Inadequate Air Removal – It’s understood that air may leak into the condenser from various connections. While the condenser sets the operating pressure, the air removal equipment needs to remove air from the condenser at the vacuum that condenser wants to operate at. If the air removal system is unable to do this, the condenser pressure will degrade. If the system has excessive air leaks or if the air removal system is mechanically damaged or has inadequate utilities, then it will cause a poor turbine back pressure. Issues with air removal often lead to large and dramatic losses of vacuum.
Cooling Water Problems – The cooling water temperature and flow have a direct impact on condenser performance. Any loss of cooling water flow or increase in the cooling water supply temperature will have a negative impact on the condenser LMTD calculation and will result in a poorer operating pressure. Over time it’s not unusual for additional heat load to be placed on the cooling tower and an increase in the flow rate demand from additional processes. This along with fluctuations in seasonal temperatures can lead to reduced condenser performance.
Fouling – The steam side of a turbine exhaust condenser is normally clean, assuming that the site does not have issues with steam quality. If there is a steam quality problem normally the turbine is also impacted with turbine blade erosion, silica build-up, or other issues. The majority of the condenser fouling in this service comes from the cooling water side of these units. Poor cooling water treatment can result in large deposits inside of the condenser tubes. Debris from the cooling tower can also cause problems. If the condenser is fed with river water, sediment debris may be a concern. Annual tube cleaning is important to maintaining performance.