Nomex Needle Punched Felts

NOMEX®, developed by DuPont , performs at high temperatures while Maintaining high strength, resistance to abrasion, and good dimensional stability. Users report filter bags of Nomex have excellent dust release properties and resist attacks from many chemicals found in industrial smoke and fumes.

NOMEX® filters offer one of the best total economies in a filtration system because of higher air to cloth ratios, higher temperature capability, and a long wear life.

Properties

Performs at high temperatures

NOMEX® can be used continuously at operating temperatures up to 218°C (425°F) , and can handle higher temperature surges. However, to optimize bag wear life, continuous temperatures of 204°C (400°F) and lower with minimum temperature surges are recommended.

Resists flexing and abrasion

Flex resistance of NOMEX® at room temperature is good, about equal to that of polyester fibers; after aging at temperatures of 121°C (250°F) and above it's toughness if excellent. Nomex should give more than three times the wear life of polyester at 121°C (250°F) and above.

Effect of moisture

NOMEX® performs well at high operating temperatures with normal amounts of moisture. The wear life projections in the below graphs were developed using 6-10% H20. Higher levels of moisture and temperature shorten wear life. When operating in high moisture environments it would be worthwhile to investigate reduction of temperature to reduce wear life. For example with 20% H20, operating hours could be increased from 2, 300 hours to 35, 000 hours (15X) by reducing the temperature from 204°C (400°F) to 148°C (300°F).

Resists Chemicals

NOMEX® aramid fiber resists attacks by mild acids, mild alkalis, and most hydrocarbons. In addition customers report it to be unaffected by fluorine compounds in gas effluent from metallurgical and rock processing operations. In acid environments, evaluation of NOMEX® should be made to ensure that the fiber will perform acceptably before insulation. NOMEX® is an acid environment, at temperatures above the dew point, will outperform polyester. Temperatures above the dew point should be maintained to minimize chemical attack on NOMEX® and the equipment. The system should be warmed before putting on stream and dried before being shut down to minimize chemical attack. To optimize bad life when acid gases are present in the gas stream, the lowest operating temperature that is safely above the dew point should be used. Higher temperatures expedite chemical attack.

Dimensional Stability

NOMEX® is one of the most dimensionally stable fibers available. Fibers of NOMEX®, properly manufactured and finished, should neither stretch nor shrink over 2% when operated at temperatures up to 218°C (425°F).

High temperatures

The most effective use of NOMEX® aramid is in high efficiency filtering systems where effluent temperatures are above 250°F or in systems with surges over 250°F. In hot gas filtration systems, fabrics of NOMEX® require less filter area, for equal gas volume and efficiencies, than fiber glass.