Ultraviolet remote visual inspection system

The invention provides an ultraviolet remote visual inspection system which enables the operator to detect minute cracks and hairline flaws in normally inaccessible places of manufactured parts. The system includes a fiberscope in combination with a source of white light and ultraviolet light and a plurality of cannisters for holding dye penetrant and other materials which can be used to facilitate the inspection. The fiberscope includes an articulated probe having a working channel, an ultraviolet light guide and an objective lens. The plurality of cannisters are connected to the working channel through a manifold. Dye penetrant, cleaning solution, drying air and developer can be individually delivered to the remote surface to be tested through the working channel from the cannisters. The fiberscope is provided with an adjuster for bending the articulated probe in different directions to facilitate application of the aforesaid materials and the subsequent visual inspection. Dye penetrant which is entrapped in cracks fluoresces brightly when illuminated by the ultraviolet light so that the cracks are easily identified.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a system for use in detecting surface defects in 
manufactured parts and the like. More particularly, the invention relates 
to a system which enables an inspector to detect hairline cracks and flaws 
in otherwise inaccessible and remote locations through the use of 
ultraviolet light and fluorescent dye penetrant. 
2. Description of Background Art 
The use of dye penetrants to detect small flaws in critical manufactured 
components such as jet engine turbine blades is well known. Typically, 
flaw detection by the dye penetrant method requires the following sequence 
of steps. 
First, the object to be tested is cleaned thoroughly, using a vapor 
degreaser, for example. Next the object is immersed in a dye penetrant 
solution which contains a solvent and a dye, typically one which 
fluoresces brightly when irradiated by long-wave ultraviolet radiation, in 
the approximate range of 300 nm to 400 nm. Alternatively, dye penetrant 
may be sprayed upon the surface of the object to be tested. Third, excess 
dye penetrant solution is removed from the surface of the part with the 
aid of another solution, and emulsifier. The part is then washed and 
dried. Finally, the part under test is illuminated with a source of 
ultraviolet radiation. Dye penetrant which has been entrapped in small 
voids such as cracks, seams or porous areas fluoresces brightly when 
illuminated by the ultraviolet radiation source, providing a visual 
indication of small defects which would otherwise escape visual detection. 
Sometimes a developer solution is applied to the surface of the part after 
that surface has been cleansed of excess dye penetrant solution. The 
function of the developer solution is to draw up to the surface of the 
part, by capillary action, dye which has been entrapped in voids some 
distance below the surface. This makes the dye and therefore the void more 
readily visible. 
The dye penetrant inspection processes just described are generally 
effective for detecting small surface flaws in manufactured parts. 
However, minute cracks and flaws can exist in places which are 
inaccessible to conventional probes. Thus, the spray method of applying 
dye penetrant can miss remote hard-to-reach locations where cracks and 
flaws may exist. Although the immersion method of applying penetrant is 
more pervasive it has the drawback that the part to be tested must be 
preheated and remain immersed in the dye for a substantial period. A 
further drawback is that large and cumbersome parts require large 
immersion tanks and large volumes of dye penetrant solution. 
Another disadvantage of fluorescent penetrant crack detection is several 
different instruments are required to accomplish each of the forementioned 
steps. After the dye penetrant is applied separate instruments are 
required to remove excess penetrant, to dry the surface to be examined, to 
apply the developer and to illuminate the surface to be examined with 
ultraviolet light for inspection. The manipulation and handling of these 
different instruments can be cumbersome and time consuming for a single 
operator. 
Accordingly, it is an object of the invention to provide an interactive and 
reactive ultraviolet remote visual inspection system which allows for the 
detection of cracks in places not normally accessible to the eye. 
It is a further object of the invention to provide a system of the type 
described in the previous paragraph wherein a single apparatus can be used 
for several different functions including illumination of the surface to 
be examined with white light, injection of dye penetrant, washing away of 
excess penetrant, drying the surface, injection of developer, illumination 
with ultraviolet light and visual inspection. 
It is yet a further object of the invention to provide an apparatus of the 
type described in the previous paragraph which includes an articulated 
probe to facilitate visual inspection of remote internal areas such as 
passages in castings. 
Additional objects and advantages of the present invention will be apparent 
to those skilled in the art by reading the accompanying specification and 
claims in view of the drawings. 
SUMMARY OF THE INVENTION 
The invention provides an ultraviolet remote visual inspection system which 
enables the operator to detect minute cracks and hairline flaws in 
normally inaccessible and/or internal places of manufactured parts. The 
system includes a fiberscope in combination with a source of white light 
and ultraviolet light and a plurality of cannisters for holding dye 
penetrant and other materials which can be used to facilitate the 
inspection. The fiberscope includes an articulated probe having a working 
channel, an ultraviolet light guide and an objective lens. The plurality 
of cannisters are connected to the working channel through a manifold. Dye 
penetrant, cleaning solution, drying air and developer can be individually 
delivered to the surface to be tested through the working channel from the 
cannisters. The fiberscope is provided with an adjuster for bending the 
articulated probe in different directions to facilitate application of the 
aforesaid materials and the subsequent visual inspection. Dye penetrant 
which is entrapped in cracks fluoresces brightly when illuminated by the 
ultraviolet light so that the cracks are easily identified.

DETAILED DESCRIPTION 
Referring to FIG. 1 an ultraviolet remote visual inspection system of the 
invention is depicted. The system includes a light guide or fiberscope 
generally depicted at 1. The light guide must be capable of carrying 
ultraviolet (UV) light efficiently and preferably white light as well. 
Standard glass fibers used in conventional fiberscopes and borescopes do 
not carry UV light effectively; there is too much loss of illumination. 
Liquid light guides have been found to transmit UV light very efficiently. 
Quartz fibers are also very effective, but they tend to be fragile. 
A preferred fiberscope for use with the invention is the new modified model 
IF7D3X3-26 (UV) fiberscope available from Olympus Corporation. This light 
guide employs a silica glass fiber and special lenses which carry both UV 
and white light very efficiently. A detailed view of such a fiberscope is 
illustrated in FIG. 2. The fiberscope includes a light guide cable 2 
having a connector 3 for connection to a source of UV light 4 (see FIG. 
1). The fiberscope includes an ocular or eyepiece 5 through which a visual 
inspection can be made. The eyepiece 5 has a yellow filter (not 
illustrated) for protection. A diopter adjustment ring 7 is provided for 
controlling focus of the fiberscope to the eye. 
The fiberscope 1 includes a probe section or insertion tube 8. The 
insertion tube 8 is preferably articulated so that it is provided with one 
or more joints 9 at which bending can occur. Bending of the insertion tube 
in various directions is controlled by one or more adjustment dials 6, 10 
which may be provided with locking means for locking the probe in a 
certain position. 
The fiberscope 1 is provided with an internal fluid proof working channel 
11 (see FIG. 3, a cross-sectional view of the insertion tube 8). The 
working channel 11 is a conduit for the materials used in the inspection 
including the dye penetrant, cleaning solution, developer and drying gas. 
The working channel 11 extends from a receiving connection 12 of the 
fiberscope to the end tip of the insertion tube 8. The working channel is 
preferably 1 to 3 mm in diameter. 
Referring to FIG. 3, a cross-sectional view of the insertion tube 8 
illustrates light guides 13, 14 which emanate from the light guide cable 
and continue through the insertion tube to its tip and which can include a 
special lens to maximize UV output. Insertion tube 8 also includes an 
objective lens 15 for focusing an image of the surface 16 (see FIG. 1) to 
be examined. 
The UV remote visual inspection system of the invention includes a source 
of UV light and preferably a source of white light. The white light is 
used to illuminate the area during the preparatory steps of applying the 
dye penetrant and the developer. 
A preferred source of both UV light and white light for use in the 
invention is the UV-6250 light source available from Olympus Corporation. 
The UV-6250 light source produces both ultraviolet illumination and white 
light. When used with the new modified Olympus 7 mm IF7D3X3-26 (UV) 
fiberscope described above, the UV output of the combination is 
approximately 2,000 microwatts per square centimeter at a distance of one 
inch from the tip of the scope. This is more than five times the output of 
other conventional UV light sources and provides sufficient UV light for 
the system of the invention. The UV-6250 has a halide discharge lamp which 
produces white light with a high concentration of energy in the 350 to 380 
nm spectrum. The UV-6250 includes a connector plug which is adapted to be 
connected to the light guide cable 2 of the fiberscope. A filter is 
interposed between the lamp and the light guide connector plug, which 
eliminates virtually all of the spectrum above 380 nm. 
The inspector can switch between white light and UV light at will, using 
white light for insertion of the fiberscope probe and for general 
orientation of the tip in the worksite. The inspector also has a choice of 
several filters, which are mounted either individually or which are 
selectable via a rotating turret, for UV spectra consistent with the 
fluorescence of different developers as known to those skilled in the art. 
The UV remote visual inspection system of the invention includes a special 
delivery system for the materials used in the inspection which allows the 
inspector to perform some or all of the preparation steps with the 
fiberscope. The delivery system includes a number of cannisters 17, 18, 
19, 20 for holding the materials used. The materials are stored under 
pressure and can be discharged through a sealable orifice 32, 33, 34 and 
35 by activating a release button 36, 37, 38 and 39. Preferably the 
cannisters are rechargeable. One preferred cannister which can be adapted 
for use in the invention is the Model A "Sure Shot Sprayer" which is 
commercially available from the Milwaukee Sprayer Mfg. Co. 
The cannisters 17, 18, 19 and 20 can include, for example, dye penetrant, 
compressed air, cleaning solution (e.g., water) and developer. It should 
be appreciated that fewer or more cannisters may be used depending upon 
the number of steps to be performed using the fiberscope. For example, 
depending upon the condition of the surface to be examined it may be 
desirable to clean off the surface with a strong cleaner such as 
methylethyl ketone prior to injection of the dye. This cleaning step may 
be conducted with the fiberscope by including an additional cannister of 
cleaner. 
Each of the orifices of the cannisters 17, 18, 19 and 20 is connected via a 
line 21, 22, 23 and 24 to a manifold 25. Lines 21, 22, 23 and 24 may be 
plastic tubing. For connection to the lines, manifold 25 is provided with 
a corresponding number of input fittings 26, 27, 28, 29. The input 
fittings should be such that they lock the tubing and seal it up to the 
working pressure in the cannisters. Preferred fittings for this purpose 
are Poly-matic.RTM. fittings which are described in detail in U.S. Pat. 
No. 4,508,369. 
Manifold 25 is also provided with an output fitting 30 which is connected 
with the receiving connection 12 of the fiberscope through line 31. To 
discharge material from a particular cannister, the operator merely 
presses the release button 36, 37, 38 and 39 of that cannister. Material 
from a cannister is delivered to the working channel 11 of the fiberscope 
from output fitting 30 through line 31. 
In operation, the ultraviolet remote visual inspection system of the 
invention is used to detect the presence of small cracks and flaws on the 
surface of metallic parts, such as for example, gas turbines, internal 
combustion engines, pipelines, process tubing, pressure vessels, remote 
welds, etc . . . The probe 8 of the fiberscope is inserted into the 
worksite. The surface to be examined is first cleaned. Through the 
eyepiece and with aid of white light the operator would target the area to 
be cleaned and discharge water from one of the cannisters to that area. If 
desired, the invention can also be provided with a cannister of a stronger 
cleaner such as methylethyl ketone. The next step is to dry the surface to 
be inspected with a drying gas such as compressed air which is discharged 
from the cannister holding the same. 
After drying, the dye penetrant is discharged from its cannister and 
injected into the worksite. The dye penetrant must be one which fluoresces 
upon exposure to UV light. A water soluble dye is preferred because excess 
dye can then be rinsed away with water. Such dyes are known to those 
skilled in the art. MIL SPEC F-134D powder is a preferred commercially 
available dye. 
After injection of the dye the operator should wait 10-15 minutes for the 
dye to penetrate any flaws or cracks. Excess penetrant is then washed away 
by using the fiberscope to inject water or other cleanser into the 
worksite. Water is delivered from the water cannister via the working 
channel. 
A developer is optionally applied to the surface to promote the drawing of 
the penetrant to any hairline cracks. The developer can be applied through 
the working channel of the fiberscope from a cannister holding the 
developer. Talc powder is a suitable developer. The developer should be 
allowed to set for 5 to 10 minutes before an inspection is made. Excess 
developer can be washed off with water injected by the fiberscope or 
through the use of an accessory pump. 
To check for flaws and cracks the UV light source is activated and a visual 
inspection is made through the eyepiece of the fiberscope. The probe can 
be manipulated and bent at its joints to inspect remote locations using 
the adjuster controls on the fiberscope. Since the dye penetrant 
fluoresces or produces visible light when illuminated by the UV light, 
hairline cracks which are difficult to see under normal conditions are 
readily seen. 
The luminescent effect which results upon exposure to UV light can be 
enhanced by simultaneously illuminating the area to be inspected with both 
UV light and white light. It has been stated above that UV light source 4 
can also be a source of white light. However, conventional sources of both 
UV light and white light cannot effectively provide simultaneous 
illumination and transmission of both types of light. Simultaneous 
exposure to both UV light and white light can be achieved by providing the 
system of the invention with an additional source of white light 40 (see 
FIG. 1) which must be separate from the source of UV light 4. The separate 
source of white light 40 may be connected to fiberscope 1 by directly 
running a light guide cable 41 from the light source into receiving 
connection 12, through working channel 11 to the tip of probe section 8. 
Alternatively, the separate source of white light can be connected through 
an input of manifold 25 via a liquid light guide tube which can feed and 
continue through the working channel of the fiberscope. 
One or more working tools may be used to assist in the inspection. For 
example, power brushes, cutting tools and grinding tools may be used to 
facilitate cleaning and preparation of the surface to be inspected. In 
accordance with the invention, cables used to connect these tools to a 
motor may be run through the working channel of the fiberscope. 
In the foregoing specification, the invention has been described with 
reference to specific exemplary embodiments thereof. It will, however, be 
evident that various modifications and changes may be made thereunto 
without departing from the broader spirit and scope of the invention as 
set forth in the appended claims. The specification is accordingly to be 
regarded in an illustrative rather than a restrictive sense.