1) The document discusses return line failure in hydraulic steering systems due to changes in hydraulic fluid properties with operating conditions. 2) It aims to analyze the causes of return line failure and fluid property changes, and suggest prevention methods. 3) Tests were conducted on a Fiat Palio steering system to understand the relationship between temperature rise in the fluid and system failure. The temperature rise was found to increase with steering load and decrease with better quality fluid.

1. By:-
Ryan D'Souza
Nitish Kulkarni
Nitish Kale Project Guide :-
Mahesh Mulik Prof S. R.Kandharkar

2. Problem Statement
The Hydraulic Steering Systems encounter a problem of Return
Line Failure due to changes in the hydraulic fluid properties with
changes in operating conditions. The return line failure can cause
entire failure of the hydraulic steering system and threatens the
safety of the driver and passengers.

3. Project Objective
 Analyze the causes of the return line failure in
steering systems.
 Analyze the changes in the various properties
of the hydraulic fluid in the system and the
parameters affecting it.
 Suggest methods to prevent return line failure.

4. Real-Life Cases
 A large-scale recall relating to the failure of power steering was
covered extensively in the news. In late May 2014, 1.4 million
vehicles were recalled by the Ford Motor Company. According to a
May 29, 2014 article in USA Today, at least 5 accidents and 6 injuries
have been linked to the Escape and Mariner defect, and 15 accidents
and 2 minor injuries have been linked to the Explorer problem.
 Warning to 223,000 Mini drivers after cars suffer sudden failure in
power steering - Daily Mail Reporter – 18 February 2009
Angry drivers are urging Mini to recall almost a quarter of a million
cars following a spate of sudden power steering failures. Many
motorists have had frightening experiences and near-miss crashes after
the system abruptly cut out, making controlling their vehicles
extremely difficult. The fault is believed to be a problem in 223,000
Minis bought between 2001 and 2007. Mini's power steering pumps
are failing so early in the car's life and is concerned by the risks the
failure can cause.

5. Hydraulic
Power Steering System
 Use mass transfer to achieve desired output with
minimum effort.
 Greatly reduces the driving effort & made driving safer
and comfortable.
 The power steering system consists of three components:
-power steering pump
-power fluid reservoir
-power steering rack and pinion gear

6. Steering System

7. The Main Components Of
Hydraulic Steering System
 Pump
 Steering Unit
 Steering Column
 Actuator
 Filter
 Reservoirs
 Hoses and Fittings

10. Advantages of Power Steering
 Power
 Flexibility
 Operator comfort
 Control
 Weight
 Smoothness

11. SETUP SPECIFICATIONS
 Pump – Max. Pressure - 140 bar at 2000 rpm
Max. Flow Rate – 8 lpm at 2000 rpm
 Actuator – 1. Bore – 90 mm
2. Stroke – 450 mm
3. Volume – 2862776.3 mm3 = 0.002863 m3
 Reservoir Capacity – 1.5 liters
 Steering Fluid – Fiat Palio Steering Fluid
1. Specific Gravity – 0.874
2. Flash Point – 185oC
3. Pour Point - -40oC
4. Viscosity Index – 155
5. Viscosity at 40oC – 37.3 cSt
100oC – 7.1 cSt

12. HYDRAULIC SYSTEMS
AND FLUIDS
 Used in a variety of applications from car brake to
heavy agricultural and construction and mining
equipment.
 Hydraulic fluids are integral part of hydraulic
systems.
 Modern hydraulic systems use petroleum based oils
with additives to inhibit foaming and corrosion.
 Fluids have primary function of transferring potential
and kinetic energy.

13. Types Hydraulic Fluids
 Types of Hydraulic fluids:
 Petroleum Based Fluids
 Synthetic Based Fluids
 Water in oil Based Fluids
 High Water Based Fluids(HWBF)/High Water
Contend Fluids(HWCF)
 Fire Resistant Fluids

14. Properties Of Fluids
 Viscosity
 Viscosity Index(VI)
 Chemical Stability
 Compressibility/Bulk Modulus
 Foaming Tendency
 Density
 Good Heat Dissipation

15. Test Procedure
 Acquirement of required components (Steering system of Fiat Palio)
 Fabricating the stand for the system to rest and work without
difficulties or collision
 Purchased the motor to run the pump , the belt required to do the same
and finally the standard oil.
 Fitting RTD’s in the inlet and outlet of return line .
 Simultaneously performing thermal analysis on software to simulate
temperature patterns.
 Test run the system to find the leakages and rectify them making the
system leak proof.
 Use of NI LabView for taking the readings .
 Taking the various readings by changing the various parameters(Oil,
No Load Steering & steering in loaded condition)

16. Continued
 Tabulation of the readings for further calculations using
Microsoft Excel.
 Generating the graphs and result table.
 Analysing the found results.

17. Calculations
 The return line is the major area of concern. The heat transfer
from the steering fluid to the surroundings is divided into three
main modes-
1. Heat transfer by convection between the steering fluid and
inner walls of return line.
2. Heat transfer by conduction along pipe thickness from inner
wall to outer wall of pipe.
3. Heat transfer by convection from outer wall of pipe to
surroundings

18. Mathematical Model of the system also called as electric analogy

19.  To find average change in the temperature over the whole return
line we have opted for finding the Logarithmic Mean
Temperature Difference (LMTD) of the same.
 Here the temperature Tin is the temperature at the inlet of the
return line.
 The temperature Tout is the temperature at the outlet of the return
line.
 Tatm is the Ambient or Surrounding temperature, taken as 26º C.
 TIA is the difference between Inlet and Ambient Temperature.
 TOA is the difference between Outlet and Ambient Temperature.
 Difference 𝞓T = TIA - TOA

20.  Logarithmic Mean Temperature Difference (LMTD) is
𝐿𝑀𝑇𝐷=𝛥𝑇/𝐿𝑜𝑔(𝛥𝑇)
 Total heat transferred in the system is Q
Q=U*A*LMTD
U is Overall Heat Transfer Rate
A is the Area of the pipe
The readings were taken in interval of 2 minutes and directly exported
to Microsoft Excel.
 These readings where converted into intervals of 5 minutes for
tabulation on results.
 The readings are from time 0-60 minutes.
 All the required calculations was done and formulated into a table.
 This final data was used for analysis and graph plotting.

21. Forecast
 As per our study the following should be the results:
1. With steering the temperature rise should be more.
2. With addition of steering load ,the temperature rise
should be more.
3. The oil with better properties should have less
temperature rise.
• We have verified the above parameters in our test
results.

22. Results Achieved
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70
HeatTransfer(Q)
Time(min)
without streering With Steering
Comparison between the condition of steering and without steering

23. 0
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70
HeatTransfer(Q)
Time(min)
Without Weight With Weight
Comparison between the condition of with and without load on the system

24. 0
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60
HeatTransfer(Q)
Time(min)
First Oil Second Oil
Comparison between the use of different oils
First oil has the viscosity of 7.2 mm2/sec & VI is 182,Second oil has the viscosity of 7 mm2/sec &
VI is 150.This justifies our results.

25. Thermal Analysis of Return Line
 Transient thermal analysis done on return line, as time interval
increases, temperature at inlet to return line increases.
 According to it temperature distribution pattern varies.
 Temperature at inlet to return line goes on increasing as the time
interval increases.
 The conditions had been achieved at no load and at room
temperatures which differs from actual working conditions as in
temperature due to engine as well as other auxiliaries which
radiate heat near steering return lines, which will cause further
increase in temperature of the fluid.

26. Temp Range (30-60oC), Time Interval : 120 Minutes
Temp Range (30-40oC), Time Interval : 40 Minutes

27. Future Scope
 Finding a relation between the Rise in Temperature and the Steering Effort
 In this a relation can be found by measuring the effort wrt the
temperature rise.
 To find the effort we need to find the torque acting
 𝑇 = 𝐸 ∗ 𝑟
T= Torque , NmS; E = Effort ,N ; r= Radius of steering wheel, m
 To find the torque we need to use a series of strain gauges, these
gauges are so placed that they measure the strain with temperature
compensation.
 The torque value is obtained mathematical
 The relation can be plotted on the graph
 This can be use fully for finding the extra effort required to be applied
by the driver with rise in temperature of the fluid

28.  Use of alternative material for making the hoses and testing their
effect on the system.
 Additives and enhancement of the oil for better properties and their
testing.
 Effects of increasing the length of return line & employing metallic
finned pipes on the system.
 Change in heat dissipation rate after employing air coolers.

29. Conclusion
 We found that temperature rise was one of the main reason of failure of
system & were selected for further studies.
 Tests were conducted & from these tests we found relationship existing
between the parameter and the system failure(Heating of oil)
 Incorrect oil selection with inappropriate properties leads to heating of
system.
 Reduction in the oil volume also heats up the system.
 Increase in steering weight also leads to heating up of the oil.
 Thus, we can conclude that use of metal hose, increasing length of the return
line, applying the principle of critical radius of insulation, and use of steering
fluid with better properties are the possible solutions to the problem of
Return Line Failure in hydraulic steering systems. The suitable measure can
be employed considering constraints on the system.