CA1053132A - Apparatus, composition and method for detecting free water in hydrocarbon fuels - Google Patents

Abstract

ABSTRACT OF DISCLOSURE

An apparatus, composition and method for detecting the presence of free water is liquid hydrocarbons in which the water reacts with freshly ground fuchsia dye and an anhydrous solid such as calcium carbonate having an average particle size of less than 10 microns and a surface area of 4 to 9 square meters per gram. The reagents are prepackaged in an evacuated glass vial, which protects the freshly ground dye from ex-posure to air and moisture. A sample of the hydrocarbon is admitted to the interior of the evacuated vial by a cannuls mounted in a special receptacle adapted to receive the vial. The sample is drawn into the vial by the vacuum and reacts with the dye and anhydrous solid to indi-cate the presence or absence of free water in the hydrocarbon. The invention is particularly applicable to detection of free water in aviation jet fuels.

Description

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This invention relates to an apparatus, composition and method for detecting the presence o~ free or undissolved water in liquid hydrocarbons, particularly aviation jet fuels.
Detection of free (undissolved) water in hydrocar~on fuels is of parti.cular importance with regard to turbojet fuels for aircraft which are subject to fuel system plugging by ice crystals when operating at hi.gh altitudes. ~o minimize this hazard, it is normal practice to inspect all fuel for the presen-ce of free water as it is bein~ loaded into aircraft. In ge.ne-ral less than about 10 parts per million of free water is accep- . .
table, but 30 parts per million is too high. Although special filter separators are used for removing free water from jet fuels, testing of individual cargoes of fuel. is nevertheless necessary to chec~ their performance. U.S. Patent 3,505,020 of D.A.
Caldwell, granted April 7, 1970, disclosed an improved composi-tion which will react with free water present in je~ ~uels and produce a pink color to indicate the presence of excessive free ~ ;
' water. That composition comprised a small amount o fuchsia ~ dye, 3 amino-7(dimethylamino)-5-phenylphenazinium chloride, mixed ; 20 with a major portion of a finely divided anhydrous solid, select-ed from the group consisting of calcium carbonate, barium carbona-te, barium sulfate, magnesium carbonate and combinations thereo~. .
The preferred anhydrous solid for the water detection composition ,l is calcium carbonate.
:~ In the prior art, it was disclosed that the dye parti- : ~
cles should have a diameter less than 200 microns in order to be ;
- effective and, in particular, a weight average particle size of .: 44 microns was preferred, The particularly preferred composition - would limit the dye particle size to under 7~ microns with about 30 40-60 wt.% of the particles having a diameter of less than about :` 44 microns. The dye that is used is a conventional dye in the textile industry and is commonly referred to as Methylene Violet,

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Basic Violç~t Five Color Inde~c 50205, fuchsia and so forth. A
further description of the dye may be found in C~l.r l~le~ S~e ~nerican _Association o~ Textile Chemists and Colorists, second edition (1956), at pages 1635 and 341~.
ALso in the prior ar-t, it WaS disclosed that the anhy-drous solid particles should be less than 10 microns in size and a technical grade crystalline powder, In addition, the portions o anhydrous solid to dye would range be-tween 20 and 10~000 and preferably between 50 and 2000 parts by weight. One part by weight of dye to about 400 to 1000 parts by weight of anhydrous solid was particularly preferred. The reagent mixture would be added to a fuel sample, about 0.05 -to 2 grams of the mixture -to 100 milliliters of hydrocarbon uel. The preferred range would be between 0,1 and 0.5 gram of mix-ture to each 100 millili-ters of hydrocarbon.
Although, as indicated in the prior art patent, this mixture generally gives satisfactory results, experience has shown that some practical difficulties arise with its use. It has been heretorore typical to package the mixed dye and solids in closed containers of a size suitable for testing of individual fuel car-goes. It has been found, however, that deterioration of the rea-gents occurs over a period of time and shelf life i9 linlited~
Accoldingly, results after an extended period of storage may be erratic. In addition, it was found that the composition of the mixture had to be adjusted before being placed into the closed ~ `~
containers in order to provide a uniform response. The foregoin~
disadvantages have been overcome by the present invention. --~
An improved composition for detection of free water in hydrocarbon fuels is obtained in the present invention by intro- ;
ducing product quality standards for both the anhydrous carbonate or sulfate and the fuchsia dye not heretofore known. It has now been found tha-t the fuchsia dye is more sensitive if it is finely ~ .
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ground immcdiately pr.i.or to being packaged rather than simply bei.n~ screened and then packaged from the material as received from the supplier. As to the anhydrous solid, it has been found that, not only particle size, but effective surface area of the carbonate or sulfate is important in obtaining a suitable sensiti-vity. Surface areas above the range of 4 to 9 square meters per ~ram are generaLly not sensitive enough and surface areas below that ran~e are too sensitive and neither too large nor too small a surface area will produce the desired results. In particular, surface araas in the range of 5 to 8 square meters per gram have been found to be preferred for this use.
-; In the present invention, both carbonate ~or sul-fate) and dye are prepac~aged in an evacuated ylass tube or vial. The glass vial serves two functions: first, to protect the quality of the chemical reagents used and, second, to provide a means for drawing a fuel sample into the vial for reaction with the reagents without ever exposing them to moisture in the air. In order to accomplish the introduction of fuel into the evacuated vial, a special receptacle is provided, supportin~ a small cannula which pierces a Ilexible closure at one end of the vial and provides a passageway for the fuel.
In the field use for detecting free water in aviation jet fue].s, a small. sample of fuel is drawn from a fueling line into a small container as an aircraft is being loaded, the recep-tacle is placed inside the con-tainer so that the open end of the cannula is suspended above the bottom of the fuel container, and thereafter the glass vial is lnserted into the receptacle.
~he cannula punctures the flexible closure :~5~ L3~

located at one end of the vial, thereby providing a passageway between the fuel in the container and the in-terior of the vi.al.
The fuel is drawn in by the vacuum existiny within the con-tainer where it reacts with the reagents, producing a pink color should an excessive amount of free water be present, or remaining clear if less than 10 ppm free water is presen-t.
In accordance with the present inven-tion, there is provided an apparatus for detecting -the presence of free water in hydrocarbons which comprises in combination:
(a) an evacuated vial containing chemicals sensitive to the presence of free water, said vial being closed at one ~;~
end and sealed at the other end by a pierceable closure to maintain said vacuum, ;~
(b) a receptacle for receiving said evacuated vial;
(c) a cannula having an inlet end and an outlet end mounted on said receptacle and disposed to pierce said closure when said vial is inserted into said receptacle, thereby provid-ing a conduit into the evacuated interior of said vial.
~` In accordance with the presen-t invention, free moisture is detected in hydrocarbons by~
(a) placing a sample of said hydrocarbons in a con- ~;
tainer, `
: (b) placing in said con-tainer the apparatus of claim "', l; - `
; .i , (c) piercing the closure of said evacuated vial with ':
said cannula;
(d) reacting said hydrocarbon portion drawn into `~
said vial with the moisture sensitive chemical reagents con~
tained therein and thereby producing a color proportional to the free water present in said hydrocarbon portion;
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:' (e) comparing the color produced in said hydrocarbon portion drawn into said vial with known standards and thereby determining the amount of free water contained in said hydro-carbon portion.
There is also provided, according to the invention, a packaged composition useful ~or the detection of free water in a liquid hydrocarbon which comprises a mixture of:
ta) a finely divided anhydrous solid having a sur-face area of from 4 to 9 square meters per gram, said solid being selected from the group consisting of calciu~ carbon-ate, barium carbonate, barium sulfate, magnesium carbonate, and mixtures thereof, and , (b) freshly ground fuchsia dye having a particle size between 44 and 74 microns, (c) the weight ratio of said dye to said solid being within the range of 1:20 to 1:10,000, .! (d) ~aid mixture having been both prepared and sealed 'J off from contact with moisture and air at the time of grinding ~-said dye.
In the drawings, Figure 1 is an exploded view of the apparatus of the invention prior to its assembly~ Figure 2 illustrates the apparatus of Fig. 1 in the assembled condition '~ immediately prior to admitting a fuel sample in-to the glass vial n Figure 3 is a vial according to the invention after having received a fuel sample in the manner indicated in ~igure 2.
; Figure 1 illustrates the three main parts of the apparatus. A small cylindrical container 10 is provided for - receiving a small sample of uel from the loading line. The container 10 has no special requirements except that it should contain sufficient sample to fill the vial 12, as discussed -5a-.~.~ ~ ' ' .
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hereinafter. The con-tainer 10 should preferably be made of a clear plastic material in ordex to avoid breakage and to per- `~
mit observation of the visual quality of the fuel d~awn in, that is, whether it is clear or cloudy and whether it contains any suspended solids. Either of these conditions may indicate a failure of the fuel filker separator which would be located upstream of the sampling point.
The receptacle 14 consists of a cylindrical tube 16 with a flange 18 at one end for convenience in handling and open at either end. Mounted within the tube 16 i9 a trans-verse disc 20 which supports a cannula 21 mounted thereon.
The cannula 21 provides a narrow passageway, being blunt at one end 21a where fuel is drawn in and pointed at the opposite end 21b for piercing the flexible closure of the glass vial 12.

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A slot 16a (or ~ther perfoxation) is provided in the side of the recep-tacle 1~ below disc 20 in order to permit fuel to pass freely into the interior of the tube 16 and be drawn into the blunt end 21a of the cannula. It is preferred that the cannula 21 not touch the ~o~tom of the container in order that any extra~
neous materials which might be drawn in are not a~mitted to the vial and, therefore, for example, the blunt end 21a of the cannul~
21 is positioned approximately one-half inch above the bottom of the receptacle 14.
The improved reagents are enclosed in an evacuated ; ;
glass vial 12 which is sealed at one end by a flexible closure 22.
This closure ~2 serves at least two purposes: first, to prevent breaking of the vacuum which was created in the tube at the time the reagents were sealed ins:lde it and second, to provide a means for ready access of fuel to the reagents when the test is made without ever exposing the reagent to the atmosphere. Use of an evacuated tube or vial permits not only protec~ion of the quality ; of the reagents, but provides ~or taking the required amount offuel sample. In addition, an indication of the quality of the reagents is obtained, for should the vacuum be lost, no fuel sam-ple would be ~rawn through the cannula, indicating that the quali-ty of the reagents was suspect and should not be used.
In general, the particle size of the fuchsia dye is essentially the same as that indicated in the prior art, but it `- has been found that freshly ground dye is particularly sensitive and that the sensitivity can be retained by packaging under va-cuum. Table I illustrates the significant improvement in sensi-- tivity of the dye when it is freshly ground as compared with the ;~
as~received material.

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TABLE I

Free ~ater Content lOppm _~as~) ~
Color Scal~ Color_Scale Readinq Sieve only 0 1/2 ~white) ~trace pink) Fresh ground 1/2 3 ~-(trace pink) (dark pink) It will be noted that, when as-received dye is merely sieved, only a small color change can be found, whereas the same dye when freshly ground has a much wider color change, which is -~
easily seen and permits some înterpolation between 10 ppm and ;~
40 ppm free water. This greater sensitivity can be maintained if the dye is kept sealed and away from moisture and air as in the evacuated vial of the invention. Use of an inert gas in ~ ;
filling the vials will further improve the stability of the dye sensitivity.
As has been mentioned heretofore, it was previously ;
necessary to make an empirical adjustment of the relative quanti~
ties of dye and anhydrous solid in order to provide a uniformity .:
~ 20 of response. It has now been found that this irregularity in .; . .
` response of the as-received materials was due, not to the particle ;, size which was heretofore thought to be important, but rather to the effective surface area of the solid~ It has now been found that a relatively low surface area in the range of 0.1 to 3.5 -;~ :
square metèrs per gram is too sensitive and should not be used.

Also, a relatively high surface area exceeding 9.S meters per gram is insensitive and should also not be used. Thus, the operable range of surface areas is 4 to 9 squaxe meters per gram.
The preferred range is 5 to 8 square meters per gram, which can include small deviations outside this range, e.g. down to about

- 4.5 or up to about 8.5 m per gram. Added adjustment to the dye-to-carbonate ratiosmay be necessary in so~e instances at the ~ :

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outer limits of the ope~rable range when th~ desired sensitivity r~sponse i9 bordering on the too sensitive and/or insensitive areas.
The preferred range of the order o 5 to 8 square : meters per gram provides good sensitivity and permits the accura~
te proportioning of dye to solid. The relative sensitivity to surface area of the solid and the merits of restricting -the sur-face area of the solid used to the reco~nended range will be evi-dent from the data given in 'rable II below.

TABLE II

CaCO Free Water ~ontent Surface lOppm (pass) 40 ppm (fail) Area Color ScaleColor Scale ~ Readin~ Readin~ _ Comment : 0.4 3 (dark pink) 3 too sensitive 1.6 2-3/4 3 2.78 2 (pink) 2-3/4 " "
6.5 1/2 (trace pink) 2-1/2 suitable sensitivity 8.53 1/2 2-1/2 " "
9.95 0 (white) 1 (light pink) insensitive ~ ..
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Figure 2 shows the principal components of the inven- ~`
tion in assembled form. Fuel 23 has been placed inside the cylin- ~:
der container 10 in a quantity suficient to more than fill the vial, but leaving some residual amount in the container after the .
vial has been ~illed. The receptacle 14 has been placed within the container 10 where it rests on the bottom and fuel is free to pass through the slot 16a or other openings placed in the side of the receptacle 14. The evacuated vial 12 containing the improv-ed reagents 24 has been placed within the receptacle 14 with the point of the cannula 2~b resting lightly ayainst the ~lexible closure 22.
It will be apparent that once the indicated downward ~S~3~ ~ 9_ motion is made, the callnul~ 21 will pierce (he flexible closure 22 and aclmit fuel, asS-Iminy vacuum within the glass vial, into the vial 12 for reaction with -the improved reagents 24. Once -the flexible closure has been pierced, fuel rushes through the cannu-la 21 into the glass vial 12 wh:ich fills extremely rapidly owing to the presence of the vacuum ~nd quick mixing of the desired amount of reagent and fuel takes place.
Figure 3 shows a vial 12, after it has recelved a fuel sample and has been withdrawn from the receptacle, the flexible closure 22 sealing behind the cannula 21 as it is withdrawn, there-by retaining the fuel sam~le therein. The vial 12 may be s~aken lightly to mix the reagents and fuel although mixture is essential-ly completed by the rapid inrush of fuel as it displaces the va~
cuum. After a short period, apporximately 2 minutes, the color of the dye has developed if the fuel contains free water in excess ; of 10 parts per million. In general, the quantities of reagent and the sensitivity of the reagents are adjusted so that no color ; change develops when the free water content is 10 parts per million or below but a pink color develops above that level which may be compared with a known standard. If an excessively dark pink color has developed during the 2-minute period, indicating that more than 30 ppm is present, the fuel must be rejected and reprocessed in o~der to rernove free water present therein. Such standards were used in the results shown in Tables I and II.
The foregoing test is primarily used in the field as a .
go/no-go test in aircraft fueling. It is within the scope of the invention, however, to package quantities of dye in measured quan-tities so as to permit a series of such tests to make a more accu-rate determination of the precise level of water containedO ~hiS
may be necessary in order to satisfy both military and commercial ; standards and to make a closer measurement of the quantity of water when a go/no-go -test is insufficient~

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Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for detecting the presence of free water in hydrocarbons which comprises in combination:
(a) an evacuated vial containing chemicals sensitive to the presence of free water, said vial being closed at one end and sealed at the other end by a pierceable closure to maintain said vacuum, (b) a receptacle for receiving said evacuated vial, (c) a cannula having an inlet end and an outlet end mounted on said receptacle and disposed to pierce said closure when said vial is inserted into said receptacle, thereby provid-ing a conduit into the evacuated interior of said vial.

2. The apparatus of claim 1 wherein said receptacle is a cylinder open at both ends and having a transverse par-tition intermediate said ends for mounting said cannula, whereby said cannula serves as a passageway through said par-tition.

3. The apparatus of claim 2 wherein one of said cylinder ends extends beyond the inlet end of said cannula, thereby preventing said cannula from touching the bottom of said container when said receptacle is inserted therein.

4. The apparatus of claim 3 wherein the cylindrical wall adjacent the inlet end of said cannula contains at least one opening in the wall thereof to admit said hydrocarbon sample when said receptacle is in contact with the bottom of said container and thereby to prevent sampling from the bottom of said container.

5. The apparatus of claim 1, 2 or 3 further comprising a container for a sample of said hydrocarbons adapted to receive said vial receptacle whereby said cannula is enabled to admit hydrocarbons from said container into said vial as urged by the vacuum therein.

6. The apparatus of claim 1, 2 or 3 wherein said chemicals for detecting the presence of free water comprise:
(a) a finely-divided anhydrous solid having a surface area of 4 to 9 square meters per gram selected from the group consisting of calcium carbonate, barium carbonate, barium sulfate, magnesium carbonate, and combinations thereof;
(b) freshly ground fuchsia dye having a particle size between 44 and 74 microns.

7. The apparatus of claim 6 wherein the surface area of the solid is in the range of 5 to 8 square meters per gram.

8. The apparatus of claim 7 wherein the weight ratio of said solid to fuchsia dye is within the range of 20:1 to 10,000:1.

9. A method for detecting free moisture in hydrocarbons comprising:
(a) placing a sample of said hydrocarbons in a con-tainer;
(b) placing in said container the apparatus of claim 1, (c) piercing the closure of said evacuated vial with said cannula;
(d) reacting said hydrocarbon portion drawn into said vial with the moisture sensitive chemical reagents contained therein and thereby producing a color proportional to the free water present in said hydrocarbon portion;
(e) comparing the color produced in said hydrocarbon portion drawn into said vial with known standards and thereby determining the amount of free water contained in said hydro-carbon portion.

10. The method of claim 9 wherein said moisture sensitive chemicals comprise:
(a) a finely-divided anhydrous solid having a surface area of 4 to 9 square meters per gram and selected from the group consisting of calcium carbonate, barium carbonate, barium sul-fate, magnesium carbonate, and combinations thereof, (b) freshly ground fuchsia dye having a particle size between 44 and 74 microns and in a weight ratio to said solid within the range of 1:20 and 1:10,000.