presentation expanders

UNION FENOSA gas SEGAS Services

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Turbine Expander

TRAINING PROGRAM - PHASE IIA

FORLNG PLANT at DAMIETTA Turbine Expander

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As per the provision of the CONTRACT, SEGAS are permitted to the use of this Product for reproduction and future reference only for SEGAS internal use. No part of this Presentation may be reproduced in any form or resold for other purposes without written permission from The Consortium.


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Compressors

Turbo Expander and Axial Flow Compressor


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Turbine Expander

There are two main types of turbo expanders: axial flow and radial flow designs. Axial flow turbines operate under the same principals as a steam turbine. They could be single stage or multistage with impulse or reaction blading or a combination of the two.

Objective One

Types of Turbo Expanders

Contd.


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Turbine Expander

Typical Turbo Expanders Cross-Section


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Turbine Expander

Objective 2A turbo expander is a machine that continuously expands a gas from a greater pressure to a lower pressure while causing the gas to do work. The turbo expander cools the gas very significantly and the process produces shaft power.

The working components of a turbo expander perform the same functions as a turbine stage. The working principle of a reaction design turbine (turbo expander) is as simple as whirling sprinkler heads or a water wheel driving a mill. There are two basic types of turbine blade designs: the impulse and reaction type.


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Turbine Expander

In the impulse style of turbine complete gas expansion occurs in the nozzle . The gas passes through one or more rotating buckets thereby reducing initial velocity. The number of buckets depends upon the desired efficiency and power requirement. Turbines smaller than 300hp are usually single stage machines. If these machines must extract high horsepower two or more impellors are used. Large turbines usually use a combination of impulse and reaction blade design.


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Turbine Expander

Helium Gas Turbo Expander

The Helium gas turbo expander is used in a cooling process. The cold high-pressure helium gas passes through a turbine which itself drives a compressor in a secondary helium loop. The gas therefore does work in the primary loop and is cooled still further. The energy extracted is transferred to the secondary loop as heat, and finally removed in a water-cooled heat exchanger.


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Turbine Expander

Objective 3

Auxiliary equipment:

All types of expanders will use a means of sealing the process gas from the lube oil or vice versa. The means, which this accomplished, is with a labyrinth style seal (non contact), a carbon ring seal (packing), a mechanical contact seal or a liquid film seal. A liquid film seal uses metallic sealing rings and uses a liquid buffer in the clearance area to provide a seal.


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Turbine Expander

Lube oil systems

All turbo expanders and their driven equipment will have a lubricating system to provide lubrication to the bearings of the rotating shafts. This system will include a reservoir to contain the oil, mechanical pumps to supply oil throughout the system, oil coolers to maintain proper lubricating oil temperatures. The system will also include safety relief valves to prevent system over pressurization and regulators to maintain proper pressures. The oil temperatures will be controlled by thermostatic valves, which direct the oil to the coolers as required. The systems must have strainers in the oil tank supply line and filters close to the bearings being supplied with oil to filter out any dirt.


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Turbine Expander

Lubricating Oil System


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Turbine Expander

Seal oil system (Buffer liquid system)

On some types of systems the process gas that is being used to drive the expander may be flammable or corrosive. If this flammable gas were to mix with the lubricating oils in the bearing cavities it may present a dangerous condition throughout the lubricating system, when the gases become entrained into the oil. Should the gases be corrosive it will shorten the life of the oil and all components in contact with the oil. A similar situation could also exist if the driven unit is a gas compressor.

In either situation the manufacturer may choose to provide a sealing flow of oil (supplied to the seals at a pressure 20 psi higher than suction pressure) into a cavity between two seals. These seals will separate the process gas from the bearing lubricating' oil. A buffer gas" supply is used on the pressure side (process gas) to prevent any seal oil from flowing into the compressor and being lost. The seal oil buffer gas mix is drained by gravity back to a trap that contains both a separator and a coalescer. The mixture is separated, the oil returns to the oil tank and the buffer gas returns to the suction port of the compressor or expander.


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Turbine Expander

On some applications an external supply of buffer gas may be introduced into the seal cavity. This gas must be supplied at a pressure of at least 50 psi higher than system inlet or suction pressure and is regulated by control equipment. The amount of buffer gas depends on compressor style and suction/inlet gas conditions

Sealing Arrangement for Turbo Expander


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Turbine Expander

Sealing Arrangement for a compressor bearing housing using a buffer gas for Sealing


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Turbine Expander

Compressor Seal Oil and Buffer Gas System


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Turbine Expander

Objective 4

Start-up running and shutdown checks.

All the specifics of the start up, running and shut down procedures for turbo expanders and driven equipment will be covered by the manufactures standard operating procedures. Each manufacture will outline all the operating limits of temperatures, pressures, vibration levels (if installed), speeds etc, of the equipment for the operations personnel. On start-ups some machines may use a pre lube cycle that runs for a set period of time prior to rolling the turbine. This'cyc1e may include the heating of the oil in the reservoir with the use of an emersion heater to a specified temperature. When all conditions are met the expander may be' operated. If the expander uses hot process gas it will have throttling valves to allow gas entry into the turbine.

Contd.


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Turbine Expander

All the specifics of the start up, running and shut down procedures for turbo expanders and driven equipment will be covered by the manufactures standard operating procedures. Each manufacture will outline all the operating limits of temperatures, pressures, vibration levels (if installed), speeds etc, of the equipment for the operations personnel. On start-ups some machines may use a pre lube cycle that runs for a set period of time prior to rolling the turbine. This'cyc1e may include the heating of the oil in the reservoir with the use of an emersion heater to a specified temperature. When all conditions are met the expander may be' operated. If the expander uses hot process gas it will have throttling valves to allow gas entry into the turbine.


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Turbine Expander