US2220720A - Flame arresting device - Google Patents

Description

Nov .5,1940. G. H;JETT' 2,220,720

FLAME ARRE'STING DEVICE Filed Oct. 8, 1937 5 Sheets-Sheet 1 m imogz BY 2 6 ATTORNEY.

Nov.5, 1940. 2 H T' 2,220,720

FLAME ARRESTING DEVICE Filed Oct. 8, 1937 3 Sheets-Sheet 2 INVENTORi JVw 7 ATTORNEY..

Nov. 5, 1940. Y G, H. JETT 2,220,720

' FLAME ARRESTING DEVICE 7 Filed Oct. is, 1957 s Sheets-Sheet s Patented Nov. 5, 1940 UNITED STATES FLAME ARRESTIN G DEVICE George H. Jett,

Application October 8,

2 Claims.

This invention relates to flame arresters and has for its particular objects the provision of a compact, simple and highly efiective device of that type which is adapted to effectively prevent the hazard of fire or explosion of volatile solvents, such as petroleum vapors and distillates, as well as coal tar distillates, etc., when the same are transported in tankers or stored in land tanks. Other objects of my invention are hereinafter set forth.

In the accompanying drawings in which I have illustrated a preferred embodiment of my invention Figure 1 is a vertical section of my improved flame arrester;

Fig. 2 is a fragmentary detail section showing a cylindrical frame of the device immediately following the insertion of a spacing ring into the clamping member of said frame and prior to its being locked therein by compression of said clamping member; m

Fig. 3 is a section, similar to Fig. 2, but showing the position of the parts after the compression of said clamping member;

Fig. 4 is a plan view, on a reduced scale, of the device shown in Fig. 1;

Fig. 5 is a transverse section on the line 55 of Fig. 1, on a reduced scale;

Fig. 6 is a vertical section showing a simplified form of my improved flame arrester wherein a single cylindrical frame, only, is employed; and

Fig. 7 is a plan view, on a reduced scale and partly broken away, of the device shown in Fig. 6.

Referring to the drawings and construction shown therein, the reference numeral l designates the supporting pipe for my improved arrester, the same comprising a pipe section having top and bottom external flanges 2 and 3 and in-' ternal projecting lugs 4. The bottom flange 3 of this base member is adapted to be bolted to a breather pipe, of similar internal diameter, of a tank containing inflammable volatile fluids, such for example as petroleum or coal tar distillates and which tank it is desired to protect against a fire hazard or explosion.

Upper and lower cylindrical frames, comprising annular grooved clamping members 5 and 5, spacing rings 6 and 6, respectively mounted therein, and outer and inner wire screens a: and y are supported respectively on the flange 2 of the pipe I and flange 2' of an intermediate shell 1, each of which flanges has its top face a, a re spectively machined to form a suitable seat therefor. The shell I is in turn supported by the top clamping member 5 of the lower cylindrical Elizabeth, N. J.

1937, Serial No. 167,913

frame and is providedwith a depending skirt 1' that projects across. the external face of the outer screen, being spaced therefrom so as to afford an annular opening or vent b for the admission of air beneath said skirt or hood. Said shell is also provided with heat-radiating ribs 8 which are disposed intermediate said skirt and the flange 2. A cover member 9 is mounted on the top of the ring 5 of the upper cylindrical frame, said cover also having a depending skirt *10 9 which extends across the face of the outer screen of said top frame and also is spaced therefrom and from the lower shell 7 so as to form an annular vent or opening b. The-cover has a circular, positioning rib ll' formed on the inner face thereof which is of slightly smaller external diameter than the internal diameter of the grooved ring 5' of the upper cylindrical frame. The bolts l2, which are threaded into tapped lugs 4 and which are provided with nuts l3 and locking nuts M on their upper ends, serve to retain the upper and lower cylindrical frames and the shell 1 and cover 9 in their assembled relation on the base 2. The grooves I5 and 05' of the clamping members 5, 5f are originally formed of uniform width from top to "bottom thereof and the spacing rings 6, 6 have concave or bevelled faces, as indicated by the reference numerals l1 and I 1, these bevelled faces functioning as hereinafter described to rigidly secure the screens a: and 1/ within said clamping rings.

In the construction shown in Fig. 6 and '7, wherein a single cylindrical frame is employed, the pipe member I is generally similar to the construction shown in Fig. 1, but the lower cylindrical frame and the intermediate shell "I are omitted and due to the abbreviated height of this type of flame arrester the bolts 20, which serve to secure the parts in their assembled position, are considerably shorter in length.

I am well aware that it has been proposed as. set forth in Patent No. 1,672,042, to provide a flame arrester for. tanks or reservoirs containing evaporative fluids which employed a pair of spaced, concentric screens mounted on a cylindrical frame, one of which screens Was of sufficiently fine mesh to serve as a flame arrester while the other was of a coarser mesh and served to protect the inner screen from mechanical injury as well as to prevent the collection of foreign material around said inner screen. Accordingly I do not broadly claim any such construction herein, the claims being confined to a combination which includes essential features other than those disclosed in said patent.-

In assembling my improved flame arrester, each of the cylindrical frames is first assembled as a unit by inserting the metal spacing rings 6 and 6 between the inner and outer fine mesh screens at and 1/, which screens are preferably 40 mesh and formed of No. 30 B 8: S Monel metal wire. The two screens with the spacing rings 6 and 6 interposed between the same at the top and bottom thereof, are then inserted in the top and bottom clamping members and 5 whereupon the side walls of said clamping members are compressed so as to force the same into snug engagement with the concave channels I! or II formed on each of the vertical sides of said spacing rings. clamping members 5 and 5 serves not only to draw the screens taut but, due to the stiffness of the metal from which the same are formed, the frame will be rigid and the upper and lower rings 5 and 5 will be maintained or spaced at a uniform distance from each other when the said frames are completed.

The cylindrical frames having been assembled, one of them is applied to the flange 2 of the pipe I, the shell I is then positioned thereon in the manner shown in Fig. 1, the second cylindrical frame is then applied to the top of the flange 2' of said shell, the cover 9 is then applied as shown in Fig. 1 to the top of said second cylindrical frame and the entire assembly is then bolted together by means of bolts I2 and nuts l3 and Hi.

It is desirable that the spacing between the screens should be not less than A,", as thereby not only the friction drop of the vapor or gases passing thereover is decreased, as compared with two concentrically arranged screens in contact with each other, but also, during a vent fire on a tanker, when such an arrester'is employed, a siren-like warning signal which will be audible to all persons on deck, will be generated in those cases where the gases issuing through the screens have a gasoline content, prior to ignition thereof, from 2 /2% to 3% and a sufiicient air content to support perfect combustion. This warning signal is due to the immediate ignition of the gases upon issuance through the screens and. the resultant flame being consequently in immediate contact with the outer surface of the outer screen, it will play overthe same and cause it to become red hot. This rise in temperature of the screen greatly augments the speed of flow of the gases through the same, thus producing the siren-like signal. On the other hand, in the case of richer mixtures, containing insufiicient air to support complete combustion, the gases will not be ignited until they have passed to some distance beyond the screen and the resultant flame, being relatively remote from the outer surface of the screen, the latter will not become so intensely heated as to result in the generation of the aforesaid warning signal.

The importance of the wedge construction as herein described for maintaining screens taut and the locking the same in their position within the cylindrical frame, can best be appreciated when it is realized that because of the high temperature which is often attained when the gases escaping through the screens are ignited, it is not feasible to employ solder to secure the screens in position. In fact, the employment of solder would be extremely hazardous. Furthermore, it is of the utmost importance to maintain the screens at all times taut so as to be spaced from each other, as otherwise the friction drop is increased because of such contact Such compression of the sides of the upon distortion of one screen with the other. Said clamping means as herein described also serves to insure excellent heat conductivity between the screens, the spacing rings 6, and 6' and the grooved rings 5 and 5 clamped thereto and thereby as above stated, the screens are protected at all times from becoming so excessively hot as to melt or rupture.

It is particularly desirable that the height of the screen should not exceed about two inches from any point on the surface thereof to a heavy supporting member having a high index of heat conductivity, such for example as the metal spacing rings 6, B and metal rings 5, 5' which intimately engage the latter, as thereby there is no possibility of the screens becoming so hot as to melt and rupture.

In my improved flame arrester, because of the manner in which the screens are disposed, namely, in concentric relation with respect to the axis, if extended, of the pipe to be vented, there is far less restriction or friction drop of the gases and consequently should an explosion occur on the closed side, there is far less likelihood of mechanical damage to the screen than in the case of multiple fiat screens placed horizontally directly across the mouth of the vent pipe.

This application is a continuation in part of my copending application No. 734,807 filed July 24, 1934, for Flame arresting device.

In the construction, as stated the screens are made preferably of Monel metal and are consequently not subjected to deterioration by salt water or by the corrosive gases resulting from use of the equipment with sour crude oil or the like. Alternatively the screens can be made of other metals combining great mechanical strength, good heat conducting qualities and resistance to corrosion by salt atmosphere or gas fumes. Such screens of Monel are quite high in chromium and nickel and low in copper, with no zinc or aluminum. The screens are strong mechanically and withstand explosions within the pipe I. The screens have excellent heat conductive properties. The screens have a large net effective area for the passage of gases therethrough, which area is at least equal to the free pipe area to which the flame arrester is connected. In the embodiment described the effective area is 1 times the area of the pipe I. The large effective area for the passage of gases is secured without excessive screen dimension by mounting the screens as concentric hollow cylinders with internal spacers to keep the screens a full apart, even after considerable exposure to flame has caused warping or bulging of the screens. The device permits of relatively great ease in cleaning, and clogging of the screens with oily material or the like is minimized.

The structure described stops a flame under all conditions when explosion occurs on the open side of the vent. By open is meant the side of the vent contained within a hood or enclosure having free access to the atmosphere. The flame arrester withstands the heat generated by a prolonged vent fire with flame playing against the outside of the grid. The design and construction is such that the materials used withstand the maximum temperatures likely to be generated in this service. The structure provides for free conduction of the heat from the wire screen by providing heat conducting joints between the arrester grid and the bell shaped cover. The

structure provides large surface external parts capable of absorbing, conducting away and dissipating the heat.

The flame arrester is immune from the passage of flame when ignition occurs in the closed pipe I. The width of the cylindrical screen ring is such that the heat can be conducted away from all parts of the screen and dissipated into the atmosphere rapidly.

Various changes may be made within the scope of the appended claims in which it is desired to claim all novelty inherent in the invention as broadly as the prior art permits.

Having thus described my invention, what I claim and desire to obtain by United States Letters Patent is:

l. A flame arresting device, comprising a cylindrical body formed of a plurality of superimposed sections united into a unitary assembly and which sections are spaced from each other to form an annular gas passage, a plurality of spaced, concentrically arranged, cylindrical flame-arresting metallic screens spanning said gas passage, spacing members interposed between said screens at the respective upper and lower ends thereof and annular clamping grooved members whose lateral surfaces inside the groove thereof are concentric with the adjacent lateral surfaces of said spacing members,

2. A flame arrester assembly, comprising a pipe end, a cylindrical frame formed of superimposed members united together and spaced from each other to form a lateral gas passage, a

plurality of spaced, concentrically arranged, cylindrical, flame-arresting metallic screens covering said openings, annular terminal supports for the ends of each screen, said supports each having an annular channel therein, and annular spacing members interposed between the adjacent ends of each pair of screens and projecting into the channels of said supports, the adjacent surfaces of each support and its associated spacing member being respectively of convex curva- 25 ture and of concave curvature.

GEORGE H. JETT.

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