When a steam turbine piping arrangement is being developed, it is important to avoid the introduction of steam condensate into the turbine case, which Could damage the blades.
A typical turbine arrangement is shown below. The steam supply comes off the top of the supply header and reduces condensate carry-over into the turbine.
The block valve isolates the turbine when it is not in use. A drip leg is provided at the low point of the system to remove any condensate. A control valve is placed adjacent to the turbine. The steam exhaust line block valve is provided for isolation.
A relief valve is also provided as a protection device should the exhaust valve be closed before cutting off the steam supply. This line must vent to a safe location away from plant personnel. Additional consideration most be given to access to the turbine for maintenance or in-spection of tube oil connections, packing glands, and the governor.
Following drawing shows an improper steam supply line arrangement; the steam trap does not come off the low point in the system. The condensate that builds up above the block valve enters the turbine when the valve is opened, damaging the blades.
This configuration must be avoided. Removal of condensate at multistage turbines is an-other serious concern because if the water slugs, the thrust bearings can fail.
A typical method of safely re-moving excess condensate without endangering the operator who drains the line is shown below.
A temperature indicator, which is visible from the blowdown valve, indicates the presence of water in the system. Opening the valve releases the hot con-densate into the exhaust stack. The hot steam can then vent safely overhead, and the condensate is dumped to
grade or directly to a drain system.