The present invention is generally related to nozzles for use in pressure vessels and is more particularly directed to a radial nozzle assembly having a nozzle that extends radially and horizontally from a cup-shaped flange disposed at one end of the nozzle.
Pressure vessels are typically subjected to cyclic thermal and mechanical stresses due to changes in internal fluid pressure and temperature. These cyclic stresses can limit the number and/or magnitude of pressure and/or temperature cycles that the pressure vessels can withstand. Historically, pressure vessels have bores, or penetrations extending through the shell of the pressure vessel. Conduits such as pipes are attached to the pressure vessel such that the penetration and the pipes are in fluid communication with one another to allow for the ingress and egress of fluids to and from the pressure vessel. Stress concentrations exist at the intersection of the pipe(s) and the shell of the pressure vessel. These stress concentrations result in higher stresses and often become a limiting factor in the design of the pressure vessel for phenomena such as fatigue and/or cracking of the magnetite layer that can form on the metal surface, and which may limit the useful lifetime.
Such a pressure vessel may be a boiler or steam drum of an evaporator system as shown in
For example, for a cold start the water temperature inside the steam drum 104 can rise from 15° C. to 100° C. in less than 10 minutes. This produces a large thermal gradient and hence compressive stress in the steam drum 104 wall. As the pressure in the steam drum 104 increases, the temperature gradient through the drum wall is reduced and consequently the stress due to pressure becomes the dominant stress in the drum. The stress due to pressure (with increased pressure in the steam drum 104) is a tensile stress. The stress range for the drum is determined by the difference between the final tensile stress at full load (pressure) and the initial compressive thermal stress. Boiler Design Codes (such as ASME and EN) impose limits on the stress at design pressure. Some codes, such as for example EN12952-3, also include limits on the permissible stress range for a startup-shutdown cycle. These limits are intended to protect against fatigue damage and phenomena such as cracking of the magnetite layer that forms on the surface of the steel at operating temperature.
Furthermore, steam boilers are provided with a means of determining the water level in the steam drum, as shown in
Referring to
A new approach is suggested by the present invention in which a radial nozzle assembly is used in place of the horizontal connecting nozzle, the radial nozzle assembly being large enough so that a continuous horizontal path is maintained from the inside of the drum to a sensing line 242 as shown in
In one embodiment of the present invention, a nozzle assembly for use in a pressure vessel is provided. The pressure vessel is defined by a wall having an inner surface of which defines an interior area. An aperture extends through the wall of the pressure vessel. The nozzle assembly includes a nozzle having an inner and outer end with a bore disposed therein along its length to provide for fluid flow therethrough. The nozzle assembly includes a flange that extends from the inner end of the nozzle. The flange is defined by a wall having a cup-shape with an open end which defines an interior area. The open end of the flange is attachable to the pressure vessel in fluid communication with the aperture of the wall of the pressure vessel.
The radial nozzle assembly 202 includes a nozzle 220 and a cup-shaped flange 222 for securing the nozzle assembly to the wall 204 of the pressure vessel 200 such that the nozzle is disposed in both a radial orientation to the flange and a horizontal orientation. The nozzle has an inner and outer end 224, 226, respectively, with a bore 228 disposed therethrough along its length to permit fluid flow through the wall 204 of the pressure vessel 200. Preferably, the bore is disposed axially along its length. The outer end 226 of the nozzle 220 has a circumferentially chamfered surface 230 to reduce the outer dimensions to accommodate the pipe, conduit or device 106 (as shown in
The flange 222 is defined by a generally cup or dome-shaped wall 232 having an open end 234. The flange wall 232 has an inner concave surface 236 that defines an interior area 238. In one embodiment, the inner end 224 of the nozzle 220 may be integrally formed in the flange 222 at a predetermined location and angle, which will be described in greater detail hereinafter. Alternatively, the nozzle 220 may be a separate piece secured to the flange 222. In such an embodiment, the flange wall 232 has a through-bore or aperture 240 at a predetermined location and angle. This location and angle of the bore 240 may be dependent on the dimensions of the flange 222 and the vessel 200, and the location of the nozzle assembly 202 on the vessel, which will be described in greater detail hereinafter. The inner end 224 of the nozzle 230 is secured within or about the bore 240 of the flange wall 232, such as by welding, to provide fluid communication from the outer end 226 of the nozzle to the interior area 238 of the flange 222. The nozzle 220 is secured to the flange 222 in one embodiment such that the nozzle is disposed radially to the curvature of the flange and horizontally when attached to the pressure vessel 200. The flange 222 may be spherical or hemispherical in shape having a predetermined radius.
The open end 234 of the flange 222 is attached, such as by welding, in or about the bore 210 in the arcuate portion of the wall 204 of the pressure vessel 200, as best shown in
Referring to
Referring to
The present invention provides an option for natural circulation for heat recovery steam generators instead of once through applications for high pressure applications.
While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
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Number | Date | Country | |
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20130313341 A1 | Nov 2013 | US |