Martin had had a great deal of success with media blasting on other jobs, but at first glance it didn’t seem like the natural choice for the boilers. The tubes had to be cleaned in place, and comfortable access for the blasting apparatus was difficult if not impossible. Successfully manipulating the stream of media around the inside of a narrow, 10-foot tube also seemed unlikely.

To get the job done, Martin first took about an eight-inch length of half-inch copper tubing and fashioned it into a corkscrew shape. This corkscrew tip was soldered to the end of a straight 12” length of one-inch copper tubing. Then the copper tubing and tip were attached to the end of a 15” length of one-inch flexible intermediate hose, which in turn was fastened to the end of the hose on the Armex Accustrip apparatus.

Martin chose the Armex Maintenance Formula XL to be blasted dry at 80psi.

The corkscrew tip caused the media to swirl, uniformly cleaning the interior of the tubes. A vacuum cleaner was positioned at the opposite end of the tube to collect the spent media, and water used to rinse the tubes was simply washed down the drain in the boiler’s blow-down area.

The flexibility and reach of the intermediate hose allowed the work crew to keep the enclosure area to a minimum.

Martin acknowledged that the indirect angle of attack caused by the corkscrew tip reduces the force of the media, but it did the job – better, faster and more economically than brushes.

While all baking soda is chemically the same (NAHCO3) only Armex, manufactured by Arm & Hammer, is formulated for use as a blast media. It can be delivered using either compressed air or water. Its benefits include ease of use and the following:

• It’s granular, suitable for use in pressure pots, cabinet systems and as an additive for pressure washer systems.

• It’s sharp, baking soda crystals delivered under relatively low pressure but at high velocity will scour virtually any coating from any substrate.

• It’s friable, meaning it fractures into smaller particles intensifying the cleaning action while softening the impact on substrates.

• It’s relatively soft, with a Moh’s hardness of 2.5, it will not damage most substrates; and

• It’s benign pH of 8.2 provides a superior worker and environmental profile, before, during, and after use.

Formulations contain uniform particle sizes from 70 to 270 microns, and ingredients for flowability and rinsabilty. The profile formulas can be uniquely blended for more aggressive removal applications.

Considered a one-pass media, Armex is unlike other abrasives in that it is extremely friable meaning that it fractures into much smaller particles upon impact.

This not only results in a more intense cleaning action and softens the impact on substrates, but also transforms the particle to a fine dust no longer suitable for coatings removal.

Using it with the right equipment maximizes cleaning efficiencies and minimizes media use. For this reason users have found the baking soda blasting process to be either more or as cost effective as other abrasive processes. In contrast, higher priced recyclable abrasives like plastic or glass bead, degenerate similarly at blast pressures over 40 psi reducing their recyclability, though their cost remains much higher.

In air driven applications, Armex can be used dry or wet with water dust suppression. Depending on the application, other portable containment may be used to control dust, like negative air and air scrubbers.

Available for full contained cabinet systems for production, and rebuild applications. Media injection devices are also available to introduce Armex into the water stream of your pressure washer, and as in all blasting operations, operators must take into account not only the abrasive being used but also the coating being removed.

The coating content will dictate other containment, waste disposal and worker safety requirements, and care should always be taken for eyes, ears, and respiratory function during any blasing operations.

When working outside, one biological process that can be disturbed by the presence of any free sodium ion, including sodium bicarbonate, is the process of photosynthesis. This process uses light in the presence of chlorophyll and water to convert carbon dioxide to sugars, used as nutrients for plant life.

Depending on the type of plant, sodium bicarbonate can produce temporary discoloration or cause more serious damage.

The most easily upset plants are flowering shrubs, such as roses, azaleas, or lilac. Trees and grass typically turn brown, then recover in 4-6 months. Some plants are completely unaffected. The speed of any reaction with plant life can vary widely, depending on the type of plant.

• Avoid contact between plants and blast media residue. Cover plants and prevent the liquid run-off from soaking the soil around plants; and

• If contact is unavoidable, the client should be aware that damage to plants can occur.

To minimize damage:

• Soak the soil and leaves thoroughly before blasting. It is best to use a sprinkler for 4-6 hours to completely soak the soil, leaves, and branches before blasting;

• Continually rinse the leaves and prevent liquid run-off from soaking into the soil around the roots; and

• After blasting, continue to soak the leaves and soil to thoroughly flush the sodium bicarbonate away from the root structure. The amount of soaking after blasting depends on the amount of residue in contact with leaves and roots.

The goal is to reduce the sodium ion concentration below 0.5 vol percent on the leaf surfaces and around the roots so that any damage will be minimized.

The Armex method can be used in any equipment manufactured for baking soda blasting. You may even be able to get results with conventional sandblasters, but systems designed for soda blasting will certainly improve performance and cost efficiencies. Pressure systems will generally work better than suction systems. When trying to strip heavy coatings, it’s also recommend that you consider using Armex designed performance nozzles.

Most cabinet systems are designed to recycle abrasives. However, Armex can not be recycled as it is extremely friable and breaks down at any pressure. There are two consequences of this action that are addressed in a soda cabinet that are not addressed in conventional recycle cabinets.

First of all, the visibility around the work piece may be greatly reduced. This may not be a problem when doing one or two pieces periodically, but if you are interested in production blasting you need the visibility.

Secondly, the dust collector may fill prematurely. As stated Armex breaks down on impact and therefore is considered a one-pass media. That means all the debris and spent media would bypass the cyclone separator and go directly to the dust collector, blinding it prematurely. In a cabinet system designed for soda, the cyclone drops out most of the debris, waste and spent media into a drum and only the very fine particulate goes to the dust collector, thus prolonging its use.

The drummed waste if tested as a nonhazardous industrial waste can then go to a sanitary landfill. These are two good reasons to invest in a dedicated soda cabinet system rather than try to use or retrofit a recycling cabinet.