US3454180A

US3454180A - Fire protective covering for stored hydrocarbons

Info

Publication number: US3454180A
Application number: US622830A
Authority: US
Inventors: Robert J Fiocco; Edward B Schumacher; Edward C Sommer
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1966-11-07
Filing date: 1966-11-07
Publication date: 1969-07-08
Anticipated expiration: 1986-07-08

Description

July-8, 1969 R. J. FIOCCO ET AL 3,454,130

FIRE PROTECTIVE COVERING FOR STORED HYDROCARBONS Filed Nov. 7, 1966 R J. H0000 E. a. sch/um:cms'l'r lmms E. a. sauna? PATEN? AffORA/EY United States Patent ABSTRACT OF THE DISCLOSURE An open roof storage vessel for fuel oil includes a fire protective roof or cover comprised of a layer of expanded, nonflammable, irregularly shaped perlite particles which are floatably supported upon the free surface of the fuel oil in the storage vessel. The expanded perlite has a particle size at least 50% of which is retained by an 8 mesh screen size and is sufiiciently thick to provide a minimum of /2 inch freeboard above the surface level of the liquid within the storage vessel. The perlite particles may be impregnated with fire retardant chemicals and the individual particles may also be cemented into larger composite particles.

This is a continuation-in-part of application Ser. No. 552,508, filed May 24, 1966, now abandoned.

invention relates in general to fire extinguishing apparatus and methods and more particularly to a new and improved method of reducing the fire hazard of hydrocarbon liquid stored in open roof storage facilities.

In accordance with the present invention, a layer of expanded non-flammable material such as expanded volcanic ash, known as perlite, of a particle size 50% or more of which is 8 mesh or larger and having a freeboard portion ofat least V2 inch above the level of oil is floated upon the top of a body of fuel oil in an open storage pit. The /2 inch freeboard is usually obtained with a 2 inch layer of oil wet perlite. Selection of the relatively large particle size in combination with the /2 inch freeboard portion of the layer of the expanded perlite has been found to produce a unique and highly efficient fire retardation surface. As a safeguard against high wind conditions and/or'for easier application, the perlite cover may be applied in the form of an oil slurry. Any excess oil in the upper surface of the cover will drain back into the main body of stored fuel in a short period of time.

The perlite blanket or cover is permanent and flexible allowing for variation in the level of fuel in the storage vessel. If the surface cover is penetrated by a sufliciently hot foreign object so as to ignite the fuel, combustion in the area of penetration will initially occur. However, the blanket will gradually reform over the penetrated area and extinguish the flame in a matter of minutes. In numerous tests to date, all flames have been extinguished in from 1 to 12 minutes after the start when a 2 inch thick perlite blanket of 50% or more of which is 8 mesh or larger particle size was used. It has been found that substantially improved performance is obtained by employing larger size particles which may be formed by the cementing or other-wise bonding of a plurality of smaller perlite particles into larger particles having a maximum dimension of up to 2 inches, preferably in the range of an inch. It has also been found that if the particles are smoothed or otherwise bufied to remove the sharp edges and corners therefrom, the performance of the fire protection blanket is improved. In addition,

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a fringe benefit of applicants invention is that the evaporative loss of hydrocarbon is prevented and at the same time emission of noxious odors is substantially reduced.

Accordingly, it is a principal object of the invention to provide an improved apparatus and method for fire protection of fuel oil in open pit storage.

Another object of the invention is to provide a novel method of rendering a body of stored hydrocarbon fuel substantially fireproof.

Another object of the invention is to provide a floating blanket of expanded perlite upon a body of stored hydrocarbon liquid sufliciently thick to support water on top thereof so that water may be flushed to any possible area of ignition that may exist on the surface of the storage pit.

These and other objects and advantages of the invention will become apparent and the invention will be fully understood from the following description and drawin gs in which:

FIG. 1 is a generalized view of the invention as it would be employed on a typical open pit storage area; and

FIG. 2 is an enlarged detailed view of a portion of FIG. 1 showing the invention.

Referring to the drawings in particular, an open fuel or storage area is shown generally at 10. The open pit disclosed is of the normal earthen type but it should be understood that applicants invention is equally suitable for application to open roof tanks as well, or any other area wherever a surface fire hazard upon a stored hydrocarbon is present. The pit 10 contains a body of heavy fuel oil 12 such as what is commonly known as No. 5 and No. *6 fuel oil. The fuel oil 12 surface supports a layer of expanded volcanic rock such as perlite 14. Referring specifically to FIG. 2, the layer 14 of perlite is preferably at least 2 inches thick and floating on the surface of the fuel oil 12. Because the layer 14 effectively is a floating object on the surface of the liquid, it will sink to some extent into the liquid and the liquid 12 will penetrate to a line designated 16. The perlite granules below the line 16 are substantially wetted with the fuel oil 12. However, the perlite granules in the blanket 14 above the dotted line 16 may or may not be oil wetted but in either case are substantially free of oil impregnation and no wicking within this area of the fuel into the top portion of the blanket will occur. The thickness of the cover above the line 16 represents the freeboard portion. Preferably the perlite granules are relatively large in size because it has been found that the larger they are in size, the better the fireproofing performance of the blanket 14. In fact, it has been found desirable that for satisfactory performance 50% or more of the granules forming the blanket 14 must have a size of 8 mesh or larger or in other words be retained by an 8 mesh screen.

It has also been found that the bonding or cementing of individual perlite particles into larger clusters up to 2 inches in diameter but preferably between A and of an inch provides an optimized fire protection blanket. Protection can be further enhanced by producing particles with smooth surfaces that drain readily or by treating the particles or clusters with chemicals that have fire extinguishment characteristics. Binder materials may be inorganic (silicates, glasses) or organic (asphalts, coal tars, solvent resistant polymers). Silicones, halogens, carbonates, etc. may be used to improve fire extinguishing properties through chemical action. Freeboard requirements may also be reduced by this additional treatment of the perlite.

An additional feature of the relatively thick floating cover or blanket 14 is that it has sufficient buoyancy to support a thin layer of water should it be desired to apply water to extinguish any fire that may occur. Because the blanket will support a thin layer of water, water may be flushed across the surface of the storage pit to the area of combustion. Direct application of water to the unblanketed surface of a body of fuel oil would obviously be completely ineffective since the Water would simply sink as soon as it hits the fuel oil and would not therefore be able to be floated across the surface of the fuel oil to the place of combustion.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In combination, an open roof storage vessel including side wall elements, a body of No. 5 or No. 6 heavy fuel oil hydrocarbon liquid within said vessel, and a layer of expanded non-flammable, irregularly shaped perlite floatably supported upon the free surface of said fuel oil, at least 50% of said aggregate having a particle size detainable by an 8 mesh size screen, said layer having a minimum /2 inch freeboard portion that is above the surface level of the hydrocarbon liquid whereby said layer reduces evaporative loss of hydrocarbon liquid to the atmosphere, prevents escape of noxious odors, and provides a fire extinguisher cover for said open roof storage vessel.

2. In combination, an open roof storage vessel including side wall elements, a body of hydrocarbon liquid, within said vessel, and a layer of expanded non-flammable irregularly shaped perlite aggregate, floatably supported upon the free surface of said fuel oil, said layer having a /2 inch thick freeboard portion substantially drained of oil whereby said layer reduces evaporative loss of hydrocarbon liquid to the atmosphere, prevents escape of noxious odors, and provides a fire extinguisher cover for said open roof storage vessel.

3. The combination of claim 2 wherein said layer of aggregate is substantially impervious to water so that should an ignition source exist at some uncovered portion of the surface of said vessel to create a fire, said layer will be capable of supporting a thin layer of water flushed over its upper surface to extinguish said fire at said uncovered portion.

4. The combination of claim 2 wherein said aggregate is formed of a plurality of smaller expanded non-flamma-ble perlite particles, which have been bonded together to form a resultant aggregate particle size up to 2 inches in diameter but preferably in the range between A of an inch and A of an inch.

5. The method of fireproofing a body of flammable hydrocarbon liquid, such as fuel oil, stored in open pit storage, comprising the steps of depositing a 2 inch or greater floatable layer of expanded non-flammable irregularly shaped particle material having a particle size at least of which is detainable by an 8 mesh screen upon the surface of said hydrocarbon liquid, and forming thereby a floating blanket of said material over the full top surface of said storage pit, the lower portion of which is saturated with hydrocarbon liquid, while an upper /2 inch thick freeboard portion of said blanket remains substantially drained by hydrocarbon liquid.

6. The method of claim 5 including the additional step of bonding a plurality of said particles into larger particles up to 2 inches in diameter but preferably between A of an inch and of an inch.

7. The method of claim 5 wherein said material comprises expanded perlite.

8. The method of claim 5 wherein additional fireproofing is provided by pretreating the particle material with carbonates and/ or halogens.

References Cited UNITED STATES PATENTS 1,404,924 1/ 1922 Bloss 220-26 2,023,308 12/1935 Cantacuzene 22026 2,710,832 6/1955 Harr. 2,798,633 7/ 1957 Cornell et a1 220-26 FOREIGN PATENTS 1,192,877 4/1959 France.

JOSEPH R. LECLAIR, Primary Examiner JAMES R. GARRETT, Assistant Examiner.