2.5   Pipework arrangement

 

Thе correct arrangement of bled-steam pipework is important to ensure that the allowable thrusts and moments on the heater and the turbine flanges are not exceeded and also that they are completely drained of any condensate which may form.

In the HP pipework, condensate should only be present when the pipework is cold and is being warmed up. To this end, drain pots with drain lines controlled by orifices or drain traps are provided at each natural collection point in the pipework.

Arrangement of HP heater bled-steam pipework for horizontal heaters at Littlebrook D power station

 

Arrangement of HP heater bled-steam pipework for vertical heaters at Drax Completion power station

Special care is taken to ensure that sections between valves which could be closed are drained. This prevents pockets of water being swept along the pipework on opening of an isolation valve. Figure 3.26 shows the pipework arrangement for a horizontal HP heater layout and Fig 3.27 for a vertical heater. The horizontal heater layout allows the pipework to be conveniently drained to the drains vessel and then to the condenser by gravity alone.

 

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