What guidelines and best practices recommended for vacuum condenser?
20 Aug '17, 06:03
The Turbo-generators/ Steam turbines performance and efficiency depend on the correct operation and maintenance of the vacuum condenser. Serious damages for the turbo-generator system due to vacuum condenser system malfunction reported.
- The temperature and quantity of cooling water should be controlled all the time. At low sea water temperature closely monitoring required S.W. Outlet temp to be maintained 41 - 42°C and avoid excessive cold sea water flow. Excess flow (fully opened outlet valve) can trouble cooling tubes and tube sheet. If no SW inlet temperature controller installed as a GOOD PRACTICE, the sea water outlet valve to be throttled as required and fastened.
- Sea Water INLET Valve to be in FULL OPEN condition.
- Check AIR VENT at every start operation.
- Be sure the level gauge is clearly visible and level maintained 50-75% at all varying loads.
- Condensate temperature must be around 45 – 46°C controlled all times of operation.
- Before starting T/G condenser – Start the Cool Sea water pump, open the inlet valve first and then open outlet valve gradually.
- When supplying feed water to the vacuum condenser at the starting operation to bring up the visible water level, be sure the water prevented from entering the turbine.
- Pay attention to the differential pressure between SW inlet & outlet to find out the susceptible reasons of failure due to the invasion of foreign matter, excessive water flow, sub-cooled condensate etc.
- Protection pieces – zinc anodes check every 3 months and replace as necessary.
Danger or sub-cooled condensate
When sea water temperature dropped to below 10°C and the cooling sea water full flow left, the sub cooled condensate formed and it can lead to serious problems in vacuum condenser like tube and tube sheet leaks, flooding in condenser promotes damage to turbine rotor etc.
The sub-cooled condensate properties are mentioned as follow:
High-pressure steam in contact with sub-cooled condensate is an unstable mixture. This can cause hammering in vacuum condenser and damages to tubes. (SUPER HEAT STEAM DUMPING CONDITION).
Don't admit steam into a line filled with sub cooled condensate. In fact, always be wary of admitting steam to any cold steam line if you cannot be absolutely certain that the line's been completely drained. (WARMING AND RE-STARTING CONDITIONS)
- Allowing sub cooled condensate to flow into a steam filled line is more dangerous than admitting steam into a line with sub cooled condensate. For example sub-cooled condensate into the boiler as feed creates knocking in boilers. (RE-CIRCULATION THROUGH HOT-WELL)
- If suspected that a pressurized steam line is filled with sub cooled condensate, don't attempt to drain the condensate. Shut the steam off first, and then drain the condensate. If a drain is opened, and the line hammers, close it and get the steam off. The line may continue to hammer until the steam gets off.
20 Aug '17, 06:32