Running head: MAIN CONDENSER
1
Main Condenser Construction and Operating Environment
Jeremiah D Walker
Excelsior College
MAIN CONDENSER
2
Abstract
Main Condensers are a major interface portion between the steam and condensate systems and
are subjected to a wide range of temperatures and pressures based on their operating conditions
and the conditions of the cooling water running through the tubes. The condenser needs to be
built of a sturdy and strong material such as a nickel copper alloy. The tubes need to be able to
allow a large rate of heat transfer through a thin layer of material, which both could be
accomplished by using titanium. Using different materials means that precautions need to be
taken to ensure the extended life of the condenser by performing preventative maintenance and
using corrosion preventative measures.
MAIN CONDENSER
3
Main condensers are the interface between the steam system and the condensate system,
and as such they need to be able to withstand large pressure and temperature transients while still
maintaining their ability to transfer heat effectively. The condensers can be subjected to fresh
water or seawater, which can affect the corrosion rate of the condenser tubes. These factors need
to be mitigated by selecting materials that not only have a high corrosion resistance, but that also
maintain their strength at extreme temperatures and pressures. By utilizing a nickel copper alloy
for the construction of the condenser shell and titanium for the condensing tubes, we can have
the best material for both needs of the system; high strength for the shell and high heat transfer
ability and strength for the tubes. Using different materials for construction means that we need
to ensure that corrosion prevention measures are taken, and that preventative maintenance is
performed to ensure the long life of the condenser.
The main condenser is the interface between the exhaust steam and the condensing water,
and as such it is required to have both the strength to handle large temperature changes and resist
corrosion from the medium being used as a heat sink. This requires the condenser tubes to be made
of material that is strong in order to resist incoming steam temperature and pressure. Having the
condenser tubes be made of titanium would ensure that the tubes could be made of a thin enough
size for heat exchange to occur and be strong enough to resist incoming forces upon it. Titanium
is expensive, and having the entire condenser made of titanium would both drive up the cost and
increase the weight dramatically of the condenser (Nuclear Power, n.d.). By only building the tubes
of the condenser out of titanium, we can both increase the heat transfer capability by being able to
use thinner tubes, as well as maintain the overall cost of the condenser lower than building the
entire condenser out of titanium.
MAIN CONDENSER
4
We can have the shell made of a cheaper material such as a nickel copper alloy in order to
mitigate the price of the condenser while still maintaining its structural integrity. Using nickel
copper alloys will allow the condenser shell to still maintain its overall strength, because nickel
copper is a strong material for construction, and since it will not be subject to the constant thermal
stresses of the condenser tubes, it doesn’t need to have the same strength and resilience that the
tubes need.
The condenser will be made of two different materials, which makes it an ideal candidate
for galvanic corrosion. Galvanic corrosion occurs when two dissimilar metals contact an
electrolytic solution. This corrosion can be mitigated by using sacrificial anodes, such as zinc.
The sacrificial anode would wear away by providing electrons for use by the different materials
inside the condenser instead of the nickel copper alloy and prevent damage to the condenser. The
condenser is also susceptible to chloride stress corrosion cracking as well as general corrosion,
which requires materials resistant to corrosion. General corrosion can cause multiple cascading
problems for the systems of the plant and the condenser is susceptible because it is filled with
water and has the potential for oxygen inside, either during shutdown, or if the water being used
is not de-oxygenated properly. These requirements are important because if the condenser were
to corrode and cause a secondary tube leak from the heat sink into the steam system, it can cause
chemistry concerns and chloride contamination in the steam system.
To preserve the integrity of the condenser and the steam system, preventative
maintenance needs to be performed on both the heat sink side and the steam system side of the
condenser. Steam side maintenance should include inspections inside the condenser to determine
the condition of the heat exchanger tubes and ensure that there is no indication of erosion from
the steam. To mitigate erosion, we can install baffles or baffle tubes that do not have water
MAIN CONDENSER
5
running through them, but are put in place to absorb some of the kinetic energy of the steam as it
moves from turbine exhaust into the condenser. This will reduce the amount of energy imparted
on the condensing tubes and allow for slower steam to have adequate heat transfer without
damaging the tubes.
The water side needs to be inspected for tube deficiencies such as tube blockages or build
up inside the tubes that would inhibit heat transfer and flow. This is done by Eddy Currant
Testing, which uses an electrical signal to detect wall thickness of the tubes and ensure there is
not a problem with scale build up. We also need to perform borescope inspections to determine if
tubes need to be cleaned by physical means. One way that condenser tubes can be cleaned is by
brushing, where a hard-bristled brush is pushed through the tubes which will remove any soft
scale buildup and push it out the opposite side to be collected. Performing hydro lancing is a
method of removing hard caked on scale by using highly pressurized water to power wash the
inside of the condenser tubes. This method requires extensive safety measures based on the
pressure of the water being used. The water side also needs to have a visual inspection performed
and sacrificial anodes replaced when they are corroded beyond minimum acceptable value.
Condensers can also employ a double-tube sheet concept to provide an early warning system of
sorts for tube leakage.
In conclusion we can see that choosing the proper materials for condenser construction
includes more than just selecting based on strength. Materials need to be selected based on
corrosion resistance, heat transfer ability, and cost. Once materials are selected, the condenser
cannot be expected to fulfill its purpose on its own without proper maintenance and inspections.
These inspections can determine failed components, or materials in need of replacement such as
MAIN CONDENSER
sacrificial anodes. Preventative maintenance and corrective actions need to be implemented and
maintained if the condenser is going to perform its function for the designed life of the plant.
6
MAIN CONDENSER
7
References
Gonyeau, J. (2001). Condenser. Retrieved from http://www.nucleartourist.com/systems/cr.htm
Nuclear Power. (n.d.) Main Condenser-Steam Condenser. Retrieved from https://www.nuclearpower.net/nuclear-power-plant/turbine-generator-power-conversion-system/maincondenser-steam-condenser/
U.S. DOE. (1993). DOE Fundamentals Handbook: Chemisty Vol 1 of 2. Retrieved from
https://www.standards.doe.gov/standards-documents/1000/1015-bhdbk-1993v1/@@images/file
U.S. DOE. (1993). DOE Fundamentals Handbook: Materials Vol 1 of 2. Retrieved from
https://www.standards.doe.gov/standards-documents/1000/1017-BHdbk-1993v1/@@images/file
U.S. DOE. (1993). DOE Fundamentals Handbook: Materials Vol 2 of @. Retrieved from
https://www.standards.doe.gov/standards-documents/1000/1017-BHdbk-1993V2/@@images/file
World Nuclear Association. (2019). Cooling Power Plants. Retrieved from http://www.worldnuclear.org/information-library/current-and-future-generation/cooling-power-plants.aspx