Power Generation Turbines

Types of TurbinesSteam Combustion generates steam

which turns turbines

Gas Combustion creates power which turns turbines

Combined Cycle

Gas first, then exhaust creates steam

Steam Turbine

Managing the Health of Fire Resistant Steam Turbine Electrohydraulic (EHC) Control Oils

Ken Brown, Utility Service Associates 

• The Electrohydraulic control (EHC) system is responsible for the critical task of governing steam delivery to turbines that drive electric generators in a power plant.

• Historically mineral oil-based fluids. Increasing steam temperatures (500°C to 550°C) and hydraulic fluid pressures (1,500 psi or 10 bar) demand the use of fire-resistant fluids to assure safe and reliable operation.

• Phosphate ester-based hydraulic fluids are the most common fire-resistant EHC fluids in use today.

• Phosphate ester fluids offer higher flash and fire points than mineral oils, and most importantly, they self-extinguish and are less likely to spread flaming streams or burning pools of oil.

Turbine Oil Functions

Lubricate journal and thrust bearings

Provide efficient cooling

Prevent sludge

Prevent Corrosion

Sometimes hydraulic and gear

Oil CharacteristicsViscosity Higher Speeds (>3,000 RPM) need ISO 22-32

Lower Speeds (>3,000 RPM) need ISO 32-68

Viscosity Index Min 95

Max 115

Demulsibility of Water

Steam LeaksCondensation in reservoirFaulty cooling systems

Oxidation Stability

RPVOT

Highly refined base oils

ASTM D2272 RPVOT

• Significance and Use• 4.1 The estimate of oxidation stability is useful in controlling

the continuity of this property for batch acceptance of production lots having the same operation. It is not intended that this test method be a substitute for Test Method D943 or be used to compare the service lives of new oils of different compositions.

• 4.2 This test method is also used to assess the remaining oxidation test life of in-service oils.

ASTM D943 TOST• Significance and Use• This test method is widely used for specification

purposes and is considered of value in estimating the oxidation stability of lubricants, especially those that are prone to water contamination.

• It should be recognized, however, that correlation between results of this method and the oxidation stability of a lubricant in field service may vary markedly with field service conditions and with various lubricants.

• The precision statement for this method was determined on steam turbine oils.

Turbine Oil Stability Test

Failure Modes

Foam Air Intake from pumps

Hi return pressure

Can damage pumps

Rust and Corrosion

Water contamination

Oxidation Temperature

Metal contaminants

System Flushing and Filtration

Initial Charge

High velocity

Filtration to ISO 17/16/14

Heating and cooling cycles

Recharge Use flushing oil

Vibration of lines and temperature cycling

Filtration to ISO 17/16/14

1-5 year Oil LifeSuitability for Continued Use (Annual)Viscosity ASTM D445

RPVOT ASTM D2272

Water by Karl Fischer Titration ASTM D1744

Acid Number ASTM D664

ISO Cleanliness Code 4406

Rust ASTM D665 A

Demulsibility ASTM D1401

Foam ASTM D892 Sequence 2

ICP Metals

Filtration• Clean Oil decreases the lifetime operation

expense of a piece of equipment• An ISO code is a set of three reference numbers

separated by slash marks and refer to the number of particles of certain sizes in 100 milliliters of a fuel or oil.

Greater than 4μm / Greater than 6μm / Greater than 14μm

ISO 22/21/18

What does it mean?