Oil contamination

HYDRAULIC TRAINING SERIES
Oil contamination – Booklet

8
Types of Fluids
Hydraulic
Fluids
Fire
Resistant
Petroleum
based oils
Biological
degradable
Water-
based
Water
based
Synthetic
based
Vegetable
based
Synthetic
based

9
Basic Requirement for Fluids
Mobile fluid power systems use mainly liquid fluids, and
we are discussing liquid fluids only.
 efficient power transmission
 effective cooling
 reliable lubricating
 efficient sealing
 effective contaminants removing
 compatible with component materials
 resistant to foaming
 used over wide operating temperature

10
Power Transmission
m1 m2
V0 V1 V2
Efficient power transmission requires a consistent & reliable
response, and optimum efficiency.
It requires a “stiff” fluid power system. The “stiffness” of
the system is mainly determined by the compressibility of the
fluids!

11
Lubrication
Lubricants are widely used in mechanical systems to reduce
the friction between components surfaces.
In hydraulic systems, many components have relative motion
in operation. Hydraulic fluids should be able to provide
lubrication in between those surfaces.

12
Sealing
Clearances inside hydraulic components cause internal leakage.
It relies on the fluid (viscosity) to minimize the leakage across
these clearances to improve efficiencies and reduce the
production of heat.

13
Contaminants Removal
There are debris in the hydraulic systems due to wearness
of the components.
It relies on the fluid motion to remove those debris away
from the system (especially from the clearances of between
the components of moving relatively.

14
Cooling
Hydraulic fluids will absorb and carry away the heat generated
in the system (mainly at valves, cylinder and/or motor).
--> The fluids act like the coolant in the hydraulic system.
The heat must be dissipated in the tank (or sometimes uses
a heat exchanger) before it can be reenter the system.

15
Fluid Properties
To adequately carry out the desired functions of hydraulic
fluids, the following are the fluid properties we should pay
attention to in selection.
 viscosity
 lubricating ability
 pour point, oxidation resistance
 compatibility with system elements
 rust/corrosion protection
 demulsibility
 etc.

16
Fluid Selection
The general categories of available hydraulic fluids are
petroleum oils and fire resistant fluids. Bio-degradable
fluids are becoming popular recently. Water hydraulics is
a relative new technology.
 No single fluids can meet all the requirements.
 Lubricating & viscosity are important for mobile systems.
 Concerns on environment increased interests in biodegradable oils
(required in many European countries).
 Fire resistance is important for machinery working at the
flammable environment.

17
Viscosity
• Viscosity of a fluid is defined as its resistance to flow at a given
temperature. It affects the fluid’s ability to be pumped, transmitted,
and its ability of lubricating and sealing.
• Both ISO and SAE have established a viscosity grade (number) to
specify the ranges of viscosity.
cSt@210 F
ISO Viscosity Grade
10
20
30
40
50
60
70
80
90
100
110
120
ISOVG100
ISOVG68
ISOVG46
ISOVG32
ISOVG22
SAE Summer #
4
6
8
10
12
14
16
18
20
22
24
26
SAE 50
SAE 40
SAE 30
SAE 20
cSt@40C
SAE Winter #
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
SAE 20W
SAE 15W
SAE 10W
SAE 5W
cP@0 F

18
Fluid Conditioning & Devices
Fluid conditioning includes:
 Fluids storage & preparation
 Contamination prevention & control
 Temperature control
The main fluid conditioning devices include:
 Reservoir
 Filter
 Seals
 Cooler

Typical Structure of Reservoirs

Key Functions of Reservoir
• Fluids container
– Provides a space on the vehicle to store hydraulic fluids.
• Fluids cooling device
– Discharges heat generated in the fluid power system.
• Air separator
– Removes as mush air as possible from the fluids.
• Debris separator
– Filters out debris to prevent possible damages.
• Inlet fluid conditioner
– Prepares the supplying fluids to the pump with a good inlet
condition for maximizing the pump efficiency.

Criteria for Sizing a Reservoirs
o Must make allowance for dirt and chips to settle and for air
to escape
o Must be able to hold all the oil that might drain into it from
the system
o Must maintain the oil level high enough to prevent a whirlpool
effect at the pump inlet line opening
o Should have a surface area large enough to dissipate most of
the heat generated by the system
o Should have adequate air space to allow for thermal expansion
of the oil
In General:
Reservoir size = 3pump flow-rate
(gal or L) (GPM or L/min)

22
Types of Contaminations
Most of the times, fluids contamination is the major
contributor to failures of hydraulic system.
 Solid contamination: It may consists of dirt, metal particles,
seal materials, etc. It is the most common cause for failure of
mobile hydraulic systems.
 Thermal contamination: The useful life of most hydraulic
fluids will be significantly reduced by overheat.
 Air/gas contamination: Dissolved air affects system stiffness,
results in poor performance.
 Water contamination: Water will degrade the fluids in
numerous ways (max of 700 ppm is allowed).

23
Major Sources of Solid Contaminations
Contamination can be introduced into the system from both
external and internal sources.
 Built-in contamination: Much of the solid contamination is
resulted from the manufacture and assembly of the hydraulic
systems.
 External contamination: Much of dirt, air, and water
contamination is resulted from operating environment.
 Internally generated contamination: It mainly caused by the
wear (esp. at break-in & wear out periods).
 Maintenance contamination: Could be all kinds of
contamination due improper maintenance procedure.

24
Typical Hydraulic Fluid Filters

25
Definition of Filtration Rating

26
ISO Fluid cleanliness measurements

27
Use of Heater Exchangers

28
Correct Use of Seals

ISO – 10/7/5 NAS class – 1
Particle size ≥ 4 μm(c) ≥ 6 μm(c) ≥ 14 μm(c)
Particle count
500 to 1000 64 to 130 16 to 32

ISO – 12/11/6 NAS(1638) class – 2
Particle count
2000 to 4000 1000 to 2000 32 to 64

ISO – 14/13/9 NAS(1638) Class – 3
Particle count
8000 to 16000 4000 to 8000 250 to 500

ISO – 16/14/10 NAS(1638) Class – 5
Particle count
32000 to 64000 8000 to 16000 500 to 1000

ISO – 17/15/13 NAS(1638) Class – 6
Particle count 64000 to 130000 16000 to 32000 4000 to 8000

ISO – 18/16/13 NAS(1638) class – 7
Particle count
130000 to 250000 32000 to 64000 4000 to 8000

ISO – 19/17/14 NAS(1638) class – 8
Particle count
250000 to 500000 64000 to 130000 8000 to 16000

ISO – 22/19/17 NAS(1638)Class – 10
Particle count
2000000 to 4000000 250000 to 500000 64000 to 130000

Damaged caused by dirty oil over a period of 5 days

Fatigue wear, 500 x
Sliding wear, 500 x
Cutting wear, 100 x

Damaged caused by water mixed oil over a period of 5 days

Corrosion from Bad Oil

Spool Damaged in Particulate contamination

Degraded Oil turned into Acids – Damaged the System (phosphate Ester
)

Oil contamination

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