1. Hydraulic Lines and Fittings
Lecture 8

2. 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

3. Steel Lines
Steel lines (tubing) is used when there is little vibration, limited space, no movement of the lines, and/or frequent replacement is needed
Steel lines have two common type of connectors: JIC Flare and Flareless Compression

4. JIC Flare Fitting
Usually has a nut, backup sleeve, and a 37° flare of the line
This type is often used on the outside of cylinders on construction or farm equipment
Can also be used for return lines

5. Flareless Compression Fitting
A special type of ferrule that replaces the flare
Bites into metal to provide a positive seal that won’t slip
Can be used for return lines
Also used for pressure lines on the frame

6. Flexible Lines
Many different types and materials used to make flexible lines
All flex lines are measured by the inside diameter of the line
Can use fraction measurement or dash size
All lines rated in working pressure, vacuum, or burst pressure

7. Line Sizes
Lines can be from 3/16” to 4” in size (Inside Diameter or ID)
Dash size is determined by taking the number and making it the numerator of the fraction 16
-3 hose size is 3/16” (3/16)
-12 hose size is 12/16” or ¾” (12/16)
Largest is –64 size (4”)

8. Hose Materials
Most hoses have an outer covering, a cloth or wire braid, and an inner material to prevent leakage
Can be damaged by high temperatures
Neoprene or Buna-N used in most hydraulic hoses
Wire braids added to handle high pressures

9. 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

10. Hose Maintenance - Replacement
Leaks at fitting or in hose. (Leaking fluid is a fire hazard.)
Damaged, cut, or abraded cover. (Any reinforcement exposed.)
Kinked, crushed, flattened, or twisted hose.
Hard, stiff, heat cracked, or charred hose.    

11. Hose Maintenance - Replacement
Blistered, soft, degraded, or loose cover.
Cracked, damaged, or badly corroded fittings.
Fitting slippage on hose.

12. 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

13. Hose Routing
Make sure the line flexes in and out rather than up and down
Minimize movement if possible

14. 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)

15. 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

16. 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

17. O-Ring Boss Uses an O-Ring to seal the fitting
Often has a jam nut that is used to compress the o-ring
Permits turning an angled fitting to a desired position without leaking

18. 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

19. Flat Faced O-Ring Fittings
Also called Forseal fittings
Similar to JIC except the seating area is flat and the fitting has an o-ring in it
Can leak if the face is deeply scratched or o-ring is bad
Newest type used on hydraulic equipment

20. Fitting Installation - NPTF
Inspect port components to ensure that male and female threads are free of nicks, burrs, dirt, etc.
Apply sealant/lubricant to male pipe threads. With any sealant, the first few threads should be left uncovered to avoid system contamination. If Teflon tape is used, it should be wrapped 1-1/2 turns in a clockwise direction when viewed from the end.

21. Fitting Installation - NPTF
Screw Fitting into female pipe port to finger tight position.
Wrench tighten fitting to the appropriate Turns From Finger Tight in the next chart, making sure the tube end of the shaped fitting is aligned to receive incoming tube or hose assembly.

22. Turns From Finger Tight Chart
Pipe Thread Size
Turns From Finger Tight 2 4 6 8 12 16 20 24 32

23. Fitting Torque – O-Ring Boss
Thread Size
Assemly Torque (in-lb)
Assemly Torque (ft-lb) 2
7 - 8 3 4 5 6 8 10 12 14