ADM Abrasive Media Products

• EnviroStrip® Wheat Starch
• EnviroStrip® XL-Corn Hybrid Polymer
• eStrip™ GP (starch-g-acrylic)
• eStrip™ GPX (starch-g-acrylic)

1.0 Overview

ADM abrasive media products are used for a variety of coating removal applications. The product lines primary focus is removing paint, primer, sealant and adhesive from aerospace substrates. While it is fairly similar to other abrasive blasting technologies, when used on aerospace materials the process requirements mandated by aircraft manufacturers are more stringent than industrial blasting applications. More emphasis on media management, equipment design and operator training is required when dealing with aircraft substrates. This operational guideline is a basic overview of areas requiring attention when using ADM abrasive products for aerospace applications.

2.0 Process Equipment Considerations

The following describes the process equipment typically used for Envirostrip® and eStrip™ Media. Each installation will include most of the equipment described herein, sized and specified to meet the application requirements.

Proper process equipment will accomplish the following:

• Recover and classify media to within the correct particle size range as determined by the application.
• Remove dust and paint particulate from recovered media mix.
• Clean and remove dense particle contaminants from recovered media (hangar applications).
• Use dry, oil-free, quality compressed air.
• Minimize process downtime for media recovery or pressure pot replenishment.
• Operate problem-free – FOD free
• Deliver consistent, repeatable process parameters to the nozzle (nozzle pressure, media flow).

2.1 Media Recovery

Recovery of media, whether from a blast room floor recovery system, hand cabinet or a closed-cycle unit, is performed pneumatically with a cyclone/blower combination. A centrifugal or positive-displacement blower provides negative pressure, conveying the media through a pneumatic recovery line.

As recovered media enters the cyclone separation stage, very fine particulate of media and paint dust are removed and sent to a dust collector. Airflow through the cyclone is usually regulated by mechanical adjustment, controlling the amount of media dust and paint removed by the cyclone. The remaining reusable media spirals down through the cyclone and is returned to the system for further processing.

On some systems a rotary air lock or similar air lock device located at the bottom of the cyclone meters the media to a vibratory screen. The air lock allows the media to leave the cyclone without affecting the negative pressure in the recovery line or the cyclone itself. The air lock also regulates the flow of recovered media onto the vibratory separating device.

2.1.2 Vibratory Media Classification

Recovered media is typically fed to a multi-deck vibratory screen. Oversized media and foreign matter are removed with the upper screen. Fines (ie. typically less than 100 mesh U.S. Std. or 0.15 mm – depending upon the application) are removed through the lower screen. If dense particle separation is required, the usable media is split into two or three streams for subsequent dense particle removal. Smaller systems typically do not utilize a vibratory classification system, relying upon the cyclone separation system to remove spent media and paint dust.

2.1.3 Magnetic Particle Separation

Ferrous material can contaminate the media. This metal particulate can come from the parts being stripped or possibly from being tracked into the room under the operators’ shoes. Process equipment, when new, can also generate ferrous contaminants that end up in the recovered media. These ferrous contaminants have a much higher density than the blast media and should be removed.

A magnetic separator, also available in a self-cleaning version, is used to treat the media as it leaves the vibratory screens and enters the storage hopper. Media falls through a bank of magnets, which attract and retain the ferrous materials as the media passes through the device. It is an important housekeeping rule to check magnets for ferrous metals and clean units to maximize their efficiency.

2.1.4 Dense Particle Separation (DPS)

If required by specification, this final cleaning step removes remaining dense particulate matter from the recovered media. Most applications do not require this step as non-ferrous materials are not typically found in blast rooms or hand cabinet applications. When stripping large structures (aircraft) in hangars it is recommended DPS units be installed due to potential contamination from the concrete floor. Aircraft OEM and USAF specifications do allow an established amount of dense particulate to be in the media.

The DPS system takes each classified media stream and passes it over a fluidized bed which separates material more dense than the media. The media travels along an air fluidized deck, usually conveyed by a vibrating eccentric motion.
The cleaned media streams are then transferred pneumatically to the storage hopper.

2.1.5 New Media Addition

An important parameter of media management is maintaining proper particle size distribution. While media fines are removed from the recycled media, new media should be added on a regular basis to maintain maximum efficiency. This can be done by adding media through the floor recovery system or into the hand cabinet work area. It is recommended that media be added often (“salted in”) in small amounts to insure a good mix.

A preferred method is the automatic (mechanical) addition of new media during processing of recovered media. The ideal addition point is after media classification and cleaning has been performed, during pneumatic transfer to the storage hopper. A small adjustable volumetric feeder, attached to a new media hopper, is calibrated to add new product to the recovered media in relationship to the amount of media being removed. The new media feeder interfaces with the on-off sequence of the blast nozzle.

2.2 Storage Hopper

After the classification and cleaning steps, the media is pneumatically conveyed to the storage hopper. Hoppers are typically inclined at 60° to 70° at the bottom to encourage good media flow from the storage vessel. Hoppers may also be epoxy lined. Flow enhancement devices located at the bottom of the hopper, such as air-fluidizing devices, can also be used to keep the media from “bridging” inside the hopper. Level sensors control the media processing system to prevent overfilling of the storage hopper. The media is transferred from the storage hopper to the pressure pot system on demand.

Select ADM Biobased Media Series

EnviroStrip®
 (wheat starch)

EnviroStrip® XL
 (corn hybrid polymer)

eStrip ® GPX
 (starch-g-acrylic)