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1、Chapter5ProcessControlSystemsUnit22ImportanceofProcessControlUnit23ProcessControlLoopsUnit24AdvancedControlLoopsUnit25ComputersinControlUnit26IntroductiontoSensorsUnit22ImportanceofProcessControlControlinprocessindustriesreferstotheregulationofallaspectsoftheprocess.Precisecontroloflevel,temperatu
2、re,pressureandflowisimportantinmanyprocessapplications.Refining,combining,handling,andotherwisemanipulatingfluidstoprofitablyproduceendproductscanbeaprecise,demanding,andpotentiallyhazardousprocess.Smallchangesinaprocesscanhavealargeimpactontheendresult.Variationsinproportions,temperature,flow,tur
3、bulence,andmanyotherfactorsmustbecarefullyandconsistentlycontrolledtoproducethedesiredendproductwithaminimumofrawmaterialsandenergy.下一页返回Unit22ImportanceofProcessControlProcesscontroltechnologyisthetoolthatenablesmanufacturerstokeeptheiroperationsrunningwithinspecifiedlimitsandtosetmorepreciselimi
4、tstomaximizeprofitability,ensurequalityandsafety.ProcessProcessasusedinthetermsprocesscontrolandprocessindustry,referstothemethodsofchangingorrefiningrawmaterialstocreateendproducts.Therawmaterials,whicheitherpassthroughorremaininaliquid,gaseous,orslurry(amixofsolidsandliquids)stateduringtheproces
5、s,aretransferred,measured,mixed,heatedorcooled,filtered,stored,orhandledinsomeotherwaystoproducetheendproduct.上一页下一页返回Unit22ImportanceofProcessControlProcesscontrolProcesscontrolreferstothemethodsthatareusedtocontrolprocessvariableswhenwemanufactureaproduct.Forexample,factorssuchastheproportionofo
6、neingredienttoanother,thetemperatureofthematerials,howwelltheingredientsaremixed,andthepressureunderwhichthematerialsareheldcansignificantlyimpactthequalityofanendproduct.IncreaseefficiencySomeprocessesneedtobemaintainedataspecificpointtomaximizeefficiency.Forexample,acontrolpointmightbethetempera
7、tureatwhichachemicalreactiontakesplace.上一页下一页返回Unit22ImportanceofProcessControlAccuratecontroloftemperatureensuresprocessefficiency.Manufacturerssavemoneybyminimizingtheresourcesrequiredtoproducetheendproduct.Ens
