Uganda Petroleum Institute

8/3/2019 Uganda Petroleum Institute

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UGANDA PETROLEUM INSTITUTE-KIGUMBA


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Questiony a) Explain the phys ical propert ies of hydr au lic fluids.y b) Explain one method of how to determ ine the

v iscosity of a fluid.


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Properties of Hydraulic Fluids

y H ydrau lic fluids are a large gro up of liquids made of m an y kinds of chem icals. They are used in au tomob ile au tom atic

transm issions, brakes, and power steer ing; fork lift tr ucks,tractors; b ulldozers; industr ial machinery; and airplanes.y The three most commo n types of hydr au lic fluids are;mineral oil, organophosph ate ester, and poly alphaolef in .

One hydr au lic fluid th at man y are f amiliar with is brakefluid; and, a well-known subst ance ofte n made in tohydr au lic fluid is canola oil.


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Phy sical properties are;y Energy Efficiency

H ydrau lic fluids are able to tr ansfer energy be cause they ha ve the ability to flow more smoothly th an solids fromlocation to lo cation when they exper ience force. Forexample, a large f ire hose h as built up press ure. Whe n the water is released and str ikes a perso n at such a great velocity, th at indi v idua l can be knocked over. The w ater isable to tr ansfer the e nergy th at was in the hose all the w a y to the indi v idua l, effecti vely main tainin g the mome ntum.H ydrau lic fluids must be able to tr ansfer energy like th iseff iciently. Ineff icient fluids lose mome ntum quic kly,causing a loss of energy.


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C onty Comp ressi o n Co nsistency

H ydrau lic fluids must re act to compress ion in exactly

the s ame wa y every t ime they exper ience the s ameamoun t of force in the s ame sett ing. Whe n the s ameamoun t of press ure is appl ied, if a fluid compressesmore at one mome nt and compresses less at another

mome nt, the hydr au lic system w ill f unc tion un pred ictably. Petrole um cann ot be used as a hydr au lic fluid be cause it does not beh a ve rel iably when compressed.


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C onty Lub ricity and wear red u cti o n

H ydrau lic systems contain mov ing parts th at come

into contact with e ach other and m ust be l ubr icated in order to preve nt d amage. Some hydr au lic fluids ha veadd iti ves th at red uce the we ar and te ar on thehydr au lic system; some fl uids must completely preve nt

met al to met al contact.


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C onty S ealant

H ydrau lic fluids are somet imes used to se al off

different areas. Fluids and gases can leak out of themechanica l equipme nt, espe cially when met als are in contact with e ach other. D ifferent hydr au lic fluids aredes igned to se al off specif ic leaks(gre ase). Leaking

mechanica l systems be come less eff icient and re qui remore fl uids to r un properly, and m ight eve n becomedamaged.


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C onty Coo ling

Hot e quipme nt can be cooled using hydr au lic fluids.

Some hydr au lic fluids are able to absorb he at and carry it a wa y from the m achinery, preve nting the m achinery from overhe ating. This, obv iously, sa ves the m achinery from d amage.


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C onty P

rop er Visc o sity This refers to a balanced s itua tion of ha v ing a v iscosity which is high enough to g i ve good se aling and properlubr ication , while not be ing too h igh as to cause signif ican tpress ure drops, de creased system eff icienc y, or h igh power

consumpt ion .y H igh visc o sity index V iscosity index is a measure of the degree of change in the v iscosity of a fluid as changes in temper ature occu r. Thehigher the v iscosity index, the less the fl uid th ins when itstemper ature increases, and the less the fl uid th ickens when its temper ature de creases. V iscosity Index be comes a moreimport an t f actor in a hydr au lic fluid s performance whe n there are wide fluctua tions in the fl uid s temperature.


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y Comp ati b le with syste mComp atibility of the hydr au lic fluid with the system s

compo nents is also very import an t. The fl uid m ust berelati vely inert in its re action to the m ater ials of construc tion and m ust be comp atible with the system sseals, f inishes, et c.


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C onty T

her m al stab

ility It sho uld be therm ally stable in moder n hydr au lic systems work ing in extreme conditions of load and temper ature as th isimproves system rel iability and clean liness.

y Excellent air release and anti-f o am p rop ertiesQuick air rele ase helps m inimizing ca v itation and slow ox idation ,main tainin g system and fluid perform ance.

y N o n-fla mm ab ility ( H igh flash po int)This is often an essential property of the f l uid. Some appl ications

requi re a specially designed f ire res istan t fluid. Flamm ability isusua lly measured by fl ash and f ire po in ts.


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C onty L o w sp ecific gravity

The h igher the spe cif ic gra v ity of the fl uid, the lower

the over all oper ating eff icienc y.y L o w po u r po int

This is import an t for fluids used o utdoors in coldclimates. Po ur po int is a measure of the lowest

temper ature at wh ich a fluid can be po ured. Po urpo ints sho uld be at least 10-20F below the lowestactua l oper ating temper ature.


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Question 4bExplain one method of how to determ ine v iscosity of a

fluid.


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v iscosit yy Def inition:

V iscosity is a measure of a fluid s resistance to flow.

The h igher the v iscosity, the gre ater the res istance toflow. The lower the v iscosity, the lower the res istanceto flow. A fluid s v iscosity changes with temper ature. As a fluid s temperature increases, its v iscosity

decreases. Con versely, as a fluid s temperaturedecreases, its v iscosity increases.


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M ars h funnelThe Marsh f unn el v iscosity is a simple dev ice for me asuring v iscosity from the t imeit t akes a known volume of l iquid to f low from the b ase of a cone thro ugh a shorttube. It is part icularly used by m ud engineers to check the qua lity of dr illing fluid.

y It consists of a cone 6 inches (152 mm) across and 12 inches in he ight (305 mm ) tothe apex of wh ich is f ixed a tube 2 inches (50.8 mm ) long and 3/16 inch (4.76 mm )in terna l diameter. A mesh is f ixed near the top across h alf the cone.


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V iscosit y measurement procedureIn use, it is held vert ically and end of the t ube closed

with a f inger. The l iquid to be me asured is poured

thro ugh the mesh. (Th is removes an y part icles which m ight blo ck the t ube.) To take themeasureme nt, the f inger is released as a stop clockis started, and the l iqui d is allowed to r un in to a measuring container. The t ime in seconds isrecorded as a measure of the v iscosity.

Below is the form ula for v iscosity calcu lation;


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Formula= (t - 25)

where = effecti ve v iscosity in centipo ise

= density in g/cmt = qua rt f unn el time in seconds


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