Blast cleaning large fabrications efficiently

In this automated blast media recovery system, the blast media falls through a grated floor, where an assembly with a hardened blade sweeps the media into a container for subsequent cleaning and reuse.

Scrutinize a manual blast cleaning operation, particularly at a heavy industrial or structural fabricator that produces very large products, and you’ll notice how little labor time it takes to perform the actual blasting, at least relative to how long it takes to do virtually everything else.

For instance, at some point employees need to sweep the blast room floor to dispose or reclaim the blast media. All this time spent sweeping and collecting used grit increases labor costs and reduces the amount of value-added time in the blast room: specifically, time spent blast-cleaning fabricated products. Moreover, steel grit blast media also happens to be very hard on blast room components.

Then comes the challenge of blasting very large structures, moved into the blasting area on large trolleys or other larger transporters, then on to the subsequent operation, usually priming and painting. And for very large structures, flash rusting can set in, should the structure be stored outside in inclement weather before a primer is applied.

Engineers at Singapore-based Blastechnik recently developed products that tackle both conundrums. One automates blast media reclamation. According to the company, this entire process, from grit retrieval to cleaning and reuse, takes between one and two minutes.

Another product, a room for extremely large fabrications like components for tanker ships and bulk carriers, allows blasting and painting to be performed in the same space—and a dual-room version ensures that the blasting and painting machinery is well-utilized.

The company’s automated blast media removal system, called TruGlide, has a grated floor. The blast media is applied and falls through the grating and into one of several channels, each of which has a moving rack assembly with a hardened steel blade. That blade sweeps the used blast media by traveling up and down the length of the floor, pushing the grit to a container below, where it is recovered, cleaned, and stored for reuse.

The material being recovered is, of course, abrasive. If a hardened steel blade continually swept used abrasive all day, continuously rubbing the media against the very bottom of the floor channels, it wouldn’t take long for the floor to wear.

For this reason, the blade sweeps away most, but not all, of the blast media. According to the company, the system is designed to allow for a 10-mm-thick layer of used blast media to collect at the bottom of the channels, protecting the bottom of the channels from excessive wear.

Regarding the challenge of blasting megastructures—again, usually moved with trolleys or other transporters—the fewer times these massive structures need to be moved, the better. With this in mind, the company developed its combination blast and paint rooms. Designed for massive products, these systems allow a fabricated structure to be blasted, cleaned, welded (if necessary), and then—to mitigate the risk of flash rusting if stored outside in inclement weather—be immediately primed and painted in the same room.

Of course, working with such massive structures can take time. Some large ship blocks may require two or more layers of protective coating, which can take several days to apply. While waiting for the coating to cure, the blasting and painting equipment sit idle—which, of course, isn’t very productive.

This dual blast and paint room is designed for extremely large structures. The two booths share the same blasting and recovery equipment.

To overcome this, the company has a dual-room blast and paint system. Both rooms use the same blasting and recovery equipment. When people in one room are blasting one fabricated product, others in the next room can be working on another product, performing abrasive cleanup or painting.

According to Mark Colk, director of business development at Blastechnik, the blast and paint combination system isn’t usually sold with automatic abrasive recovery. “In a lot of the markets we’ve sold to, [fabricators] prefer manual sweep-up or other systems, as the cost of labor is very low.”

This isn’t the case in the U.S., of course, and according to Colk, a blast and paint combination system could be designed with automated blast media recovery, tailored for large-scale structures transported on carts and trolleys.

Regardless, the company said that, whether used separately (as has been the norm) or together, both technologies, blast and paint combination as well as automated blast media recovery, aim to minimize the non-value-added time in manual blasting and painting—which, for large and heavy fabrications, can be quite extensive.

Photos courtesy of Blastechnik, 65-6505-9098, www.blastechnik.com.