US2613655A - Anticavitation device for removing boiling liquids from steam and water drums - Google Patents

Description

Oct. 14, 1952 R. F. M. WAESELYNCK 2,513,655

ANTICAVITATION DEVICE FOR REMOVING BOILING LIQUIDS FROM STEAM AND WATER DRUMS Filed Oct. 25,1945 2 SHEETS-SHEET 2 INVENTOR Patented Oct. 14, 1952 ANTICAVITATION DEVICE FOR REMOVING BOILING LIQUIDS FROM STEAM AND WATER DRUMS Raymond Francois Maurice -Waeselynck, Indret, par Basse-Indrc, France, assignor of one-half to Socicte Rateau (Societe Anonyme), Paris, France, a company of France Application October 23, 1945, Serial No. 624,037

In France April 13, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires April 13, 1963 4 Claims. 1

When the liquid and gaseous phases of a substance are in equlibrium inside a container, any lowering of pressure at a point inside the liquid which is not overcome by the head of liquid above the corresponding point, causes the appearance of the pnenomenon of cavitation. The latter is apparent in particular at the inlet of downcomers in steam boilers, and the bubbles of steam which are generated, accumulated in the vicinity of said inlet or driven b the liquid flowing to said inlet oppose the downward movement of the water in circulation.

The above phenomenon is amplified, and its consequences aggravated:

Firstly, if the liquid is already emulsified before arriving in the vicinity of the downcomer inlet, that is to say if it is mixed with a substantial quantity of steam bubbles;

Secondly, if the downcomer inlet is disposed in such a way that the liquid penetrates into it with a downward movement, and if said inlet is immersed to a sufiiciently small extent for the vertical movements which take place in the vicinity of said inlet to extend up to the surface of the liquid. Inv this latter case cavitation starts at the surface of the liquid and extends spontaneously to the whole central zone of the vortices, thus creating a direct communicating chimney between the gaseous phase in the boiler and the downcomer and causing the complete failure of the latter.

The occurrence of these cavitation phenomena,

in a steam boiler, for example, prevents normal circulations of the water from being established and may be the cause of serious damage.

It is the object of the present application to provide a simple remedy for these disadvantages, this remedy being applicable, moreover, not only to downcomers of steam boilers, whether the boilers are to be manufactured or are already in service, but also to tubings conductin any kind of liquid out of a reservoir where this liquid is to be found near its boiling point.

According to this invention, I provide upstream with respect to the usual inlet port of the downcomer a suction chamber the inlet to which is entirely submerged in the liquid and the top part of which is cooled by any suitable means (injection of cold liquid, surface refrigeration, etc): The inlet aperture of the chamber has a large cross-section disposed in such a way that the liquid before entering it has no substantial vertical velocity which is likely to start surface VOI'' tical movements. Shortly after its admission into the chamber the velocity of the liquid should 2 be at first ascendent or horizontal in such a way as to facilitate the discharge of steam bubbles or gas bubbles towards the top part of the chamber which thus forms a steam trap where these bubbles are condensed as they arrive. The liquid thus deemulsified and slightly cooled then moves downwards towards the port of the discharge piping.

The chamber may be completely submersed in the liquid or its top part may partiallyemerge in such a Way as to form a syphon. Its inlet opening is generally, but not necessarily, at a lower level than that of the axis of: the discharge port. In the case of a discharge pipe of small diameter the chamber may be constituted simply by a plunger tube which prolongs the outlet tube to the interior of the boiler; this plunger tube is flared at the inlet and has a high point or steam trap where the refrigeration which produces the condensation is carried out. If the discharge pipe is of large diameter the chamber may be constructed by means of a partition at its top section.

The following description with reference to the appended drawings given solely by way of examples will show how my invention may be carried out.

Fig. 1 is a sectional elevation on line II of Figure 2, the middle part of the drum being omitted.

Fig. 2 is a horizontal section on Figure 1.

Fig. 3 is a cross-section taken along, line IIIIII on Fig. l. i

Fig. 3a is an exploded perspective view illustrating the details of the joint between certain elements of the feed water system.

Fig. 4 is a cross-section, drawn on a larger scale, taken along line IV-IV on Fig. 2.

Fig. 5 is a longitudinal section taken along line v v on Fig. 4.

Fig. 6 is a view analogous to Fig. 1, showing a'modification.

. Fig. 7 is a corresponding horizontalsection analogous to Fig. 2.

Referring to Figs. lto 5, the reference char acter l denotes the body portion of a water and lil'le II-II of steam drum of a boiler, wherein in steam-generatingtubes (not shown) open in the zone between ac and bb; cup-shaped end portions'z; 3

are secured to the ends of drum I. Passing through end portion 2 are a pair of feed water pipes 4, 5 merging into a common trunk 6' which is then bifurcated. into a .pair of short sections I, 8 having end flanges 9, l0; secured through flanges l I, I2 thereon are a pair of feed water discharge pipes I3, id opening towards the bottom of the boiler body to discharge feed water into said boiler body. Squeezed between flanges 9, l l and H3, I2 respectively are a pair of perforated diaphragms such as i I (Fig. 3a) provided for the purpose of building an increased water pressure upstream.

Passing through the drum l in the neighborhood of the ends thereof are four water return pipes or downcomers l5, l6, l1, 18; all of them are similarly constructed so that one only need be described in detail; pipe IT, for instance, downwardly directed outside the boiler, is connected to the discharge port He bored in the wall of the boiler or drum I. Instead of permitting the liquid issuing from the boiler to enter directly the downcoming pipe I! through port He that would result in the above-mentioned disadvantages, a suction chamber covering the port He is. arranged within the boiler upstream with respect to said port.

Inthe embodiment of Figs. 1 to 3, said chamber consists of a plunger tube connected to the original discharge port [1e and extending the downcomer ll within the boiler. Said plunger tube or chamber H for instance, includes, from the drum wall, a slightly ascending portion Ila, then a top part or bend l'lb, forming a steam trap, which merges into a downwardly directed u portion llc with a downwardly opening flared end I'Id'. ,Said flared end I'ld is the inlet aperture for the liquid into the suction chamber or tube Hf preceding the original discharge port He.

Said. inlet end "id is entirely situated below the. liquid level in the boiler or drum 1, the downcomer I! with the plunger tube I I! acted then as av syphon. Moreover portion He is directed to the right as seen in plan view, so that said flared end Hd is-located within the end portion 3, i. e.

awayfrom bb.

Branching ofi from feed Water pipes l3, M at points upstream with reference to the perforated diaphragms ll, I2 between flanges 9, ll, [0, I2 are four small pipes I9, 20, 2!, 22 which enter chambers I57, I67, l'lf, I8), respectively; pipe 2| for instance includes an end portion 21a, located inthe bend Nb of chamber [1 that is to say near the top of said chamber; said portion has a closed end 23 and is formed with a double row of perforations 24 in its upper zone.

Owing to the foregoing arrangement, relatively cool feed wateris injected at the high point of pipes such as IT) under a pressure which may amount, for instance to some hundreds of grams per sq. cm. and is built up by reason of the provision of perforated diaphragm in feed water discharge pipes; said relatively cool feed water condenses any steam carried along with water in return pipes l1. 7

It should be understood that the diaphragm is merely an example of means to build up an increased pressure in the main feed water pipe, and obviously other known means providing a restriction in said main pipeupstreamwith respect to its discharge end may likewise be resorted to.

Referring to Figs. 6 and '7, wherein like parts are denoted by like reference characters, a downcoming pipe 25 is shown secured to end portions 2 and a partition 26 supported in the boiler drum l extends from the top thereof to a point substantially above the bottom, forming with the end portion 2 a trap for steam bubbles and leaving an inlet opening 21 which has a sufficiently large cross-section, in such a way that water passing into the chamber 28 between said partition 26 and end portion 2 moves substantially horizontally. Passing through the wall of end portion 2 is a rising feed water pipe 29 which opens into a horizontal tube 30 closed at both ends and perforated in its upper portion. Hanging from end portion 2 above tube 30 is a bell-shaped member 3| shown as comprised by a semi-cylindrical sheet metal with end cheeks.

Any steam carried along with Water past opening 21 and into the trap between the end portion 2 and partition 26 is condensed by relatively cool feed water from tube 30.

While I have described and illustrated specific embodiments which are believed to be efficient and reliable, my invention is not restricted thereto and many modifications may be brought about without departing from the spirit of this invention as comprehended by the following claims. The term boiler shall be construed broadly as meaning any vessel or reservoir containing a boiling liquid.

What I claim is:

l. The combination of a vapor-and-liquid boiler body for containing a liquid to be heated, an aperture provided in the wall of said boiler body through which liquid contained in the boiler body may be withdrawn, an external downcomer communicating with said aperture for receiving liquid withdrawn through said aperture, a steam trap chamber formed within said boiler body, said chamber having three openings therein, one of which is said aperture, the second of said openings being adjacent to the bottom of said boiler body and beneath the level of the liquid contained in said boiler body, a portion of said chamber extending upwardly to a point above both said aperture and said second opening, and means extending through said third opening and positioned in the said upwardly extending portion of said chamber for cooling the liquid which enters said chamber, whereby vapor in the liquid entering said chamber is condensed and liquid only is withdrawn through said aperture.

2. The combination of a vapor-and-liquid boiler body for containing a liquid to be heated, a feed liquid supply pipe opening into said body, an aperture provided in the wall of said boiler body through which liquid contained in the boiler body may be withdrawn, an external downcomer communicating with said aperture for receiving liquid withdrawn through said aperture, a steam trap chamber formed within said boiler body, said chamber having three openings therein, one of which is said aperture, the second of said openings being adjacent to the bottom of said boiler body and beneath the level of the liquid contained in said boiler body, a portion of said chamber extending upwardly to a point above both said aperture and said second opening, and means extending through said third opening and positioned in the said upwardly extending portion of said chamber for cooling the liquid which enters said chamber, comprising piping extending from said feed liquid supply pipe to the upwardly extending portion of said chamber whereby vapor in the liquid entering said chamber is condensed and liquid only is withdrawn through said aperure.

3. The combination of a vapor-and-liquid boiler body for containing a liquid to be heated, a feed liquid supply pipe opening into said boiler body, an aperture provided in the wall of said boiler body, a downcomer extending thru said aperture into the boiler body and terminating adjacent to the bottom wall of said boiler body and below said aperture and the level of the liquid contained in said boiler body, the portion of said downcomer within said boiler body having an intermediate section positioned at a point above said aperture to form a vapor trap, and piping extending from said feed liquid supply pipe to said intermediate section, whereby vapor in the heated liquid passing through said intermediate section is condensed by the cooler liquid supply introduced into said intermediate section through said last named piping.

4. The combination of a Vapor-and-liquid boiler body for containing a liquid to be heated, said boiler body consisting of a body portion and two end portions, an aperture provided in one of said end portions toward the bottom thereof through which liquid contained in said boiler body may be withdrawn therefrom, a downcomer communicating With said aperture to receive the liquid withdrawn therethrough, a partition within said boiler body separating the upper sections of said one end portion and said body portion to form a vapor trap in said one end portion, the lower sections of said one end portion and said body portion being in communication with one another through an opening provided in the lower section of said partition beneath the level of the REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 565,986 Hogan Aug. 18, 1896 985,834 Parker Mar. 7, 1911 2,169,935 Vorkauf Aug. 15, 1939 FOREGN PATENTS Number Country Date 130,736 Germany May 16, 1902 257,100 Germany Feb. 27, 1913 OTHER REFERENCES Page 197 of Power, published Mar. 4, 1919, vol. 49, No. 9.

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