j 2.02 ^ : t t j t I / The average values f tw measurements rerded n th< spiral element type pressure red rder.

33 27 Plate III Plt f rtameter reading versus stati pressures measured t estimate air lss thrugh air-lk feeder.

34 D 3 E q: Stati Pressure,fP,

35 29 Q =_ V /P (1) 1 1 Q = v r P~ T (2) q ^ F (3) 2 2 Q ' = ' 51. i7fir T W 2 2 where Q. and Q are air vlume flw rates (rtameter readings in perent) as the feeder was sealed and unsealed, respetively. P and P_ ' are rrespnding stati pressure measurements at 1 1 tap I. The subsript 2 indiates the ase at tap II. Fr a given flw rate, the pressure differenes at tw psitins, taps I and II, when the feeder was sealed and unsealed, uld be aused by air lss thrugh the feeder. Sine Q is prprtinal t the square rt f P, the flw rate differene at the rtameter fr a given pressure uld be nsidered as the air lss thrugh the air lk feeder. Therefre, tw estimatins uld be made fr air lss thrugh the feeder by mparing tw pairs f equatins, (1) and. (2), and (3) and (4), whih are, V - Q i x A = ± n x 100 (5), V A 2 = Z, Z x 100 (6) where A and A are perent air lsses (vlume basis) thrugh the feeder estimated by stati pressure measurements at tap I and tap II, respetively. The air lss estimated by equatin (5) was redued slightly by inreasing airflw rate. The range f lss was 6.^0» 6.56

36 30 perent fr the rtameter range f #. n the ther hand, the air lss estimated by equatin (6) was within the range f fr the same range f flw rate. The differene between the tw estimatins was 0.22^ at maximum. Therefre, the average value f 6.52 air less was seleted fr the entire range f air rates used in the pneumati nveyr system. Air temperature and pressure in the nveyr pipe during the peratin, depended upn the atmspheri nditins and the airflw rate int the system. Sine the rtameter has been alibrated at the pressure f 2 p.s.i.g. and temperature f 100 F, the flw rate ther than that f the alibrated nditins shuld be rreted fr the nditins that were atually enuntered. Fr the duratin f perating the system, air temperature fr a given airflw rate was fund t be quite different frm the atmspheri temperature. Theref're, rretins were btained fr the wide range f temperature hange that might be expeted during atual peratin f the system. n the ther hand, pressure hanges were pratially negligible fr atual range f temperatures in a given flw rate f air. ene, the pressure rretins were made nly fr different airflw rates y taking the atmspheri pressure, 1^.7 p.s.i.a., as the standard. 1/ The rretin fatrs fr temperature and pressure are presented in Table 5 alng with the average air velities in the nveying pipe. It shuld be nted that the air velities in 1/ Crretin fatr urves fr Flwratr meters, Fisher & Prter C., Warminster, Pennsylvania.

37 v i 1 P C ft) ft ft 0) <D. -P W \ -P <n ^ h p h 3 p. d a5 as 0) f M C3 3? -P CSS U Si ft S X E-i -P un r Cfl Eh A r N. n r N j t- UN n -3- r Cv] N n. r N CM u^ n N UN N - N N CN- _^- x CM N N r- N. 00 J r-i CM CvJ rr N i}- r r-) r-\ i -P L 00 r r N N u^ UN CA u j^n -tf n -r ^3- n r u ' \ UN CM UN N CM (N b 00 n Q r CM CM P N -J r-l r r-l r- N N n N - r CM N n ViN n C^- N - 2 -V * N P 00 CN- _ - n. UN N d l n r-i CM N N ^Jh r-1 r ft un UN CN- CM -^j N CM N N_ CM -3" UN UN N N n CV CM P rn N r- N N - CN 00-3" UN N - J N N r 03 ^ &h. -V -3- tn CM N N ^t J CM 0 N ~ - N UN N UN un N UN CM N N CM - : n N CN- N N CM CM.. ~ n r UN n CA CN n N N- N n UN UN - 3 N p r UN N --J- UN N as N - n N CM U a ~ ft U^ N N N Q UN u ^3- i r a N - N N r r UN \ N un CM 00 C^\ r- B -3" un -3- IN* -3- n FN N N ^J- N n n un CXI CM - a r CM n N - ^s P un C**- n CM -\ ^3- UN N N Cj- u^? N N u h Ph bn ^rll w &0 p M r r CM N h N N - P - N UN C -3- UN N CM a UN as K ^ CM - u~\ ^ N r^. CM 01 P. CM Cm N N -, -3- ^t UN N N CN- -P -P as U P i UN VA UN UN CM N (3 s^% ; -3- un N N - - N N fn p r-\ Tl < *h p r e r x: -P t as r <r* 31

38 . 32 Plate IV Average air velity in the nveying pipe f nveying system used in this experiment

39 33 J ~ LL '.0 V, D <D <D < v _. E h- V < si as J9d jj 'Ajj 8/\ Jiy s5dj9a\y

40 3* Table 5 have been rreted, fr temperature and pressure, but that air lss thrugh the air lk feeder has nt been aunted fr. Figure 4 shws the average air velities rrespnding t rtameter readings at varius temperatures. When grain was intrdued thrugh the feeder, the vlume rate f air was redued t a ertain rate until the steady state was btained. The redutins in flw rate due t grain intrdued were *5 ±0,5$ 5*5+0.5 and 6.5 ± 0,5 perent fr 48, 65, 75 t and 92 perent f the riginal rtameter setting, respetively. Therefre, the atual air velity in the nveying line as grain is fed. int it shuld be based n the redued vlume rate. Sine the pneumati system in this investigatin was mpsed f vertial and hrizntal pipe lines with many elbws, the grain velity is different frm ne pint t anther. Therefre, the average grain speed is mre meaningful than the velity at a speifi pint. The average grain speeds, btained by the methd as explained earlier, fr different rn size and/r shapes are summerized in Table 6. Exept fr the nveying air velity f 66 feet per send, it may be nted that these average grain speeds were higher than Bilanski's published terminal velity f 34.9 feet per send. Fr this air velity, it was bserved, that a small prtin f nveying rn settled dwn in the nveying pipe. The measured feeding rates in punds per minute used thrughut all the experiments are als shwn In Table 6.

41 35 Table 6. The average m speed in fps. and feeding rate in the pneumati nveyr*/ Air velity at Feeding Crn size (ft..per send) rate and/r shape 6*~~ B (Lbs./min.) Rund shape ' Small small flat size Large medium flat size ^ * Average f three measurements

42 36 ANALYSIS P GRAIN DAMAGE The results f mehanial damage evaluated, by the dye testarid, dkage tester are shwn in Tables 7 thrugh 12 in Appendix I, In these tables the ttal damage in perent is the perent sum f the brken, large, and. small raks. Sine sme damaged grains wuld usually be present befre the grain vjas ever nveyed, the devaluatin number an be used as an index fr expressing the extent f mehanial damage aused by pneumati nveying. The devaluatin number E in perent is defined as fllws D, E = [l - ±] x 100 (7) where D is the perent fratin f sund grains befre nveying in the system, D is the perent fratin f sund grains after passing i times in the pneumati system, i being the number f the repeated run. The devaluatin numbers based n ttal damage were alulated and shwn alng with the ther damage data in Table 7 thrugh 12 in Appendix I. A. Statistial Analysis Statistial analysis f the fatrial experiments in this investigatin was perfrmed with data frm eah lassifiatin f grain damage. As mentined earlier, fatrs studied were nveying air velity (V), ttal pipe length fr grains nveyed

43 3? (L), and grain size and/r shape (S). The mathematial mdel used fr the analysis was X ijkl =7* + S i + V j + L K + < SV ij < SL lk f)j (SVL) ijk + E 1Jkl (8) where X = a sample rn damage with ith size and/r shape,. 1 j k 1 j air velity, and k nveying length; M = the grand average f all X neivable fr the ' ijkl speifi rn size and/r shape, air velity, and nveying length; S =. the true average effet f i treatment f size and/r shape relative t W, with the speifi air velity and nveying length. ene, L (3 ) = i=l i and the expeted value f S, E(S.), is equal t' V V. = the true average effet f i treatment f air velity, with the speifi size and/r shape and nveying length. ene, I (V.) = and 3=1 J E(V.) = V. J J L. = the true average effet f k treatment f the nveying length relative t M, with the speifi size and/r shane and air velity. ene, k S (I, K ) = and E(I^) =- k=l 1^ (SV) = ij the true average effet f mbining i level f size and/r shape and j level f air velity treatment relative t u, with the speifi nveying 1 engths. ene, j

44 1 J 1 J E [(SV).,] = E [(SVh,] = E E C(SV), lj,1=0 1J 1=13=1 1J 1=1 J=l (SL)., = the true average effet f mbining i level f sizes and/r shapes and k level f nveying length: relative tm, with the speifi air velities. ene, i ' k Ik E [(SL) ] = E [(SL) ] = E E [(SL) ] i=l lk k=l lk i=lk=l lk = (VL) ^. the true average effet f mbining j levels f air velities and k level f nveying lengths relative tm, with these speifi sizes and/r shapes. ene, J r k J k E [(VL) ] = E [(VL) ]= E [(VL) ] = C 1K j=l k=l Jk j=lk=l J k (SVL),., = the true average effet f mbining all three ijk fatrs fr their speifi ijk mbinatin, ene, ZEE [(SVL),,,] = 1JK ijk E..,., = the randm errr f damage evaluatin assiated ljkl with the 1 damage data within the i size and/r shape, j air velity and k nveying length. It is assumed that the E.., -, are nrmally independently distributed variates, r NID(0, p x ) % Tables 13 thrugh 20 in Appendix II shew the analysis f variane fr dkages, small raks, brken damage, and the devaluatin

45 i 39 numbers, The "F" distributin furnishes the deisin whether a hypthesis wuld be aepted r rejeted. The fllwing hyptheses were tested against althernative hyptheses, fr eah mpnent effet f the fatrs invlved within a lassifiatin f grain damage (a). ypthesis. C/f.-, = /L.] against the alternative hypthesis & [/i rl ^ /1 r2 ] where w ^ and Al? are means f bservatins in repliatin 1 and repliatin 2, respetively. (b) (all the treatment effets are the same) against,_ (sme treatments are nt the same) a () (all S =0) against the alternate hypthesis i (sme S, 4 0) a i (d) (all V, = 0) against (sme V. 4 ) a j 7 (e) (all L, = 0) against K (sme L, -d ) a k ' (f) all (SV) 4. = ij sme (SVh 4 a ij r J against (g) all (SL),_ = against ik sme (SL), ± a ik r (h) all (VL).. = against JK sme (VL) 4, ^ a ik (i) all (SVL) 4., = C against ijk sme (SVL). 4 a ljk '

46 /I0 B. Results f Analysis (1). The brken damage f rn at lwer misture level (12;?)«(a) ^/'rl "/W is aepted ver a L/ rl t/ r? 1 beause F(l, 35) = is muh less than F (n, 3^).05 = 4.12 (b) (all treatment effets are the same) is rejeted in favr f (sme treatment effets are nt the same), fr a FC35.35) = » F 05 (35,35) = () (all S = 0) is rejeted in favr f (sme S, f 0), fr F(2,35) = 16.13, F nn {2,35) = a i.01 k (d,e) In a similar way, (all V. =, 0) and (all L = 0) are rejeted in favr f (sme V i 0) and a j (sme L. -t ) by mparing their bserved F values a k with the rrespnding values f "F" distributin at a =: (ffgfh) With respet t the first rder interatins, [ all (SV). =0] and [all (SL) = 0] are ij Ik rejeted ver sme (SV). ± and sme (SL) ±. n the a ij a ik ' ther hand, all (VL).. r is rejeted in favr f jk sme (VL) =t. a jk T (i) Fr the send rder interatin, [all (SVL). M = ] " ijk is aepted ver E [sme (SVL)..,? 0], -1 a J^

47 d 1*1 It may be nluded frm the results f (a) abve that there were n differenes between the tw repliatin means fr brken damage, in ther wrds, that very reliable data fr brker; damage were btained. Frm the results f testing hypthesis frm (b) t (i), the nlusin may be drawn that n the brken damage there were very signifiant effets f air velity, nveying pipe length, and the mbined air velity and nveying length. Size and/r shape was als a signifiant fatr statistially, but may nt be as imprtant as ther signifiant fatrs The results f hypthesis tests frm (a) t (i) w'ere summarized in the F" lumn in Table 15 in Appendix IT. T avj an unneessary dupliatin, nly the nlusin fr analysis results f eah kind f grain damage mpnent will be presented. (2). Ttie brken damage at higher misture (abut 20/i). Fr higher misture rn as shwn in Table 16 in Appendix II, the same fatrs as thse fr lwer misture rn have the signifiant effets but the rder is hanged. In this ase the size and/r shape effet was the mst imprtant fatr fllwed by nveying length, velity, and the mbined effet f nveying length and velity. (3)«The small raks. As seen in Tables 13 and 14 in Appendix, three main fatrs and VXL interatin were signifiant effets n prduing the small raks fr either misture level f rn but with rder. Air velities were the mst prnuned effets fr bth mistures. Size and/r shape effet fr lwer misture level

48 h2 was mre signifiant than the ne fr higher misture level. (*0. Devaluatin number. Fr either misture level there were highly signifiant effets frm air velity and nveying length, and there were signifiant effets f size and/r shape, and velity and. nveying length. The mpnents f varianes fr high misture level were generally smaller than the rrespnding mpnents fr lw misture level. The size and/r shape effet was muh mre prnuned fr lw misture ntent rn than was the VXL interatin; this effet was reversed in high misture level. (5)«Dkage It appeared that dkage data may nt fllw nrmal distributin. In rder t ensure the nrmality, dkage data was transfrmed int Arsin angular values befre perfrming an analysis. The results are shwn in Tables 17 and 18 in Appendix II. Fr either mistue level, 12 r 20 perent, the test f hypthesis shwed n differene between repliatins, Fr high misture rn, the size and/r shape fatr was the mst signifiant, fllwed by nveying length, air velity, and their three first rder interatins. n the ther hand, fr lw misture rn the effets f air velity and nveying length were s signifiant that the size and/r shape fatr and the Interatins related t it were pratially negligible even thugh they shwed statistially signifiant.

49 f3 DISCUSSIN F RESULTS It has been shwn statistially what fatrs and interatins f fatrs had signifiant effets en ausing eah ategry f mehanial damage during pneumati nveying. Mstly, air velity fllwed by nveying length was s signifiant that the ther effets were t small t mpare. wever, there was*an exeptin where size and/r shape fatr was the mst imprtant amng all the effets nsidered. The diretin and relative imprtane f effets f fatrs investigated fllws. As a part f ttal damage, the large raks, nt analyzed statistially, shwed nt nly small perentage but als little respnse t the hange f fatrs. Rather,, it wuld be inluded in the lassifiatin f small raks, naming the small and large raks all tgether as "raks". The small raks were generally inreased with air velity and nveying length fr either misture level, regardless f size and/r shape f kernel, as seen in Figures 5 thrugh?. in Appendix III. wever, an exeptin urred at the highest air velity, abut 120 feet per send, in whih the small raks fr lw misture rn were rapidly dereased after fur repeated runs r 800 feet nveying. Suh a derease f small raks was diretly related t the inrease f brken kernels. Fr higher air velities, usually abve 100 feet per send, the differene In small raks between high and lw misture rn tended t inrease, while at lw air velities (abut 60 t 86 feet per send) the differene was very small.

50 *j4 The brken damage als was inreased with air velity and nveying length fr either misture level and different grain size and/r shapes, as seen in Figures 8 thrugh 10 in Appendix III. Fr higher misture level, the brken damage aused during pneumati nveying was less than 10 perent even at the highest air velity and lngest nveying distane studied. n the ther hand, at lev; misture level, the respnse f the brken damage was s aute that abut?0 perent f the grain samples at the extreme perating nditin belnged t this damage ategry. Dkage was the nly damage evaluatin that was nt invlved in human judgment fr lassifying damages. Therefre, it shuld be nsidered t be the mst nsistent and reliable data. The effets f air velity and nveying length fr different misture levels are shwn in Figures 11 thrugh 13 in Appendix III. Dkage inreased very rapidly with air velity and nveying length, espeially in lw misture level. Fr lw misture level, dkage fr the rund shape was the mst and dkage fr large medium (flat) size was the least fr eah mparable treatment. wever, fr high misture level, the small small (flat) size had a greater amunt f dkage than the ther tw materials. This may result frm the larger amunt f damage in riginal small small (flat) size samples mpared t the ther tw materials. Devaluatin numbers as an index f ttal damage aused during pneumati nveying were mpared fr different air velities, nveying length, and misture level. The results are shwn in Figures 14 thrugh 19 in Appendix III. Ttal

51 ' damage at lwer misture ntent was muh higher than that at high misture level fr eah rrespnding peratin nditin. At high misture level, the devaluatin number uld be kept belw 30 perent even fr the highest air velity f 120 feet per send and the lngest nveying distane f l feet, while devaluatin numbers f lw misture rn were far beynd this range fr 100 feet per send f air velity and 800 feet f nveyane. By statistial analysis, size and/r shape were shwn t have effets n the extent f devaluatin number. As "the devaluatin numbers were mpared with three different size and/ r shape fatrs fr eah rrespnding peratin nditin, the rder f magnitude f devaluatin number was frm the highest, rund shape, large medium (flat), and small small (flat) size, the latter tw f whih were nearly the same. It is interesting t mpare the extent f devaluatin number with the stati mpressive strength f kernels as shwn in Table 3» Kernels at high misture level shwed higher strength than nes in lw misture fr eah rrespnding size and/r shape. The strengths f small small size and large medium size were nearly the same, but were higher than thse f rund shape kernels fr a given misture ntent f rn. These results indiated that the devaluatin numbers varied the same diretin as the results f stati mpressin tests, even thugh tw ases were subjeted t different kinds f fres ausing grain damage. Beause f pratial imprtane, an attempt was made t <

52 h6 wrk ut the relatin between devaluatin number and dkage. If s, the ttal damage r devaluatin number an be predited frm dkage test. wever, the devaluatin number fr a given dkage "varied s widely that, perhaps, reasnable preditin wuld nt be well btained, as seen in Figure 1 in Appendix III Instead, the brken kernels, as the mst ritially damaged, were pltted against dkage fr all treatment mbinatin fatrs studied. The result is shwn in Figure 2 in Appendix III. The brken versus dkage relatin shwed tw distint trends. Fr less than abut fur perent f dkage, the general trend f the brken inreased at lw rate with dkage, the mst f the brkens within this limit being less than 20 perent. wever, the brken damage inreased rapidly with further inrease f dkage. This may be the ase when the pneumati nveyr was perated with higher air velity and with lng distane f grain nveyane. Deleting thse pints belnging t abut fur perent f dikage, the regressin analysis was perfrmed t give B =_ lg D (9) where B = the estimated brken damage in perent D = the dkage r the brken damage, in perent, that passed thrugh N. 12 sieves in dkage mahine, where 0.05 < D < k% 95 perent nfidene band fr equatin (9) was shwn in Figure 2 in Appendix III. The brken, B', fr the dkage larger than *$, D', was related by the equatin

53 . hi B' - -18, *23 lg D' (10) Fr disussing grain damage, it is desirable t refer t the U.S. Grade requirements f rn in terms f the results f this investigatin. As grade standard in referene t mehanial damage, N, 12 sieve (12/6if inh rund hle) was used t rder t separate the raked in and freign material whih rrespnds t the dkage lassifiatin in this investigatin. Fr instane the maximum limits f raked rn and freign material allwable is tw perent in Grade 1, three perent in Grade 2 and fur perent in Grade 3 (27). The present grain grading standard wuld nt indiate the extent f ttal damage in the whle sample beause, as seen in this investigatin, prtin f the sample, nt passed thrugh N. 12 sieve, ntained a large amunt f damaged kernels, and the rrelatin between dkage and devaluatin number was pr. wever, if nly brken kernels are t be nsidered in evaluating grain damage, a fairly gd indiatin f grain damage an be made by the present grain grading standard whih uld be explained by equatin (9)«T btain infrmatin n damage-ausing mehanisms pertaining t pneumati rn nveying, the graphial differentiatins were perfrmed, n devaluatin number versus nveying length urves in Figure 16 in Appendix III and devaluatin number versus air velity in Figure 19 in Appendix III. The results were shwn in Figures 3 and U in Appendix III. The same urves fr different materials were nt shwn here beause f having almst the same harateristis

54 **8 In referene t Figure 3» fr a given misture ntent the average damage rate with respet t the nveying length was generally very high in the first stage f nveying but dereased rapidly as the length inreased. Suh a high rate f damage in the initial stage may aunt fr the fat that the large amunts f small raks were aused at the very initial stage f nveying and that prbably quite a large prtin f small raks merely enlarged the mark r image f skin damages withut affeting muh their prprtin. This fat uld be explained by the urves in Figures 5i 61 and 7 in Appendix III, *in whih the small raks were very high in the initial stage f nveying. In referene t Figure k in Appendix III, the rrespnding urves fr tw different misture levels revealed a differene In damaging harateristis. Fr high misture rn, the damaging rate with respet t air velity has almst the same dd pattern regardless f nveying length. The value f ~- fr a given air velity was f urse high fr lnger nveying length and ~= value even fr high air velity was maratively dv lw. Therefre, the suessive handling f high misture in with a pneumati nveyr an be made with even the highest air velity studied (120 ft/se) withut ausing exessive damage. n the ther hand, suh trend fr lw misture rn was shewn nly at relatively lw air velity, and there was an extreme dd value fr eah urve where hanges sharply. It may be dv imprtant t nte that air velity shuld be kept belw that whih gives suh an extreme value f ~ t avid severe inrease dv f damage.

55 hq The analysis available in this investigatin shws that arund 90 feet per send uld be used generally as the upper limit f nveying air velity whih was btained n the basis f -~ d v versus air velity urves. Fr this air velity, the damaging rates with respet t air velity were almst the same values regardless f nveying length and/r may be reasnably lw enugh t avid the extreme value f ~-2. It may be nted the dv prpsed limit f air velity, 90 feet per send r 5^00 feet per minute, belngs t the lwer limit f Aid en's remmended range (1) f nveying air velity, feet per minute. is range may be t high t avid the mst ritial rate f ttal damage fr lw misture rn. In nluding this setin, the fllwing illustratins fr the appliatin f the develped rrelatins and results are demnstrated! (1) In a pneumati rn nveying, ne wishes t knw the perent f the brken damage expeted if dkage was three perent after nveying a dkage free rn. Then, frm equatin (9) r Figure 2, the brken damage an be estimated t be 16 perent. (2) In perating a system similar t the ne used in this investigatin ne uld hse an apprpriate peratin nditin within a ertain limit f damage allwable shwn in the results f this investigatin. The fllwing table shws the limit f perating nditins fr nveying a dkage Tree rn s that a ertain grade requirement uld be satisfied after nveying.