GB2220678A - Removal of contaminants from articles - Google Patents
Removal of contaminants from articles Download PDFInfo
- Publication number
- GB2220678A GB2220678A GB8910253A GB8910253A GB2220678A GB 2220678 A GB2220678 A GB 2220678A GB 8910253 A GB8910253 A GB 8910253A GB 8910253 A GB8910253 A GB 8910253A GB 2220678 A GB2220678 A GB 2220678A
- Authority
- GB
- United Kingdom
- Prior art keywords
- ultrasonic vibrations
- articles
- chemical
- wave
- contaminant
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/08—Apparatus, e.g. for photomechanical printing surfaces
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/44—Compositions for etching metallic material from a metallic material substrate of different composition
Abstract
Articles are decontaminated by immersing the articles to be cleaned in a chemical which is reactive with the contaminant and subsequently subjecting the immersed article to ultrasonic vibrations. An example is given of the removal of particles of zinc-based alloy from gas turbine engine components with the use of nitric acid solution, the components being subjected to ultrasonic vibrations whilst being in the acid solution. This prevents or hinders the formulation of a passive coating on the contaminant particles. The wave-length or frequency of the ultrasonic vibrations maybe varied for increased cleaning efficiency where components have internal passages or cavities, e.g. by varying between full-wave and half-wave modulation. Besides the use of tanks containing the reactive chemical there may also be interspersed wash tanks.
Description
Decontamination Method and Apparatus
The present invention relates to a method and apparatus for the removal of contaminants from articles.
A known method of holding articles for the purpose of performing machining or other operations on them is to cast a block of zinc based alloy or other metal around a portion of the article. The cast block serves both as a datum and member for holding the article during machining.
Blades for gas turbine engines is one example of articles which may be held and machined by this method. Zinc alloy is commonly used as the holding metal. When using this method of holding for gas turbine engine components it is essential that all traces of the zinc are removed after machining. If the zinc is not compltetely removed catastrophic failure of the component may occur in service.
The problem of zinc removal is greatly exacerbated where the components have complex internal cooling passages which may entrap zinc particles.
After breaking away of the zinc block it is common practice to treat the components with 50% nitric acid to remove any zinc adhering to the surface. It has been found, however, that particles of zinc may become passivated by the action of the nitric acid creating a protective layer on the surface. Typical cleanliness specifications require a maximum zinc content of one part per million in the final acid dip. Components may, therefore, be passed through a cleaning operation in the erroneous belief that aLl the zinc contamination has been removed.
A possible consequence of unremoved contamination is that components which have been rejected for dimensional tolerance reasons may be returned to the foundry for remelting. Remelting of contaminated components could easily cause corruption of the alloy melt and severely affect the operation of the foundry; such is the scale of importance of the problem.
According to a first aspect of the present invention a method for the decontamination of articles comprises the steps of immersing the article to be cleaned in a chemical which is reactive with the contaminant and simultaneously subjecting the immersed article to ultrasonic vibrations.
The ultrasonic vibrations limit or hinder the formation of a passive coating on the contaminant.
Where the articles being cleaned have internal passages or cavities it is preferable to vary the wavelength of the ultrasonic vibrations for increased efficiency. Such variation may be accomplished by manual means but is preferably effected by automatic programmed variation.
Where zinc or zinc alloys are to be removed the reactive chemical may be an aqueous solution of nitric acid.
The method of the invention also includes various washing operations to minimise carry-over of contaminants from one immersion tank to another.
According to a second aspect of the present invention apparatus for the decontamination of articles comprises at least one tank having a chemical which is reactive to the contaminant to be removed and also having means for transmitting ultrasonic vibrations through the chemical.
Preferably the apparatus also includes means for varying wavelength or frequency of the ultrasonic vibrations.
The apparatus may also comprise more than one tank having reactive chemical and such tanks also having means for transmitting ultrasonic vibrations. Such tanks may also be interspersed with wash tanks or means for washing the articles between immersions in reactive chemical.
A tank having a second chemical for neutralising any residual first reactive chemical may be included in the apparatus.
Means may also be included for transporting the articles between tanks.
In order than the present invention may be more fully understood an example will now be described by way of illustration only with reference to the accompanying drawings, of which:
Figure 1 shows a schematic representation of a decontamination apparatus according to the present invention;
Figures 2(a) and 2(b) show a schematic representation of contaminants being acted upon by ultrasonic vibrations of different frequencies; and
Figure 3 which shows a graph of residual contaminant level versus the number of articles passed through the decontamination apparatus of Figure 1.
Referring now to Figure 1 of the drawings and where a decontamination process line 10 is shown schematically.
Gas turbine engine blades (not shown) having internal cooling passages and which have been removed from zinc holding blocks are contained in wire mesh baskets 11. The baskets may be lowered into and raised from the tanks in the line by known hoist means. The baskets are transported along the line between tanks by known conveyor means 12.
The blades are firstly vapour degreased in tank 13 then liquid degreased in tank 14. The degreased blades are then immersed in 50% nitric acid aqueous solution in tank 15 and simultaneously subjected to ultrasonic vibrations from a transducer 16. The vibrations are also varied automatically by known controls 17 through a cycle which changes both the power level and the frequency. After a predetermined time the basket is transferred to a cold water wash tank 18 and then to a second 50% nitric acid tank 19 also having a transducer 16 and controls 17 to vary power level and frequency. A second cold water wash in tank 20 followed by a third 50% nitric acid and ultrasonic treatment in tank 21 is given. After treatment in tank 21 the acid is sampled into container 22 to determine the zinc level.Tank 23 comprises a third cold water wash whilst tank 24 contains ammonia solution to neutralise any residual nitric acid. The final tank 25 is a hot water wash.
Figures 2(a) and 2(b) represent the effect of varying the frequency between two wavelengths to ensure that all entrapped particles 30, 31 in internal passages 32 may be acted upon by ultrasonic vibrations of maximum amplitude.
In Figure 2(a) the first particle 30 is removed at the first wavelength whilst the second particle 31 is substantially unaffected. At the second wavelength of
Figure 2(b) the second particle 31 is removed. In typical applications the wavelength may be varied between 40KHz and 90KHz. Some components, however, may contain internal passages or cavities of widely differing cross sectional areas and the variation of frequency range may be much greater.
Variation of power level has been found very effective in removing air bubbles around entrapped particles. Such bubbles prevent proper access of reactive chemical to the contaminant. Power level may be varied or alternatively the ultrasonic vibrations may be varied between full-wave and half-wave modulation.
Variation of power level and frequency may be effected either independently or simultaneously within a particular tank. Furthermore, it may not be necessary to vary both or either parameters for a particular component which, for example, does not have any internal passages or cavities.
Figure 3 shows a graph of zinc contaminant level versus the number of blades which have passed through the decontamination line. The data is based on analyses of samples taken in the container 22 after the passage of each basket. Each basket may contain, for example, five or more components.
Claims (12)
1. A method for the decontamination of articles the
method comprising the steps of immersing the articles
to be cleaned in a chemical which is reactive with
the contaminant and simultaneously subjecting the
immersed article to ultrasonic vibrations.
2. A method according to Claim 1 wherein the ultrasonic
vibration wavelength is varied during the
decontamination cycle.
3. A method according to either Claim 1 or Claim 2
wherein the power level of the ultrasonic vibrations
is varied during the decontamination cycle.
4. A method according to either Claim 1 or Claim 2
wherein the ultrasonic vibrations are varied between
full-wave and half-wave modulation during the
decontamination cycle.
5. A method according to any one preceeding claim
wherein the contaminant to be removed is a zinc-based
alloy.
6. A method according to Claim 5 wherein the reactive
chemical is nitric acid.
7. Apparatus for the decontamination of articles, the
apparatus comprising a tank having a chemical which
is reactive to the contaminant to be removed and also
having means for transmitting ultrasonic vibrations
through the chemical.
8. Apparatus according to Claim 7 further comprising
means for varying the wavelength or frequency of the
ultrasonic vibrations.
9. Apparatus according to either Claim 7 or Claim 8 and
further comprising means for varying the power level
of the ultrasonic vibrations.
10. Apparatus according to either Claim 7 or Claim 8 and
further comprising means for varying the ultrasonic
vibrations between full-wave and half-wave
modulation.
11. A method substantially as hereinbefore described with
reference to the accompanying specification and
drawings.
12. Apparatus substantially as hereinbefore described
with reference to the accompanying specification and
drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB888811259A GB8811259D0 (en) | 1988-05-12 | 1988-05-12 | Decontamination method & apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8910253D0 GB8910253D0 (en) | 1989-06-21 |
| GB2220678A true GB2220678A (en) | 1990-01-17 |
Family
ID=10636796
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB888811259A Pending GB8811259D0 (en) | 1988-05-12 | 1988-05-12 | Decontamination method & apparatus |
| GB8910253A Withdrawn GB2220678A (en) | 1988-05-12 | 1989-05-04 | Removal of contaminants from articles |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB888811259A Pending GB8811259D0 (en) | 1988-05-12 | 1988-05-12 | Decontamination method & apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8811259D0 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0617173A1 (en) * | 1993-03-22 | 1994-09-28 | Societe Anonyme D'application Des Derives De L'asphalte- S.A.A.D.A. | Method and apparatus for cleaning a porous road surface |
| WO1995030032A1 (en) * | 1994-05-02 | 1995-11-09 | United Technologies Corporation | Effective cleaning method for turbine airfoils |
| WO2000000667A1 (en) * | 1998-06-29 | 2000-01-06 | General Electric Company | Method of stripping a coating from a rotary seal of an aircraft engine |
| EP1108803A2 (en) * | 1999-12-14 | 2001-06-20 | General Electric Company | Method and apparatus for removing a coating from a passage hole in a metal substrate |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB453880A (en) * | 1935-03-21 | 1936-09-21 | Alfred Edward Ridley | An improved method of and apparatus for pickling, cleansing, swilling and washing metal plates and the like |
| GB763391A (en) * | 1953-07-30 | 1956-12-12 | Capito And Klein Ag | A process and apparatus for de-scaling metals |
| GB860580A (en) * | 1957-06-07 | 1961-02-08 | Detrex Chem Ind | Method and apparatus utilizing focused ultrasonic tranducers to produce radially dispersed compression waves for cleaning or degreasing objects |
| GB894048A (en) * | 1959-10-12 | 1962-04-18 | British Oxygen Co Ltd | Manufacture and treatment of wires |
| GB943652A (en) * | 1960-05-12 | 1963-12-04 | Branson Instr | Method and apparatus for surface cleaning using ultrasonic energy |
| GB957366A (en) * | 1961-07-03 | 1964-05-06 | Bendix Corp | Sonic cleaner |
| GB1236999A (en) * | 1967-12-07 | 1971-06-23 | Branson Instr | Method and apparatus for applying ultrasonic energy to a workpiece |
| GB1331100A (en) * | 1969-11-03 | 1973-09-19 | Crest Ultrasonics Corp | Transducer suitable for use with ultrasonic processing tanks |
| GB1456664A (en) * | 1973-02-15 | 1976-11-24 | Dawe Instr Ltd | Method of cleaning an article utilizing ultrasonic or other vibrational energy |
| GB1557016A (en) * | 1977-07-06 | 1979-12-05 | Lanzetter S | Machines for cleaning watches and other instruments |
| EP0205355A1 (en) * | 1985-04-16 | 1986-12-17 | Omega Technologies | Ultrasonic cleaning device for mechanical parts |
-
1988
- 1988-05-12 GB GB888811259A patent/GB8811259D0/en active Pending
-
1989
- 1989-05-04 GB GB8910253A patent/GB2220678A/en not_active Withdrawn
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB453880A (en) * | 1935-03-21 | 1936-09-21 | Alfred Edward Ridley | An improved method of and apparatus for pickling, cleansing, swilling and washing metal plates and the like |
| GB763391A (en) * | 1953-07-30 | 1956-12-12 | Capito And Klein Ag | A process and apparatus for de-scaling metals |
| GB860580A (en) * | 1957-06-07 | 1961-02-08 | Detrex Chem Ind | Method and apparatus utilizing focused ultrasonic tranducers to produce radially dispersed compression waves for cleaning or degreasing objects |
| GB894048A (en) * | 1959-10-12 | 1962-04-18 | British Oxygen Co Ltd | Manufacture and treatment of wires |
| GB943652A (en) * | 1960-05-12 | 1963-12-04 | Branson Instr | Method and apparatus for surface cleaning using ultrasonic energy |
| GB957366A (en) * | 1961-07-03 | 1964-05-06 | Bendix Corp | Sonic cleaner |
| GB1236999A (en) * | 1967-12-07 | 1971-06-23 | Branson Instr | Method and apparatus for applying ultrasonic energy to a workpiece |
| GB1331100A (en) * | 1969-11-03 | 1973-09-19 | Crest Ultrasonics Corp | Transducer suitable for use with ultrasonic processing tanks |
| GB1456664A (en) * | 1973-02-15 | 1976-11-24 | Dawe Instr Ltd | Method of cleaning an article utilizing ultrasonic or other vibrational energy |
| GB1557016A (en) * | 1977-07-06 | 1979-12-05 | Lanzetter S | Machines for cleaning watches and other instruments |
| EP0205355A1 (en) * | 1985-04-16 | 1986-12-17 | Omega Technologies | Ultrasonic cleaning device for mechanical parts |
Non-Patent Citations (1)
| Title |
|---|
| Metal Finishing, vol 86. No.4, April 1988, pages 9-10 * |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0617173A1 (en) * | 1993-03-22 | 1994-09-28 | Societe Anonyme D'application Des Derives De L'asphalte- S.A.A.D.A. | Method and apparatus for cleaning a porous road surface |
| FR2703088A1 (en) * | 1993-03-22 | 1994-09-30 | Saada | Method and device for cleaning a porous pavement |
| WO1995030032A1 (en) * | 1994-05-02 | 1995-11-09 | United Technologies Corporation | Effective cleaning method for turbine airfoils |
| WO2000000667A1 (en) * | 1998-06-29 | 2000-01-06 | General Electric Company | Method of stripping a coating from a rotary seal of an aircraft engine |
| EP1108803A2 (en) * | 1999-12-14 | 2001-06-20 | General Electric Company | Method and apparatus for removing a coating from a passage hole in a metal substrate |
| EP1108803A3 (en) * | 1999-12-14 | 2003-05-07 | General Electric Company | Method and apparatus for removing a coating from a passage hole in a metal substrate |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8811259D0 (en) | 1988-06-15 |
| GB8910253D0 (en) | 1989-06-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |