Surface Condensor Vacuum

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  • Author
  • #100938
      • Expert

      Dear Sir,
      Very detailed answer by Prem Baboo. However following points could also be considered
      1- Cooling water flow and delta T across the exchanger, Any chance of cooling water bypassing exchanger we experienced this type of problem.
      2- In any oppurtunity of shutdown, Please make a static test to identify the leakage point.
      3- If you share little details of condenser design(CW in/out and any strainer on CW, level in condenser)

        • Expert

        Dear channing spears
        The problem generally the sealing of rear side(vacuum) due to variation of leakage pressure, please check behaviour of Dump valve and import valve. and also check following points. As turbine exhaust is Connected to a condenser which is operated below atm pressure so there are chances of air ingress or vacuum brake in turbine which is eliminated by gland sealing.During the turbine start up there is a vacuum at the exhaust side so in both end steam glands we provide an external steam through a drilled hole in steam gland which creates a barrier for air to enter in turbine. Pressure of this steam is less than 1 bar (0.3 bar-0.8).While operation the steam supply valve which supply gland sealing is closed but the stream leaks through the front side of the turbine which is high pressure side enters in gland sealing line and goes to the exhaust end.Both the side gland leadoff line are connected to gland condenser through dump valve. And sealing steam lines are connected to a flush chamber through a pressure control valve.
        Checking following points
        1. Increase the motive steam pressure in ejector by 1-1.5 bar
        2. Try to take in line with hogging ejector what happens ?(improve or not)
        3. Check un condensed steam passing with trap, check Trap performance by opening trap bypass valve.
        4. Upstream drain of Condenser must be closed.
        5. Check air locking in C.W lines.
        6. Check water sealing (barometric leg) in condenser.
        7. Turbine vacuum side sealing steam to be checked.
        8. Check import valve position and dump valve position of sealing steam.
        9. To increase turbine seal steam pressure by 0.1-0.2 kg/cm2, how much pressure you are maintaining?
        10. If the front side leakage is minimum, then rear (vacuum side) pressure will not be that case import valve must be opened.

        Prem Baboo


          • Participant

          Dear Sir,

          Our refrigeration turbine compressor faced similar problem post major turnaround startup.
          We have verified the cooling water inlet flow to above said turbine compressor’s surface condenser. Indeed the actual flow was way lower than expected design figure.
          During our supplier outage. We took opportunity to clean the cooling water side. We found cooling tower fills fragments and hand tool inside the inlet chamber.
          Lesson learnt will be, intensifying cooling water supply subheader flushing prior critical heat exchanger box up.

            • Participant

            Dear all,

            We are currently experiencing low vacuum at our surface condensor for our CO2 turbine. We have had this issue several times in the past and it turned out to be different things each time, such as, boot leak, closed inert valve, build up of deposits in cooling water lines to/from surface condensor. We have checked everything so far except the cooling water flow, which is where we suspect the problem is. Has anyone else ever had this issue and what can be done to prevent it from happening?

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