Are You Covered?
If you are an engineer in a pulp and paper, converting or printing plant, then you know how hot a steel calender roll can get. You also know that during breaks in production cycles, when maintenance is being performed, you need to adequately protect your workers from the heat.
This was the case with one pulp and paper producer. Its steel calender roll got to be 500oF (260oC) during runs, and the company needed to protect its workers in the immediate area during production breaks and maintenance. To solve the safety problem, the company decided to use a cover on the heated roll. When selecting a cover, the paper maker knew that it needed to satisfy four requirements:
- Insulate extremely well at elevated temperatures for quick cooldowns.
- Be moisture- and oil-resistant.
- Be tough, yet flexible, to ease installation and removal.
- Be reusable in order to be cost effective.
According to Kathie Leonard, president and CEO of Auburn Manu- facturing Inc., Mechanic Falls, Maine, it was with direct communication between the paper plant and Auburn that a removable/reusable insulation pad was created by combining various heat-resistant textiles, each with special characteristics.
Leonard says that the outer layer was made of a silicone-coated fiberglass cloth, which provided the moisture and oil resistance needed, while continuously withstanding temperatures to 500oF. The middle layer was composed of aramid nonwoven fabric 0.125" thick to withstand the same temperature, while exhibiting insulation value and durability. The inner layer was constructed of 100 percent fiberglass cloth to withstand up to 1,000oF (538oC) continuous protection. The pad's drawstring was made from a combination of aramid and fiberglass cord to tie the 2 x 12' cut and sewn pad to the roll. The sewing thread was coated with PTFE-coated fiberglass.
Working Safer With TextilesHeat-resistant fabrics can be an essential part of safe work practices, according to Leonard. They are used to protect people in the way of protective clothing and gloves. And they are used to protect the plants and equipment by making hose coverings and blankets.
Textiles can act as barriers when used to make curtains and pads in areas of extremely high radiant heat. They also can maximize heat retention when used to make removable insulation covers. And when used to make pipe/valve/fitting insulation, seals and gaskets, Leonard says that textiles can save energy and improve process efficiencies. See the sidebar for a short list of the most popular fibers and coatings used for industrial applications today.
Leonard says that a quick search for makers of heat-resistant fabric on the Internet should yield several manufacturers' web sites, where product specifications, material safety data sheets (MSDS) and other resources can be downloaded.
For more information about Auburn Manufacturing's textiles, visit www. auburnmfg.com.
Are you using textiles in your processing plant to ensure your workers' safety? Drop me a line with the specifics.
Sidebar: Popular Fibers and Coatings for Industrial ApplicationsFibers
Fiberglass. The most commonly used heat-resistant fiber. Withstands 1,000oF (538oC) continuously with a melting point of 1,400oF (760oC). Texturized fiberglass yarn provides good high-heat insulating characteristics.
Amorphous Silica. Chemically treated fiberglass, resulting in even better heat protection -- up to 1,800oF (982oC) continuously with a melting point over 3,000oF (1,649oC).
Carbon. Technically the product being used by industry is partially
carbonized acrylic fiber. Overall heat resistance is 500oF (260oC), but direct heat tends to travel across the fabric surface rather than penetrating through it.
Aramid. A synthetic fiber with excellent strength and insulation characteristics up to about 600oF (316oC).
Silicone Rubber. Withstands temperatures to 500oF with minimal smoke generation when exposed to excessive heat and flame.
Vermiculite Dispersion. Mineral-based finish applied to fiberglass fabrics boosts heat resistance by about 50 percent. Like carbon, heat tends to travel across rather than through it.
PTFE (like DuPont's Teflon) Coating. Temperature limits similar to silicone rubber but with better chemical resistance.