In this guide: INTRODUCTION 3 Why manage your energy use? ENERGY MANAGEMENT THEORY 4 Your energy fingerprint 5 Map your energy use

Transcription

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2 In ths gude: INTRODUCTION 3 Why manage your energy use? ENERGY MANAGEMENT THEORY 4 Your energy fngerprnt 5 Map your energy use INJECTION MOLDING MACHINES 6 Spend to save 7 The moldng cycle 8 The rght drve technology 9 Check your hydraulc ol 10 Check your perpherals MOLDING PLANT SERVICES 11 Mnmze & optmze 12 Manage resources MANAGING YOUR OPERATION 13 People 14 Improve your buldngs 2 An energy savng gude for njecton molders

3 Why manage your energy use? Plastcs njecton moldng s an energy ntensve process. And, because energy carres both an envronmental and fnancal cost, t makes sound sense not to waste t. Energy spendng n a typcal plastcs njecton moldng plant often approaches the cost of drect labor. But, whle labor ranks hgh among management concerns, lttle effort s expended on controllng energy spendng. The potental savngs are consderable, however. For an njecton moldng plant that has mplemented no effectve energy reducton measures, experence shows some 30% of total energy use s dscretonary. Ths s avodable energy spendng that can be clawed back through practcal management, mantenance and nvestment actons. Water pumps 5% Energy use by applcaton n a typcal njecton moldng operaton Lghtng 5% Compressed ar 10% Chllers 11% Heatng 2% Offces 1% Polymer processng 66% The rules for savng energy are smple: spend tme and effort where the returns are the greatest. That calls for a structured energy management system. Such systems wll vary from one moldng plant to another but wll nclude: l A company energy polcy; l A nomnated person responsble for energy management; l A method for montorng and targetng short and long-term performance; l An dentfed, costed and approved lst of energy-savng projects; l A reportng system to show the status of projects; l And an audtng system to drve actons and mprovement. Read on to learn more about developng a strategy for savng energy n your njecton moldng operaton. An energy savng gude for njecton molders 3

4 Energy management theory Your energy fngerprnt Energy use n njecton moldng s varable, controllable and drectly related to producton. The key to understandng your energy consumpton s the Performance Characterstc Lne (PCL), whch provdes a unque energy fngerprnt of your plant. Armed wth ths, you can predct plant energy usage for any perod based on actual or antcpated producton volumes and ntegrate that data nto your busness accountng system for reportng and montorng purposes. To determne your plant s PCL, plot energy use (kwh) aganst producton volume (kg) over at least 12 months then fnd the lnear best ft (Fgure 1) to determne base and varable loads. ENERGY USAGE = (VARIABLE LOAD x PRODUCTION VOLUME) + BASE LOAD Base load s the energy used at zero producton and s determned where the PCL ntersects the vertcal axs. For most moldng stes t wll be between 20% and 40% of total energy usage. In the example n Fgure 1 t s 282,038 kwh. Fgure 1: The Performance Characterstc Lne holds the key to understandng plant energy use Varable load s determned from the slope of the PCL and s the energy needed to produce one klogram of product. It s dependent on the njecton moldng process and wll typcally range from 0.9 to 1.6 kwh/kg. In the Fgure 1 example t s kwh/kg. Base load savngs can be qute readly acheved; varable load savngs are more dffcult as they requre fundamental process mprovements. The PCL can also be used to determne the plant s correlaton coeffcent (R 2 ). An R 2 value of >0.7 ndcates good operatonal consstency and suggests energy effcency measures wll also be consstent and effectve. An R 2 of <0.7 ndcates the opposte. 4 An energy savng gude for njecton molders

5 Energy management theory Map your energy use To dentfy where your energy s gong you need an energy map for your moldng plant. Ths wll lst your man energy users, typcal power drawn (kw) and operatng hours and wll help you dentfy the bggest consumers. Your energy supply blls can help you save money and energy but you need to understand and analyze the nformaton they contan then make nformed management decsons. Avalable capacty (measured n kva) s the maxmum amount of power that can be drawn from the supply and s pad for whether t s used or not. Maxmum demand (also measured n kva) s the maxmum amount of power actually drawn. If maxmum demand greatly exceeds avalable capacty you wll pay penaltes; f much less you are buyng capacty that s not needed. Select an approprate capacty fgure. Power factor (cos φ) s the rato of useful power (kw) to apparent power (kva). The deal s a value of 1.0; for most plastcs processors t s around If your power factor s very low you wll need more avalable capacty and may be charged for reactve power (kvarh). In such cases, t may be worth nvestng n power factor correcton equpment. Interval data can be used to analyze energy use by tme and s a good way to check for costly usage patterns, such as shut-downs and startups. It s usually avalable free from your suppler. Benchmark your performance Whle your PCL formula allows you to montor your plant effectveness, benchmarkng allows you to compare t aganst other njecton moldng operatons or machne types. Tangram Technology, whch compled ths gude, has carred out energy surveys of more than 200 njecton moldng stes around the world and has compled benchmark curves 1 allowng ste or machne performance to be benchmarked aganst global averages. 1 More detals of the Tangram Technology Ltd benchmarkng method are provded n the book referred to at the end of ths publcaton. An energy savng gude for njecton molders 5

6 Injecton moldng machnes Spend to save Today s njecton moldng machne technology s far more energy effcent than that of 20 years ago. At a conservatve estmate, modern hydraulc njecton moldng machnes are 25% more energy effcent than those manufactured n Meanwhle, today s best all-electrc machnes may be up to 80% more energy effcent than ther 20-year old hydraulc predecessors. It wll pay you to make use of these machnery developments. Usng old machnery s not savng you money; t s costng you more to run your processes and placng your busness at a permanent cost dsadvantage to compettors. In almost every case, the cost of energy requred to run a moldng machne over a 10-year perod wll be greater than ts ntal purchase cost. Ths cost gap wll only wden as energy prces ncrease. For ths reason, energy assessment must become part of the purchasng process for every new moldng machne. Old machnery s not savng you money Consderng the whole lfe cost of a machne s dffcult but t s the only way to control future energy expendture. It wll help ensure that an attractve low cost machne does not become an energy hog that rases producton costs through ts entre lfetme. Remember, there s no conflct between energy management and producton rate. Beng effcent does not mean slowng the process down; the realty s that the energy effcency of a plant and ts machnes gets better as producton rate ncreases because the base load s amortzed nto a greater process load (explaned n the next secton). 6 An energy savng gude for njecton molders

7 Injecton moldng machnes The moldng cycle Montorng the power drawn by an njecton machne presents a pcture of the moldng cycle (Fgure 2) and can be dvded nto two elements: base load and process load. For standard hydraulc machnes, the base load (energy consumed when the machne s dlng such as durng coolng phases) can amount to 75% or more of total energy consumpton. A hgh base load can ndcate that the machne s too large for the job. In the example n Fgure 2, the base load s 64%. The hgh base load of standard hydraulc machnes means t s essental that the man motor s swtched on as late as possble durng start-up and off when producton s nterrupted or shut-down. The latter can be automated usng controls lnked to platen movement. For all-electrc and hybrd machnes, the base load s much lower as motors are only runnng when requred. Typcal base loads are n the regon of 10-20% and are largely accounted for by barrel heatng. Process load can also be explored through examnaton of a machne s power draw. Fgure 3 shows an expanded vew of the 38.6s cycle n Fgure 2 (the large peak shows the njecton phase and the smaller peaks platen movement and coolng). Usng graphs such as ths, energy use can be optmzed by adjustment of process settngs such as barrel temperatures and profle, njecton speed, back pressure, clamp force, hold pressure, hold tme, coolng tme and screw back speed whle preservng process consstency, producton rate and producton qualty. Fgure 2: Injecton moldng machne power draw plotted aganst tme showng a base load of 64% Fgure 3: Ths expanded vew of njecton machne power draw shows detaled cycle stages Process load Process Load 1 cycle = 38.6s Base load 0 11:04 11:05 11:06 11:07 11:08 11:09 11:10 11:11 11:12 11: Base Load 11:05:30 11:06:00 11:06:30 11:07:00 An energy savng gude for njecton molders 7

8 Injecton moldng machnes The rght drve technology Injecton moldng machne drve technology has changed dramatcally over the past couple of decades. In energy terms, the most sgnfcant change s the arrval of allelectrc and hybrd machnes. However, even tradtonal hydraulc machne drve desgn has evolved wth an extensve choce of motor and drve optons. Hydraulc machnes have tradtonally used a fxed speed motor contnually runnng a fxed volume pump but ths arrangement has largely been superseded by new desgns that am to adapt ol volumes to demand. Fxed speed motor/varable volume pump machnes use an adjustable swash plate on the pump to adjust the delvery of hghpressure ol. Varable speed motor/varable volume pump machnes use a varable speed drve (VSD) to add further flexblty. Servo motor/fxed volume pump combnatons take flexblty and energy savng even further. Hybrd machnes use a combnaton of hydraulc and servo motor drve technologes, wth a typcal confguraton combnng hydraulc machne operaton wth servo motor drve on the plastczng screw. Ths allows a smaller hydraulc drve system to be used, reducng the base load of the machne. All-electrc machnes use servo motor drve technology on all the man machne movements (but not always on mnor movements such as Know your machne drve technology Motor optons Hydraulc Hybrd All-electrc nozzle pressure and ejectors). By only usng energy when a movement s requred, base loads are dramatcally reduced and overall energy savngs of up to 60% are possble. Intally lmted to smaller clamp capactes, motor mprovements have gradually lfted the sze lmts whle economes of scale n producton have reduced the prce premum. Fxed speed motor/ varable volume pump Varable speed motor/ varable volume pump Servo motor/ fxed volume pump Varous combnatons, e.g. electrc screw drve 8 An energy savng gude for njecton molders

9 Injecton moldng machnes Check your hydraulc ol Hydraulc ol expendture represents a fracton of the cost of runnng njecton moldng machnery. But a small change n hydraulc ol can result n bg performance breakthroughs, such as prolonged component lfe, mprovements n overall equpment effcency and reduced cycle tmes. Operatng challenges: In njecton moldng, hydraulc ol s generally exposed to compresson, shear stresses and a wde temperature range. Ths can trgger the ol s molecular breakdown, whch reduces ts lubrcty and component protecton. Ths means your equpment has to work harder, s less protected and may use more energy. Hgh temperature operaton can lead to ol oxdaton, whch can result n corroson, a buld-up of damagng lacquer and an ncrease n vscosty. Hydraulc ols can also become contamnated wth process materals, water, dust and wear debrs. Ths can trgger pump falures whle ncreasng fltraton costs. Swtch to advanced hydraulc ol: To combat all of these ssues, t s mportant to use a hydraulc ol wth excellent shear stablty and a hgh vscosty ndex. Hgh performance hydraulc ols mantan ther optmum vscosty across a wde range of operatng condtons, helpng to protect equpment, mprove energy effcency and extend ol dran ntervals. That, n turn, can help to reduce mantenance, cut costs and enhance operatonal safety by reducng employee nteracton wth machnery. Extendng ol dran ntervals can also cut waste lubrcant dsposal, mprovng a company s overall envronmental credentals. In the feld A leadng plastcs manufacturer reduced energy consumpton by 5.1% after swtchng to Mobl DTE 10 Excel 46, a hgh performance hydraulc ol. The Mobl lubrcant was tralled n one of the manufacturer s Arburg Allrounder 820S njecton moldng machnes. The test showed that Mobl DTE 10 Excel 46 enhanced the overall productvty of the machne compared to the prevous lubrcant, and mproved ts energy effcency. Used ol analyss: Mantenance can be further reduced by the use of a used ol analyss program, such as Mobl Serv SM Lubrcant Analyss. By analyzng ol samples, t s possble to gan nvaluable nsghts nto how both the equpment and lubrcant s performng. Issues can also be detected before they become a problem, helpng mantan peak operatonal effcency and productvty. 2 Ths Proof of Performance s based on the experence of a sngle customer. Actual results can vary dependng upon the type of equpment used and ts mantenance, operatng condtons and envronment, and any pror lubrcant used. An energy savng gude for njecton molders 9

10 Injecton moldng machnes Check your perpherals Compared wth the man njecton machne drve, decsons on perpherals such as barrel heaters or temperature controllers may seem relatvely straghtforward. However, these can be sgnfcant energy consumers and can present real energy savng opportuntes. Infrared mages show how barrel nsulaton can reduce energy losses. It wll also mprove operator safety Energy losses from mold temperature controller ppng can be consderable Barrel heatng uses 10-25% of the energy nput of a typcal njecton moldng machne. Heat losses from unnsulated barrels are hgh due to the elevated temperatures nvolved; unnsulated barrels are also a health and safety ssue. Fttng barrel nsulaton mproves safety and can reduce barrel heatng energy requrements by up to 50%. Ensurng that heater bands are bedded-n and usng conductve metal heat transfer compounds between the heater and barrel also helps to optmse thermal effcency. Mold temperature controllers can consume a consderable amount of energy but are rarely gven detaled consderaton. In most njecton moldng operatons the ppework carryng hot water (sometmes ol n very hgh temperature systems) to the mold s left unnsulated and heat s lost to the envronment. And where the ppework s carryng coolng water, energy s lost through parastc heat gan. In cases where losses or gans are sgnfcant, t can be worth nstallng low cost nsulaton. Downstream ancllary equpment, such as conveyors, granulators, assembly machnes and automaton systems, s often left runnng n moldng plants when the njecton machne s stopped. Ths s a waste of energy that can easly be elmnated by lnkng downstream equpment nto the machne control or usng other forms of automated montorng. 10 An energy savng gude for njecton molders

11 Moldng plant servces Mnmze & optmze Servces such as compressed ar, chlled water and dryers are vtal n any njecton moldng plant and account for an estmated 30-35% of energy used. But despte presentng some of the easest opportuntes for energy savng, they are rarely gven much thought. There are two basc steps to effectve energy management of any servce: 1Ensure target demand s approprate for the requrement of the plant. It makes lttle sense to attempt to optmze supply of any plant servce f the assumed demand s unrealstc or unnecessarly large from the outset. 2Optmze equpment to supply the requred demand at the mnmum energy usage and cost. Ths requres a holstc approach n whch the entre system s examned n detal to determne areas of potental mprovement. Compressed ar Compressed ar s a convenent but expensve utlty that accounts for up to 10% of total energy cost n an njecton moldng plant. An effectve compressed ar management program can result n energy savngs of up to 50%. Reduce leakage Leaks can account for as much as 50% of the compressed ar generated n a badly mantaned system and 20-40% n most typcal njecton moldng plant. Reduce use Compressed ar costs around 1.00/kwh at the pont of use, more than ten tmes the equvalent quantty of electrcal power. Use t only when essental. Reduce generaton costs Reduce system pressure to the mnmum. Halvng system pressure decreases cost by three quarters. Reduce treatment costs Treat the bulk of your compressed ar to the mnmum level necessary. Replace manual condensate traps wth electronc types. Improve dstrbuton If the dstrbuton ppework s too small, flow wll be restrcted and hgher pressures requred. An energy savng gude for njecton molders 11

12 Moldng plant servces Manage resources Provdng chlled water for molds and coolng water for machnes consumes between 11-16% of the total energy used n a typcal njecton moldng plant. Reduce heat gan Allowng chlled water to gan heat from the plant envronment or crculatng t through noperatve machnes wastes energy. Use nsulated ppng between chller and mold and solate crcuts that are not n producton. Increase temperatures Chlled water temperatures should be maxmzed; rasng set temperature by 1 C decreases chller operatng costs by around 3%. Optmze runnng costs Coolng towers can be ftted wth VSD fans lnked to the sump water temperature, whch wll cut energy use and mprove temperature consstency. Where external temperatures allow, use ambent ar to provde free pre-coolng. Convert dstrbuton pumps from fxed to VSD operaton. Some words about motors Motors are bg energy users; every kw of fully loaded motor wll cost you around $1,000 a year. Cut that cost by turnng off motors that are not contrbutng to producton, nstallng VSDs to match motor speeds to demand, practce good mantenance, and upgrade to new technology when possble. Control dryng Dryng polymers can use up to 15% of total process energy so should only be performed when and as lttle as necessary. Dry the rght materals Lmt dryng to the materals that need t: hygroscopc polymers. Store materals correctly Hygroscopc polymers wll absorb less mosture f stored n a warm and dry envronment n a sealed contaner. Proper storage pays off for non-hygroscopc materals, too, as surface condensaton can occur f moved from a cold storage area to a warm moldng shop. Improve control systems Replace temperature/tme or process ar dew pont control wth systems that montor materal mosture content to save energy and avod overdryng, whch can harm the resn. Cut dryng costs Install nsulaton and mprove sealng. Recover heat and and, where possble, recycle t for space or water heatng. 12 An energy savng gude for njecton molders

13 Managng the operaton People Energy effcency s not all about hardware; the way a moldng plant s operated plays a key role, too. Management and operatonal mprovements can be made at low cost but, as they requre changng the way people work, can be dffcult to mplement and sustan. Empower your people Tranng staff and empowerng them to swtch off machnes, processes and servces can lead to energy reductons of up to 20%. Make a good start Use check sheets to ensure machne start-ups are correctly sequenced to brng the bggest energy users, such as man motors, on lne at the latest possble tme. Ths apples to servces, too; don t turn on chlled water untl the mold requres coolng. Manage processes Process settng has a major mpact on energy use as well as qualty and productvty. So apply scentfc moldng prncples; determne optmum settngs then ensure they are recorded and appled. And make sure machne settngs are not changed wthout management approval. Mnmze consumpton Machnes should be placed n stand-by mode durng temporary producton nterruptons (man motors and downstream equpment swtched off and heaters set back). Shut-down completely durng extended stoppages. Improve mantenance All producton plant must be well mantaned and controls fully functonng to acheve effcent producton. Machne montorng can provde early warnng of essental mantenance; a preventatve mantenance programme s even better. An energy savng gude for njecton molders 13

14 Managng the operaton Improve your buldngs Buldngs and ther assocated servces account for around 8% of total energy use n a typcal njecton moldng operaton. It s a relatvely small contrbuton but there s scope for savngs. Lghtng s not a major energy consumer but lghtng upgrades can carry an addtonal beneft n provdng a clearly vsble sgn of management commtment to energy savng. LED lamps are hghly energy effcent, offer a long lfe, provde hgh qualty llumnaton and requre very lttle mantenance. Heatng has tradtonally been a low energy prorty for njecton moldng stes as process losses provde consderable amounts of space heatng. However, the PCL technques descrbed earler n ths gude can be used to montor and target heatng and coolng energy use. Improvement measures nclude ar leakage reductons, better nsulaton and optmzed settng and control. Survey your ste Ste surveys are a key element n an energy management strategy allowng current ste status to be determned, mprovement optons to be dentfed, and reference ponts for future progress to be set. Your basc energy consumpton data and plant energy map wll provde the nsght needed to allow targetng of the largest energy use areas. Improvement projects should be prepared and mplemented based on ths data and reported n fnancal terms to gan top management support. Few njecton moldng operatons today do not operate a qualty management system; ths same approach can be used as a model for energy nonconformance reportng. 14 An energy savng gude for njecton molders

15 Glossary cos O power factor (actve power/apparent power) kg mass, klogram kva apparent power, klovolt.amps kvarh reactve power, klovolt.amps.reactve hours kw actve power, klowatt kwh energy consumpton, klowatt.hour LED lght emttng dode PCL Performance Characterstc Lne R 2 VSD correlaton coeffcent varable speed drve About ths gude Ths short gude has been produced for ExxonMobl by Appled Market Informaton Ltd n assocaton wth Robn Kent, Founder and Managng Drector of Tangram Technology Ltd. Robn s a recognzed authorty on energy management n plastcs processng and has carred out energy surveys and assessments for more than 450 companes throughout the world. Robn holds a BEng(Hons) degree n Materals Engneerng from Monash Unversty (Australa) and a PhD n Polymer Physcs from the Unversty of Surrey (UK). He s a also Fellow of the Insttute of Materals, Mnerals and Mnng, a Fellow of the Energy Insttute, a Chartered Engneer and a Chartered Energy Manager. More detaled nformaton about energy effcent plastcs processng can be found n the author s book Energy Management n Plastcs Processng - strateges, targets, technques and tools, Elsever, ISBN: The publsher would lke to acknowledge the permsson of the Brtsh Plastcs Federaton ( to use some data n the gude. Tangram Technology Ltd. 35 Brdge Street Htchn SG5 2DF Unted Kngdom Appled Market Informaton Ltd 6 Prtchard Street Brstol BS2 8RH Unted Kngdom Regstered n England No: ExxonMobl Sprngwoods Vllage Parkway Sprng, TX Unted States of Amerca An energy savng gude for njecton molders 15

16 Publshedby ProducedbyAppledMarketInformaton nassocatonwthtangram Technology