More flexible, more durable, more profitable:
There are very good reasons why high-pressure feedwater heaters
of the header type, shortly called header-type heaters, have been
used for many decades in almost all large coal-fired power plants
in Europe, South Africa and Australia:
They offer excellent technical and commercial advantages
over conventional U-type high-pressure heaters, also known as
tubesheet-type heaters. They permit much greater power plant
operation flexibility with a higher number of load changes and
last up to four times as long. In addition, they are by far a more
cost-effective solution, both in terms of investment and operating
costs. In short, header-type heaters are a superior heat exchanger
technology that is gaining popularity around the world.
The high pressures of supercritical water/steam cycles require the
tubesheet walls of U-type heaters to be extremely thick. Irreparable
thermal cracks often occur at the joints with the thin shell after
just 10 to 15 years of operation. In addition, the especially large
feedwater mass flows make it necessary due to construction
reasons to arrange twice the number of U-type heaters in two
parallel piping trains.
In contrast, header-type heaters have a service life without repairs
of up to 50 years thanks to their excellent thermo elasticity and
can be arranged in a single piping train, which reduces the cost of
piping, valves and buildings.
Advantage of header-type heaters due to single-train arrangement
■ World’s No. 1 supplier of header-type heaters
■ Designer and manufacturer of header-type heaters since 1935
■ Over 1,200 references for header-type heaters in 100 to 1,100
MW power plants
■ Proven technology with convincing advantages over U-type
– More flexible power plant operation
– Longer service life (up to 4 times longer)
– Lower investment and operating costs
3D model of a header-type heater
■ Designs for vertical and horizontal installation
■ Almost zero failure rate (0.00015 %) in approximately one
million installed snake tubes
■ Special device to plug snake tubes is available
■ Easy access to the headers through inspection opening with
As nuclear power plants are frequently operated according to
Unlike in U-type heaters, the water and steam sides in header-type
heaters are separated by two thick-walled pipes, the inlet and outlet
headers, instead of by a tubesheet. Moreover, the heat exchanger
tubes are arranged in a snake shape instead of U shape, generally
in 3 or 4 water passes through the shell area.
A complete high-pressure heater train generally consists of three
header-type heaters and a separate desuperheater. The heaters
are installed vertically in most cases and only rarely horizontally.
Header with snake tubes
Fabrication of header-type heaters is more complex than for U-type
heaters. Special attention is paid to the connections between the
headers and snake tubes, which are welded together indirectly
using nipples. The automated welding process used is especially
reliable. In the over 1,200 header-type heaters manufactured
since 1935, with around one million tubes, only 15 tubes had to
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Investing in header-type heaters instead of U-type heaters usually
pays off in power plants with nominal capacities from about 500
MW. Above this threshold, investment costs for U-type heaters
escalate since they must be arranged in two trains instead of in
a single train. Consequently, the cost of equivalent header-type
heaters is generally exceeded. Maintenance costs for U-type
heaters are much higher in large power plant units or in cycling
operation because heaters of this type are susceptible to damage
and require frequent repairs and not seldom must even be
450 MW Avedöre 2 coal-fired power plant, Denmark:
The four header-type heaters were manufactured in the Neubeckum
facility and have been operating since 2000.
Tube bundle in the manufacturing facility
950 MW Niederaussem K lignite-fired power plant, Germany:
Equipping one of the world’s most modern lignite-fired power
plants (BoA 1) with header-type heaters (2000).
Header-type heater during installation in the power plant