Retrofitting a process control computer to the cornigliano hot strip mill with an integrated MIS system

Digital Computer Applications to Process Control, Van © IFAC and orth-Holland P lishing Company (1977)

auta Lemke, ed.

RETROFITTI HT b

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TEH Fran

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Belgran , Proce s C ntr 1 Italsider .p. . lien a, Ital

AB TRA\jT

LAB REHEA T

~1anager

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( riginally

CE (R T TYPE) x -z ne, m dified to 5-z ne in

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n aft r the initiati n f the t tal managestem pr ject n the e isting ment inf rmati n 0" hot strip mill, inigaglia \v rks d cided to upgrade the mill with a process c ntrol computer, a new furnac c ntr 1 pulpit with new regulation contr 1 equipment, and a new pulpit tor the scale breaker and reversing mill with new speed and screw positi n regulation equipment. The basic obj ctives f the project were t improve the competiveness of the mill by increasing productivity, improving temperature and width control and reducing labor costs and fuel c nsumption. The installation wa to be achieved with minimum interruptions to mill operations. The work involved and the results obtained are included.

Length Width Firing

erall - 2 meters - 6.1 meters - Preh at: il liter/hr lOter/hr Heating: il gas m /hr lOter/hr aking: oil gas 2,5 m /hr (\lE T -I.. E~'TI) 2-high LE BREAKER: mm Horizontal 2 - 5 mm x 20 19.2 rpm 500 Hp mm 104 -114 mm x 17. rpm 1020 Hp ( lE T ) 4-high REVERSI. G MILL: H ri:: ntal 22-1422 x mm

Vertical Th h t strip mill was riginall built in 1 and r vamped in 1970. The hot trip mill is in-line with the slab mill and some slabs are dir ct r lIed without reheating. There are three 5 = ne pusher ty~e slab reheat furnace. The rolling train consists f a scale breaker, a reversing mill, a plate shear, a crop hear, a six tand fini hing mill, co ling prays and three d wn-c iler. (ee Table 1 f r ph-sical hara teristics).

17 mm -ne. \ ith horiz ntal

FL I HI. G \1ILL:

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6 6- 95/12 5-1 52 125-

4-high 19 mm

rpm Hp

o LIXG PRAY 10 Banks f high pressure Banks f laminar Length f c ling table 1 ILER: 1 2

6 4

At the time the pr ce s c ntrol pr ject \{as started a management inf rmati nand rder tra king system \vas being implemented. The \11 was completel c mputer dependent \nth n paper back-up system, theref re c mputers, signals data links, etc. are all uplicated \\~th aut matic s\ntch ver in ca e f failure.

m

x mm mm

coil max diameter mandrel diameter

5 Hp T BLE 1. - PHY I

L HARA TERI TI TRIP 1ILL

F Hr

pr ducti n data as the slab is being pr ce sed. ( ee Figure 1).

The 1IS inf rms the perat rs f slabs t be r lIed, tracks the labs r m the slab -ard thr ugh the furnaces r directl from the sla mill, thr u h each f the mills and nt the il c n e r, c lIe ting qualit c ntrol and

The c mpetitive pressures n the h t strip mill from the ne\er mills and newer qualit· require-

721

722

RETROFITTI G A PROCESS CO

ROL CO PUTER TO THE CO

IGLIA 0 HOT

TRIP

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PEAK.

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SPR YS COILE JEI Err

TRACK ING SI~ALS

F'ROt-4 t-4lll

ROLLING

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OPERATING QUALITY DATA FROt-4 t-4ILL

ROLLING PROGRAM TO EACH

PULPIT

SLAB CHARGING

FIGURE 1 -

(Duplication of signals and computers is not shown) . ments of customers ,ere increasing. Therefore it was decided t continue the up-grading program ,hich had been started in 1 7 when new automatic gage control equipment was installed on the finishing mill. The objectives established to maintain the competitive position of the mill were to increase producti ity, to improve width and temperature c ntr I and t reduce lab r and fuel costs. Production experience had indicated that the mill would not be able to satisf the new restricted t lerances which customers were beginning t expect. The s urces f the ,..- idth variati ns included: a.-slab ,idth ariati ns (16~ f the slabs ,ere pr duced utside the . . W rks ; b.-the edgers f b th the cale breaker and the reversing mill did n t ha e adequate p sitin regtilati n; c.-the ingle edger f the re ersing mill limited the width reducti n attainable with ut increasing the number f passe ; d.-inter-stand tensi n in the finishing mill. \vith a manuall perated mill it was n t p ssible t is late and eliminate the maj r s urces f the ,vidth variati n.

Pr ducti it temperature c ntrol and fuel aving were interrelated i.e. during appr imately ~5~ f the perating time, the pr ducti n rate is limited b~ furnace heating capacit , the balance f the time the pr ducti n rate is limited b the rIling mill. H wever, ,,·ith variables including the number of passes in the re ersing mill and adjustments in thickness from the scale breaker and reversing mill and adjustments f finishing mill speeds to c mpens ate for real r imaginary variations in mill conditions, it was difficult to maintain finishing temperature control. (Head-end finishing temperature control is critical because the fini hing mill does not have 'zoom" capabilities so the full temperature range is used to insure the trip tail will be within limits) . T

,

Strategies for pacing and recovering after mill delays, were the responsabilit of the individual perat rs. The scale-breaker operat r called slabs to be dropped ut f the furnace and the furnace operators adjust the firing rates. This manual practice led to variations in production rates, finishing temperatures and fuel c nsumption. There were separate ntrol pulpits f r each furnace and separate pulpits f r the scale-breaker and reversing mills which were manned by different perat rs. The revamping and process control computer project was initiated t achieve: 1. Cniformit of peration 2. Feed-back and feed-f nard data f r adjusting the pr cess. Reducti n f operat r work load to permit c mbining certain perat r functions.

pr ject team was established with pers nnel rom the pr cess control maintenance, metallur~ical, perating and instrumentati n groups. ince this ,as essentially the first cl sed I op pr ess c ntrol c mputer pr ject at . . \ rks man) ther individuals w rked "ith the pr ject team t gain training and experience. The c mputer selecti n ,as limited t a determinati n f the adeq uac a H neY1 ell H- 1 t ace mplish the desired pr cess c ntrol functi ns. H- 16's were being used as part f the

(-8

723

~lIS

being installed and since there \,'ere only limited nWl1ber of experienced persolU1el availCl ble it \,'as decided to use the H-,3 H) for this project also. Pre-I.lating the initiation of the project, models for various segments had been under 1.1evelopment. Cl

A furnace model h,h1 been developed and partially tested. A rolling model for the reversing mill \,'as in use on the card program controlled equipment. A rolling model for the finishing mill for pre-calculated mill set-ups off-line was being developed and tested. It \,'as decided to use the applicable parts of these models, to further develop them and to develop additional models for the other parts of the process as required. (Individual models \,"ill be discussed later. ) Armco Steel Corp. \,'as retained as a consultant at the begiluung of the project to utili::e their experience in a similar project at the Ashland, Kentucky \vorks. CO~lprTER

CO\TIGlJRATIO\ :\\1)

rr~TIO\S

The computer configuration is ShO\\11 in Figure :2. The process control computer is not duplicated as the ~lIS computers because the operators are the back-up system (by manual operation) that does not exist in the case of the ~lIS. The second disc \,'as added soon after the system \,'as installed to increase system reliability. In the early stages of the project the original disc did not have a satisfactory availability his tory. (It \,'as eventually returned to the manufacturer to be rebuilt.) The ASR interfaces, \,"i th modified transmission rates, Kcre selected for the videos and for cornnlluucation \,"ith the other H-316 r s on the basis of cost and ease of use. They could be used on both the process control and ~lIS H-316 r s v;ithout increasing operating system overhead and could l"'e inserted into the ~lIS H-316 's \,'i thout major modi fications to the application so ftKare. The computer used the OLERT (On-line Executive for Real Time) operating system. The OLERT system is heavily oriented to optimi:ing memory (core and bulk) utili:ation and in so doing sacrifices operating speed. The OLERT system requires 12K of core memory Khich in retrospect seems to be a heavy o"\-erhead requirement for a 32K computer.

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The basic interconnections bet\,'een the computers of process control and the ~lIS are ShO\'11 in Fig. .3. Firing and temperature infonnation is calculated, \,'ith a static model, in the r\l:VAC .+90 and transmitted to the P.C. H-316. Rolling pre-set data are calculated in the r\IVAC 1100/'+2- upon request from the r\IYAC .+()O, for all slabs intended for each roll chill1ge. The data is stored in the r\l:YAC .+oC' and then transmitted to the P.C. H-316 as slabs are actually charged into the furnaces. The ~lIS H-316 tracks each slab through the mill and transmits any deviations from normal processing, slab removals, etc., to the P.C. H-316 Also, final thickness and \,'idth data are collected by the ~lIS H-316 and trill1smi tted to the P.C. H-310 for use as trending corrections. :-\ote - Originally a t\l:VAC 11C't1 \"as used, but .., it has no\,' been replaced Kith a r\l:YAC 1100/'+2.

724

RETROFITTI G A PROCE S CO TROL CO!·1PUTER TO THE COR IGLIAl 0 HOT STRIP

L,t4'VAC 1100/42 CAI

UL~TF.S

PRESETS

ROUGHING AND FINISHING MI LlS AND SPRAYS (STATIC

DELS)

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SLAB CH1R3ED

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UN I VAC 490

ROLL 0 I AMETERS CALCULATES FURNACE PRESETS

ITH PASS I VE

I DUPLICATE

(STATIC ~OELS) (~o~ KSR '5)

I

HONEYWELL H-316

~EYWELl

TRACKS

CONTROLS PROCESS

PI fCES

COLLfCTS OOAlITY DATA

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WITH PRESETS

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CORRECTI<»4S

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CONNECTION TO PROCESS

2. R ughin_ .[111 a. H ri= ntal an yert.i al 11 p iti nin cr f 'cale bre ker. b. H ri= ntal and yerti al r 11 p i ti rlinQ: f r v rsin cr mill. c. p d and irecti n f r ver in cr mill r 11 ani tabl . Fini hing ~[ill R 11 p siti n el citie . b. L per t n i n . c. C rrecti n f r a tual ntry temperature. d. Redi tribution f mill 1 adin cr ( p rator request) . e. Trendin c rrecti n f head-end aacre. f Run- ut table pray nfiguration (initial and up-late for actual F6 and c iler temperature) . R calibrati n f crew -le neral a. Emercrency t p f entry tables f ea h mill if mill i n t ready. b. 11 de cale prav. ee Figure -le f r the aut matic on-line c rrecti n functi ns. ~

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Thi d ign f data d t av id excessive duplicati n f functi ns already b ing implemented n the MI H- 16' and t p rmit a H- 1 , ,,,hi h i a smaller c mputer than ~ uld n rmallv be used t c ntr 1 a mplete h t strip mill, by utili=in cr the c mputin cr apacitie f the xi ting C\"TYA'"' 4 and 111 /.+ ' . rh ntr 1 'un the P. . H- 1 include: 1. Furna e

a. Heatin cr and re id nt time lab in each urna e. b. lab call ~hen ea h la i pr perly heated. c. R feren es f r firin cr c ntr 1 re~lat rs. d. Adju tments f pa in and irin cr r line d lay. A ju tment firincr and pa in dependent need-back temperature fr m the mill.

:-ICK. FEE -FOR.ARDS

F r m t the calculat 1 fun ti ns the yalue are di pla-e i e s in the yari u pulpit . Pr visi are included r the perat r t adjust these values r t intruct he c mputer t u e di ferent value . perat r input t the c mputer i via thurnb~heel , rhe stat, elect r witche and pushbutt n by which the c mputer reads the actual m dificati ns he has made.

F r implementati n, the pr ject was divi ed int everal ecrment; furnace , r ucrhing mill in-

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i5hin~ r~li11

anJ C\.'If'lmUllicat i\.'In:-;. The :-;~"~mcnt" natural JiYisions frl..'IJ:] the "ic\," ~'I\.'Iint 1..'1 f ph~"s ical ~"'1..1uirtilcnt, moJ~"'ls anJ 1l10--ii fications tl...'I tlh.. . ph~"sicdl eI..1uipJ11l"nt \,"hich hCl'C schcl..lul~",l t\.'I be c\.'Ir'lplet~>J e1t Jif(el'ellt time~. \,'l>r~" th~"

l~,-el'dll prl..'Ij~"'ct :-;ch~"Julill~

h(l:-; c\.'II:lplil..'dtL",l L~y i ty t 1..'1 maint a in 11 1.. '1 rma 1 ~'Il~l'l ,~uct i\.'In I..~urill~ tIll"' installat i\.'I1l \.'If th~" ne" Cl..luip!1l~"llt anJ th~> start-u~'I \.'If the cl..'Imputer cl...'Illt1'l..'Il. ~Iuch 1..'11' tilt."' \'·I..'I1'k CI..'Iul,l l..'Inl~" h . . ,L.'.Inl" ,lu1'in~ the \\'cekly rnaintcndllcl" turn, :-;\..'II1l~" \,·\.'Irk hed t\..'I l~e delayed until t he annual or t, i-alllluCl 1 :-; tl..'Ippa ~es l'lf the mill \..'11' ilh1iYidual furnaces for ex""ten\..lc..... j maintenance. t

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This se~lllentation subsequcntuall~" pn.'.IYeI..1 t\..'I l.. . l.. yery adYanta~el..'Ius because c'ach se~ment has started up \,"hen the physical ins t allat il'lns \,'ere completed and \,"ere testel..l on-line separately. The communication se~ment \,'as started first, then the furnaces \,"ere started in op~"n-l\.'II..'Ip mode tl..'I permit the continuation 0 f the model deYclopment, then the finishing mill \,'as tested open-loop Clnd close--i-loop, then the furnace 100p \,"as closed alh1 fina ll~' tIll.." 1'l"'yersing mill \,"as brought on-line. The reYcrsing mill \,"as last because of the extensiye re~l1a­ tl..'Ir and pulpit modi ficatiol1s. The se~mentation did creatl" a prl..'Il.. . leFl, in thclt, the material trackin::, fe(',l-l.. . ack lllhl fee,l-(I..'Ir\,'ar,l data collcction \,-ithin each :-;e~ment \,'as an integral part of the se~ment. The tr,h'king and da t Cl c (\ 11 e c t ion fC' l' t IH.'" co mp1 l' t e 1 ine i s n\.'1 h a separate se~ml"'nt so thC1t the yarious se~111ents are not interdepelhient. furnace Control Implementation A nc\,' single furnC1cc pulpit \,'as l.. . uilt \,'ith ne\," recl..'I1'1..1I:."rs, rcgulatC'rs, \..'I~'I~"'rat\.'Irs I ~i~~~k, ~.. tc; \,·Iuch rcplacl:."j the 0ri~il1a1 thrce inJiyiJuCll pulpits. The changc-0Yl"'1' t\.'I the ne\,' ~'Iulrit \,'as jonc OIW furnace at Cl tine as they \,'erl' shut....1.0\,11 for maint~~nance. :\ cIa s sic a 1 he a tin g :~1 0 ...1 e 1 ha.j l.. . e e n J~'" ,-~.. 10 p l' ...1 ani testl'J \,'ith satisfactory results rrior to starting this project (Sec :\rren~lLx 1 f\.."r thl' furnace r10 Jl:."l 5 ). The r10jel \,-as an iteratiYe calculation an...l ilutial l.. . l:."nchnark tests inl..1icatcd that it \,as too large anj t00 slo\,' to be run on the r\IrAC '+l)('l. Therefore, a c0nrlete set of calculate..:i results of the !~10.jel \,"as :~la.je 1'\.'11' all the possil~le coml.. . inations of furnace, fi-

l' i n ~ Cl n j ~ L I l--- Y Cl ri cl t, 1 e ~ t h Cl t c \." u 1 J ph .\" s i (' a 11 ~" \.'Iccur in the furnacc \..'Ipel'at il...'In.

.\ re::ressi\.'In Cl..1uatil...'In \'"as then Jt... . \"elored frol:1 this cal\..'llLlt~.. j ,lata set, \,'hieh prol..1uced the same results \,'ithin -'-2 ~~l~ hitlh'ut iterati011 cud \,·ith the min\..'Ir ,"aricll~ll's The e'luipmellt alL1 pulrit \,'ere illstallej \,"hile the line \,"as runnin:: anj the eh(ll~­ ge-oYers maJI..~ during the heekl~- maintenance turn. (l'lne creh fitu~hej r\."lling in the 01-.1 pulpit anJ ei~ht hour~ later an\.'Ither CTeh startcj rolling in the ne\,' rulpi t I.

The ~---a"s 5chejules are calculated ..~y the r\Ir"h.~ 1 h'll'l .+2 anJ tran5']ittej Yia the r\Ir,\\..~ ~~)\..'I t\.'I the P.\..~. H-,~lc'. (See :\rrenjix 2 f0r rou~hin~ nill r~ojels.) The :~:0jels are l'.3.scj 0n the p0her a ppliej ani the e ige rejuc t i\.."n li:~li tat i0ns o~­ the reYe1'sing :~:ill. The P.\..~. H-..~lt' calculates the ti:~1ing 101' outrutting the scre\,' anj sreej references anj the srray per!~1issiYes \,'ith snaIl on-line rh.~je Is .

726

RETROFITTI G A PROCESS CO TROL CO PUTER TO THE CO

IGLIA 0 HOT STRIP

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puter functi ns " uld be th se m st useful t the operat rand achei ed in the m st acceptable manner. ide di pIa s \ere used in each pulpit f r c mmunicati n with the perat r . Inf rmation fr m the perat r t the c mputer is b thumbwheels, elector witch s r push-butt n depending n the pecific information, these are all inc rp rated in the perat r panel . r

The rIling m del is more the retical and compIe than man m del on sec nd generation hot strip mills because this mill has more elasticit , deflection and pIa . ( ee Appendix 3 for finishing mill models). On-line fed-forward adju tments are made to the mill set-ups f r variati ns in the actual delivery age from the reversing mill, variati n in actual entry temperature to the finishing mill and feedback adjustments for variations of head-end gage of preceding strips. Communications and tatic 10del Implementation in MIS The integrati n of process control into the 11 required some reevaluation of the signifiance real-time to a process control computer vs. real-time to a MIS computer, particularily an intermediate level computer in a MIS hierarchical c nfiguration. The MIS H-316' s \,'ere allcore machines acting as intelligent interfaces and data concentrators of the process. pward data transmission occurred only after a coil was weighed, and the operator had entered the final qualitative data. Some of the data for the P.C. H-316 which originally \as to come from the 11 H-316's had t be gathered directly by the P.C. H-316. The original concept of the integrated system was to use the VAC 1100/42 t calculate the static models. However, the NI C 11 / 2 "ere batch s stems and the resp nse time f r the heating m del was n t adequate. Theref re the heating m del was put in the .~v 4 IS, which meant that the m del had t be written in ssembler because FORTRA was n t supp rted. The rIling m del were put in the C.~\ 11 / 2, because the n rmal resp nse time was sufficient. (Time availa le wa r m the time a sla was char ed int the furnace until it was extracted.) H wever, problems still existed ,henever unsheduled roll changes ~ere made or a stand was dummied. E

perat rs \ ere iny lved in the pr ject from the ery earliest stages, t insure that the com-

The basic phil s ph of the man-c mputer interfa e is f r the c mputer to inf rm the perat r of the c ntrol values f r the various units of the process and t permit the operator to take a particular control functi n awa fr m the computer b selecting manual mode r the modify the computer c ntrol b erriding the computer without switching to 'manual . And finally for many of the control functions he ma change the computer values to compensate for minor errors in the,models or for special equipment conditions. Furnace Pulpit The firing mode of each furnace zone and control m de of each furnace is selected by the operator. Each mode change is sensed b the computer and all the mode statuses are displa ed on a s noptic panel. \arning lights on the s n ptic panel warn the operator ,hene er the computer enses a delay in furnace pushing or intends to reduce firing because of a delay. slab called to be pushed from a furnace is flashed in the furnace pulpit and in the pusher pulpit. The vide identifies the critical slab in each furnace, the critical furnace, the control m de of each furnace, the times that the first slab in each furnace will be called, the current furnace pacin rr c nditi n (i.e. heating limit, r llin limit r delay rec veT}-), the deviati n f the temperature f the la t lab pushed fr m the predicted temperature f r that lab and the feed-back c rrecti ns f reach furnace. (Pr visi ns have been included f r future m nit ring f furnace perati ns and r ari us perati nal I rr t appear n the urna e ide ut the e have n t been im lemented at this time . R ughing Mill Pulpit The furnace vide als appears in the rourrhing mill pulpit t assist the roughing mill perat r in making an decisi ns t alter the furnace pacing. Th se changes are made b- thum

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RETROFITTI G A PROCESS CO TROL C01PUTER TO THE CORNIGLIA 0 HOT STRIP

hheel a ju tment t in r ment pacing in Sr changes.

r de rement

727

the

The r ughin mill rIling ide displa s the slab identificati n and pertinent dimensi n rew p siti ns f the next slab f r each mill, (hori= ntal and vertical), rolling speeds (f r the re er ing mill) and the descale pray pra tices t be us d. F r the re ersing mill all passes are displa ed simultane usly. rmally all functions are in computer mode but the perat r ma elect any functi n in manual m de or if h wishes he ma make adjustments without taking the function out of computer m de. An screw adjustments the operator makes on the re ersing mill are read and recorded b the computer, if after completing a slab the operator wishes the computer to us hi adjusted screw positi ns for subsequent slabs in the same order he presses a Retain butt n which instructs the computer to substitute the values recorded for the original values. imilaril the operat r ma change the scre\ positions in the scale breaker and "Retain tl them, instructing the computer to read and substitute his value . The Retain" function in the reversing mill is m re automatic becaus of the timing and because the operator must complete the entire pass schedule before deciding to retain the adjustments. Finishing Iill Pulpit The ide in the finishing mill pulpit displa s the lab id ntification, and pertinent dimensi ns f the next slab t be r lIed, screw p sitions, mill speeds and 10 per tensions. When the slab head arrives at the crop shear and the temperature eed-f n,ard adjustments are made, the adjusted alues are displa ed. The perat r can make adjustments t individual value by ernier, \"ith ut taking the functi n ut f c mputer m de r he can instruct the c mputer t change the alue by etting indi idual thumbhheels and Retainin . The Retained value \,'ill be used r the remaining slab in the same rder. The perat r als has I ad distributi n sele t r s\itche \hich are used t change t mill loading distributi n. The ide als displa s the pra nfigurati n t be used r the run- ut ta le. The perat r ha the pti n t chan e the pra~ c n igurati n and instruct the c mputer t Retain his change • r

ILL ...

The c ntinual in 1 ement f perating pers nnel durin the specificati n, implementati n, and devel pment insured the acceptance b the perat rs. s s n as the ari us functi ns had been checked ut by the hardware and s ftware pers tIDel the perat rs be in t u e them. Thr ugh ut the entire pr ject t~le perat rs have made very useful suggestions. ERED

The verall pro j ect schedule \,Ta 1 nCTer than ori inally anticipated. everal of the problems encountered have been discussed ab ve, the w rst of these were the dela s of equipment installati n during mill perations. everal other problems ccurred which also effected the total schedule. In the early stage of the project the workers feared that the computer would create jobI ss and a down-grading of job levels. Following an intensive series of discussions at the management level, reorganization of the department, and training of the workers for a better understanding of process contr I computers and their implications, the work proceded with the full support of the workers. The instrument maintenance department hadt o'ere me s me initial difficulties to be a'le t upp rt real time process c ntrol computer s stem. All of the instrumentation and videos are their resp nsibility. In addition, the are called r all computer hardware failures, some of which they fix. The more difficult or extensive hard\are pr blems are repaired by Hone~ell maintenance persolIDel. r

everal f the interrupt signals did n t have the expected reliability. ignals were either missed r spuri us si nals \ere recei'ed. pecial s ftware and hardware had t be devel ped t ~arantee the inte rity f the interru ts. The r ughin mill hardware installati ns haye just recently been c mpleted. The ac ual resp nse times f the p siti n and speed regulat rs c uld n t be determined until after the equipment was perati nal. The resp nse t peed inersi n ignals fr m the c mputer did n t c nrm t the expected resp nse that m di 'icati ns t the s ~stem have been required.

728

RETROFIT I G A PROCESS CO

ROL·CO PUTER TO THE CO

The pr blems enc untered in the interrupt ignals necessitated expanding the ftware t in rea the c n ruen y checkin f the si nals. The incr a d w rk I ad vertcu ed the speed an mem ry i=.e af the H- 1 s that many f the pr gram had t be redesigned and re\vritten t increase s})eed and decrease iz. 1any of the pr gram that had been riginally \vritten in RTRJ. have been re\vritten in ssembler. FORTRA_ had been used riginall becau e of the magnitude f the pr gramming effort f the pr ject and the inexperien e of the pr grammers. Within the original concepts of the project the FORTRA programs presented no pr blem but as work was added, as the project ev lved, the FORTRA become a limitation.

At this time all segments of the project except the roughing mill contr I have been operated for extended periods f time. me minor problems are still occurring in these areas but now they are ab ut read for 24 hour/da unattended operation. The roughing mill segment is being tested as rapidly as possible to bring it completel on-line \nth the ther segments. Certain aspects of the project can onl be evaluated when the all the area are functi nal. RE

IGLIA 0 HOT STRIP

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supp rt the ther phases f the project, t achieve a unif rmit f peration f the finishing mill and t permit a relaxati n f heduling rules regarding gage change between rders. These results ha e been achieved but the full significance f these \rill n t be reali=ed until the pr ject is c mpletely n-line. FUT RE lORK

The future plans r the pr ject include c ntinuing m del devel pments and the inclusi n of the furnace operation monit ring ystem. However, the most important future w rk \rill be the modificati n of scheduling practices of optimize the producti it using the ad antages of the rel~ ati n f finishing mill scheduling rules.

The slab heating m del was derived from the classical heat transfer model, assuming transfer through a solid material in a single directi n (perpendicular t the surface) \rith infinite dimensions in the ther directi ns. The phen men n is represented:

LT

The results, to-date, of the w rk n the furnaces have been achieved in t\\ phase. The first pha e was an impr vement f manual peration, \ hich resulted fr m the erall stu y f the project and the devel pment f the c ntr I I gic. The perat rs have learned and are using the ne\ c ntr I chemes for manual perati n which has resulted in a . ~ reducti n in pecific fuel c n wnpti n.

~­

et -

lith initial c nditi ns: t

T

2

0

And b undary c nditi ns: T ts f the c mputer c ntr I ystem n-line have achieved an additional 11~ reducti n in specific fuel c nsumpti n. In additi n, the variati n f the temperature f the bar arriving at th fini hing mill is 25=:; le s \,-hen the urna e are under mputer ntr I as c mpared t manual perati n. It is expected that further impr vements \all be achieved when the re ersing mill is als under c mputer c ntrol.

Tx=O=

f 1 (t

TX.-=H=

f

t)

The heat that must be furni hed t the lab as it pa ses thr urrh the furnace is determined by:

Cpper lth u h the fini hing c ntrol has been tested extensi ely, n uantitative e aluati n f results i a aila le at thi time. The riginal bjecti e f the finishing mill c ntrol as t

2

C-8

RETROFITTI G A PROCESS CO TROL CO PUTER TO THE CO

In the s aking z ne the 10, r is replaced b~ a c nstant heat 1 ss t the hearth bricks. mp nents The in id nt heat fl, ha three press d a f 11 ws:

0'

=cr{(Tw4_T s JJ )

+(}clf.J T f 4

-ol~ 5 4

)

+ ho(Tf -T 5 ) Fr m this relationship it is p sible t determine the thermal profile f the furnac and the time r quired t obtain a specific lab surface temperatur with a specified internal gradient. This m del, as first erified ,,,ith instrumented slab test in the furnac • Then a data t of calculated results was obtained using the model with input data covering the productivities, slab characteri ti s and heating characteristics ,hich actuall exi t in this plant. From this data set a regression equation was derived ved of the form: Productivit = t(T,H,AT e ) This relationship is used ff-line t determine the slab resident time under maximum firing conditions. To obtain this it is necessary to first determine the required lab dr p- ut temperature, which is calculated from the line temperature loss model:

The calculated slab resident time, drop- ut temperature, e timated temperatures at each p rometer 1 cation and the ph sical characteristics f each slab is transmitted fr m the _~ 4 t the P.C. Has ach lab is char rr d int the furnace. The ff-line values alculated are tati m del alues and must be adju ted t reflect a tual line operating c nditi ns. e eral small rrecti n m dels are used n-line, these were derived by partial differentiati n the ffline m del. The lab surface temperature is measured after the scale breaker, this is c mpared t the e timated temperature at that pint and when the trend exceeds the c ntr 1 bands, the furnace pacing i adju ted b : Av = f(T,H, AT' \Vhen the pacing arm t be a ju ted because rIling time limitati ns, then the firing must be adjusted. This is fir t d ne b a feed-f rward adju tment ,hen the limit c nditi n changes rom furnace limit t line limit b T:

IGLI

0 HOT STRIP

~R =

ILL ...

729

f(H,A-)

When the actual slab temperature i mea ured, a feed-back adjustm nt is made when the trend e ceeds the contr 1 bands b : A1R = f (,6T' ,H, L.) dditional c ntrol logic is included in the furnace s stem t c mpensate for the ariati ns in efficienc f the three furnac . This 1 rric trims the firing f the two h tter furnac that all three furnaces will be heating at the ame rate.

T t x

temperature time distance perpendicular t the slab surface a thermal conductivity H slab thickness heat nux coefficient of heat conduction ~ tefan-Boltzmann constant E coefficient of mutual radiati n between slab and, all Tw wall temperature TS slab surface temperature £1 coefficient of mutual radiation between slab and gas £~ gas emissivit Tf ga temperature 0( gas absorptivit ho c efficient f con ecti n ATe = temperature gradient between the surface and the center f the lab = f(T,H) T po lab dr p ut temperature Ti) rdered inishing temperature at F6 AT 1-6= temperature 1 ss in the fini hing mill = f(T 6 H6 H6 rdered thickness ATR.F·= temperature 1 ss r m reversin rr mill t fini hing mill (T bar thickness and transp rt time are assumed c nstant ~T!8'H temperature 1 s r m cale breaker thr uo-h reversing mill (Ttf --) TR = temperature at Re ersin mill _- = number f pa ses AT" temperature 1 ss r m urnace throu h cale breaker = c nstant r sla vel city thr ugh urnace f(pr ducti it ) AV c rrecti n f slab el cit~ thr ugh urnace

n

=

RSTROFITTI G A PROCE S CO TRO

730

CO PUTER TO THE CO

AT' = t mperatur AR

(alculated) - temperature (m a ure firing adju tment

Jj\ '

\

\~

slab vel city through fUTIlaCe when limited by line r llin time.

-

L.

APPE The rolling sets calculated ff-line for the r ughing mill includ : ertical screw position - scale breaker Horizontal screw position - scale breaker ertical screw positi n - re ersing mill Horizontal crew position - reversing mill Entry speed - reversing mill Rolling speed - reversing mill cceleration - reversing mill The relationship for the rtical scre,v positi n of the scale breaker i : = f("'£, B,K,o<:.,l) The "idth reducti n is then checked t a id exceeding to edg r mot rapacity. The horiz ntal cre, position of the scale breaker is determined by perating practice by a table look-up which depends n: = f ("'S ,H~, o<..,~) The vertical screw p siti n of the re ersing mill is calculated b first determinin rr the lateral spread of each pass: p = f ("'S , Ho' H 1 , cL. The crew p siti n: = f( p,~.,~) Edger m tor capacity and ffilnlmum reduction for the last pass are c nstraint applied t the edgin rr calculati ns. The minimum la t pa s reducti n is requir d t permit "idth fee -ba k c rrecti n n the last pa s. r

H rizontal cr w p siti n is selected b dividing the requir d redu ti n bet,een the number ~ passes. minimum reducti n mu t e ma e n the last pass t permit g d edrring. Fr m the reducti n practice elected t m t r t rque is calculated.

T=

f(\

e,R, oc:,H o

The mill speed "\ alues are selected t minimi::e the r llin rr time, b- selecting entr and rIling speeds and a s iated accelerati ns fr m the m t r chara teri tic curve. The entry speed f the f n,ard pa se must al be he ked t a id ex e sive impact a the bar enter the mill. r

ILL ...

C-8

ing f the inversi n ignals. self-learnin table 1 k-up y tem ha been de el ped f r thi functi n. The c ntrol nunimize the lab ut- ff -null time. The cells in the table are = f (H, , \ B , \T, ,D) • A feed-forward iunal f the actual rtical r 11 p siti n f the cale breaker i u d t determine any width deviati n arrivin t the re ersing mill. c rrecti n i distributed t all the odd pass s except the last pa s. \idth error si nal is recei ed fr m the width ga e n the next t last dd pa s which i used t adjust the edging on the last pa s.

screw po ition slab width \vs bar width K coefficient of thermal expansi n 0( te 1 rade number f pa se in reversing null HS slab thickness p spread Ho entry thickness H, exit thickness Ru n minal width reduction = vertical stand deformation T = t rque R reducti n \, exit el city, before low-down D distance ut- f-mill (required t clear descale sprays) S

"'S

PPE~~IX

3 -

FI~

The ff-line fini hing null m del calculate the: tand el city crew p siti n Le per tensi n The cal ulati n irst elects the sixth tand vel city: \"6 = f(H 6 To ,T6 ~ ing the mass fl w fr m the six~h stand and a predetermined reducti n practice the -el ciie the ther stan s are calculated: \ j Hj c nstant '"6 H6 The re" p siti n is calculated fr m the age meter equati n: i = Hj

-

F j /1 j

The the retical rolling f rce is from the ims-Ekelund equati n: Fj=K j

The n-line c ntrol system c ntrols the mill sI w-d \Vll be re tail ut f-mill an the tim-

IGLIA 0 HOT STRIP

\

alculate

j~

The actual rIling rce i alculated using the the retical rolling f rce ,\"ith an experimentally

C-8

RETROFITTI G A PROCESS CO TROL CO PUTER TO THE CORNIGLIA 0

determined regression equati n: F j = Cj Fj

where C j = f(Hj,Ho,Rj,HF,Qj,T j , j ,W) The 10 per tensi n is a functi n f the desired specific tension and strip dimensions. The 10 per m tor current is calculated from the t tal tension and the looper m tor characteristics.

H T F M

F K W

= = = =

Q

On-line models are used to adjust screw position in both feed-forward and feed-back modes. Operator changes of load distribution effect both screws and speeds, also the operator may directly alter the individual speeds or screws. s each bar arri s to the finishing mill the head end temperature is checked, if this differs from the temperature expected, then a feed-forward correction is distributed to all the stand screw positions b : l1S j = O. 2ATFj/Mi Finished strip gage data is collected at each order change. This data is used to determine the trend of the finishing mill for the variables not included in the models, i.e. roll thermal expansion, roll wear, etc. The trend data is used as a feed-back adjustment to the values calculated off-line. The ff-line models use a pre-established reduction practice, if there is an operating problem on the mill, such as shape or drive problems, the operat r modifies the load distribution, by selector switches, and the computer recalculates the interstand thickness, rolling forces, screw positions and velocities. The perator can also instruct the c mputer t modif the values of screw p sition or vel cit , b thumbwheel entry. The c mputer will use the values entered by the ope rat r and recalculate the interstand thickness, reducti n practice and r lling f rces. These changes are als inc rp rated into a disc ta le f reach gr up f strip dimensi ns and steel grades. These table alues are subsequently used each time a si ilar order is rolled. In this wa the computer learns the corrections the operators are making t the models. LIST OF SYMBOLS FOR FT

rrSHI~

G MILL

(Subscript refer t the stand number or the exit side of the stand).

R

6H C

HF

=

HO~

STRIP

ILL ...

731

el cit thickness temperature screw p siti n actual rolling f rce mill m dulus the retical rolling force resistance t deformation width geometric fact r roll radius absolute reduction = Hj - l - Hi regression correlation for rolling force hardness factor

o

T TABLE COOLI G MODEL

The volume of cooling water is calculated b an off-line model, which was experimentall determined by regression analysis: Q = f(H 6 ,T 6 ,T e ) The spra configuration is then determined by a table look-up for the volume required. On-line corrections are made when the head-end of the strip passes under the finishing mill pyrometer and again when the head-end arrives at the coiler, using the same expression as above but with actual instead of estimated values. Q = volume f cooling water H6 finishing mill thickness To finishing mill temperature Te coiler temperature.