HYDRAULICS THE BASICS

• WHAT IS HYDRAULICS?

• COMPONENTS OF A BASIC HYDRAULIC CIRCUIT

• HOSE ASSEMBLIES

• RUBBER HOSE STRUCTURE LOAD Direction of uid ow ACTUATOR VALVE CONTROL DIRECTIONAL Fig. 1 - A simple hydraulic circuit VALVE RELIEF PRESSURE PUMP At its most basic level, hydraulics is the generation, control generation, control is the basic level, hydraulics At its most pressurised by the use of of power and transmission liquids. by means energy is a system to supply A hydraulic circuit pressure. of a liquid under Sometimes referred to as a “prime mover”, this is an Sometimes referred the purpose device (usually electrical) externally powered of which is to drive the pump. into fluid of the motor Converts the mechanical energy reservoir fluid out of the by drawing the hydraulic power, and sending it into the circuit. This is a fundamental safety device which allows fluid to in the system if the pressure drain back into the reservoir value. exceeds a predetermined

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COMPONENTS OF A BASIC HYDRAULIC CIRCUIT OF A BASIC HYDRAULIC COMPONENTS

WHAT IS HYDRAULICS? WHAT HYDRAULICS - THE BASICS - THE HYDRAULICS

6 HYDRAULIC POWER

TIP REF REM TIP WA REF REM WA S E E S R E E R & R M & N R M N T E T IN E IN N B N B R R G G C E C E I I

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S S circuit. and towhichitreturns afterbeingtransmittedthrough the This isthetankfrom whichthehydraulicfluidisdrawn, actuator typeisahydraulicmotor. systems isacylinderorlinearactuator. Theothercommon load. Themostcommonformofactuatorusedinhydraulic power backintousefulmechanicalenergy tomovethe Hydraulic actuatorsconvertthetransmittedhydraulic control requirements. types withvaryingnumbersofportsdependingonthe hydraulic circuit. Directional control valvescomeinvarious different pathsinorder tocontrol elementswithinthe Allows thefluidfrom oneormore sources toflowalong power inthe system. So increasing theloadorflowratewill result inincreased the circuit. The pumpcausesthehydraulic fluidtoflowatarate(Q)in not bythepump. The pressure (p)inahydraulic circuit iscreated bytheload Hydraulic poweriscalculatedusingthefollowing equation: hydraulics isthecalculationofhydraulicpower (P) One ofthemostfundamentalequationsrelating to Power (kW)=Pressure(bar)xFlowRate(L/min) HYDRAULICS -THEBASICS

600 pxQ P = 600

7 Insert / Tail Insert / Tail Termination End Termination End Termination Ferrule Ferrule Termination End Termination End Termination FERRULE FITTING FERRULE FITTING Uncrimped Uncrimped Ferrule Ferrule Crimped Crimped HOSE HOSE Fig. 3 - Complete hydraulic hose assembly Ferrule Ferrule Crimped Crimped Ferrule Ferrule Uncrimped Uncrimped Fig. 2 - Individual components of a hydraulic hose assembly Fig. 2 - Individual components of a hydraulic An incorrectly made hose assembly can be lethal - only An incorrectly allowed to assemble suitably trained people should be them. The flexible conduit used to transfer fluid from one point from to transfer fluid conduit used The flexible to as a hose system is referred in a hydraulic to another assembly. of hoses assemblies in the overall size and design Variation certain but they do all share or less infinite, is more features. Termination End Termination End Termination Insert / Tail Insert / Tail

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HOSE ASSEMBLIES HYDRAULICS - THE BASICS - THE HYDRAULICS

8 FERRULE FITTINGS HYDRAULIC HOSE pressure isapplied. fitting from beingforcibly ejectedfrom thehosewhen crimped toprovide asafe,secure sealandtoprevent the when thefittingisinserted.Theferrulethen mechanically This isametalsleevewhichfitsovertheendof thehose fitting thatisinsertedintotheendofhose Insert (sometimescalledaTail) -thisisthepartof assembly tooneoftheportsonasystemcomponent Termination End-thisconnectstheendofhose comprises of: shapes, sizes,thread typesetc.Ahydraulicfittingtypically two endsofthehose.Thesefittingscomeinavariety Each assemblywillhaveafittingattachedtoeachofthe are covered inmore detaillaterinthisbooklet. and covertypes.Thesevariationsinhydraulichosetypes different diameters,pressure ratings,reinforcement types two partsofthehydrauliccircuit. Hydraulichosescomein The hydraulichoseistheflexibleconnectionwhichjoins components: A basichoseassemblyismadeupofthefollowing HYDRAULICS -THEBASICS

9 Properties High resistance to mineral and High resistance biodegradable oils and fuels Resistant to a wide range of fluids oil, fuel and High temperature, chemical resistant Used for phosphate ester based fluids Reinforcement  Cover  Reinforcement Tube Tube Material Tube NBR (Nitrile Butadyene Rubber) CR (Chloroprene)Polyammide Mineral oil resistant PTFE EPDM (Ethylene Diene Propylene Rubbers) Table 1 – Typical tube materials and their properties 1 – Typical Table The innermost layer of the hose, the tube’s function is to of the hose, the tube’s The innermost layer containment of full fluid and provide convey the hydraulic the hydraulic fluid. for the tube is usually a synthetic The material used resist chemical for its ability to rubber chosen specifically fluid(s). degradation by the intended hydraulic shown in the are tube materials and their uses Typical below table: The structure of hydraulic hoses comes in a variety of hoses comes in of hydraulic The structure always will almost the overall composition forms, but arrangement: to the following conform

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RUBBER HOSE STRUCTURE RUBBER HYDRAULICS - THE BASICS - THE HYDRAULICS

10 REINFORCEMENT Braided Hose to classifythehoseintooneoffollowingtwofamilies: Hose reinforcement comesintwobasicformsandisused depends ontheintendedworkingpressure ofthehose. The typeandamountofhosereinforcement required the hydraulicfluidonhoseduringoperation. strength pressure andintegritytowithstand theinternal of The reinforcement provides thehosewithstructural hose’s structure isthereinforcement. on itsown.Forthisreason, thenextelementofahydraulic rubbertubewouldnotsurvivelong systems, theinternal Due tothehighpressures encountered inhydraulic or ametalwire weave forhigherpressure applications. or Polyester)forlowpressure applications upto100bar, The wovenmaterialcan beatextile(eg:Nylon,Aramide to containthepressures rubbertube. ontheinternal Hoses withbraidedreinforcement useawovenmaterial Fig. 4-Typical wirebraidedhosestructures HYDRAULICS -THEBASICS

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Fig. 4 - Typical wire spiral hose structure Fig. 4 - Typical When a higher level of pressure resistance is required, is required, resistance When a higher level of pressure of steel wire by layers is provided the reinforcement spirals. or six in either four usually present are spirals Wire may be as cases there layers, but in some extreme many as ten layers. spiral is wound in the opposite Each layer of wire be will only ever one, and there to the previous direction to balance the forces an even number of layers in order within the structure. spiral layers are As with braided hoses, the individual wear. separated by adhesive rubber layers to prevent Wire braided hoses usually have either one or two layers either one or two usually have braided hoses Wire many may have as in some cases but of reinforcement, as three. they are present, are braided layers When multiple which prevents rubber by a layer of adhesive separated other and causing rubbing against each the layers from wear. Spiral Hose HYDRAULICS - THE BASICS - THE HYDRAULICS

12 TIP REF REM WA S E E R & R M N T E IN N B R G C E I

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K S Smooth RubberCover The maincategoriesofcovertypeare asfollows: temperature resistance. more safetycriticalfactorssuchasfire, abrasionand factors suchaseconomyofmanufacture andcolour, to selected foravarietyofreasons rangingfrom simple world.Hosecovermaterialsareexternal manyandvaried, The outercoverofahydraulichoseisitsinterface withthe Table 2–Typical pressureapplicationsbasedonhosereinforcementtype by thereinforcement typeasshownbelow: Typically, thepressure applicationofahosecanbejudged required performanceofthehose. combination ofbothreinforcement typesdependingonthe It isalsopossibletohavehosesconstructedwitha High Pressure High Pressure Low Pressure mould. with steamathightemperatures plastic orwithexternal The outerrubbercoverisvulcanizedindirect contact Applications Applications Applications Application High /Very Medium / Pressure HYDRAULICS -THEBASICS rsueRtn Reinforcement Pressure Rating 100 –300bar 0 a Wire SpiralHose > 200bar < 100bar Textile Braided Wire Braided Hose Hose Type

13 e Dirt Ozone UV Rays Abrasion Fire Temperatur This option is usually only used in situations where a in situations where This option is usually only used braid is used, often on PTFE hoses. stainless steel wire A woven fabric (often impregnated with rubber adhesive) with rubber impregnated A woven fabric (often weight minimal in situations where cover may be used Due to its relatively required. are and heat dissipation usually only used in this type of cover is low strength, hoses. low / medium pressure The outer rubber cover is wrapped in a wet nylon tape wrapped in a rubber cover is The outer tolerances and for tighter allowing during vulcanization, When the nylon of cover defects. chance a reduced making it its imprint, will retain the hose tape is removed easily distinguishable.

Coverless Fabric Braided Cover Fabric Braided Wrapped Rubber Cover Rubber Wrapped • • • • • Hydraulic systems are used in a huge variety of Hydraulic systems are place in locations and applications, many of which take less than ideal for the materials used that are environments in hydraulic hose construction. best line of defence The cover of a hose is its first and against these harsh conditions. type of cover can become a potential Choosing the wrong time-bomb for the system as a whole. to hoses are: threats The biggest environmental •

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14 TIP REF REM WA TIP REF REM WA S E E R S E E R & R M N & R M N T E IN T E IN N B N B R R G G C E C E I I

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S S applications. specifically designedto meettheneedsofthesespecialist Manuli hasanextensive rangeofhoseswhichhavebeen make itaworthwhileinvestment. extended lifeandsuperiorperformanceofthehose would hose maybemore expensivepiece-for-piece, butthe cold resistance wouldbethebetterchoice.Thespecialist Selecting aspecialisthosewithenhancedabrasion and effective. long andwouldneedreplacing more oftenthaniscost In theseconditionsageneralusehosewouldnot survive temperature. high degree ofabrasionaswellextremes ofcold For example,inforestry, hosesare subjecttoaparticularly which willattackthehosecoverinspecificapplication. high resistance tooneor more oftheenvironmental factors These specialistcompoundswillusuallyhaveaparticularly required. In thesesituationsaspecialistcovercompoundmaybe others combined. factor whichisoverwhelminglymore significantthanallthe However, insomeapplicationsthere isoneenvironmental options whichare suitableforthesetypesofenvironments. Manuli offers severalhigh-quality, general-usecover use. enough toseethehosethrough therigoursofday-to-day In theseinstancesahigh-qualitycovercompoundwillbe may bepresent toaparticular extreme. in combinationtoattackthehose-althoughnoneofthem on hosecovercompounds,andinmanycasestheywillact Each oftheaboveconditionshasitsowndetrimentaleffect HYDRAULICS -THEBASICS

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SHARC Manuli’s specialist cover compounds are typically designed typically designed compounds are cover specialist Manuli’s of the the requirements exceed and greatly to meet international standards. relevant ozone resistant high abrasion and the Manuli For example, shown perform as and ShieldMaster) SHARC covers (TUFF, below:

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Fig. 5 - Abrasion and ozone resistance performance of Manuli cover compounds Fig. 5 - Abrasion and ozone resistance performance

Conventional

0.5 - Abrasion resistance test performed to test conditions required by ISO 6945 - 2,000 cycles with a mass of 2.5kg - lower values are better Abrasion resistance - 20% cover elongation - higher values are better concetration, at 40°C, - Ozone resistance test performed to test conditions required by ISO 27326 - 50 pphm Ozone 1 2 EN 853 EN HYDRAULICS - THE BASICS - THE HYDRAULICS

16 www.manuli-hydraulics.com