U.S. patent number 3,929,664 [Application Number 05/513,084] was granted by the patent office on 1975-12-30 for water-washable inspection penetrant employing triglycerides and polyglycerides of fatty acids.
Invention is credited to James R. Alburger.
United States Patent |
3,929,664 |
Alburger |
December 30, 1975 |
Water-washable inspection penetrant employing triglycerides and
polyglycerides of fatty acids
Abstract
A water-washable inspection penetrant composition and process in
which a low-solubility fatty oil is used as the penetrant vehicle.
The solvent liquids of the invention provide enhanced stability of
penetrant entrapments in surface flaws, so as to increase the
allowable time interval of wash water contact before an excessive
depletion of the entrapment occurs. The flaw detecting capability
of the water-washable penetrant is thereby improved.
Inventors: |
Alburger; James R. (La Canada,
CA) |
Family
ID: |
27047295 |
Appl.
No.: |
05/513,084 |
Filed: |
October 8, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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482465 |
Jun 24, 1974 |
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Current U.S.
Class: |
252/301.19;
73/104; 250/302; 252/960 |
Current CPC
Class: |
G01N
21/91 (20130101); Y10S 252/96 (20130101) |
Current International
Class: |
G01N
21/91 (20060101); G01N 21/88 (20060101); C09K
011/06 (); G01N 019/08 (); G01N 021/16 () |
Field of
Search: |
;252/31.2P,408 ;250/302
;73/104 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mack; John H.
Assistant Examiner: Weisstuch; Aaron
Parent Case Text
This application is a continuation-in-part of my copending
application Ser. No. 482,465, filed June 24, 1974 for "Enhanced
Stability Water-Washable Penetrant Composition and Process
Therefor."
Claims
I claim:
1. In a water-washable inspection penetrant process in which a
water-dispersible dyed liquid penetrant is applied to test parts,
surface penetrant is removed by washing said test parts with water,
and said parts are inspected for residual entrapments of penetrant
liquid in surface flaws, the improvement wherein said
water-washable penetrant consists essentially of the following
formulation, stated in weight percentages:
said low-solubility solvent liquid being at least one member
selected from the group consisting of:
Cottonseed oil,
Palm kernel oil,
Peanut oil,
Coconut oil,
Linseed oil,
Olive oil,
Soybean oil,
Castor oil,
Sunflower seed oil,
Rape seed oil,
Safflower oil,
Lard,
Tallow,
Fish oil,
Sardine oil, and
Whale oil,
and said solvent coupler being at least one member selected from
the group consisting of:
Methanol,
ethanol,
butanol,
isopropanol,
1-propanol,
2-butanol,
ethylene glycol monobutyl ether,
ethylene glycol monoethyl ether,
ethylene glycol monomethyl ether,
diethylene glycol monomethyl ether,
diethylene glycol monoethyl ether,
diethylene glycol monobutyl ether,
butoxytriglycol,
methoxytriglycol,
ethoxytriglycol, and
1-butoxyethoxy-2-propanol,
said low-solubility solvent liquids being selectively employed
singly and in combination.
Description
The invention relates to inspection penetrant materials. More
particularly, the invention relates to water-washable inspection
penetrant compositions which exhibit enhanced values of indication
stability in the presence of wash water.
Heretofore, water-washable inspection penetrants have been
comprised essentially of a water-dispersible liquid carrier
containing a dissolved indicator dye. The liquid penetrant
composition is selected or formulated so as to be readily soluble
or self-emulsifiable in water. The indicator dye may be a
visible-color dye or a fluorescent dye, but for high sensitivity
usage, fluorescent dyes are most generally utilized.
In use, the water-washable penetrant is applied to parts to be
tested for the presence of surface flaws. After a suitable dwell
time, during which the penetrant enters any surface cracks which
are present, the test parts are washed with water to remove surface
penetrant, leaving entrapments of the tracer-dyed liquid in the
surface cracks. Following the wash-remover step, the test parts are
dried and sometimes they are treated with a fine-powder developer
which acts to draw out penetrant entrapments to a point where they
can be seen. In any event, the parts are inspected for the presence
of surface flaw indications, using white light in the case of
penetrants containing visible-color dye, or under black light in
the case of penetrants containing fluorescent dyes. Entrapments of
dyed penetrant which are retained or developed on a coating of
powder particles are detected by their visible color or
fluorescence, as the case may be. Normally, the step of development
is considered to be part of the inspection step in the process.
In the past, it has been the practice to formulate water-washable
penetrants in such a way that the compositions exhibit a feature of
"good washability", such that the surface penetrant is easily
removed when test parts are washed with water. Acceptable penetrant
formulations have apparently been chosen for their ability to wash
quickly so as to provide a relatively clean test surface with a
minimum background of residues of dye penetrant. I have discovered
that existing water-washable penetrants suffer from a serious
drawback, in that they are characterized by an excessive degree of
emulsifiability or solubility, such that in the process of
wash-removal of surface penetrant, entrapments of penetrant in
small, shallow surface flaws are also removed, or at least are
depleted to an excessive degree.
I have endeavored to improve the retention of entrapments in flaws
by various means. One method which I have devised involves the
formulation of so-called gel-forming penetrants, as exemplified by
the teachings of my U.S. Pat. Nos. 3,282,843, 3,349,041, and
3,429,826, and my copending application Ser. No. 127,681, filed
Mar. 24, 1971, for "Inspection Penetrant Compositions and Processes
Employing Balanced Surfactant/Synergist Detergent Systems."
I have also devised various methods of inhibiting the solubility of
certain kinds of penetrants (particularly the gel-forming
penetrants), by adjustment of the detergent balance of the
composition, by introduction of certain solubility-inhibiting
chemicals into the penetrant or into the wash water, or by raising
the temperature of the wash water above a critical point of
solubility inversion, as exemplified by the teachings of my
copending application Ser. No. 163,643, filed July 19, 1971, for
"Method and Means for Improving Flaw Entrapment Efficiency in
Water-Washable Inspection Penetrants".
I have devised a technique for measuring the rate at which flaw
indications are depleted by the action of wash water, and I have
found it possible to assign values of "Indication Depletion Time
Constants" to various materials such as water-washable penetrants,
emulsifiers, and solvent removers. In essence, my method of
evaluation involves the measurement by photoelectric means, of the
loss of brightness of a standardized pattern of indications during
the course of remover application, in the present case, the remover
being water. The method yields, for each water-washable penetrant,
a time constant which is a measure of the time in seconds of wash
water contact required to deplete the effective magnitude of the
flaw entrapment to 50% of its initial value. In some cases it may
be preferred to state the time constant in terms of the time in
seconds of wash water contact required to deplete the brightness of
an indication to 50% of its initial value. Measurements of
Indication Depletion Time Constants are made using a "standard"
cracked panel having a pattern of closely spaced cracks or randomly
distributed cracks of known effective magnitude.
I have found that the measured rate of indication depletion depends
in part on the magnitude of the cracks in the testing panel. I have
made and tested various kinds of testing panels in which I have
been able to generate crack defects having effective magnitudes
varying from less than a micron up to 20 or 30 microns, and where
the depth-width ratio of the cracks may vary from about 3 up to 100
to 1. For many types of penetrant materials, it is practical to
determine depletion time constants using a cracked anodic panel of
the types described and claimed in my U.S. Pat. Nos. 3,785,936 and
3,791,198, in which the cracks are about 20 microns deep and 6
microns wide.
The significance of the Indication Depletion Time Constant is that
in cases where processing conditions require a prolonged contact
time of the wash water with the test surface, the Indication
Depletion Time Constant must be large, otherwise indications may be
lost. By using the methods which I have devised, and which have
become standard procedures under Air Force MIL-Specifications and
industrial specifications, I have been able to assign Indication
Depletion Time Constants to penetrant process materials, and have
thus been able to assign ratings of relative indication stability
for such materials. It turns out that Indication Depletion Time
Constants for typical water-washable penetrants (using a cracked
anodic panel for example) fall in the range of from about 3 to 10
seconds, while for certain of the above-mentioned gel-forming
penetrants, time constant values may be as high as 40 seconds.
While Indication Depletion Time Constant values in the range of 3
seconds up to about 40 seconds are suitable for most industrial
inspection requirements, there are numerous cases where it is
necessary to obtain a considerably higher degree of indication
stability, as might be provided by water-washable penetrants having
Indication Depletion Time Constants in the range of from about 40
seconds up to as much as 6000 seconds. One such inspection
application is in the study of inter-crystalline separations in
plated surfaces, or ceramics. Another application is in the testing
of molybdenum disilicide heat resistant coatings for the presence
of irregularities and discontinuities. In any of these
applications, and others, which require extremely high flaw
detection sensitivity combined with an extremely high degree of
indication stability, it is essential that the water-washable
penetrant shall resist the leaching of wash water during the time
normally taken for the wash step.
The principal object of the invention, therefore, is to provide
water-washable inspection penetrant compositions with features of
enhanced flaw indication stability in the presence of wash
water.
Another object of the invention is to provide a method of adjusting
and controlling the Indication Depletion Time Constant value of a
water-washable penetrant to a point within the approximate range of
from about 40 seconds up to about 6000 seconds.
These and other objects of the invention will be in part be obvious
and will in part become apparent from the following description
thereof.
I have discovered a family of solvent liquids which satisfy the
requirement of high values of Indication Depletion Time Constant,
and I find that such solvent liquids may be suitably defined as
solvent liquids which are soluble in water or compatible with water
to the extent of from slightly less than 0.01% up to about 3%. If a
solvent liquid has a water solubility or compatibility much lower
than 0.01%, then penetrant formulations using such liquid may
exhibit an unduly large depletion time constant, making wash
removal of unwanted background indications excessively difficult.
On the other hand, if the compatibility with water of the solvent
liquid is much greater than 3%, then the depletion time constant
becomes small, to the point where there is no advantage gained over
materials already available which provide depletion time constants
up to about 40 seconds.
It will be understood that the term "compatibility with water"
refers to either the solubility of a liquid in water or the
solubility of water in the liquid. It appears that the removal of
penetrant entrapments from crack defects by washing with water
takes place by a mechanism of diffusion of the two liquids,
penetrant and water, into each other, and wash-removability of
penetrant may take place at an acceptable rate provided that the
solubility of water in the penetrant or penetrant in water fall
within the above-stated percentage range. The percentage range of
water compatibility of from slightly less than 0.01% up to 3% is
given merely to indicate the physical-chemical property (with
respect to water solubility) of the solvent liquids which are
suitable for the purpose of the invention.
The penetrant compositions of the invention are comprised
essentially of one or more low-solubility liquids drawn from the
group to be described and identified below, the low-solubility
liquids being selectively employed, singly and in combination. When
so used, these liquids will provide Indication Depletion Time
Constants within the range of about 40 to 6000 seconds. Among the
various solvent liquids which are suitable as ingredients in the
water-washable penetrants of the invention are:
Cottonseed oil,
Palm kernel oil,
Peanut oil,
Coconut oil,
Linseed oil,
Olive oil,
Soybean oil,
Castor oil,
Sunflower seed oil,
Rape seed oil,
Safflower oil,
Lard (grease),
Tallow,
Fish oil,
Sardine oil, and
Whale oil.
All of the foregoing oils, fats and greases fall in the same
chemical category, being triglycerides or polyglycerides of fatty
acids, such as oleic acid, linoleic acid, linolenic acid, etc. Some
of the materials are solid at room temperature, but become liquid
at slightly elevated temperatures. They are all considered to be
water-insoluble, but I have discovered that they are in fact
sufficiently soluble in water, particularly at elevated
temperatures, so as to permit wash-removal in the water-washable
inspection penetrant process.
I have found that it is possible to extend the polyglyceride oils
of the invention with an inexpensive aliphatic mineral oil, for
purposes of cost saving, or for purposes of reducing the viscosity
of the penetrant composition. Normally, aliphatic mineral oils are
not compatible with the polyglyceride oils of the invention, and
yield hazy mixtures which separate on standing. However, I have
discovered that a small amount of a suitable solvent coupler may
act to couple the polyglyceride oil with the mineral oil to form a
clear solution. For example, in testing mixtures containing 20 ml.
of castor oil and 100 ml. of a light mineral oil (Chevron No. 2
Absorption Oil), I have found that clear mixtures are obtained by
the addition of 5 ml. of diethylene glycol monobutyl ether, or 4.5
ml. of dibutyl phthalate, or 3 ml. of isodecanol. In all cases,
where the polyglyceride oil of the invention is extended by means
of a light mineral oil, I find that the flaw detection capability
of the penetrant composition using such an extended vehicle is
about the same as is obtained by use of pure polyglyceride oil.
This feature of similarity is evident at concentrations of the
mineral oil extender in the penetrant vehicle up to 80% or more. I
have noticed that the actual value of Indication Depletion Time
Constant which is characteristic of a given penetrant composition
of the invention may vary as the concentration of indicator dye is
varied. Since the flaw detection capability, or "sensitivity", of
an inspection penetrant increases as the indicator dye
concentration is increased, it follows that for a composition which
utilizes a given solvent liquid of the invention, the Indication
Depletion Time Constant will change as the sensitivity level (or
dye concentration) is changed.
For example, if castor oil is utilized as the carrier liquid, and
if different concentrations of fluorescent dye are tested,
corresponding to relatively low up to relatively high sensitivity
levels, as such levels are known in the art, then Indication
Depletion Time Constant values may be obtained ranging from about
200 seconds for the low sensitivity composition up to about 10,000
seconds for the high sensitivity composition. It will be understood
that the rate of solution, and the consequent Indication Depletion
Time Constant, may be varied and adjusted by adjusting the
temperature of the wash water. Depletion Time Constants are reduced
as the water temperature is increased, partly because the
solubility of the oil increases, and partly because the viscosity
of the oil becomes lower and effects of diffusion become more
rapid.
I have found that the Indication Depletion Time Constants of the
compositions of the invention may be conveniently reduced and
adjusted to desired values by the addition of an appropriate amount
of a water-soluble solvent coupler. For the purpose of this
specification, the designation "solvent coupler" shall be meant to
include water-soluble alcohols and glycol-ethers. Among the various
solvent couplers which are suitable for use as additives for
reducing the Indication Depletion Time Constant are the
following:
methanol,
ethanol,
butanol,
isopropanol,
1-propanol,
2-butanol,
ethylene glycol monobutyl ether,
ethylene glycol monomethyl ether,
ethylene glycol monoethyl ether,
diethylene glycol monoethyl ether,
diethylene glycol monomethyl ether,
diethylene glycol monobutyl ether,
butoxytriglycol,
methoxytriglycol,
ethoxytriglycol, and
1-butoxyethoxy-2-propanol.
Any of the above-identified solvent couplers may be included in the
compositions of the invention at concentrations ranging from zero
up to about 40% relative to the low-solubility solvent liquid of
the invention, the proportional amount used depending on the dye
sensitivity which pertains, the particular solvent which is used,
and the desired Indication Depletion Time Constant.
Visible-color or fluorescent indicator dye concentrations in the
compositions of the invention may range from about 0.2% up to about
30%, in accordance with known practices.
Accordingly, a water-washable inspection penetrant composition of
the invention may be expressed by the following formulation, stated
in weight percentages:
Low-solubility solvent liquid 30% to 99.8% Indicator dye .2% to 30%
Solvent Coupler zero to 40%
Although the invention has been described with reference to
particular embodiments thereof, it will be understood that various
changes and modifications may be made therein without departing
from the spirit of the invention nor the scope of the appended
claim.
* * * * *