US2041392A - Tank - Google Patents

Description

y 1%, mm.

A. C. BEAN ET AL TANK Filed Jan. '7, 1955 ATTORNEY.

Patented May 19, 1936 TANK ' Albert 0. Bean, Kansas City, Mo., and Joseph B. Bay, Fort Worth, Tex.

Application January 2 Claims.

our invention relates to tanks, and more particularly to oil storage tanks.

In many areas, such as in West Texas, crude oils are produced which are known as "sour oils. These oils bear sulphur compounds, such as hydrogen sulphides, mercaptans, alkyl disulphides, triophens and other sulphur containing hydrocarbons. These sour crudes quickly corrode tanks in which they are stored, and bad leaks develop suddenly. Cases have been known in which holes have been. corroded through oil storage tanks in five months time. Tanks have become riddled in periods of from six months totwo years to such extent that they have had to be junked. The corrosion of tanks not only results in a distinct loss of capital investment for the tanks themselves, but in. loss of crude oil with the attendant danger of fire.

Many types of coatings have been tried, but none of them have met with marked success.

One object of our invention is to provide a tank which is corrosion-resisting.

Another object of our invention is to provide an oil tank which is adapted to store corrosive or sour crudes.

Other and further objects of our invention will appear from the following description.

In the accompanying drawing which forms part of the instant specification and which is to be read in conjunction therewith;

Figure 1 is a sectional elevation of an oil tank according to our invention.

Figure 2 is a sectional fragmentary view showing the oil tank of our invention just after the coating has been applied.

Figure 3 is a view similar to Figure 2, showing a fragmentary sectional view of the oil tank after the coating has dried.

In general, our invention contemplates the provision of an oil tank having an interior corrosionresisting coating, it being remembered that the invention is in the combination rather than in the coating per se.

More particularly, our invention contemplates the provision of a tank to the. interior surfaces of which a corrosion-resisting coating composition has been applied. The coating composition is not only corrosion-resisting, but is also insoluble in hydrocarbon oil. The coating consists, in general, of a substance insoluble in hydrocarbon oil, a binder such as fibrous material, as, for example, asbestos fiber, and a solvent which will enable the composition to be applied. The solvent is such that it is soluble in hydrocarbon oil, while the composition is insoluble. Thus,

7, 1935, Serial No. 640 (01.220-84) when coating is applied and hydrocarbon oil is placed in the tank, the solvent will go into solution in the hydrocarbon oil, leaving the insoluble coating behind.

We have discovered that coal tar pitch is insoluble in hydrocarbon oil, and is adapted to act as an excellent protecting medium to protect the steel surfaces of the tank interior. A typical coal tar pitch which maybe used as a base has the following characteristics:

Water-none.

Total distillate up to 300 C.-not more than 50% by weight and not less than 30% by weight.

Residue after distillation-'mot more than 70% and not less than 50% by weight.

Melting pointbetween 110 F. and 155 F.

Total bitumen soluble in carbon disulphide- '78% to 97%.

A base having the characteristics pointed out above, is dissolved in a coal tar solvent, such as benzol, toluol, xylol, or the like. A suitable quantity of the fibrous material is then added. In practice we employ 2% to 30% by weight of the finished coating composition of asbestos fiber.

The coating composition is adapted to form an 25 adhering film when applied to the metal surfaces of the interior of the oil tank. This film will be suificiently ductile to allow the coating composition to expand and contract as the metal base expands and contracts, without cracking or rupturing the film. In the coating compositions attempted to be applied in the prior art, cracks develop due to expansion and contraction of the tank. The corrosion started at these cracks and the purpose of the coating was defeated. Other coatings attempted disintegrated. v

The function of the fibrous material is to toughen the coating film and prevent it from running when applied or if the interior surface of the oil tank should reach a temperature above the 'pour point of the coal tar pitch.

In forming an oil tank according to our invention, the interior bottom and side walls of an oil tank are thoroughly cleaned so that they are dry and free of anoil film. Sand-blasting 5 may be resorted to as an eilective cleaning method. The coating composition is then applied by a brush. A time period is then allowed for slight drying. A period of four hours has been found to be satisfactory. During this period only 50 the outer surface of the coating will be dry. The purpose of this preliminary drying is to prevent the coating composition from being removed by erosion or the mechanical effect of the oil when it is pumped into the tank. After the oil is put 55 into the tank the solvent will go into solution into the oil and leave the coal tar pitch, with its binder, as the coating upon the walls of the tank, due to the fact that the coal tar pitch is not soluble in oil, while the solvent is soluble in the oil. The coating composition will harden and set, and the tank is thus provided which will be resistant to sour" crudes. Protection will also be afforded against those crudes which contain corrosive brine in emulsion therethrough.

In practice, if it is desired, a priming coat of any suitable coating composition, such as red lead, aluminum paint, cement paint or the like, may be applied to the tank and allowed to harden before applying the coal tar pitch'coating composition in order to make the tank of our invention.

It will be seen that we have accomplished the objects of our invention. We have provided an oil tank which will be corrosion-resisting and may be used with "sour crudes.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is. therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. In an oil tank, a metallic shell having an internal coating of coal tar pitch in the tom of an impervious film in direct contact with the metallic shell to protect the same against internal corrosion, said film having sufficient fibrous binder incorporated therein to prevent said film from flowing.

2. In an oil tank, a metallic shell having an internal coating of coal tar pitch in the form of an impervious film in direct contact with the metallic shell to protect the same against internalcorrosion, said film having from 2 percent to percent by weight of a fibrous binder incorporated therein to prevent said film from flowing.

ALBERT C. BEAN. JOSEPH B. RAY.

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