RE: Drain pots in HP Steam lines

From: <Steve>
Date: Sat Oct 02 2004 - 18:31:00 EDT

Hi Paritosh Garg

Your first question is partly correct in that the traps will work during warmup. However the condensate quantities may be larger than you expect. The traps may also provide a limited amount of protection if there is a problem with the boiler attemperator spray. If the superheater is of the split type with the attemperator between the two superheater sections, this is unlikely to be a problem, however, at least from the turbines perspective.

I take it you are using a steam separator prior to the turbine inlet as this protects the turbine against major malfunction such as a boiler prime.

Your second question answers itself, as the slope is to assist condensate drainage. It there is no condensate, then the slope has no function.
Suggest you finalise your "other method" prior to finalising the line slope.If you have a steam dump valve close to the turbine, then you may be able to warm up first with the superheater partially venting (to prevent overheating) and next with the dump valve gradually opened as the superheater vent is closed. The turbine drains would be manually operated as usual. When the steam condition (pressure,temperature, quality) is within spec, then the dump valve could be slowly closed as steam is admitted to the turbine.
It wou have multiple boilers/turbines then things may be easier; controlling the venting is the difficult bit in a single boiler/turbine setup; especially if they are a long way apart. Suggest you carry out a HAZOP before going too far.

Cheers

Steve

-----Original Message-----
From: pari2dce@vsnl.net [mailto:pari2dce@vsnl.net] Sent: Friday, October 01, 2004 7:03 PM
To: pipingdesign@yahoogroups.com
Subject: [PipingDesign] Drain pots in HP Steam lines

Do drain pots provided in HP Steam line come into action in the operating conditions in power plants ? The reason I am asking this is because as per the heat balance diagram , the steam conditions in the line are superheated, which means that the steam is totally dry.

As per my understanding, the only time , condensate may form in the line is during the start-up when the pipe's inner surface is cold, and small amount of superheated steam may be condensed after coming in contact with this cold surface.

My next question comes from the previous one, if no condensate is formed during the normal operating conditions. Is there any way by which the slope given in the HP Steam line may be removed, and some other method may be employed to drain out the condensate formed during start-up.

Regards
Paritosh Garg

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