Preliminary Requirements

Safety Requirements

WARNING

THIS PROCESS USES WATER AT A PRESSURE OF UP TO 55,000 PSI (379212 KPA). IT IS THEREFORE ESSENTIAL THAT THE OPERATING MAINTENANCE INSTRUCTIONS ISSUED BY THE EQUIPMENT MANUFACTURER ARE FOLLOWED CLOSELY.

Procedure

1. SUBTASK 70-15-01-160-001 General Data

   1. This process is not approved to remove antigallants, RTV or paint prior to fluorescent penetrant inspection. It is not to be used as a general cleaning process before fluorescent penetrant inspection. The high pressure water stripping may affect the sensitivity of the fluorescent penetrant inspection.

   2. This process cannot be used on rotating parts, or blade/airfoil applications unless it is specifically called out in the engine manual.

   3. High pressure water is used in the engine manual repairs to strip materials from metallic components if grit blasting is currently used either for the removal of the coating or surface preparation before coating re-application.

   4. It is approved to use TASK 70-15-01-160-501 to remove the materials in the subsequent list:

      1. Combustion wire and powder coatings, wire arc and plasma sprayed coatings.

      2. Rubbers and adhesives.

      3. Fibremetal.

      4. Reference TASK 70-33-59-300-503 for coatings and base materials for which high pressure water stripping is approved.

   5. It is not approved to use TASK 70-15-01-160-501 Strip Coatings By High Pressure Water Blasting to remove the materials in the subsequent list:

      1. D-Gun or other high velocity deposited metal coatings (for example: IAE 36206).

      2. Braze metal.

      3. Chrome Plate.

      4. Nickel Plate.

   6. See TASK 70-33-59-300-503 for coatings and base materials for which TASK 70-15-01-160-501 STRIP COATINGS BY HIGH PRESSURE WATER BLASTING is approved.

   7. Some engine conditions can cause the complete removal of engine-run IAE 53-5 by TASK 70-15-01-160-501 STRIP COATINGS BY HIGH PRESSURE WATER BLASTING to be more difficult. Therefore, it is possible that it will be necessary to do TASK 70-33-90-300-503 to break down engine-run IAE 53-5 coating before you do TASK 70-15-01-160-501 STRIP COATINGS BY HIGH PRESSURE WATER BLASTING.

   8. Some engine conditions can cause the complete removal of engine-run IAE 265 base coat by TASK 70-15-01-160-501 STRIP COATINGS BY HIGH PRESSURE WATER BLASTING to be more difficult.

   9. All blade, airfoil and knife-edge seal applications require special approval. Refer to the applicable step below for the SPECIAL APPLICATION authorization procedure.

2. SUBTASK 70-15-01-160-002 Validation of the Process

   1. Material removal shall be determined by comparison of the masked and unmasked areas metallurgically.

   2. Typical parameters to be controlled include the following:

      1. Nozzle or stripping head required.

      2. Orifice size/s.

      3. Nozzle or stripping head traverse rate.

      4. Part rotational speed.

      5. Nozzle rotational speed.

      6. Part to nozzle stand-off distance and angle.

      7. Special fixtures or techniques required.

   3. Base Metal Removal.

      1. The base metal removal must be less than 0.001 inch (0.025 mm).

      2. This shall be demonstrated using a test piece of the same material as the component to be stripped. Adjacent masked and unmasked areas shall be exposed to the water blast and the material removal shall be assessed using metallurgical section.

      3. The material removal should be uniform.

      4. No grain plucking or pitting shall occur.

3. SUBTASK 70-15-01-160-003 Approval to Use High Pressure Water Stripping

   1. GENERIC APPLICATION AUTHORIZATION. High pressure water stripping must not be used on rotating parts without the permission of IAE. Equipment manufacturers and equipment operators can get generic application authorization to do TASK 70-15-01-160-501 based on a GENERIC QUALIFICATION of their equipment and its operating parameters. Manufacturers with generic qualification may request from IAE the authority to self-qualify additional equipment. Operators Manufacturers and operators can use their equipment at parameters less aggressive than those evaluated in the generic qualification, and can do so without any further approval from IAE. Operators may contact IAE to determine which manufacturer has self-qualification authority. For generic application authorization, write to IAE at the address shown below. Manufacturers with generic approval are in the list that follows by source code. Refer to the Vendor List - Organizations Technical Information Repository source names/addresses identified by these numbers.

   2. Approved equipment suppliers are as follows:

      1. 01EK9 Pratt & Whitney Automation, Inc.

      2. 26057 TAFA Inc.

      3. 27528 Progressive Surface.

      4. 7U188 Flow International.

      5. Self-qualification authorization will include a program that demonstrates the manufacturer's testing capabilities. The manufacturer must agree to provide a summary of their self-qualified equipment to P&W on a regular basis.

   3. For SPECIAL APPLICATION authorization of either an equipment supplier or user of the equipment to do TASK 70-15-01-160-501 Strip Coatings By High Pressure Water Blasting for applications not specified in the generic approval, or to use parameters that are more aggressive than those tested in the generic approval, write to IAE at the address shown below.

      1. All blade, airfoil, knife-edge seal, and some other applications require special application authorization from IAE.

   4. For equipment authorization, please write to IAE to request and submit Request for Repair Consideration Form (RRC) at::

      IAE International Aero Engines AG

      400 Main Street

      M/S 121-10

      East Hartford CT 06118

      U.S.A.

      Attn: Manager Technical Services

4. SUBTASK 70-15-01-160-004 General Equipment Requirements and Capabilities

   1. Must include stripping equipment manufactured by one or more of the manufacturers in the list of manufacturers with generic approval in this SUBTASK.

   2. Must be automated to assure continuous relative motion between the waterjet nozzle and the workpiece. Automation should control nozzle position and movement, part movement, and water pressure.

   3. Must include fail-safe devices to prevent part damage caused by excessive dwell time due to mechanical failures.

   4. Typical stripping pressures are between 20,000 psi (137,895.1 kPa) and 55,000 psi (379,211.6 kPa) with water flow from 0.05 - 6 gal/minute (0.19 - 22.71 liters)/minute).

   5. It is not necessary to use high pressures to remove soft materials, such as rubber. During the development of a procedure to remove rubber or other soft materials, start with the lowest pressure setting practicable, and then do tests of the procedure at intervals as you increase the pressure until you find the pressures that correctly remove the material.

5. SUBTASK 70-15-01-160-005 High Pressure Water Blasting Procedure

   
   WARNING
   REFER TO THE MANUFACTURER'S MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIAL'S INFORMATION SUCH AS: HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES.

   1. Fixture the part to prevent movement during blasting.

   2. Water blast the part; use the previously qualified parameters. The maximum set point water pressure is 55,000 psi (379,211.6 kPa).

   3. Remove the part from the fixture.

   4. Do a visual inspection for total coating removal. If there is any remaining coating, do one of the steps that follow:

      1. Make additional passes if permitted by the GENERIC QUALIFICATION OR SPECIAL APPLICATION authorization.

      2. Strip the part by the usual stripping process that the Engine Manual or CIR Manual repair instructions specify for the part. The part must agree with all minimum wall thickness requirements and all other dimensional requirements after the removal of the remaining coating.

6. SUBTASK 70-15-01-200-001 Inspection

   1. Visually inspect stripped production workpiece to ensure water jet stripping requirements listed below are met:

      1. No swirl patterns (shallow circular ridges caused by inadequate overlap of jet erosion patterns). See Figure.

      2. No energy lines (visual linear indications which result when a rotating nozzle momentarily stops during stripping procedure causing nozzle jets to produce a linear indication until nozzle rotation resumes). See Figure.

      3. Complete coating removal (no residual coating remains adhered to the substrate).

      4. Stripped areas must not show base metal erosion. See Figure.

      5. No increase in surface roughness (surface roughness of any area exposed to water jet stripping) beyond that allowed by controlling technical data.

      6. If boundary is specified for stripped area, but no tolerance is given, stripping must be complete within boundary and may extend up to 0.125 inch (3.175 mm) outside boundary.

      7. Surface texture must be uniform and matte in appearance.

      8. Part geometry shall remain predominantly unchanged.

Figure: Example of Swirl Pattern

Example of Swirl Pattern



Figure: Example of Energy Lines

Example of Energy Lines



Figure: Example of Base Metal Erosion

Example of Base Metal Erosion