One of the most important things an operator can do for his machinery is to make sure it is properly lubricated. So what is a lubricant and how does it affect operations when used properly? In this webinar we will answer these questions and more by covering the fundamentals of lubrication. During this webinar we will discuss how a lubricant works to remove friction, the physical and chemical properties of the lubricant, and the many functions of a lubricant.
9. Lubricant Types
• Mineral Oils
– Crude Oil
– Solvent Refining
– Hydro-Cracking
• Synthetic Fluids
– Man made or altered
– Molecules have identified structure
– Properties are predictable
10. API Base Oil Categories
Category
Sulfur (%)
Saturates (%)
Viscosity
Index
Manufactured
Group I
>0.03
and/
or
<90
80 to 120
Solvent Refining
Group II
<0.03
and
>90
80 to 120
Hydrocracking
Group III
<0.03
and
>90
>120
Hydrocracking
and ISO
Dewaxing
Group IV
Polyalphaolefin (PAO) – Synthetic Hydrocarbon
Group V
Esters, silicones, PAG,
11. Mineral Oil vs. Synthetic
• Mineral Oil
– Molecules not uniform
• Synthetic
– Molecules nearly identical
13. Synthetic Oils
• Advantages
– Extended range of
service temperatures
– Resistant to oxidation
– Extended service life
– Cleaner system
– Energy savings due to
lower internal friction
• Disadvantages
– Cost
– Compatibility issues
•
•
•
•
seals
paints
packings
other fluids
– Higher disposal costs
– Film strength
consideration for gear
applications
14. Additives
• Chemical compounds added to
impart specific properties
• Added to improve performance
characteristics
• Formulated to provide specific
set of performance parameters
• Can have detrimental side
effects
15. Lubricating Oils
• Composed of base oil and additives
– 70 - 95% Base Oil
Gear Oil
AW Hydraulic Oil
Engine Oil
Turbine Oil
R&O Hydraulic
Oil
Transmission
Fluid
Compressor Oil
17. Typical Additive Packages
Oil Type
Magnesium
Calcium
Zinc
Phosphorus
EP Gear
0
0
0
220
AW Hydraulic
0
40
320
450
Turbine Oil
0
0
0
0
Compressor Oil
0
0
0
0
550
1300
1100
1200
0
2500
1100
1200
PCMO (gas)
HDMO (diesel)
parts per million (ppm)
18. Viscosity
Defined as a fluid’s resistance to flow
Most important characteristic of an oil
and has a direct correlation to
temperature.
Kinematic Viscosity
Reported in Centistokes (cSt)
Measured at 40 or 100 degrees C
Saybolt Viscosity
Reported in Saybolt Universal
Seconds (SUS)
Measured at 100 or 210 degrees F
21. Multi-Grade Oils
Weight that oil
emulates in cold
temperatures
Stands for
“winter”
Oil weight under
normal operating
conditions (warm)
10 w 30
A 10 w 30 is an SAE 30 weight oil that acts like a 10
weight oil in the winter.
22. Proper Viscosity
Factors that effect proper choice of viscosity
LOAD, TEMPERATURE & SPEED
• Low viscosity
–Good cooling
–Poor load handling
–Low internal friction
• High viscosity
–Poor cooling
–Good load handling
–High internal friction
23. Rules of Thumb
• Load
– The higher the load, the heavier the oil
– The lighter the load, the lighter the oil
• Temperature
– The lower the temperature, the thinner the oil
– The higher the temperature, the thicker the oil
• Speed
– The faster the speed, the lighter the oil
– The slower the speed, the heavier the oil
Physically separate opposing friction surfaces with the oil film
reduces friction
reduces wear
reduces the amount of energy needed
Additives enhance the ability of the oil to reduce friction and wear
Oil absorbs heat generated by the friction surface
Transfer heat to reservoir where it is dispersed
Oil can pass through a cooler to assist in heat exchange
(left image) A newly commissioned fire water pump at a Middle East refinery repeatedly suffered high non drive end (NDE) bearing temperatures during periodic test runs and eventually caused a bearing failure. It was revealed that bearing failure was caused by a lack of lubrication since the failed bearing showed signs of lube oil starvation. However, the constant level oiler sight glass showed the oil level as full.
(right Image) This bearing displays the results of high running temperatures commonly associated with over-greasing. When the dropping point is reached, the bearing begins to bleed, the grease runs dry and eventually failure occurs.
Oil holds contaminants in suspension
Carries them away from friction surface
settle out in reservoir
filtered out
Additives disperse solids, avoiding sludge formation
Oil is periodically changed removing contaminants from system
Physical boundary (oil film) protects surfaces from corrosion
Additives enhance rust and oxidation inhibiting properties.
Some oils use alkaline additives to neutralize acid as it is formed
Lubricant Viscosity Oil viscosity is just as important as oil quantity to ensure adequate lubrication. Required viscosity depends on operating temperature. Inadequate lubricant viscosity appears as a highly glazed or glossy surface. As damage progresses, the surface appears frosty and eventually spalls. This type of spalling is fine-grained compared to the more coarsely grained pattern produced by fatigue failure. In the frosty stage, the fine slivers of metal pulled from the raceway create a “nap” that can sometimes be felt. The frosted area will feel smooth in one direction but have a distinct roughness in the other. As metal is “pulled” from the surface, pits appear and frosting advances to pulling.
Oil forms a viscous seal to keep water and dirt out
Grease serves as a physical barrier
Fluid under pressure actuates moving parts
Oil cleanliness is essential
Oil must have anti-foaming characteristics
Some systems require fire resistant fluids
(Image)
Too much grease volume (overgreasing) in a bearing cavity will cause the rotating bearing elements to begin churning the grease, pushing it out of the way, resulting in energy loss and rising temperatures. This leads to rapid oxidation (chemical degradation) of the grease as well as an accelerated rate of oil bleed, which is a separation of the oil from the thickener. The heat that has been generated over time along with the oil bleed eventually will cook the grease thickener into a hard, crusty build-up that can impair proper lubrication and even block new grease from reaching the core of the bearing. This can result in accelerated wear of the rolling elements and then component failure.
Chemical compounds added to impart specific properties
Added to improve performance characteristics
Formulated to provide specific set of performance parameters
Can have detrimental side effects
Oil additives are chemical compounds that improve the lubricant performance of base oil
Anti-Wear Additives
Zinc
Phosphorus
EP Additives
Phosphorus
Molybdenum
Detergents & Dispersants
Magnesium
Sodium
Calcium
Alkaline Additives
Calcium
Anti Foam Additives
Silicon
Viscosity Index Improvers
Pour Point Depressants
Rust & Oxidation Inhibitors
Barium
Tackifiers
ISO Viscosity Grade
Refers to Kinematic Viscosity at 40 degrees C
ISO VG 68 = 68 cSt @ 40C
SAE - Oil Weight
Automotive Grade (10w-30, 30, 5w-40)
Gear Grade (75w-90, 80w-90)
Oil’s Kinematic Viscosity at 100 degrees C is compared to SAE scale
Image description
Steel balls of equal weight dropped into test tubes filled with motor oil fall at different rates. Their rate of fall depends on the viscosity of the oil. The ball traveling through the light SAE 20 oil has traveled farthest, while the ball in the heavy SAE 50 has traveled least