Doug Wright, StoneAge
The removal of refractory from lines and vessels in the petrochemical industry is necessary for inspection, repair, maintenance and replacement. Refractory materials are installed in vessels, boilers and process lines to provide insulation and erosion resistance. The primary components are alumina and silica, and the lining may be cast in place, gunned or manually applied. Small spaces and difficulty of access have otherwise limited methods of removal to manual labor with handheld chipping hammers.
Refractory materials can be safely removed through the proper application of high-pressure waterjets and mechanization, from localized repairs to complete cleaning. Moreover, the removal of refractory by high-pressure waterjet has been proven to be more than 10 times faster than manual chipping, resulting in the elimination of over 500 hours of worker exposure to silica dust, noise and vibration within a confined space on a typical refractory replacement.
The application of water for the suppression of silica is a well-known control, dating to the early use of pneumatic rock drills in underground mining. These drilling operations were performed dry, with operators breathing the dust produced. This resulted in an average life expectancy of four years for the miners due to silicosis, leading to the “widow maker” name for these first drills. The addition of water through the drill steel to the bit completely eliminated the dust and saved many lives going forward.
Refractory removal 1
Figure 1
A demonstration of manual chipping with a 15-pound pneumatic hammer was conducted in Type 1 refractory, 5-inch thickness, installed within a 40-inch diameter section. The operator of the hammer worked for one hour within a 12-inch square. The result was an estimated removal rate of 0.1 cubic feet per hour, illustrated in Figure 1.
Figure 2 shows the effect of one hour with high-pressure water, operating at 18,000 psi and 73 gallons per minute, resulting in a removal rate of 9.5 cubic feet per hour. The waterjet removal rate was 100 times faster than manual chipping in this application.
Refractory removal 2
Figure 2
Operating pressure and flow rate are dependent on the refractory type and thickness, the expected standoff distance from the surface that can be achieved, the rate of production desired and the type of equipment to be used. As with most other materials, the most efficient pressure is around two to three times the minimum effective pressure. The complex geometry of some internal structures may require a support system for the waterjet tooling to maintain effective standoff distances.
High-pressure waterjetting, when properly applied, has proven to be an effective method of removing refractory. The use of high-pressure water allows the transmission of hundreds of times the power of handheld chippers, with resulting refractory removal rates on the order of days to weeks faster, while removing these workers from exposure to the hazards of silica dust, extreme noise, vibration and physically exhausting labor in a confined space.
For more detailed information, test results and estimations of removal rates, download the complete white paper at www.stoneagetools.com/engineering-papers or call (866) 795-1586.
