Pelincir

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Pelincir merupakan bahan (biasanya cecair) yang diletakkan antara dua permukaan bergerak bagi mengurangkan geseran dan haus antaranya. Pelincir memberikan lapisan nipis pelindung yang membenarkan kedua permukaan berasingan dan kekal "licin", dengan itu mengurangkan geseran antara keduanya. Pelincir bertindak secara kimia dengan semua permukaan dengan itu hubungan hanya berlaku dengan pelincir yang licin dan bebas. Melalui proses ini, zarah mengkakis dilarutkan dalam pelincir, dengan itu menjadikannya pelarut dan pembersih yang baik. Pelincir berasaskan petroleum seperti Vaseline cenderung melarutkan keluaran petroleum seperti getah dan plastik, sementara pelincir berasaskan air cenderung melarutkan kimia berkutub (seperti air dan kotoran); sebab itu tambahan digunakan. Pelincir perlu digantikan apabila kadar bahan larut mencapai peringkat tepu, kerana ketidakupayaan melarutkan kotoran tambahan membenarkan zarah mengkakis bergesel dengan atau melekat pada permukaan bergerak, dengan itu mencipta ruang bagi hubungan fizikal antara keduanya. Pelarut yang melarutkan permukaan (seperti Vaseline pada getah) menghilangkan kelebihannya dengan menghakis permukaan licin dengan keupayaan melarutnya,dengan itu melemahkan keutuhan struktur, permukaan licin, dan mencemar keseluruhan sistem. Ia juga mampu menghilangkan gula-gula getah dari rambut anda.

Salah satu kegunaan terbesar pelincir, dalam bentuk minyak enjin, adalah melindungi enjin pembakaran dalam dalam kenderaan bermotor dan perkakasan berkuasa.

Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral oils) and less than 10% additives. Vegetable oils or synthetic liquids such as hydrogenated polyolefins, esters, silicone, fluorocarbons and many others are sometimes used as base oils. Additives deliver reduced friction and wear, increased viscosity, improved viscosity index, resistance to corrosion and oxidation, aging or contamination, etc.

Lubricants such as 2-cycle oil are also added to some fuels. Sulfur impurities in fuels also provide some lubrication properties, which has to be taken in account when switching to a low-sulfur diesel; biodiesel is a popular diesel fuel additive providing additional lubricity.

Non-liquid lubricants include grease, powders (dry graphite, PTFE, Molybdenum disulfide, tungsten disulfide, etc.), teflon tape used in plumbing, air cushion and others. Dry lubricants such as graphite, molybdenum disulfide and tungsten disulfide also offer lubrication at temperatures (up to 350 °C) higher than liquid and oil-based lubricants are able to operate. Limited interest has been shown in low friction properties of compacted oxide glaze layers formed at several hundred degrees Celsius in metallic sliding systems, however, practical use is still many years away due to their physically unstable nature.

Another approach to reducing friction and wear is to use bearings such as ball bearings, roller bearings or air bearings, which in turn require internal lubrication themselves, or to use sound, in the case of acoustic lubrication.

In addition to automotive and industrial applications, lubricants are used for many other purposes, including as a personal lubricant, bio-medical applications (e.g. lubricants for artificial joints) and others.

Matlamat[sunting | sunting sumber]

Pelincir melakukan fungsi penting di bawah:

  • Kekalkan bahagian bergerak berasingan
  • Mengurangkan geseran
  • Memindahkan haba
  • Menyingkir bahan cemar dan serpihan
  • Memindah kuasa
  • Melindungi dari kehausan
  • Menghalang hakisan
  • Mengurangkan risiko asap dan kebakaran objek

Kekalkan bahagian bergerak berasingan[sunting | sunting sumber]

Pelincir biasanya digunakan bagi memisah bahagian bergerak dalam sistem. Ini memberi kebaikan bagi mengurangkan geseran dan kelesuan permukaan bersama mengurangkan penghasilan haba, bising beroperasi dan gegaran. Pelicin melakukannya dalam beberapa bentuk. Cara paling biasa adalah dengan membentuk halangan fizikal contoh. lapisan nipis pelicin yang memisahkan bahagian bergerak. Ini diistilahkan sebagai pelicin hidrodynamik. Dalam kes tekanan permukaan yang kuat atau suhu tinggi lapisan cecair adalah lebih nipis dan sesetengah kuasa dipindahkan antara permukaan melalui pelicin. Ini diistilahkan sebagai pelicin elasto-hidrodynamik.

Mengurangkan geseran[sunting | sunting sumber]

Biasanya geseran pelicir kepada permukaan adalah kurang berbanding geseran permukaan pada permukaan tanpa sebarang pelicir. Dengan itu kegunaan pelincir mengurangakn geseran keseluruhan sistem. Pengurangan geseran mempunyai kebaikan mengurangkan haba dan mengurangkan pembentukan partikle haus termasuk meningkat keberkesanan keseluruhan. Pelincir mungkin mengandungi tambahan yang dikenali sebagai pengubah geseran yang mengikat kepada permukaan logam secara kimia bagi mengurangkan geseran walaupun apabila tidak terdapat pelincir mencukupi hadir dalam pelincir hidrodynamik, conton. menlindungi jaluran valve pada enjik kereta semasa mula dihidupkan.

Memindahkan haba[sunting | sunting sumber]

Kedua-dua pelicir gas dan cecair mampu mengalih haba. Bagaimanapun, pelincir cecair adalah lebih berkesan disebabkan keupayaan haba khusus tingginya. Biasanya pelincir cecair sentiasa dikitar dari dan kepada kawasan paling sejuk dalam sistem, sungguhpun pelicir mungkin juga digunakan bagi memanaskan selain menyejukkan apabila pengawalan haba diperlukan. Aliran kitaran ini turut menentukan jumlah haba yang dibawa keluar dalan jenis unit yang digunakan pada masa tertentu. Sistem aliran tinggi mampu membawa banyak haba dan mempunyai kelebihan tambahan bagi mengurangkan tekanan haba pada pelincir. Dengan itu pelincir lebih murah boleh digunakan. Kekurangan utamanya adalah aliran tinggi biasanya memerlukan pam lebih besar dan unit penyejuk lebih besar. Kelemahan kedua adalah sistem aliran tinggi bergantung kepada kadar aliran bagi melindungi pelincir dari tekanan haba cenderung kepada kegagalan membinasakan semasa kegagalan sistem mengejut. Kereta pengcajturbo disejukkan minyak adalah contoh biasa. Pencaj turbo menjadi merah berpijar semasa beroperasi dan minyak yang menyejukkannya hanya selamat kerasa tempoh ia berada dalam sistem amat pendek contoh . kadar aliran tinggi. Sekiranya sistem ditutup mengejut seperti (berhenti dikawasan servis selepas memandu laju dan menghentikan enjin) minyak yang di dalam pencaj turbo akan serta merta teroksida dan menyumbat laluan minyak dengan mendakan. Selepas sekian lama mendakan ini mampu menyumbat lalaun minyak sepenuhnya, mengurangkan penyejukkan dengan itu menyebabkan pencaj turbo mengalami kegagalan fizikal sepenuhnya biasanya dengan bering lekat. Pelincir tidak mengalir seperti gris & dan pasta tidak begitu berkesan sebagai pengalir haba sungguhpun ia ada menyumbang kepada pengurangan penghasilan haba pada mulanya.

Menyingkir bahan cemar dan serpihan[sunting | sunting sumber]

Lubricant circulation systems have the benefit of carrying away internally generated debris and external contaminants that get introduced into the system to a filter where they can be removed. Lubricants for machines that regularly generate debris or contaminants such as automotive engines typically contain detergent and dispersant additives to assist in debris and contaminant transport to the filter and removal. Over time the filter will get clogged and require cleaning or replacement, hence the recommendation to change a car's oil filter at the same time as changing the oil. In closed systems such as gear boxes the filter may be supplemented by a magnet to attract any iron fines that get created.

It is apparent that in a circulatory system the oil will only be as clean as the filter can make it, thus it is unfortunate that there are no industry standards by which consumers can readily assess the filtering ability of various automotive filters. Poor filtration significantly reduces the life of the machine (engine) as well as making the system inefficient.

Memindah kuasa[sunting | sunting sumber]

Pascal's law is at the heart of hydrostatic power transmission. Hydraulic fluids comprise a large portion of all lubricants produced in the world.

Melindungi dari kehausan[sunting | sunting sumber]

Lubricants prevent wear by keeping the moving parts apart. Lubricants may also contain anti-wear or extreme pressure additives to boost their performance against wear and fatigue.

Menghalang hakisan[sunting | sunting sumber]

Good quality lubricants are typically formulated with additives that form chemical bonds with surfaces to prevent corrosion and rust.

Sejarah[sunting | sunting sumber]

Romans used rags dipped in animal fat to lubricate wagon wheels; however the science of lubrication (tribology) really only took off with the industrial revolution in the nineteenth century.

Komposisi umum[sunting | sunting sumber]

Lubricants are generally composed of a majority of base oil and a minority of additives to impart desirable characteristics.

Jenis pelarut[sunting | sunting sumber]

Pelarut cecair[sunting | sunting sumber]

Liquid lubricants may be characterized in many different ways. One of the most common ways is by the type of base oil used. Following are the most common types.

  • Lanolin (wool grease, natural water repellant)
  • Water
  • Mineral oils
  • Vegetable (natural oil)
  • Synthetic oils
  • Others

Note: although generally lubricants are based on one type of base oil or another, it is quite possible to use mixtures of the base oils to meet performance requirements.

Lanolin[sunting | sunting sumber]

A natural water repellent, lanolin is derived from sheep wool grease, and is an alternative to the more common petro-chemical based lubricants. This lubricants are also corrosion inhibitors, protecting against rust, salt and acids.

Air[sunting | sunting sumber]

Water can be used on its own, or as a major component in combination with one of the other base oils. Commonly used in engineering processes, such as milling and lathe turning.

Minyak galian[sunting | sunting sumber]

This term is used to encompass lubricating base oil derived from crude oil. The American Petroleum Institute (API) designates several types of lubricant base oil identified [1] as:

- Manufactured by solvent extraction, solvent or catalytic dewaxing, and hydro-finishing processes. Common Group I base oil are 150SN (solvent neutral), 500SN, and 150BS (brightstok)

  • Group II – Saturates >90% and sulfur <0.03%, and SAE viscosity index >80 to <120

- Manufactured by hydrocracking and solvent or catalytic dewaxing processes. Group II base oil has superior anti-oxidation properties since virtually all hydrocarbon molecules are saturated. It has water-white color.

  • Group III – Saturates > 90%, sulfur <0.03%, and SAE viscosity index >120

- Manufactured by special processes such as isohydromerization. Can be manufactured from base oil or slax wax from dewaxing process.

Such as naphthenics, PAG, esters, and etc.

In North America, Groups III, IV and V are now described as synthetic lubricants, with group III frequently described as synthesised hydrocarbons, or SHCs. In Europe, only Groups IV and V may be classed as synthetics.

The lubricant industry commonly extends this group terminology to include:

  • Group I+ with a Viscosity Index of 103 - 108
  • Group II+ with a Viscosity Index of 113 - 119
  • Group III+ with a Viscosity Index of >= 140

Can also be classified into three categories depending on the prevailing compositions: - Paraffinic - Naphthenic - Aromatic

Minyak sayuran (asli)[sunting | sunting sumber]

These are primarily triglyceride esters derived from plants and animals. For lubricant base oil use the vegetable derived materials are preferred. Common ones include high oleic canola oil, castor oil, palm oil, sunflower seed oil and rapeseed oil from vegetable, and Tall oil from animal sources. Many vegetable oils are often hydrolyzed to yield the acids which are subsequently combined selectively to form specialist synthetic esters.

Minyak sintetik[sunting | sunting sumber]

Pelincir pejal[sunting | sunting sumber]

Teflon or PTFE[sunting | sunting sumber]

Teflon or PTFE is typically used as a coating layer on, for example, cooking utensils to provide a non-stick surface.

Mineral[sunting | sunting sumber]

Graphite, hexagonal Boron nitride ([2]), Molybdenum disulfide and Tungsten disulfide are examples of materials that can be used as solid lubricants often to very high temperature. The use of such materials are still restricted by their poor resistance to oxidation (for example, molybdenum disulfide can only be used up to 350C in air, but 1100 in reducing environments).

Lihat juga[sunting | sunting sumber]

Rujukan[sunting | sunting sumber]

Nota[sunting | sunting sumber]

Sumber[sunting | sunting sumber]

  • API 1509, Engine Oil Licensing and Certification System, 15th Edition, 2002. Appendix E, API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils (revised)

Pautan luar[sunting | sunting sumber]