Modular bundle of tubes for a steam condenser, and a steam condenser using such modular bundles

A modular bundle of tubes for a steam condenser comprises two perforated plates (24, 25), a series of tubes (22) interconnecting the perforated plates, and a set of intermediate supporting plates (23) distributed between the two perforated plates. The improvement wherein both perforated plates are the same size, each being surrounded by a reinforcing frame (24, 25) which is thicker than the perforated plate, and wherein drawbars (26) fitted with length-adjusting means (27) interconnect the perforated plates, said drawbars being fixed to said frames and being distributed along the said frames.

The present invention relates to steam condensers. A steam condenser for an 
electricity power station is constituted by an assembly of tubes having 
each of their ends connected to a perforated plate, the assembly being 
placed inside a condenser body which is connected to the exhaust from the 
turbines, and a water tank is connected to each perforated plate. 
BACKGROUND OF THE INVENTION 
Generally speaking, the tubes are mounted in the perforated plates and are 
then fixed thereto by expanding or by welding at the power station size. 
This operation takes a long time since there are many tubes to be put into 
place. 
Work has thus been done to provide modular bundles of tubes which are 
factory-built so as to minimize the number of operations that need to be 
performed on site, and hence to reduce the time spent on site. 
FIGS. 1 and 2 thus show an example of a known arrangement used at the San 
Onofre power station in California, USA. The steam condenser comprises a 
bundle of tubes 1 between perforated plates 2 and 3 which is constructed 
in a factory and then assembled, on site, with the body of the condenser 
4. 
The bundle of tubes comprises four modules which are assembled together on 
site. Before the modules arrive, the condenser body is terminated by two 
right-angled portions 5 and 6. In known manner the portion 6 has four 
windows as shown in FIG. 2. The left hand side of the body 4 as seen in 
FIG. 1 terminates with a portion 7. The perforated plate 3 of each module 
is connected to a frame 8 by means of screws 9. Portions 10 and 11 are 
welded to appropriate faces of the frame to close the condenser body. The 
left hand water tank 12 on site is terminated by a plate 13 which is of 
the same shape as the part 6 shown in FIG. 2, which is why the part shown 
in FIG. 2 is referenced 13-6. The plate 13 is fixed to the four perforated 
plates 3 to hold them together. 
Assembly thus takes place as follows: each module comprises a simple 
perforated plate 2 at its right hand end (as seen in FIG. 1) while at its 
left hand end it comprises the perforated plate 3 together with the parts 
8, 10 and 11. The module made in this way is inserted from right to left 
through one of the four windows in the portion 6 until the perforated 
plate 2 abuts against the portion 6 via a gasket 18. The assembly is then 
fixed by means of screws 15 and the plates 11 are welded to the body 4. 
The water tank 12, 13 is then fixed on by means of screws 16. 
Gaskets 14 and 19 are disposed on either side of the perforated plate 3, 
between the perforated plate and the frame 8 and between the perforated 
plate and the frame 13. 
This structure has several drawbacks. In particular, it is impossible to 
verify the gaskets 18 and 19 once the parts are assembled and the weld 17 
has been made; the welding 17 is done on site; the assembly is 
asymmetrical; and prior to assembly the modules are insufficiently rigid. 
Preferred embodiments of the present invention mitigate these drawbacks and 
provide a solution which is more satisfactory, more practical, and more 
reliable. 
SUMMARY OF THE INVENTION 
The present invention provides a modular bundle of tubes for a steam 
condenser comprising two perforated plates, a series of tubes 
interconnecting the perforated plates, and a set of intermediate 
supporting plates distributed between the two perforated plates, the 
improvement wherein both perforated plates are the same size, each being 
surrounded by a reinforcing frame which is thicker than the perforated 
plate, and wherein drawbars fitted with length-adjusting means 
interconnect the perforated plates, said drawbars being fixed to said 
frames and being distributed along the same frames. 
The invention also provides a steam condenser comprising a skin containing 
a bundle of tubes which is associated at each end with a water tank, 
wherein the said bundle of tubes is made by assembling in parallel a 
plurality n of such modular bundles of tubes. 
In a preferred embodiment of the invention, the n bundles of tubes are 
assembled at each end by means of an assembly frame having n windows and 
bearing against and fixed to the reinforcing frame of each modular bundle 
on the outside thereof relative to the tubes, the outer perimeter of the 
assembly frame having an external extension projecting beyond the outer 
perimeter of the assembled bundles of tubes, said assembly frame being 
fixed along said outer edge to a flange on the skin of the condenser, the 
size of the passage through the flange being the same at each end of the 
condenser.

MORE DETAILED DESCRIPTION 
FIG. 3 shows a modular bundle of tubes in accordance with the invention. It 
comprises two perforated end plates 20 and 21, and a plurality of 
intermediate supporting plates 23. Each perforated plate is surrounded by 
a reinforcing frame: 24 for the plate 20; and 25 for the plate 21. The 
reinforcing frames are welded to their respective plates. Finally, a 
series of drawbars 26 interconnect the two plates and include 
length-adjusting means that enable them to set the distance between the 
plates with accuracy. These means are shown in greater detail in FIG. 4. 
The drawbars are at a spacing of about 500 mm. At least some of the 
intermediate supporting plates 23 are connected to the drawbars to 
increase the rigidity of the assembly. The length-adjusting means comprise 
a turnbuckle 27 having a bore which is tapped from each end with opposite 
handed threads. The drawbars are made in two parts 26a and 26b, and their 
respective ends have opposite handed external threads which are screwed 
into the turnbuckle. Lock nuts 28 at the other ends of the draw rod parts 
lock them in position in the end frames. 
The frames 24 and 25 and the drawbars 26 together with the intermediate 
supporting plates 23 give the assembly excellent rigidity. The module is 
symmetrical and the perforated plates at both ends of the tubes in the 
bundle are of the same size. 
FIG. 5 shows the manner in which a module, such as the module shown in FIG. 
3, is assembled together with three other identical modules and then 
inside a condenser enclosure. 
The condenser has an outer skin 29 which is shown in part. 
At each end of the condenser skin there is a flange 30 which is welded to 
the skin and serves to fix the set of four assembled modules inside the 
skin. 
FIG. 5 shows only a small portion, but the overall assembly is symmetrical, 
left to right and top to bottom. 
The modules are assembled to one another by means of an assembly frame 31 
which bears against the four end frames 25 of the modules to be assembled 
together. The parts are fixed to one another by stud bolts 32 passing 
through holes 32a in the frame 31, with nuts 33. Gaskets 34 and 35 are 
interposed around each of the frames 25 on each module between the frame 
31 and the respective frames 25. 
Likewise, bearing strips 36 are interposed all along the frame in 500 mm 
lengths between the nuts 33 and the frame 31. 
Finally, the outer perimeter of the frame 31 has an outward extension 37 
which projects beyond the outside perimeter of the complete assembled 
bundle of tubes for fixing to the flanges 30 by means of threaded rods 38 
passing through holes 38a in the assembly frame, together with nuts 39 and 
40. Gaskets 43 and 44 are interposed between the outer edge 37 of the 
frame 31 and the flange 30. 
Likewise, a bearing frame 45 and a gasket 46 are interposed between the 
flange 42 and the frame 31. 
FIG. 7 is a view on an enlarged scale of the part marked VII in FIG. 5. 
FIG. 8 shows a variant of FIG. 7 in which the gaskets 34 and 35 are 
protected by a hydraulic barrier. Each reinforcing frame 25 is thus 
provided with facing 47 all around its periphery, the facing is connected 
by channels 48 and 49 to a water supply, not shown, at a higher pressure 
than the cooling water arriving in the water tank 41 (FIG. 5). The bearing 
plates 36 are then replaced by individual thick washers 50. The gaskets 51 
and 52 are interposed between the frame 31 and the washers 50 and between 
the washers 50 and the rods 32. 
In the example described, the assembly frame 31 is fixed to the frames 25 
of the modules by screws, which is the preferred reinforcing method. 
However, other fixing means could be used, and the assembly frame 31 could 
be welded to the reinforcing frames 25, for example.