Turbine Cold Box

Introduction to cold box turbine operation

Specific Linde turbine

K Hafi

TE-CRG-OP

Avril 2020

Introduction to cold box turbine operation

• Contents

• Theory refresher

• The different turbines at CERN

• Bearings

• Some definitions

• Turbine operation

• Interlocks

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• Theory refresher

• Turbines

They decrease the helium temperature by expansion and extract heat by the brake system and cooling water.

Whatever the type of turbine we will look at the principle stays the same although the solution is different.

HP

MP/LP

Turbine

Coolingwater

shaft

Q

Brake system

P

P T

F

n

F

P

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• The different types of turbine

Two types of turbine at CERN LHC

• Horizontal turbine (air liquide)

• Vertical turbine (Linde)

Turbine

Brake system

Turbine

Brake system

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• The different types of turbine

• Horizontal turbine(air Liquide)

Constant bearing supply during turbine operation

Critical speed to avoid

Regulation of turbine speed (outlet temperature is a consequence)

• Vertical turbine (Linde)

Bearing supply only during the start and stop of turbine

No critical speed

Regulation of outlet temperature (speed of turbine is a consequence)

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• Definitions

• Bearings

Linde: They enable the wheel of the turbine to levitate during the starting and the stopping of the turbine. The wheel is free to turn without friction

The bearing supply gas is not required during normal operation, the wheel levitates due to the flow of helium gas

Air Liquide: They enable the turbine to balance and levitate. The bearing supply is constant during normal operation

• Brake

Linde: We can adjust the brake of this turbine. We regulate the turbine speed. (xSC211)

Air Liquide: It can be fixed or adjusted. We regulate the brake pressure (xPC213).

• Exchanger

For all turbines, the heat of the turbine work is extracted by the exchanger

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• Bearing

Linde AirLiquide

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Bearing supply

Flow

weight

The turbine has its weight

Supplying the bearing to levitate the turbine

The helium flow levitates the turbine so we can stop supplying the bearing

Bearing supply

Flow

weight

The turbine has its weight

Supplying the bearing to balance and levitate the turbine

The helium flow unbalances the turbine so the bearing must remain supplied

• Turbine operation

• Turbine presentation

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• Turbine operation

• Turbine presentation

Differential pressure of bearing -enable confirmation of wheel levitation

Brake valve - regulate the turbine speed

Bearing valve - supply to the bearing to levitate the turbine during starting and stopping.

Inlet valve - enable outlet temperature regulation

Brake exchanger - enable extraction of the turbine work

Turbine speed

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• Turbine operation

• Start turbine step by step

• Manuel ON on the PCO of the turbine, and then …

1. Locking of brake valve at 50%

To control the turbine speed when the inlet valve opens.

2. Opening of bearing supply valve to levitate turbine

Check if the differential pressure is ok using xPDSH210

3. Gradual opening of the inlet valve

Check the wheel rotation with the differential pressure between inlet and outlet of the turbine.

4. Closing of bearing supply valve when the speed is over 500rps.

5. Thermalisation of the turbine

Speed control at 80% of the nominal speed during 10 min and brake valve position between 90 and 99%

6. Turbine regulation in normal conditions

The speed controller regulates the nominal speed whilst the outlet temperature controller regulates the turbine outlet temperature

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• Turbine operation

• Start turbine step by step

1

2 &4

3

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• Interlocks

• Start interlocks (No start possible)

No water (brake circuit and turbine cartridge)

Inlet turbine pressure lower than 1 bar

Turbine speed higher 500 or 400 rps

• Temporary stops (Stop turbines and automatic restart)

No water (brake circuit and turbine cartridge)

• Full stops (Stop turbines, no restart without acknowledge)

Brake temperature too high

Over speed

Under speed

Outlet temperature too low

Outlet valve not fully open

More 3 temporary stops in 1 hour

Circuit breaker open

Turbine not started (4 bar deltaP and speed < 400 rps)

No bearing pressure when the speed is lower than 400 rps

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• Some recommendations

• Turbine attenuation

We regulate the turbine outlet temperature and we can reduce the power of the cold box by reducing the speed of turbine.

For this, we increase the temperature controller set point. The consequence is the closing of the inlet valve. The minimum valve position is 45%.

Contrary to the theory, it is better to keep the turbine running, even at minimum speed. This avoids passing the gas hot point during the restart and help in economiser mode (cycle flow).

• Thermalisation

During the thermalisation step, it is possible that the inlet valve begins oscillating. The problem is that the turbine can’t finish this step and the power of turbine is limited.

You must take the inlet valve in manual mode and adjust its position by a tenth of a percent per tenth of a percent until the conditions of thermalisation (80% of the nominal speed and brake valve position between 90 and 99% during 10 min). When the set point of the speed controller changes to nominal speed, you can put the inlet valve in automatic mode.

• Starting turbine

Do not hesitate to consult particular points of installation before starting turbine. Some of them need help.

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Good luck, you are ready to play

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