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Digital control in the food industry
Digi tal Computer Applications to Process Con trol, © IFAC and ort -Holland P lishing Company (1977)
a ta Lemke, ed.
DIGITAL CO TROL I
S-5
T!lE FOOD IND STRY
A. Eli is nf Id Fjsh r Controls Company larshalltm-Jn, Iowa
ABSTRACT
,\ 1 itera llre s~ ar h disclos d 207 t hni al arti 1 s and pap rs d ribing th appli ation of digital omput rs to th· f od pro ssing industry. Thirty-s v n f th s pap rs wer by quipm nt manufacturers d scribing pot ntial, not actual, appli ati ns. 143 of the pap rs d scrib applications which had no s mblanc of control. Of the appli ations d s rib d in th r maining papers, mor than 2/3 were batch applications. In this writ r' opinion, th re ar onl. a few signifi ant f atures in these applications. One is the tr nd towards compl t ngineer d computer systems such as those offered by the major instrument manufacturers or th specialty software houses.
is typical f about 70 such syst ms which will not b dis ussed h r . Th xc ption \-Jh ich makes th is sy t m \-Jor h r port ing is the dynamic natur of the d finition of an ff normal condition. Th Schmidt's system does not m r ly ch k current valu s or tatus against preset alarm conditions. ost of th alarms check the execution of an operator nt red instruction. For xample if th perator tri to start a new compressor engin , this "act" instru ts the comput r to confirm the "run" status of th ngine. If after a specified time the "run" status is not confirmed, the comput r will print and sound an alarm. A mor comprehensiv digital control system is in use in SCOTTISH BREWERIES plant in Jew Fountan, Edinburgh Scotland. This syt m controls 57 v ssels in which fermentation, aging and preshipm nt storage are conduct d. The computer is in control of the sequencing and direction of the Wort from th wort house through coolers to one of eleven fermenter v ssels. fter the operator mak s the appropriat' onn ctions in the manifolding th computer takes over.
Several of the papers dedicat more attention to sensors or how th comput r system solves an inadequate sensor problem. Energy conservation has been the most important single factor to justify comput rization. In the C.S. th g neral 1 vel of analog instrum ntation is lower than in Europ. In th last two years D.S. food processors have spent mor money upgrading instrumentation than on truly control ori nted digital computers. Howev r this capital was sp nt as part of 1 ng rang plans to pr vide computerization. The application of on-lin computers for proc ss control should, th refore, b easier.
This operator manifolding change and comput r take 0 r is repeated for s v ral different steps. The first of th se aft r fermentation is to dir ct th product to on of two yea t sludg vessel , then to c ntrifuging. Th c ntrifuge is only monitor d by th computer~ no control is used at the time of this writing. After centrifuging the product is s nt to ither an aging tank or to "aste vessels via t\O parrallel lines. The manifolding in this s:st m is done auto atically \ ith pilot operat d val es. After aging th omput r directs the product to a tank ruck-loading station or to one of 32 automatically sel cted torage tanks.
The balanc of this paper 18 specific applications. oft he a pp 1 i cat ion \\ ill b g i en f 0 11 m, e db: a di cussion of th techniqu used benefi obtained and any it m of sp cial int r t. Of thes 1 papers six are in\olv d in the production of alcoholic beverag beer wine, whiskies and liquers. Surprisingl J , no par'r~ on canning or pastuerizin were found. BE TERAGE L;DCSTRY
Th SC lIDT' Bre\ er: in Philad lphia PennsJ'l\ania claims to haY aved more than 50 000 per year b. implementin a digital c pu er ba ed 10 -alarm y te on the bre\ er." s re rig rati n plant. This co puter y te onitor 250 points cri ical to operation of th refri eration co pr sors at the rate of 10 points per s cond and alarms 0 n rmal situations. hith one ex ption, this system T
31
The yste consi ting 0 a dual cpe executes predet r ined sequences a direct d by op rator pushbuttons. Co unication to the field elements is ia a data highway. The signals are coded relative to th equip ent selected and decoded locall~. There are 200 unctions per data hi h\ay for a total of 8 data high\ a.-s. The syste do in lude auto atic start 0 th appropriat Clean In Place sub-system, thereby pro\iding irtually complete auto-
32
QIGITAL CO TROL I
THE FOOD I DUSTRY
S-5
mat ion. ~ ' th br w-mast r is still king of th p ration.
Th comput r is r3th r small, consisting only l2K re memory.
A very similar op ration is condu ted in a SEAGRAN distill ry. H r hm.v v r, th mphasis i n th feeding of ingr di nt into a bat 'h and the contr 1 of the co kino cl . This syst m ontrols 8 cooking v ss Is with a singl CPU. Two significant fa ts about thi installati n ar th hardwar controll d variabl s anning and th appliation pr gramming and technolog
At th
J
All inputs ar s nn d at a rat of 5,000 points p r second by a hardwar ontroll d scanner. This guarant s that curr nt information as to th c ndition of a v ss 1 or th proc ss is available for all phases of op ration for all vess Is. Th application programming is also greatl. simplifi d. Th c ntr 1 t hnology was d riv d fr m the v ndor's onsiderable xp ri n e in ch mi al plant and pharma uti al plant bat h r actor control proj cts. All logic and qu n ing functions ar xecuted by DDC· modulating contr 1 functions ar impl m nted via supervis ry ntrol. The application programs ar written in a tabl driven languag which is actually an xt nsion of a high lev 1 languag similar to BASIC. On line chang in r cipe, s qu nc , and sup rvisory c ntrol configuration ar af ly and ffici ntly x ut d without any d gr dation of control. Thi s ction of th pap r started with th discussion of two br w ries progr ed to a distill ry and shall now continue with th di cussion of a liqu r, PER ·OD. This will b -ollow d with a discussion of wine manufactur. At the Pernod factory in Ci teil the digital computer ontrols th batch preparati n, extraction, distillati n blending and bottling to make the various anis d drinks produ d at this plant. Th computer p rform all operation of blending holding filtering and run d wn to abov 150 sel t d storage tanks. The operator ets th production sch dules generally on a daily ba i and can also o rride a particular run or days sch dule. Th comput r calculates the amount of alcohol and water to b add d into each recipe bas d on a perc nt alcohol in the bas. It then correct the inished product a ter an analy is is perfor ed off line and entered by th operator. All operating sequences are controlled b the computer as ell as the essel preparation and clean-up functions. In this application as in many discussed here a key actor is n ors. El ctronic load cells are used \ith temp rature co pensation for densit.'. Although th author has b en unable to c nfirm this the user believ s th treatment of th load cell signals and t mp rature comp nsation by th comput r ha significantly nhanced th op ration.
a 16K
l
California th must ps of th
r
pr paration and \vorld's larg
\vinery.
The win ry i a c op rativ s gr at are must b tak n to determi~ th quantity and quality of win brought to th win ry from ach of th farmer. Sampl s ar ,'tract d fr m a h batch of grap s brought t the winer and an lyz d. Th gondola with th wine is dump d into a sp cifi crush r. Th p rator at ea h of th five rush rs ha his own control pan 1. Inf rmati n as to th s urce of th grap sand th ir quality and type is nt r d into th omputer through thes ontrol station. Th comput r th n det rmines th ferm ntation tank to which th must will b direct d and displays this information on th op rator onsol. Aft r a knowl dg m nt fr m the op rator th c mput r operat th olenoid valv s which in turn direct air to th appropriat val s in a omplex manifold. hith this st p compl t d an operator acknowl dg ment allows th crush rs to start. The must is measur d by magnetic flow tubes as it go s to its sp cified tank. Th co mput r in t grat . t h q 11 :1 n tit Y 0 f mu s t going into ea h v ss 1 for a ount ir.g purpo s. This m asur m nt is also us d to d t rmine the volume in a sp ific fermentation tank. High lev 1 prob in th tank provid ba kup to pr v nt v r-filling. A paper on this system is b ing pr sented at this congres . At the ROBERT ID~A\I WI.ERY in Oakville California, a digital comput r is more directly associat d with th wine making proc ss. Th R b rt . londavi hTinery produc s th finest Am rican win sand i not d for its Cab rn t Sauvignon, and Pino t . '0 i r wines as well a som ut tanding whit s. Accurat preci control of th rate of f rm ntation is one ke.· to the succes 0 this \..' in ry. The computer monitors the f rmentation t peratur s for excursions from the desired temp rature. :ot only is the absolute valu of t mperatur checked but also th rate of change. Careful control 0 a anifolded refrigeration s.'ste ensur that the in or a ion pro\ided by the computer can be executed. Becaus the refinery is unattended during the third shift the computer has a all-up system ith a oice simulation that alerts winer_ personnel at hom f an impending probl Control of entrifuges has been i pI ented but it i so ar onl.' partially succe sful. Ihis is probabl.' due t the in le.-ibilit: 0 the co put r sel ct d. A a dedicated patron of thi \viner:, I am per onally grateful for the succ ss of this computer.
S-s
DIGITAL CO TROL I
THE FOOD I DUSTRY
33
SUGAR Conversion of sugar and starch s to alcohol has been th focus of this survey so far. Let us now switch our mphasis to sugar production. Th BRITISH S GAR CO IPA ' has installed and is evaluating a micropro ssor bas d omputer syst m for the contr 1 of th vacuum pan evaporators. Primarily a batch operation, the critical pint of the vacuum pan concentration is the nd point. tany types of sequencing contr llers ar in use on this equipment, but th control s_ stem mploy d bv British Sugar is reported to ff ctively control this nd point. 0 further information is available at this tim. Howev r, PFEIFERLA GE SUGAR COMPA Y in W st Germany employs a sp cial sensor which they call a Rheom ter to d tect this end point. This Rheometer is interfaced at present with a solid-state logic controller for the vacuum pan. PfeiferLangen reports that work is underway to implement this logic controller on a microprocessor. At the AISTAR SUGAR REFI ERY in ew Orl ans, a digital blending system is used. Specifics of the products being blended are unavailable. However, in this applicati n to sensors ar strongly stressed. It appears that a major benefit of this system is to increase the accuracy of blending by inhancing the performance of the sensors. Actually, this control system uses digital logic and analog control rather than being a general purpose computer. However, in one application being developed, to this author's knowledge, the concept of this type of blending are being implemented as one of many functions on a large digital computer.
d t rmin d it was more economical to buy a small g neral purpose computer and compon nt parts and do th engineering themselv s. Besid s their basic application programming, thes ngineers had to write all of the computer utilit. functions. On stream nm , to som d gr e at least, this project, though perhaps deemed u cessful, was significantlY over budget and behind schedule because some overly z alous engin rs decided to re-invent th wh 1. COR
ERS
During the period of very high sugar prices and scarce supply, corn sweetners became an important factor on the market. Two existing corn sweetner plants were computerized and a grass-roots plant was built with a digital control omput r as part of the basic design. These comput rs are performing essentially batch sequ ncing control. The processes are proprietary but it is significant to note that these projects w r all implemented on schedule and reasonably close to budget amd that th manufa'turcrs ar already executing plans to comput rize additional plants. One important fact r mentioned above, causing computerization of food processing plants, is the high price of energy. One sugar refinery in Hawaii has installed a digital computer to monitor its nergy produ ti)n Jnd distribution systems. Data gath red by this ystem is now being analyzed to determin an optimizing program for this sugar plant. DAIRY
The melt house of the CALIFOR lA A D HAhAII S GAR CO IT Y plant in California is the object of a computer control system. The computer is to control the consistenc_ in the mingler by calculating the mingler motor load and its 1 el. The rate of sugar flow is to be calculated from the elevator motor load and the flow rate of affination s~rup will be in direct ratio to the rate of raw sugar. Applying a three-mode control al orithm to the consistency as calculated above, the co puter will modif~ the yrup to raw su ar ratio. Syrup is to be measured and a dc algorithm applied to control the syrup val e. In addition the computer also controls the centrifuges as follows. The sequence time for sugar rate control is adjusted as is the water spray wash time. These two control function~) allow the maximization of spin time within specified limits.
In Rian , Franc , LAITERIE TRIBALLAT operat s a goat cheese plant with the aid of a digital control computer. Here as in many other plants two s nsors are the key. They measure milk weight and specific gra ity and fixed volume receiving tanks. The major 'ustification for the computer system is to determine the exact ~olids content of the milk and to detect watering of the milk by the farmers upplying raw product to the dairy. The improved measurements have the additional benefit of decreasing whey losses.
Several other control functions are planned for this computer. Howe er, installation and execution of these strategies as se erely impeded b. the approach used. Rather than purchase an engineered s.stem as mentioned earlier in this paper, plant engineers
All operations are initiated b~ the operator using special function pushbuttons on a central con oleo hith operator direction the co puter controls 650 valves and motors. Eight turbine eters pro ide the basic flow measurements.
A m re ophisticated computer at the LriiARP DAIRY in S\eden helps proces 5 tons of ra\ milk per hour. The comput r routes the ra mat rial into blending and cooking tank and the finished product into storage and packaging area. Here too sensors pla_ an i portant part. T
34
DIGITAL CO TROL I
The omputer controls formulation of r cip after the operator t lIs how much of ach r cipe to make during a specific time p riod. The computer l6K of cor with a 64K di c uses a sp cial s qu ncing languag to implem nt this control. A background machine set up for automatic takeov r on failure of th foreground ma hin ,monitor and verifi s all data and produces managem nt r ports. PET FOODS So far this paper has discussed food for human consumption. Let us n t forg t, howev r, food for man's best fri nd, the dog. At an ALPO food plant, a digital computer do s batch sequencing f 13 diff r nt r cip s. This syst m operat s 8 storag bins, 2 h pper stations, and 4 mix r-h aters to produc a vari ty of products. The control problem is eas d by th fact that there ar only 7 steps in ea h s qu nce. How ver, improv m nts in production rate and reduction in off-spec material ar a dramatic example of what ev n a simple digital computer application can do.
The food industry is benefiting from the control t hnology developed primarily in the chemical industry. Special high 1 v 1 languag s develop d for chemical and pharmac utical plant batch rea tors have be n embraced bv the fo d industry. With few exceptions the food industry used complete systems such as those supplied by major instrument vendors such as Fisher Controls, Kent and Si m ns. Although predominantly batch control up to this point, it is this author's prediction that the food industry will rapidly xpand its computer activities into its continuous operations.
THE FOOD I DUSTRY
S-5
a ta Lemke, ed.
DIGITAL CO TROL I
S-5
T!lE FOOD IND STRY
A. Eli is nf Id Fjsh r Controls Company larshalltm-Jn, Iowa
ABSTRACT
,\ 1 itera llre s~ ar h disclos d 207 t hni al arti 1 s and pap rs d ribing th appli ation of digital omput rs to th· f od pro ssing industry. Thirty-s v n f th s pap rs wer by quipm nt manufacturers d scribing pot ntial, not actual, appli ati ns. 143 of the pap rs d scrib applications which had no s mblanc of control. Of the appli ations d s rib d in th r maining papers, mor than 2/3 were batch applications. In this writ r' opinion, th re ar onl. a few signifi ant f atures in these applications. One is the tr nd towards compl t ngineer d computer systems such as those offered by the major instrument manufacturers or th specialty software houses.
is typical f about 70 such syst ms which will not b dis ussed h r . Th xc ption \-Jh ich makes th is sy t m \-Jor h r port ing is the dynamic natur of the d finition of an ff normal condition. Th Schmidt's system does not m r ly ch k current valu s or tatus against preset alarm conditions. ost of th alarms check the execution of an operator nt red instruction. For xample if th perator tri to start a new compressor engin , this "act" instru ts the comput r to confirm the "run" status of th ngine. If after a specified time the "run" status is not confirmed, the comput r will print and sound an alarm. A mor comprehensiv digital control system is in use in SCOTTISH BREWERIES plant in Jew Fountan, Edinburgh Scotland. This syt m controls 57 v ssels in which fermentation, aging and preshipm nt storage are conduct d. The computer is in control of the sequencing and direction of the Wort from th wort house through coolers to one of eleven fermenter v ssels. fter the operator mak s the appropriat' onn ctions in the manifolding th computer takes over.
Several of the papers dedicat more attention to sensors or how th comput r system solves an inadequate sensor problem. Energy conservation has been the most important single factor to justify comput rization. In the C.S. th g neral 1 vel of analog instrum ntation is lower than in Europ. In th last two years D.S. food processors have spent mor money upgrading instrumentation than on truly control ori nted digital computers. Howev r this capital was sp nt as part of 1 ng rang plans to pr vide computerization. The application of on-lin computers for proc ss control should, th refore, b easier.
This operator manifolding change and comput r take 0 r is repeated for s v ral different steps. The first of th se aft r fermentation is to dir ct th product to on of two yea t sludg vessel , then to c ntrifuging. Th c ntrifuge is only monitor d by th computer~ no control is used at the time of this writing. After centrifuging the product is s nt to ither an aging tank or to "aste vessels via t\O parrallel lines. The manifolding in this s:st m is done auto atically \ ith pilot operat d val es. After aging th omput r directs the product to a tank ruck-loading station or to one of 32 automatically sel cted torage tanks.
The balanc of this paper 18 specific applications. oft he a pp 1 i cat ion \\ ill b g i en f 0 11 m, e db: a di cussion of th techniqu used benefi obtained and any it m of sp cial int r t. Of thes 1 papers six are in\olv d in the production of alcoholic beverag beer wine, whiskies and liquers. Surprisingl J , no par'r~ on canning or pastuerizin were found. BE TERAGE L;DCSTRY
Th SC lIDT' Bre\ er: in Philad lphia PennsJ'l\ania claims to haY aved more than 50 000 per year b. implementin a digital c pu er ba ed 10 -alarm y te on the bre\ er." s re rig rati n plant. This co puter y te onitor 250 points cri ical to operation of th refri eration co pr sors at the rate of 10 points per s cond and alarms 0 n rmal situations. hith one ex ption, this system T
31
The yste consi ting 0 a dual cpe executes predet r ined sequences a direct d by op rator pushbuttons. Co unication to the field elements is ia a data highway. The signals are coded relative to th equip ent selected and decoded locall~. There are 200 unctions per data hi h\ay for a total of 8 data high\ a.-s. The syste do in lude auto atic start 0 th appropriat Clean In Place sub-system, thereby pro\iding irtually complete auto-
32
QIGITAL CO TROL I
THE FOOD I DUSTRY
S-5
mat ion. ~ ' th br w-mast r is still king of th p ration.
Th comput r is r3th r small, consisting only l2K re memory.
A very similar op ration is condu ted in a SEAGRAN distill ry. H r hm.v v r, th mphasis i n th feeding of ingr di nt into a bat 'h and the contr 1 of the co kino cl . This syst m ontrols 8 cooking v ss Is with a singl CPU. Two significant fa ts about thi installati n ar th hardwar controll d variabl s anning and th appliation pr gramming and technolog
At th
J
All inputs ar s nn d at a rat of 5,000 points p r second by a hardwar ontroll d scanner. This guarant s that curr nt information as to th c ndition of a v ss 1 or th proc ss is available for all phases of op ration for all vess Is. Th application programming is also greatl. simplifi d. Th c ntr 1 t hnology was d riv d fr m the v ndor's onsiderable xp ri n e in ch mi al plant and pharma uti al plant bat h r actor control proj cts. All logic and qu n ing functions ar xecuted by DDC· modulating contr 1 functions ar impl m nted via supervis ry ntrol. The application programs ar written in a tabl driven languag which is actually an xt nsion of a high lev 1 languag similar to BASIC. On line chang in r cipe, s qu nc , and sup rvisory c ntrol configuration ar af ly and ffici ntly x ut d without any d gr dation of control. Thi s ction of th pap r started with th discussion of two br w ries progr ed to a distill ry and shall now continue with th di cussion of a liqu r, PER ·OD. This will b -ollow d with a discussion of wine manufactur. At the Pernod factory in Ci teil the digital computer ontrols th batch preparati n, extraction, distillati n blending and bottling to make the various anis d drinks produ d at this plant. Th computer p rform all operation of blending holding filtering and run d wn to abov 150 sel t d storage tanks. The operator ets th production sch dules generally on a daily ba i and can also o rride a particular run or days sch dule. Th comput r calculates the amount of alcohol and water to b add d into each recipe bas d on a perc nt alcohol in the bas. It then correct the inished product a ter an analy is is perfor ed off line and entered by th operator. All operating sequences are controlled b the computer as ell as the essel preparation and clean-up functions. In this application as in many discussed here a key actor is n ors. El ctronic load cells are used \ith temp rature co pensation for densit.'. Although th author has b en unable to c nfirm this the user believ s th treatment of th load cell signals and t mp rature comp nsation by th comput r ha significantly nhanced th op ration.
a 16K
l
California th must ps of th
r
pr paration and \vorld's larg
\vinery.
The win ry i a c op rativ s gr at are must b tak n to determi~ th quantity and quality of win brought to th win ry from ach of th farmer. Sampl s ar ,'tract d fr m a h batch of grap s brought t the winer and an lyz d. Th gondola with th wine is dump d into a sp cifi crush r. Th p rator at ea h of th five rush rs ha his own control pan 1. Inf rmati n as to th s urce of th grap sand th ir quality and type is nt r d into th omputer through thes ontrol station. Th comput r th n det rmines th ferm ntation tank to which th must will b direct d and displays this information on th op rator onsol. Aft r a knowl dg m nt fr m the op rator th c mput r operat th olenoid valv s which in turn direct air to th appropriat val s in a omplex manifold. hith this st p compl t d an operator acknowl dg ment allows th crush rs to start. The must is measur d by magnetic flow tubes as it go s to its sp cified tank. Th co mput r in t grat . t h q 11 :1 n tit Y 0 f mu s t going into ea h v ss 1 for a ount ir.g purpo s. This m asur m nt is also us d to d t rmine the volume in a sp ific fermentation tank. High lev 1 prob in th tank provid ba kup to pr v nt v r-filling. A paper on this system is b ing pr sented at this congres . At the ROBERT ID~A\I WI.ERY in Oakville California, a digital comput r is more directly associat d with th wine making proc ss. Th R b rt . londavi hTinery produc s th finest Am rican win sand i not d for its Cab rn t Sauvignon, and Pino t . '0 i r wines as well a som ut tanding whit s. Accurat preci control of th rate of f rm ntation is one ke.· to the succes 0 this \..' in ry. The computer monitors the f rmentation t peratur s for excursions from the desired temp rature. :ot only is the absolute valu of t mperatur checked but also th rate of change. Careful control 0 a anifolded refrigeration s.'ste ensur that the in or a ion pro\ided by the computer can be executed. Becaus the refinery is unattended during the third shift the computer has a all-up system ith a oice simulation that alerts winer_ personnel at hom f an impending probl Control of entrifuges has been i pI ented but it i so ar onl.' partially succe sful. Ihis is probabl.' due t the in le.-ibilit: 0 the co put r sel ct d. A a dedicated patron of thi \viner:, I am per onally grateful for the succ ss of this computer.
S-s
DIGITAL CO TROL I
THE FOOD I DUSTRY
33
SUGAR Conversion of sugar and starch s to alcohol has been th focus of this survey so far. Let us now switch our mphasis to sugar production. Th BRITISH S GAR CO IPA ' has installed and is evaluating a micropro ssor bas d omputer syst m for the contr 1 of th vacuum pan evaporators. Primarily a batch operation, the critical pint of the vacuum pan concentration is the nd point. tany types of sequencing contr llers ar in use on this equipment, but th control s_ stem mploy d bv British Sugar is reported to ff ctively control this nd point. 0 further information is available at this tim. Howev r, PFEIFERLA GE SUGAR COMPA Y in W st Germany employs a sp cial sensor which they call a Rheom ter to d tect this end point. This Rheometer is interfaced at present with a solid-state logic controller for the vacuum pan. PfeiferLangen reports that work is underway to implement this logic controller on a microprocessor. At the AISTAR SUGAR REFI ERY in ew Orl ans, a digital blending system is used. Specifics of the products being blended are unavailable. However, in this applicati n to sensors ar strongly stressed. It appears that a major benefit of this system is to increase the accuracy of blending by inhancing the performance of the sensors. Actually, this control system uses digital logic and analog control rather than being a general purpose computer. However, in one application being developed, to this author's knowledge, the concept of this type of blending are being implemented as one of many functions on a large digital computer.
d t rmin d it was more economical to buy a small g neral purpose computer and compon nt parts and do th engineering themselv s. Besid s their basic application programming, thes ngineers had to write all of the computer utilit. functions. On stream nm , to som d gr e at least, this project, though perhaps deemed u cessful, was significantlY over budget and behind schedule because some overly z alous engin rs decided to re-invent th wh 1. COR
ERS
During the period of very high sugar prices and scarce supply, corn sweetners became an important factor on the market. Two existing corn sweetner plants were computerized and a grass-roots plant was built with a digital control omput r as part of the basic design. These comput rs are performing essentially batch sequ ncing control. The processes are proprietary but it is significant to note that these projects w r all implemented on schedule and reasonably close to budget amd that th manufa'turcrs ar already executing plans to comput rize additional plants. One important fact r mentioned above, causing computerization of food processing plants, is the high price of energy. One sugar refinery in Hawaii has installed a digital computer to monitor its nergy produ ti)n Jnd distribution systems. Data gath red by this ystem is now being analyzed to determin an optimizing program for this sugar plant. DAIRY
The melt house of the CALIFOR lA A D HAhAII S GAR CO IT Y plant in California is the object of a computer control system. The computer is to control the consistenc_ in the mingler by calculating the mingler motor load and its 1 el. The rate of sugar flow is to be calculated from the elevator motor load and the flow rate of affination s~rup will be in direct ratio to the rate of raw sugar. Applying a three-mode control al orithm to the consistency as calculated above, the co puter will modif~ the yrup to raw su ar ratio. Syrup is to be measured and a dc algorithm applied to control the syrup val e. In addition the computer also controls the centrifuges as follows. The sequence time for sugar rate control is adjusted as is the water spray wash time. These two control function~) allow the maximization of spin time within specified limits.
In Rian , Franc , LAITERIE TRIBALLAT operat s a goat cheese plant with the aid of a digital control computer. Here as in many other plants two s nsors are the key. They measure milk weight and specific gra ity and fixed volume receiving tanks. The major 'ustification for the computer system is to determine the exact ~olids content of the milk and to detect watering of the milk by the farmers upplying raw product to the dairy. The improved measurements have the additional benefit of decreasing whey losses.
Several other control functions are planned for this computer. Howe er, installation and execution of these strategies as se erely impeded b. the approach used. Rather than purchase an engineered s.stem as mentioned earlier in this paper, plant engineers
All operations are initiated b~ the operator using special function pushbuttons on a central con oleo hith operator direction the co puter controls 650 valves and motors. Eight turbine eters pro ide the basic flow measurements.
A m re ophisticated computer at the LriiARP DAIRY in S\eden helps proces 5 tons of ra\ milk per hour. The comput r routes the ra mat rial into blending and cooking tank and the finished product into storage and packaging area. Here too sensors pla_ an i portant part. T
34
DIGITAL CO TROL I
The omputer controls formulation of r cip after the operator t lIs how much of ach r cipe to make during a specific time p riod. The computer l6K of cor with a 64K di c uses a sp cial s qu ncing languag to implem nt this control. A background machine set up for automatic takeov r on failure of th foreground ma hin ,monitor and verifi s all data and produces managem nt r ports. PET FOODS So far this paper has discussed food for human consumption. Let us n t forg t, howev r, food for man's best fri nd, the dog. At an ALPO food plant, a digital computer do s batch sequencing f 13 diff r nt r cip s. This syst m operat s 8 storag bins, 2 h pper stations, and 4 mix r-h aters to produc a vari ty of products. The control problem is eas d by th fact that there ar only 7 steps in ea h s qu nce. How ver, improv m nts in production rate and reduction in off-spec material ar a dramatic example of what ev n a simple digital computer application can do.
The food industry is benefiting from the control t hnology developed primarily in the chemical industry. Special high 1 v 1 languag s develop d for chemical and pharmac utical plant batch rea tors have be n embraced bv the fo d industry. With few exceptions the food industry used complete systems such as those supplied by major instrument vendors such as Fisher Controls, Kent and Si m ns. Although predominantly batch control up to this point, it is this author's prediction that the food industry will rapidly xpand its computer activities into its continuous operations.
THE FOOD I DUSTRY
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