Use of oil cooler in power Generation?
The use of oil coolers in power generation is absolutely critical and non-negotiable across all major technologies. They are a fundamental component for ensuring reliability, efficiency, and longevity of multi-million dollar assets.
1. Gas Turbine Power Plants
This is one of the most demanding applications. A gas turbine’s lube oil system is its lifeblood.
- What it cools: Lube oil for the main turbine bearings, the accessory gearbox, and often the hydraulic control oil.
- Source of Heat:
- Friction: High-speed rotation of the massive turbine rotor generates immense heat in the bearings.
- Heat Soak: Extreme heat from the combustion process (can exceed 1500°C) radiates and conducts into the turbine casing and shaft.
- Why it’s critical: The turbine rotor is supported on a thin film of oil. If the oil overheats and loses its viscosity, this film can break down, leading to metal-to-metal contact. This can cause a catastrophic bearing seizure, which would destroy the entire rotor and casing in seconds, resulting in millions of dollars in damage and months of downtime.
- Cooler Type: Typically a large, shell-and-tube heat exchanger. The lube oil is on the tube side, and the cooling medium is usually water from a closed-loop cooling water system (which is itself cooled by a cooling tower).
2. Steam Turbine Power Plants
Steam turbines, often found in coal, nuclear, and combined-cycle plants, have equally critical oil cooling needs.
- What it cools: Turbine Governor Oil and Lube Oil.
- Source of Heat:
- Friction: Heat from the journal and thrust bearings.
- Shaft Heating: The very hot steam turbine shaft heats the oil in the bearings.
- Why it’s critical: Besides preventing bearing failure, the oil cooler is vital for the control system. The turbine’s control valves are actuated by high-pressure hydraulic fluid (often the same oil). If this oil gets too hot, its viscosity changes, leading to sluggish and inaccurate valve control, which jeopardizes the stability and safety of the entire turbine generator set.
- Cooler Type: Again, shell-and-tube heat exchangers are standard, cooled by the plant’s central cooling water system.
Wind Turbine Power Plants
The gearbox in a wind turbine is a notoriously high-stress component, making its cooling system essential.
- What it cools: Gearbox lubricating oil and often generator bearing oil.
- Source of Heat: Intense mechanical friction from the gearbox, which multiplies the low rotor speed (~10-20 RPM) to the high speed needed for the generator (~1500-1800 RPM). Churning losses in the oil sump also generate significant heat.
- Why it’s critical: Wind turbine gearboxes are incredibly expensive and difficult to replace (requiring a massive crane and weeks of work). Overheating quickly breaks down the oil, leading to accelerated wear, micropitting, and eventual gearbox failure. Keeping the oil cool is the single best way to extend gearbox life.
- Cooler Type: Often air-cooled oil coolers (with fans) or water-cooled plate heat exchangers, depending on the turbine design and climate.
4. Diesel and Reciprocating Engine Generators
Large backup generators and some power plants use massive diesel engines.
- What it cools: Engine lubricating oil.
- Source of Heat: Friction from piston rings, cylinder walls, crankshaft, and connecting rod bearings. This is in addition to the immense heat of combustion.
- Why it’s critical: To prevent the oil from “coking” (turning into carbon deposits) inside the hot engine, which can clog oil passages and lead to catastrophic engine failure due to lack of lubrication.
- Cooler Type: Can be shell-and-tube or plate-and-frame heat exchangers, often cooled by the engine’s jacket water cooling system