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In the event that the existing steam surface condenser cannot meet the expected performance criteria set for the power uprate, there are a range of considerations and options for design improvements. Given the fixed surface area nature of the condenser, the options are limited.
Cooling water: The option of improving the cooling water system to the condenser is usually reviewed in the early stages of the power uprate. It is worth revisiting this option after the initial review, if the feasibility of physical modifications to the condenser proves to be difficult. Revisions to the cooling water conditions can often dramatically improve condenser performance, namely:
- Reduction of cooling water inlet temperature
- Increase in cooling water flowrate
Assuming that modifications to the existing condenser are not possible, or desired, the option for improving the cooling water design conditions can lead to significant improvements in condenser performance, such that an existing steam surface
Bundle modifications: A variety of alterations to the existing tube bundles might be possible. Older condensers can often benefit from minor bundle improvements, such as relocated and redesigned baffles, splash trays, airdraw off piping, re-heat trays, condensate cross-over piping, etc. which may enhance the overall performance.
It should be understood that in these types of cases the scale of the possible increases in thermal performance are considered to be limited and are often implemented in conjunction with other options, in order to meet expected condenser performance during power uprate conditions.
Re-tubing: Use of the thermo-hydraulic model for the existing condenser can often reveal that the original design conditions are not being met. Frequently, existing condensers can suffer from a high proportion of plugged tubes after many years of operation. Condensers with a high proportion of plugged tubes can often benefit from a selective re-tubing, which will assist in reinstating 100 percent of available surface area per the original design conditions.
The failure mechanism of the original tubes and the reasons for plugging should be understood when ascertaining the option of retubing a condenser. With respect to improving performance for power uprate conditions, a partial, or total re-tube of the existing condenser, with alternate tube materials, and/or lighter (thinner) tube gauges could also possibly improve the thermal performance of the condenser so that it could meet expected condenser performance during power uprate conditions. Extreme caution should always be exercised for this option when different tube materials and gauges are used. The potential for tube vibration may increase and the suitability of the existing support plate spacing should be checked per HEI standards.