Abstract:
A system and method for reducing the damaging effects of bypass steam in a cylindrical steam surface condenser in a steam turbine/bypass power plant application consisting of a hat-like steam admission chamber located external to the condenser shell having a header with orifices and dummy rods or tubes arranged between the bypass header and the condensing tubes.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to power generating systems and methods of introduction of bypass steam into steam surface condensers. 
     The primary function of steam surface condensers in a power plant application is to condense the turbine exhaust steam. In certain applications such as combined cycle plants, trash to steam plants, etc., the steam surface condenser is required to condense the steam that has bypassed the steam turbine. In the bypass scenario, the steam turbine is usually not functioning. The steam from the steam generating devices bypasses the steam turbine and is admitted to the condenser at a suitable pressure and temperature. 
     In large rectangular condensers the bypass steam is admitted in a steam dome. Such steam domes have large steam spaces and provide ample space for the bypass steam to expand and dissipate it&#39;s energy. 
     In cylindrical condensers, however, the steam space adjacent to the tubes is very limited, requiring the bypass steam to expand in confined spaces. The design of dump inlet headers, therefore, is very critical. During expansion, the bypass steam must not cause any damage to the condenser shell internals. The bypass steam must be permitted flow into the all parts of the tube bundle and condense efficiently. 
     In cylindrical steam surface condensers, the bypass steam is usually admitted in the confined space between the shell of the condenser and the tubes, or in the steam inlet. If admitted in the confined space between the shell and the tubes, the expanding bypass steam tends to cause damage to the tubes and the shell. If admitted in the steam inlet, the bypass header tends to block the flow of incoming turbine exhaust steam, thereby affecting the performance of the condenser. In each of the conventional systems for admission, the shell internals are exposed to the damaging effects of expanding bypass steam. Repairing of replacing the damaged shell internals is a very time consuming and expensive proposition. 
     It is an object of the present invention to avoid the damaging effect of introducing bypass steam to cylindrical steam surface condensers in power generating steam turbine systems. 
     It is another object of the invention to introduce bypass steam to cylindrical steam surface condensers with greatly reduced damage to the condensing tubes and other shell internal components. 
     A further object is to introduce bypass steam to condensers with reduced noise. 
     SUMMARY OF THE INVENTION 
     These objects, and others which will become apparent from the following disclosure and drawings, are achieved by the present invention which comprises in one aspect a system for introducing bypass steam to a cylindrical steam surface condenser, the condenser having condensing tubes and a condenser shell, the condenser shell with a opening to accept bypass steam, the system comprising a hat-like steam admission chamber external to the condenser shell, the admission chamber adapted to fit the opening in the condenser shell, the admission chamber including a header having orifices arranged within the admission chamber, the system also comprising dummy rods or tubes located above the tube between the condensing tubes and the opening. 
     In another aspect, the invention comprises method of introducing bypass steam to a cylindrical steam surface condenser having a condenser shell and condensing tubes comprising providing an opening in the condenser shell and a hat-like steam admission chamber external to the circumference of the condenser shell; securing the admission chamber to the opening in the condenser shell, the admission chamber including a header having orifices arranged within the admission chamber; and providing dummy rods or tubes arranged within the circumference of the condenser between the condensing tubes and the opening to buffer the impact of the bypass steam released through the orifices prior to the bypass steam reaching the condensing tubes. 
     It is preferred to construct the bypass inlet header of stainless steel. The header can be a single steam inlet with orifices for release of the steam into the admission chamber, or can be two or more steam inlets with orifices which can be arranged one within the other. In embodiments of header systems with two steam inlets, a low pressure inlet can be inside a high pressure inlet. 
     It is preferred to construct the admission chamber of a large lower cylinder and a large upper cylinder, with the lower cylinder welded to the opening, and the upper cylinder welded to the lower cylinder. Alternatively the upper cylinder can be directly welded to the opening in the condenser. The upper cylinder can have a cover with an opening through which the header is arranged. 
     The hat-like steam admission chamber is preferably covered with a suitable material to reduce the noise emanating from the expanding steam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a hat-like steam admission chamber with a single header according to the invention. 
     FIG. 2 is a cross-sectional view of a hat-like steam admission chamber with dual headers, according to a second embodiment of the invention. The dual header arrangement can similarly be adapted to multiple inlet header arrangement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, bypass steam  1  flows into the condenser  15  through a stainless steel header  2 . The stainless steel header  2  is equipped with orifices  3 . The stainless steel header  2  is installed in a cover which is welded on top of a large upper cylinder  4 . The large upper cylinder  4  is welded to a large lower cylinder  6 . The large lower cylinder  6  is welded to the cylindrical condenser shell  7  (upper portion of shell is illustrated). Two rows of dummy infringement rods or tubes  8  are installed above the condensing tubes  9  so as to protect the condensing tubes from the impact of the bypass steam  1  released through the orifices  3 . 
     Sound insulation is arranged on in the external surfaces of the large upper cylinder  4 , lower cylinder  6 , header  2 , and cover to reduce the noise emanating form expanding steam in dump mode. 
     Referring now to FIG. 2, a dual bypass steam inlet is illustrated wherein a second inlet  14  for lower pressure bypass steam  11  directs steam through a second header  12  arranged within first high pressure header  2  and having a second set of orifices  13 . In this embodiment, bypass steam is introduced at multiple pressures into the condenser  15 . The second stream of bypass  11  steam is admitted through a second header  12  constructed of stainless steel pipe installed inside first bypass header pipe  2 . The height of the large upper cylinder  4  is larger in this second embodiment so as to provide adequate expanding height for the two streams of bypass steam  1  and  11 . 
     More than two headers and sets of orifices can be provided if desired, and each can handle bypass steam at different pressures. 
     When the system is in bypass mode, bypass steam  1  flows through the stainless steel header  2  (or headers  2  and  12 ), and expands through the orifices  3  (or  3  and  13  according to the second embodiment). The expanding steam with high velocity impinges on the inner walls of the large upper cylinder  4 . The large upper cylinder  4  is located external to the condenser shell  7  and absorbs the brunt of the energy from the expanding bypass steam. The bypass steam bounces off the inner walls of the large upper cylinder  4  and impinges on the dummy infringement rods or tubes  8  prior to impacting on the condensing tubes  9 . The dummy infringement rods or tubes  8  present a second line of defense against the damaging effects of the expanding bypass steam. The bypass steam then enters the condensing tube bundle  9  carrying cold water. The hot steam comes in contact with the cold tubes  9  and condenses. 
     The expanding bypass steam create loud noise. These noise levels can be reduced by treating the inner walls of the large upper cylinder  4  or applying sound insulation on the external surfaces of large cylinders  4  and  6 . In the event of excessive erosion or corrosion, the entire top section consisting of the large upper cylinder  4 , cover  5 , large lower cylinder  6 , and the inner stainless steel header  2  (or headers  2  and  12 ) can be replaced for a relatively small expense in a very short amount of time. 
     The system and method of the invention provide several advantages over prior systems and methods as a result of the bypass steam expanding externally to the condenser shell containing the tubes. The energy of the expanding steam is absorbed by a cylinder which is not a part of the main shell. If damaged in regular or transient operation, the entire upper section of the bypass inlet arrangement can be replaced easily and inexpensively. This system allows reduction of high noise levels by applying local sound insulation around the cylinders  4  and  8 , header  2  and optional header  12 , and any additional headers, or by treating the inside surface of the cylinders  4  &amp;  6 . 
     The design is easily adaptable to multiple bypass admission streams. 
     While the invention and the preferred embodiments have been described in detail, various alternative embodiments, alternatives, and improvements should become apparent to those skilled in the art without departing from the spirit and scope of the invention.