Contributor: Sherry Heinly, KSB North American Marketing Manager
The Heat Recovery Steam Generator is the major connection from the Combustion Turbine Generator to the Steam Turbine Generator with modern combined cycle power/steam generation plants.
Start-up (sometimes multiple starts daily) are the plant duty cycles that most affect the CTG exhaust gas temperature, STG trips, and simple cycle operations along with supplementary firings, such as duct-burners which can lower plant efficiency but increase unit power.
But what about the critical service pump that feeds the treated, de-mineralized water to the HRSG?
High CTG exhaust gas temperatures usually equal substantial amounts of dissolved oxygen being introduced directly to the HRSG via the Boiler Feed Water Pump (BFWP), in turn setting up the BFWP for potential early wear and possible damages from corrosion and cavitation. BFWP operating at offload duty also can experience vibrations due to extended running time on system recirculation while waiting for the STG to be ready to accept steam.
What is it that you are looking for in your BFWP’s routine and, periodic manner inspections that will increase reliability and availability?
Chances are that your original EPC firm already furnished you with robust, custom-engineered, high-quality BFWP’s such as KSB’s ring section type HGC with custom-engineered hydraulics selected for your exact HRSG operating conditions along with forged chrome steel casings and diffusers, chrome steel internals; however, now you are several years into operations and maintenance cycles on all of the plant equipment and would like to gain detailed knowledge as to how your BFWP’s are doing.
- Data collection, monitoring, and trending are important pieces of information to have. Data such as suction, discharge, and intermediate take-off flows and pressure, as well as vibration information both at peak loads, and off-load conditions allow you to spot exactly where further investigation should be occurring. KSB is always pleased to review data sent to us for evaluation and recommendations for improvement if needed. Most reviews can be completed within 2 days if the data is complete.
- Internal pump clearances can be checked without removing it from the system. These clearances indicate the extent of radial and axial wear and predictions can easily be made for future planned outage repairs if needed. Assuming the pump can be isolated, in-situ checkouts can be performed on one pump even if located on common suction and discharge headers while the sister pump is hot and operating, thus avoiding any HRSG outage. The checkout would normally utilize refurbishment or replacement of common exterior wear parts if necessary (main bearings, mechanical seals, balance disc, throttle sleeve, etc.) Most in-situ checkouts can be performed with one (1) KSB Service Engineer acting as supervisor, and two (2) plant Maintenance Techs within 2-1/2 days per pump at your site.
- If internal components require renewal or replacement as indicated from an in-situ inspection or loss of pressure or decay inflow at full load then a complete out-of-base repair/overhaul with dynamic balancing is available and can be conveniently scheduled. KSB can also provide upgrades and changes to pump performance when needed. KSB has several fully owned and equipped Repair and Overhaul Shops located in strategic areas of the USA and Canada. Contact your Service Regional Manager for KSB can result in a quick “ball-park” overhaul quotation based on data supplied, and can be further refined into a hard quote including total overhaul cycle time and guaranteed firm costs on a lump sum or Time & Material basis as the pump is inspected.
KSB, Inc. Service Regional Managers, Field Service and Technical Support personnel are always available to consult on a personal level regarding your individual application and any pump issues or concerns you may have. Fill free to contact them at 1-800-945-PUMP (7867) or via email at email@example.com.
As a tool to help you supervise the performance of your boiler feed water pump, you can download our Supervision Plan.