Dry Ice Blasting

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This post is coming out a little later than I wanted it to, but we have had a very busy few weeks here in the lab. We had some outdoor projects to finish before the weather turned cold. Some of our activities in the last few weeks have included assembling and installing a new anode rig in the tank holding the pieces we used to test the dry ice blasting, winterizing the tank farm and having adventures in the skeg tank. The skeg tank adventures will get their own post after Thanksgiving, today I want to tell you about dry ice blasting.

We were fortunate enough to have the opportunity to try out a SDI Select 60 dry ice blaster from Cold Jet. The set up for this machine is not overly complicated. You hook it up to an air compressor; load the hopper with either dry ice pellets or blocks, in our case we found that pellets worked better, the block or pellets are pressed into an auger that shaves them and then the shaved pieces are fired down a hose and out a nozzle held by an operator. The system set up is not so different from other abrasive cleaning methods, but the unique thing about dry ice blasting is that there is no aggregate left at the end to clean up. If you are doing abrasive cleaning using glass beads, sand, ground walnut shell or any other medium you will have to clean bits of that medium off of your object when you’re done. You get to skip this step with dry ice blasting since your medium just sublimates away.   Read more

National Treasure

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As concretion removal on the turret has continued, a host of new finds have been discovered!!! The focus of concretion removal has shifted around a bit during the last several weeks (look at previous blog posts). We began work with the documentation and removal of the roof stanchions, which then moved to the excavation of concretion between the roof rails and beams, and currently to the removal of corrosion and concretion in and around the nutguards.

The following images show the variety of discoveries we found during the excavations.   Read more

New Turret Anodes

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We’ve placed a new anode for the impressed current system to improve the corrosion protection of the Monitor’s turret. This anode is suspended within the turret to protect the interior metal surfaces.

The turret is made of eight layers of 1-inch thick wrought iron plate. You can see each of the layers in the photo below.