The biggest reason to replace a condenser is if it does not have enough capacity due to the current or expected steam loading. With additional steam load to the condenser the condenser may not be able to handle the load as it may not have enough surface area. Higher loading entering the steam inlet may cause unwanted high steam velocities. Also additional load to the condenser will make the steam inlet pressure degrade, therefore it will need to be determined if the loss in pressure will impact that process enough to replace it. The best way to determine if a replacement condenser is needed would be compare the cost of the condenser versus the lost performance and its associated cost. The increased fuel cost to operate the turbine should be factored into the decision when considering condenser replacement.

In addition to checking the pressure versus the cost of the condenser, the equipment supporting the condenser needs to be evaluated. On a turbine exhaust condenser, the air removal package needs to be checked to see if it is designed for the right amount of air removal. With additional load the air removal package may be required to be larger. Also the atmospheric relief valve or rupture disc will need to be reviewed as additional load increases the size required to protect the condenser. 

Another reason to replace a condenser would be the physical condition of the condenser. Most of the condenser is carbon steel, except the tubes and tubesheets, which are normally a type of stainless steel, admiralty or copper nickel, or titanium. Over time the internals and externals will begin to wear. This will be where it is determined if a complete replacement is better than re-tubing or replacing the bundling of the condenser. The shell of the condenser along with the waterboxes should to be examined for wear and thinning. If there is any evidence of thinning the entire condenser is best to be replaced.

The main reason to re-tube a condenser would be to replace tubes that are leaking and most likely plugged to a point where it is affecting performance. With re-tubing, there are many things to consider to insure re-tubing is your best option. The age of the equipment and material are important factors to consider when re-tubing. As discussed above, if the condenser is thinning, especially the tubesheet, re-tubing may not be the best option. Not only do you have to look at the thickness of the tubesheet, but the tube holes as well. This is especially true for copper based tubesheets, like naval rolled brass or muntz. The softer materials may be harder to seal with roller expansion, especially if the tubes have been replaced before. For units with stainless steel tubesheets, it is important the stainless has not been work hardened due to previous re-tubes.

If your re-tubing plans call for a change in the tube material, please contact Graham. We will be happy to evaluate any performance or compatibility issues.

The other option in replacing part of a condenser would be going with a bundle kit. There are many factors to consider before selecting this option. As before the thickness of the materials should be checked, in this case especially the shell as a bundle kit typically includes all the internals. Again with any replacement of a condenser part or whole the age of the equipment should be considered. Older designs may have welded internal tube support plates that need to be replaced. The tubesheet may be welded to the shell or there is a shell side seal that needs to be installed correctly to insure no leaks. Updated codes like ASME will need to be considered when replacing the internals. Over time ASME code has changed and the shell or shell flanges may not be thick enough to meet the new code. Also replacement bundle kits for the condenser does not typically add any additional capacity to the condenser. The bundling kit does allow the option to add additional tube support plates per update HEI standards and removes the risk associated with corroded tube support plates and tie rods if only re-tubing is completed. 

To summarize if the operating conditions of the condenser have changed and the condenser is at the end of life with corrosion and thinning the condenser should be replaced. If the operating conditions have not changed and the condenser is in fairly good shape, but there is a good amount of tubes plugged affecting performance the condenser should be re-tubed. Then there is another option to replace the bundle is with a bundle kit if the internals are worn, but the shell is still in good condition.