LUBRICANTS, MATERIALS AND LUBRICATION ENGINEERING

Sažetak Prošlo stoljeće i kraj tisućljeća obilježeno je bogatim razvitkom tehnike, tehnologije, materijala i maziva. Međutim, zadnje godine prošlog stoljeća pokazale su da nije samo napredak u tehnologiji i ekonomski razvitak od društvenog značaja, nego i očuvanje okoliša i zdravlje ljudi. Štednja energije i prirodnih izvora postala je središnja briga za očuvanje okoliša. Povećana je briga javnosti za maziva zbog toga što svake godine 40-50% od oko 5 milijuna tona rabljenog maziva završava u okolišu a ne reciklira se nekom od metoda. Cilj je razviti tribološke sustave, manje štetne za okoliš koji će istovremeno imati i visoka radna svojstva. To je moguće ostvariti primjenom novih materijala ili prevlaka na dodirnim površinama ili primjenom maziva manje štetnih za okoliš i zdravlje s visokim radnim svojstvima. Osim toga kompjutorizacija i razvitak numeričkih metoda, koji su alat za dizajniranje tribološkog sustava te bogata baza podataka i nove metode održavanja i ispitivanja jamče bolju primjenu.ABSTRACT The past century and the end of the millennium have been marked by a rich development of technique, technology, materials and lubricants. However, the last years of the former century have shown that not only the technological advancement and economic development have social significance, but also environmental protection and human health. Energy saving and natural resources have become the central environmental protection concern. Public concern about lubricants has been raised because each year 40-50% of around 5 million tons of used lubricants ends up in the environment instead of being recycled using any of the available methods. The goal is to develop tribological systems that are less environmentally harmful, while at the same time offering high performances. This is possible to achieve by applying new materials or coats over the contact surfaces or by applying less environmentally and health hazardous lubricants with high performances. Apart from that, development of informatics and numerical methods, as tools for designing the tribological system, as well as a rich database and new maintenance and testing methods, guarantee improved application

METHOD OF METALWORKING EMULSION SPLITTING AS IMPROVEMENT OF TOTAL FLUID MANAGEMENT

Odabir podobne tekućine za obradbu metala nije moguć bez sustavnog razmatranja cijelog životnog vijeka koji uključuje proizvodnju, primjenu i zbrinjavanje. Emulzije za obradbu metala primjenjuju se za hlađenje i podmazivanje pri operacijama obradbe metala kao što su valjanje, izvlačenje, bušenje, brušenje, glodanje, piljenje, itd. Emulzije se dobivaju miješanjem koncentrata emulgirajuće tekućine s vodom u radionicama obradbe metala. Koncentrati moraju biti pažljivo formulirani kako bi se dobila potrebna svojstva radnih emulzija. Oni se sastoje od baznih ulja, emulgatora, inhibitora korozije, aditiva za poboljšanje mazivosti, sredstava protiv pjenjenja, biocida i drugih komponenata. Tijekom primjene radne se emulzije onečišćuju "stranim" uljima, mikroorganizmima i drugim nečistoćama koje skraćuju radni vijek emulzije. Rabljene emulzije mogu sadržavati do 10 % mineralnog ulja, pa ih treba tretirati radi odvajanja mineralnog ulja i drugih nečistoća prije nego što se ispuste u kanalizaciju. Odvajanje ulja iz emulzije za obradbu metala je teško jer one trebaju biti stabilne tijekom cijelog vremena primjene. Rabljena emulzija se može obraditi na mjestu primjene u tehničkim postrojenjima ili se može predati certificiranim tvrtkama. U radu su dani rezultati ispitivanja fizikalno-kemijskih svojstava rabljenih emulzija i postupka cijepanja u skladu s lokalnim i državnim zakonima.Selection of a suitable metalworking fluid is not possible without systematically lifecycle considerations that include material production phase, application phase and disposal phase. Metalworking emulsions are used for cooling and lubricating at metalworking operations like rolling, drawing, boring, grinding, milling, sawing, etc. Emulsions are prepared mixing emulsifying concentrate with water at metalworking plant production. Concentrates must be properly optimised in order to obtain the required emulsion working properties. They consist of base oils, emulsifiers, corrosion inhibitors, lubricating additives, biocides, defoamers and other components. During application into working emulsions inflow “tramp” oil, micro-organisms and other contaminants that shorten its working life. Used emulsions can contain up to 10 % of mineral oil, so they should be treated in sense of the separation of oil and other impurities before they are disposed in sewage system. The separation of oil from metalworking emulsions is difficult because they should be stable during whole time of application. Used emulsion can be treated at the site on technical equipment or can transport to the certificated company. The paper shows examination results of used emulsions physical chemical properties and splitting process concerning local and state laws

POSSIBILITY OF BIODEGRADABLE BASE OILS APPLICATION IN NEAT METALWORKING OILS

Osnovna svojstva čistih ulja za obradbu metala: podmazivanje, hlađenje i ispiranje čestica te ostala svojstva postižu se izborom baznog ulja i aditiva. Glavni faktori koje treba uzeti u obzir pri razvoju tekućina za obradbu metala su, osim razvitka tehnologija obradbe, briga o sigurnosti ljudi pri radu i zaštita okoliša. Stoga se štetne komponente u sastavu ulja nastoje zamijeniti manje štetnima ili biološki lako razgradljivima. Tako se i za bazna ulja mineralnog podrijetla, koja se u primjeni najviše rabe, istražuju moguće zamjene. Mineralna bazna ulja se mogu zamijeniti sintetičkim uljima ili tekućinama, te uljima i mastima prirodnog podrijetla. Prirodna ulja i masti su esteri masnih kiselina, a mogu se primijeniti u izvornoj formi ili prerađena odgovarajućim fizikalnim i kemijskim postupcima s ciljem dobivanja stabilnijih spojeva i definirane kemijske strukture. U ovom su radu osmišljene i ispitane nove formulacije ulja za obradbu metala koje sadrže biorazgradljiva ulja kao zamjenu za mineralna bazna ulja. Također je ispitana mogućnost njihove primjene u nekim procesima obradbe metala.The main properties of neat metalworking oils: lubrication, cooling and chips cleaning and other properties are achieved by base oil and additive selection. The concern of people safety at work and ecological protection become leading factors in metalworking fluid development and application. Besides, the modern fluids should meet severe demands of machine constructions and also take place in total costs lowering of metalworking operation. Increased material disposal costs and also ecological concern lead customers to the selection of less harmful fluids and optimal procedures of their disposal. In metalworking fluids composition there is an influence of cutting down the harmful compounds as are chlorinated paraffines, nitrites, diethanolamine, compounds with aromatic nucleus, borates, etc. Base oils which are commonly of mineral origin can be changed with other types, especially with renewable origin. The aim of this work was to create and examine several new formulations of metalworking fluids containing biodegradable oils as possible replacement of mineral base oils. The possibility of their applications in some metalworking operations was examined as well

METHOD OF METALWORKING EMULSION SPLITTING AS IMPROVEMENT OF TOTAL FLUID MANAGEMENT

Odabir podobne tekućine za obradbu metala nije moguć bez sustavnog razmatranja cijelog životnog vijeka koji uključuje proizvodnju, primjenu i zbrinjavanje. Emulzije za obradbu metala primjenjuju se za hlađenje i podmazivanje pri operacijama obradbe metala kao što su valjanje, izvlačenje, bušenje, brušenje, glodanje, piljenje, itd. Emulzije se dobivaju miješanjem koncentrata emulgirajuće tekućine s vodom u radionicama obradbe metala. Koncentrati moraju biti pažljivo formulirani kako bi se dobila potrebna svojstva radnih emulzija. Oni se sastoje od baznih ulja, emulgatora, inhibitora korozije, aditiva za poboljšanje mazivosti, sredstava protiv pjenjenja, biocida i drugih komponenata. Tijekom primjene radne se emulzije onečišćuju "stranim" uljima, mikroorganizmima i drugim nečistoćama koje skraćuju radni vijek emulzije. Rabljene emulzije mogu sadržavati do 10 % mineralnog ulja, pa ih treba tretirati radi odvajanja mineralnog ulja i drugih nečistoća prije nego što se ispuste u kanalizaciju. Odvajanje ulja iz emulzije za obradbu metala je teško jer one trebaju biti stabilne tijekom cijelog vremena primjene. Rabljena emulzija se može obraditi na mjestu primjene u tehničkim postrojenjima ili se može predati certificiranim tvrtkama. U radu su dani rezultati ispitivanja fizikalno-kemijskih svojstava rabljenih emulzija i postupka cijepanja u skladu s lokalnim i državnim zakonima.Selection of a suitable metalworking fluid is not possible without systematically lifecycle considerations that include material production phase, application phase and disposal phase. Metalworking emulsions are used for cooling and lubricating at metalworking operations like rolling, drawing, boring, grinding, milling, sawing, etc. Emulsions are prepared mixing emulsifying concentrate with water at metalworking plant production. Concentrates must be properly optimised in order to obtain the required emulsion working properties. They consist of base oils, emulsifiers, corrosion inhibitors, lubricating additives, biocides, defoamers and other components. During application into working emulsions inflow “tramp” oil, micro-organisms and other contaminants that shorten its working life. Used emulsions can contain up to 10 % of mineral oil, so they should be treated in sense of the separation of oil and other impurities before they are disposed in sewage system. The separation of oil from metalworking emulsions is difficult because they should be stable during whole time of application. Used emulsion can be treated at the site on technical equipment or can transport to the certificated company. The paper shows examination results of used emulsions physical chemical properties and splitting process concerning local and state laws

BIOLUBRICANTS FROM NATURAL WASTE OILS AND FATS

Porast ekološke svijesti potakao je istraživanja sirovina obnovljivih izvora i u industriji maziva. Zbog sve veće potrošnje raznih vrsta maziva, koja su uglavnom mineralne i sintetske sirovinske osnove, dolazi do akcidentnog, ali i neizbježnog dospijeća znatnih količina maziva u okoliš. Stoga biološki lako razgradiva maziva proizvedena iz prirodnih ulja i masti dobivaju na važnosti ukoliko je njihova primjena moguća. Biološki lako razgradiva maziva proizvedena klasičnim postupkom iz visokokvalitetnih prirodnih ulja i masti mogu biti višestruko skuplja. Niže cijene otpadnih prirodnih ulja i masti čine biološki lako razgradiva maziva konkurentnijima na tržištu. U ovome radu biti će prikazan i postupak kemijske sinteze u kojem je biodizelsko gorivo (smjesa metilnih estera masnih kiselina) sirovina za pripremu TMP (trimetilolpropan) maziva.The increase of ecological concern inspires research of raw materials from renewable sources in lubricant industry. Growing consumption of different lubricant types which are mostly mineral based or synthetic, leads to accidental but unavoidable inflow of considerable lubricants quantity into the environment. Therefore biodegradable lubricants produced from natural oils and fats become important if application is possible. Biodegradable lubricants produced by classical procedure from high quality natural oils and fats can be several times more expensive compared to conventional lubricants. Lower prices of waste natural oils and fats makes biodegradable lubricants much more competitive on the market. In this work the procedure of chemical synthesis, in which biodiesel (mixture of fatty acid methyl esters) is the raw material for TMP lubricants preparation will be presented as well

EXAMINATION OF CORROSION CAUSE OF WELDED PIPES

U procesu proizvodnje šavnih cijevi primjenjuje se tekućina za hlađenje, podmazivanje i ispiranje, koja osim funkcijskih svojstava ima i svojstva zaštite od korozije. Nakon procesa proizvodnje, cijevi se transportiraju u skladište. Tijekom skladištenja, nakon nekog vremena zamijećene su na određenim mjestima na cijevima korozijske pojave. Cilj ovoga rada je bio istražiti uzroke korozije šavnih cijevi. U tu svrhu su kao mogući uzročnici korozije detaljno ispitani kemijski sastav čelika za izradbu cijevi, tehnološki parametri pri njihovoj proizvodnji i mogućnost kontaminacije cijevi tijekom proizvodnje i skladištenja cijevi. Kako se u procesu proizvodnje cijevi rabila emulzija za obradbu metala, pretpostavljeno je da je jedan od mogućih uzročnika korozije i emulzija. Rezultati istraživanja su pokazali da emulzija nije uzrok korozije šavnih cijevi.In the production of welded pipes the fluid for cooling, lubricating and rinsing is applied, which acts as an anticorrosion agent as well. As the production process is finished, pipes are transported to a warehouse. After being stored for a certain period of time, on some pipe areas a corrosion process was observed. The aim of this work was to examine the causes of welded pipes corrosion. Therefore, the chemical composition of the pipe steel, technological parameters of the pipe manufacturing process and the possible pipes contamination during the manufacturing process and storage were examined in detail as possible corrosion causes. As in the pipe production process the metalworking emulsion was used, it was assumed that one of the possible causes of the corrosion could be the emulsion. The results of the examination show that the emulsion did not cause corrosion of welded pipes

Utjecaj sastava sredstava za gašenje na brzinu ohlađivanja

Correct selection of quenching media decreases the risk of tensile stresses, and also cracking and workpiece distortion. High-performance quenching oil must have excellent oxidation and thermal resistance and low sludge formation, must be non-staining and have an elevated flash point and acceptable heat-transfer characteristics. The quenching media contain base oil and different types of additives according to application requirements. As the base oil, it is possible to use mineral oils, synthetic and natural oils separately or in combination. Mineral base oils are widely used because of their advantages in stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous compounds available for use but, besides functional properties, the environmental and safety requirements have a strong influence on components selection. Based on that the barium additives must be replaced with less harmful compounds. Petroleum derivatives should be changed with renewable base stocks that are biodegradable, as the general trend in lubricant development. By changing the composition of quenching oils, base oils and additives, heat transfer characteristics are also changed. In this study the examination results of physical-chemical properties and also cooling characteristics of new quenching oils with different compositions are presented. Cooling curves for different compositions have been evaluated according to ISO 9950 standard.Ispravnim odabirom sredstva za gašenje smanjuje se rizik od nastajanja napetosti kao i pojave pukotina i deformacija obratka. Visokovrijedna ulja za kaljenje moraju imati odlična svojstva otpornosti na oksidaciju i postojanost pri povišenoj temperaturi, niski stupanj stvaranja taloga, što više plamište i prihvatljiva svojstva prijenosa topline. Ulja za kaljenje sastoje se od baznog ulja i različitih vrsta aditiva prema zahtjevima primjene. Kao bazno ulje mogu se primijeniti mineralna ulja, sintetička i prirodna ulja kao i njihove mješavine. Mineralna ulja su u najširoj primjeni zbog bolje stabilnosti u odnosu na prirodna ulja ili zbog niže cijene u odnosu na sintetička ulja. Postoji cijeli niz tvari koje se mogu primijeniti, ali osim radnih svojstava, ekološki i sigurnosni zahtjevi imaju velik utjecaj na izbor sastava ulja za kaljenje. Temeljem toga aditivi na osnovi barija moraju se zamijeniti manje štetnim spojevima. Slijedom općenitog trenda razvitka maziva, mineralna bazna ulja treba zamijeniti baznim uljima iz obnovljivih izvora koja su biorazgradljiva. Promjenom sastava ulja za kaljenje, baznog ulja i aditiva, svojstva prijenosa topline također se mijenjaju. U ovome radu prikazani su rezultati ispitivanja fizikalno kemijskih svojstava a također i svojstva sposobnosti ohlađivanja novih ulja za kaljenje s različitim sastavima. Ispitivanim uljima za kaljenje snimljene su krivulje hlađenja prema normi ISO 9950

MICROBIAL DEGRADATION OF EMULSIONS FOR COOLING AND LUBRICATION AT METALWORKING

Sažetak Kvarenje materijala je problem koji zaokuplja pozornost stručnjaka oduvijek, jer, prije svega, dovodi do velikih ekonomskih gubitaka. Zato su uzroci kvarenja različitih materijala predmet istraživanja već dugi niz godina. Organizirane grupe istraživača većinom u kemijskoj industriji podržane vladinim organizacijama bave se analizama i istraživanjima u tome području. Najveću ulogu u kvarenju ima biološko kvarenje koje je po definiciji svaka neželjena promjena svojstava materijala uzrokovana aktivnostima živih organizama. Biorazgradnja pod nazivom kvarenje, nepoželjan je proces kada je u pitanju proizvodnja i čuvanje materijala, ali je vrlo poželjan proces kada taj materijal postaje otpad, a u pitanju su obično često iste vrste mikroorganizama. Emulzije za hlađenje i podmazivanje pri obradbi metala s velikim udjelom vode do 98% upravo su zato vrlo podložne rastu mikroorganizama. Uljna faza je dobra hranjiva podloga za mikroorganizme kao izvor ugljika. Zbog raspršenih kapljica u vodi dodirna međufazna površina ulje/voda vrlo je velika pa je i površina za rast mikroorganizama dovoljna budući da je voda neophodni medij za razvoj. Pod utjecajem metabolizma mikroorganizama proizvod se mijenja kemijski i funkcionalno zbog čega nastaju sluzave mikrobne nakupine koje uzrokuju stalno čepljenje filtara i uređaja. Iako su koncentrati emulgirajućih tekućina od kojih se spravljaju radne emulzije obično sterilni, što je ispitano i u našem radu, mikroorganizmi se vrlo brzo nakon namješavanja s vodom razvijaju, jer niti okolina niti voda nisu sterilni. Budući da u spremnicima već postoje mikrorganizmi, nove emulzije se brzo inficiraju pa broj mikroorganizama vrlo brzo raste, ako nema antimikrobnog agensa i ako se uređaji i spremnici pravilno ne održavaju. Kako kvarenje napreduje, pjena i sluz postaju vidljivi. Suspendirane nakupine na površini upućuju na infekciju gljivama, a često se pojavljuje miris na amonijak, ali češće na sulfide. Emulzija promijeni boju, pH vrijednost progresivno pada, a isto tako i svojstvo zaštite od korozije. Naša ispitivanja su pokazala da su spremnici za emulzije u dva pogona bili znatno inficirani s više vrsta mikroorganizama, što je dokazano uzgojem na selektivnim hranjivim podlogama, kao i mikrobiološkom kontrolom u ovlaštenim laboratorijima. Ispitivanja su, nadalje, pokazala da se pravilnim postupanjem i održavanjem postrojenja i spremnika uvelike smanjuje kvarenje emulzija a time i zastoj u pogonu, čega je posljedica znatna financijska ušteda.Abstract Material degradation is a problem which has always been occupying the attention of experts, because, first of all, it leads to major economic losses. That is why the causes of deterioration of various materials have been the object of research for a number of years now. Organized groups of researchers, mostly in chemical industry, supported by governmental organizations, are engaged in analyses and research of this particular area. The biggest role in degradation is that of biodeterioration, defined as any unwanted change of the material properties caused by the activities of living organisms. Biodegradation in the form of deterioration constitutes an unwanted process when it comes to the production and storage of materials, but is in turn a most desirable process when the material in question becomes waste, both of these processes usually involving often the same kinds of microorganisms. Emulsions for cooling and lubrication at metalworking with a high water content of up to 98%, and are precisely for this reason most prone to microorganisms growth. The oil phase makes a good nutritional basis for microorganisms as a source of carbon. Because of the tiny drops dispersed in water, the contact interphase oil/water surface is very large, which is why the surface for microorganisms growth is sufficient as well, water being the essential medium for their development. Under the impact of the metabolism of microorganisms, the product changes both chemically and functionally, which is why the slimy microbial growths cause constant clogging of filters and devices. Although the concentrates of emulsifying fluids from which working emulsions are made are usually sterile according also to the results of this paper, microorganisms, after blending with water, develop very soon. That is because neither the environment nor the water are sterile. Since there already are microorganisms in the containers, new emulsions are soon infected and the number of microorganisms grows very fast unless there is an antimicrobial agent present, respectively unless the devices and containers are properly maintained. As deterioration progresses, the foam and the mucilage become visible. Suspended growths on the surface point to infection by fungi, while the smell of ammonia and even more frequently that of sulphides also frequently appears. Emulsion changes colour, while pH progressively decreases, along with the corrosion protection property. Our tests have shown that reservoirs for emulsions in two plants were quite infected with several kinds of microorganisms, which has been proven by cultivation on selective nutritive media, as well as through determination of species in authorized laboratories. The tests have furtherly shown that proper handling and maintenance of the plants and reservoirs considerably reduces emulsion deterioration, and hence also plant standstills, resulting in considerable financial savings