Thin-walled silicon carbide inserts for tubular air preheaters in boilers that burn abrasive fuels.
Fly ash turns into the air heater tubes and cuts the first inches.
A ceramic insert takes that wear instead of the tube.
Ceramic inserts stop air heater tube erosion by taking the wear themselves. A thin-walled silicon carbide sleeve sits in the inlet, and where needed the outlet, of each tube in a tubular air preheater, exactly where fly ash turns into the tube and wears it fastest. The insert protects the tube-to-tubesheet weld and the first inches of the tube, so the ash cannot cut a leak path from the flue gas side into the combustion air.
When erosion reaches the tube-to-tubesheet weld, dirty hot gas leaks into the clean air stream. The leak spreads erosion into places that are hard to reach, and the usual repair is to cut out the damaged tubes and replace them, which is slow and expensive.
The damage often stays hidden until the unit is opened. Then the outage gets longer than planned. While the leak runs, the fans have to move more air in direct proportion to the size of the leaks, and the air heater recovers less heat.
Fly ash does most of its damage in the first inches of an air heater tube, so a short ceramic sleeve in that spot takes most of the wear.
Each insert is designed for the tube it goes into, with thin walls, a flange and tight tolerances.
The insert absorbs the fly ash where it turns into the tube, in place of the tube wall.
The flange and the first inches of the sleeve cover the tube-to-tubesheet weld.
Cast with thin walls, so the insert narrows the tube as little as possible.
In many cases an insert can close holes already worn at a tube end and keep the plant on line until the next outage.
Air heater inserts run in power generation boilers that burn coal, biomass, bagasse, wood or hog fuel, in pulp and paper boilers, and in package and firetube boilers. The same design protects tube ends in thermal oxidizers, heat exchangers and hot gas recuperators. In cement plants, the matching part is the clinker cooler wear insert.
Inserts are cast in OXYTRON and other abrasion resistant silicon carbide grades. More on oxide bonded silicon carbide. Blasch is tooled for most tube sizes and lengths, keeps standard sizes in stock and has engineered several installation methods for different air heater designs.
For heat exchangers where hot process gas rather than fly ash is the main load, see boiler tube ferrules. Material choice in coal-fired plants is covered in the article Ceramics Win the War on Erosion.
Both ends can be fitted. The inlet usually wears first, because that is where the ash turns into the tube.
No. Blasch does not coat or spray. The insert is a cast silicon carbide sleeve with its own wall, set into the tube end.
Standard sizes are kept in stock. Other sizes are designed from your tube dimensions.
The tube diameters, how much of the tube end to cover, the fuel and its ash, and the fixing method you prefer. A drawing is not required.
Send the tube size and the fuel you burn. A Blasch engineer designs the inserts and the way they are fitted.
