US 3916032 A
Method and apparatus for transporting and applying a liquid developer to a test piece having dyed indications therein indicative of the presence of flaws, involving directing a stream of a readily volatilizable solvent for a liquid developer from a pressurized source into a container containing the liquid developer to thereby displace some of the liquid developer at a controlled flow rate from the container, injecting the displaced stream into the mixing chamber of a spray nozzle, and propelling the liquid developer and the readily volatilizable solvent through the spray nozzle by the use of an additional stream of the readily volatilizable solvent.
Description (OCR text may contain errors)
United States Patent Conner 1 Oct. 28, 1975 METHOD OF TRANSPORTING AND APPLYING A LIQUID DEVELOPER  Inventor: Kenneth F. Conner, Lombard, Ill.
 Assignee: Magnaflux Corporation, Chicago,
 Filed: Dec. 2, 1971  Appl. No.: 204,004
 US. Cl. 427/8; 427/127; 427/128; 427/130; 427/145; 427/157; 427/197; 427/212; 427/336; 427/421  Int. Cl. v. B05C 5/00  Field of Search 117/235,104,105.1, 117/105.3105.5; 118/302; 239/373,'143; 252/6252; 427/8, 127, 128, 130, 145, 427/157,197, 212, 336, 421
 References Cited UNITED STATES PATENTS 2,842,465 7/1958 Harrison 239/373 X 2,942,787 6/1960 Bok et a1. 239/373 3,026,045 3/1962 Reading 239/143 3,140,050 7/1964 Elmore 239/143 3,609,532 9/1971 Van Kirk 252/6252 Primary ExaminerBernard D. Pianalto Attorney, Agent, or Firml-lill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson  ABSTRACT Method and apparatus for transporting and applying a liquid developer to a test piece having dyed indications therein indicative of the presence of flaws, involving directing a stream of a readily volatilizable solvent for a liquid developer from a pressurized source into a container containing the liquid developer to thereby displace some of the liquid developer at a controlled flow rate from the container, injecting the displaced stream into the mixing chamber of a spray nozzle, and propelling the liquid developer and the readily volatilizable solvent through the spray nozzle by the use of an additional stream of the readily volatilizable solvent.
6 Claims, 1 Drawing Figure METHOD OF TRANSPORTING AND APPLYING A LIQUID DEVELOPER BACKGROUND OF THE INVENTION Field of the Invention The dyed penetrant inspection process employing either a fluorescent or visible dye penetrant has been commercially practiced for the last several decades. Basically, this inspection procedure involves applying an oily penetrant containing either a fluorescent dye or a visible dye over the surface of the test piece and permitting the penetrant to wet the metal, and become lodged in any surface discontinuities which may exist. Excess penetrant is then removed from the surface by emulsification, scrubbing or washing to leave only the entrapped dye penetrant in the flaws. The surface tension characteristics of the penetrant are such that it tends to exude from the flaws, seeping out to the surface where it can be observed and thereby indicate the location and the extent of any surface flaws.
The visibility of the indication is enhanced'by the application to the surface of the part of a developer 'containing light-colored pigment particles which render the dyed penetrant exudate or residue contrastingly visible. The pigment particles act in the manner of a blotter to extract residual penetrant by capillary action and also to provide a background against which the dyed penetrant residue is rendered more clearly visible. The developer may consist solely of finely divided particles, but in many instances, the developer is applied as a suspension of finely divided pigment particles in a nonaqueous liquid which contains or is itself a volatile solvent for the dye. The solvent thereby enhances the development action by dissolving the dyed penetrant and bringing it to the surface where it spreads into the finely divided layer of pigment particles.
Another form of non-destructive testing involving dyed testing materials is that which concerns itself with the use of magnetic particles colored with a dye which becomes visible upon activation by certain solvents, and magnetic particles coated with a fluorescent dye. Examples of methods and compositions employing such magnetic particles will be found in the de Forest US. Pat. No. 2,365,253; Kazenas US. Pat. No. 2,936,287; Borrows US. Pat. No. 3,404,093; Borucki et al. US. Pat. No. 3,485,758; and Lorenzi US. Pat. No. 3,480,855.
A novel method and apparatus for jointly employing both the magnetic particles colored with a solvent activated dye and magnetic particles colored with a fluorescent dye and described in the aforementioned US. Pat. No. 3,609,532. That patent describes a method of detecting inhomogeneities, defects, flaws or other discontinuities in work pieces and, in general, solid objects that are magnetizable such as ferrous metal objects. A'flowable mixture of fluorescent dye-colored magnetic particles and visible dye-colored magnetic particles is "applied to the work piece by sprinkling, pouring or spraying. The particles can be applied in dry form or they can be applied in a liquid suspending medium. Preferably, relative movement is effected between the flowable mixture during its application to the work piece and the surface to which the mixture of particles is applied so that an accumulation. of magnetic particles occurs only where there is a magnetic leakage field caused by a surface discontinuity. The adherent 2 magnetic particles are then subjected to the action of a liquid solvent which is a solvent for the visible dye of the visible dye-colored particles, thereby causing a dissolution of the visible dye in the solvent or a bleeding of the dye.
One of the advantages of the aforementioned process is that it gives an early and easily observed indication of surface discontinuities in the work piece due to the accumulation of fluorescent magnetic particles at any surface discontinuities, while the subsequent color indication provides by the bleeding of the visible dye affords a highly contrasting color indication under ordinary, or white light. By incorporating a light-colored pigment in the solvent for the visible dye, a desired color contrast is obtained.
The aforementioned type of inspection process has proven to be very satisfactory in the location and identification of inhomogeneities. There has been some difficulty encountered, however, in the matter of applying the liquid developer containing suspended pigment SUMMARY OF THE INVENTION The present invention provides a system for transporting and applying a liquid developer to a test piece in which dyed indications are present which involves directing a first gaseous stream of a readily volatilizable solvent for the liquid developer from a pressurized source into a container containing the liquid developer to thereby displace some of the liquid developer at a controlled flow rate from the container. The displaced stream is directed to the fluid nozzle of a spray means and there combined with a stream of the readily volatilizable solvent, which also propels the mixed streams and serves to eject the combined developer-solvent mixture through the spray nozzle as a finely divided atomized spray. The continuous solvation of the liquid developer by the presence of the readily volatilizable solvent keeps the material from drying out and also serves to prevent plugging or the orifice nozzle from continued use.
BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:
The single FIGURE in the drawing is a somewhat schematic representation of a spraying system which can be used for delivering and atomizing a liquid developer composition in accordance with the improvements of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, reference numeral 10 has been applied generally to a pressure vessel which holds a material which is a solvent for the liquid constituent of the developer. The fluorocarb'ons are particularly preferred, but other low boiling liquids or pressurized gases such as low boiling hydrocarbons and the like can be used as long as they produce the desired effect of acting as a solvent for the liquid being sprayed and provide the pressure to convey the liquid through the'system and secure the desired spray pattern.
Any of the commercially available fluorocarbon's can be used either alone or in combination to provide the requisite vapor pressure characteristics, as is well known to those skilled in this art. The following represents a partial list of such fluorocarbons:
Commercial name Chemical name 'Freon-l l trichloromonofluoromethane Freon l 2 dichlorodifluoromethane Frconl 3 monochlorotrichloromethanc Freon-13B] monobromotrifluoromethanc Freonl4 tetrafluoromethane Q Freon-22 'monochlorodifluoromethane Freon-H3 trichlorotrifluoroethanc Freon-l l4 dichlorotetrafluoroethanc of light colored pigment particles of very finely divided particle form in-a non-aqueous, readily volatilizable ve- -hicle. Such non-aqueous vehicles can be alcohols or volatile liquid materials such as trichlorethane, methylene chloride, or trichloroethylene. The solvent may also be a liquid ketone such as acetone or methyl isobutyl. ketone, or the like. The developer may also include resinous materials which serve to increase the viscosity of the developer while inhibiting spreading of the visible dye indication to the proximity of the surface discontinuity. Such resinous materials may be polyvinyl chloride dissolved in a relatively volatile hydrocarbon solvent or a lacquer-type solvent developer such as nitrocellulose and amyl or butyl acetate.
The finely divided particles contained in the developer may be material such as talc or chalk, to cite two common examples. A uniform dispersion of the finely divided particles in the non-aqueous vehicle is provided by employing an agitator 16 which is driven by an air motor 17 having a compressed air inlet 18 and an air exhaust 19.
Upon introduction'of the pressurized gas from the pressure vessel 10 into the tank 15,'the additional pressure serves to force liquid in the tank through a discharge tube 20 having its inlet end near the bottom of the tank 15. This discharged liquid is passed into a conduit 21 under the control of a manual shut-off valve 22 and then into a metering valve 23 by means of which 4 ber 26. The gas, being a solvent for the liquid in the developer solution keeps the solution solvated and at a viscosity suitable for spraying as well as atomizing the developer as it passes through the spray nozzle.
On-off control for the spray nozzle is provided by a branch conduit 31 which is connected behind the manual valve 11. A solenoid operated valve 32 disposed in a branch line 33 is actuated by an electrical signal to inject the propellant gas through a pressure regulator and gauge assembly 34 into an inlet 35.
Disposed within the spray nozzle assembly 25 is a needle valve 36 having a headed portion 37 slidably received within a cylinder 38. A spring 39 normally biases the needle valve 36 in a position in which it closes off the spray nozzle 27. The inlet 35 introduces the pressurized gas into a space between the headed portion 37 and a rigid plate 40 through which the needle valve 36 may slide, but which prevents gas flow into the mixing chamber 26. When the gas pressure is sufficiently high, the needle valve 36 is unseated, and the mixture of developer and solvent is sprayed out into the atmosphere.
Any one of a wide variety of developer compositions can be used and the following areoffered strictly for purposes of example:
Trichloroethylene l l0 gals.
TiO CaCO silica l 10 lbs.
lsooctyl phcnoxy polyethoxy ethanol (9-l0) oxyethylenc groups) 3 galsv 6 lbs.
Zinc stearatc 50/50 mixture of ethanol and ethyl acetate I I0 gals. Mixture of TiO and SiO I ll) lbs.
Nonyl phenol polyethylene glycol ether 3 gals.
The solvent contained in the developers when applied to a visible dye contained on ferromagnetic particles results in the production of a visible dye solution which spreads out over the magnetic pigment particles in the manner of a paint to give a brightly colored enlargement of the indication against a strongly contrasting background created by the white or light colored pigment contained in the liquid developer. The system lends itself to automatic operation through the use of an automatic black light scanner so that developer is sprayed on only at the location required or indicated by the presence of the fluorescent indications.
I claim as my invention:
1. The method of transporting and applying a liquid developer to a test piece having dyed indications therein indicative of the presence of flaws which compn'ses directing a first gaseous stream of areadily volatilizable solvent for a liquid developer from a pressurized source into a container containing said liquid developer to thereby displace some of said liquid developer at a controlled flow rate from said container, directing the displaced liquid developer to a spray means,
directing a second gaseous stream of said solvent at a controlled rate from said pressurized source into said spray means,and discharging from said spray means a spray of a resulting developersolvent liquid at the sur- 4 face of said test piece.
4. The method of claim 3 in which said particles are pigment particles which provide a contrasting background for said dye.
5. The method of claim 3 in which said vehicle is an alcohol.
6. The method of claim 1 which includes the step of directing a third pressurized gaseous stream of said solvent into said spray means to actuate said spray means.