hydraulic lines and fittings

7/28/2019 Hydraulic Lines and Fittings

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Hydraulic Lines and

Fittings


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Purpose of Lines

All hydraulic lines are designed to transmit fluid

from one place to another without leaking

Lines are built to withstand pressure, vacuum,and the hydraulic fluids used in the system

There are two different types: Flexible and Steel

All lines have fittings on the end of them to

connect to hydraulic devices


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Steel Lines

Steel lines (tubing) is used when there is little

vibration, limited space, no movement of the

lines, and/or frequent replacement is neededSteel lines have two common type of

connectors: JIC Flare and Flareless

Compression


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JIC Flare Fitting

Usually has a nut, backup sleeve, and a 37

flare of the line

This type is often used on the outside ofcylinders on construction

or farm equipment

Can also be used forreturn lines


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Flareless Compression Fitting

A special type of ferrule that replaces the flare

Bites into metal to provide a positive seal that

wont slip

Can be used for return lines

Also used for pressure lines on the frame


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Flexible Lines

Many different types and materials used to make

flexible lines

All flex lines are measured by the insidediameter of the line

Can use fraction measurement or dash size

All lines rated in working pressure, vacuum, or

burst pressure


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Line Sizes

Lines can be from 3/16 to 4 in size (Inside

Diameter or ID)

Dash size is determined by taking the numberand making it the numerator of the fraction 16

-3 hose size is 3/16 (3/16)

-12 hose size is 12/16 or (12/16)

Largest is64 size (4)


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Hose Materials

Most hoses have an outer covering, a cloth orwire braid, and an inner material to prevent

leakageCan bedamaged byhigh temperatures

Neoprene or Buna-N used in most hydraulichoses

Wire braids added to handle high pressures


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SAE Hose Designations

SAE Number Braids Pressure

100R1 1 Wire 500 2500 PSI

100R2 2 Wire 1200 3500 PSI

100R3 2 Cloth 375 1250 PSI

100R4 1 Wire Spiral 50 300 PSI

100R6 1 Cloth 300 600 PSI

100R12 4 wire 2500 5000 PSI


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Hose Maintenance - Replacement

Leaks at fitting or in hose. (Leaking fluid is a fire

hazard.)

Damaged, cut, or abraded cover. (Anyreinforcement exposed.)

Kinked, crushed, flattened, or twisted hose.

Hard, stiff, heat cracked, or charred hose.


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Hose Maintenance - Replacement

Blistered, soft, degraded, or loose cover.

Cracked, damaged, or badly corroded fittings.

Fitting slippage on hose.


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Hose Routing

Make sure to install hoses so that they are as

close as possible to the component

This keeps the line from being pulled off

Keep a little slack in all lines to allow movement


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Hose Routing

Make sure the line flexes in and out rather than

up and down

Minimize movement if possible


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Hydraulic Fittings

Several types of fittings used on hydraulic

components

NPTF (National Pipe Tapered - Fuel)

JIC (37)

O-Ring Boss

O-Ring Flange Flat Faced O-Ring (Forseal)


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NPTF Fittings

The most commonly used on older equipment

Seals by a tapered thread

The farther you turn it, the better it seals

Standard pipe thread can leak without the use of

pipe sealant


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JIC Fittings

The next most common fitting used

Seals by seating an angled flared area against

another angled area

Can leak if the seating area

is scratched

Hose end can be easily

disassembled and repositioned


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O-Ring Boss

Uses an O-Ring to seal the

fitting

Often has a jam nut that is usedto compress the o-ring

Permits turning an angled fitting

to a desired position withoutleaking


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O-Ring Flange Fittings

Primarily used on hose ends

Has a round flat surface that uses an o-ring to

seal it against the component

Is compressed by a separate backup flange that

usually has 4 bolts

Can leak if the flange is bent or

the surface is scratched


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Flat Faced O-Ring Fittings

Also called Forseal fittings

Similar to JIC except the seating

area is flat and the fitting has ano-ring in it

Can leak if the face is deeply

scratched or o-ring is bad

Newest type used on hydraulic

equipment


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Fitting Installation - NPTF

Inspect port components to ensure thatmale and female threads are free ofnicks, burrs, dirt, etc.

Apply sealant/lubricant to male pipethreads. With any sealant, the first fewthreads should be left uncovered toavoid system contamination. If Teflontape is used, it should be wrapped 1-1/2 turns in a clockwise direction whenviewed from the end.


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Fitting Installation - NPTF

Screw Fitting into female pipe portto finger tight position.

Wrench tighten fitting to theappropriate Turns From FingerTight in the next chart, making

sure the tube end of the shapedfitting is aligned to receiveincoming tube or hose assembly.


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Turns From Finger Tight Chart

Pipe Thread Size Turns From Finger Tight

2 2.0 - 3.0

4 2.0 - 3.06 1.5 - 3.0

8 2.0 - 3.0

12 2.0 - 3.0

16 1.5 - 2.5

20 1.5 - 2.5

24 1.5 - 2.5

32 1.5 - 2.5


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Fitting Torque O-Ring Boss

Thread Size Assemly Torque

(in-lb)

Assemly Torque

(ft-lb)

2 85 - 95 7 - 8

3 160 - 180 13 - 154 205 - 235 17 - 19

5 245 - 275 21 - 23

6 300 - 340 25 - 29

8 545 - 595 46 - 50

10 1010 - 1100 85 - 95

12 1250 - 1350 105 - 115

14 1675 - 1825 139 - 151

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