Yanbu

Operational reliability significantly increased

Double oil cooler optimises power plant operations in Saudi Arabia

Author: Marvin Lechel, Projekt Manager

A heat transfer specialist from Lower Saxony is one of the international outfitters of two large power plant projects on the west coast of Saudi Arabia. Oil coolers were supplied for a total of nine turbine lube oil systems for both power plants.

The power plant Yanbu 3 in Saudi Arabia, which is being built near the same city on the Red Sea, is an important element for the infrastructure development of the prospering region between the cities of Jeddah, Mecca and Medina. The heart of the power plant with a capacity of 2700 MW is five steam turbo groups with 620 MW each from the company GE. Heavy fuel oil or natural gas is used as primary energy. The steam turbines, super-critical boilers, generators, electric filters and flue gas desulphurisation plants for the four 720 MW units of the power plant Shuqaiq, approximately 800 km further south which is fired with heavy fuel oil, are also from GE.

Heat exchanger specialist Funke was commissioned by GE with the production of the oil cooler for all nine turbine lube oil systems. Both power plants will feed power into the public grid as of 2017 and furthermore provide electricity and process steam for the connected seawater desalination plants.

Plate heat exchangers in a redundant configuration

Yanbu

For reliable cooling of turbine lubricating oil in the nine power units, so-called redundant designed "utility double oil cooler skids" are used.

Each of these largely identical systems consists of two powerful plate heat exchangers, which are connected to each other by a change-over valve on the side of the lubricating oil circuit (inlet with inlet, outlet with outlet).

On the cooling water side, both heat exchangers are separately connected to the cooling water intake and drainage. When one oil cooler is on, then the second one is in standby mode.

In case of trouble or during a scheduled service, the function can easily be switched from one cooler to the other.

Thus, the reliability of the individual power plant units against unplanned downtime is significantly increased.

The modular design facilitates plant access

All components of the skids are completely assembled and bolted on a base support. Among the heat exchangers and the switch-over device, there are three drip trays made of stainless steel with drain holes.

All piping and pipe sockets that are welded to the plate heat exchangers are equipped for maintenance purposes with draining and vent pipes, and are mounted on ball valves.

Sight glasses allow visual inspection of the pipe interior and the state of the media. Safety valves protect the heat exchanger from damage due to excessive pressure in the cooling water circuit.

Preservation processes protect the system from corrosion

This complex and targeted method was developed in close cooperation between the project teams of GE and Funke. Funke uses demineralised water for leakage tests of all skids whose pH value is adjusted in such a way that no surfaces can be attacked by corrosion after the subsequent drying and conservation processes.

After draining of the testing medium, residual humidity in the plate heat exchangers is reduced to 3-5% with a special drying machine. The devices are then hermetically sealed so that no surrounding air can enter.

Within the following 24 hours, the plate heat exchanger skids reach the surrounding temperature; then all lines are flushed again with dry compressed air. After the moisture-enriched air has been replaced by cool, dry air, residual humidity with an average or less than 3 g/kg can be achieved and measured in the devices.

By immediate use of a sufficient amount of drying agent, which is filled into the process connections and the direct airtight closing by means of blind flanges, the devices for shipment are best protected against corrosion during the time up to the assembly in the power plant.

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