Spark-Resistant Construction (SRC) for Industrial Fans and Blowers

A spark-resistant fan with nonferrous construction elements
Industrial Air Technology Corp.

Commercial and industrial ventilation systems often have to handle airstreams that contain more than just air. There can be a host of combustible gases, solid particulates, and aerosols in the airstreams. Since they are in the stream movement, they become more hazardous. A simple ignition and spark along the path of the moving airstream can result in an explosion.

Historically, blower and exhaust fan has been involved in many such mishaps. A regular industrial fan or blower can turn into a matchbox for such airstreams. The time-based wear and tear of the fan, the abnormal industrial settings, and high operating temperatures can create sparks in the fan housing that can come in contact with the combustible gases and particles of the airstream. In other cases, when a bearing fails, the shaft stops very suddenly. It results in the forward and backward movement of the shaft in the housing. This can subsequently cause a steel-on-steel strike, which would lead to sparks.

Given these intrinsic shortcomings, the Air Movement and Control Association (AMCA) has worked out a proposal for spark-resistant construction of industrial fans and blowers. Standard 99-0401 of AMCA outlines the classification of spark-resistant construction.

Three Types of Spark-Resistant Design for Industrial Fans and Blowers

There are three types of spark-resistant designs that AMCA proposes for industrial fans and blowers.

1.      Type A Spark-Resistant Design, Most Expensive

The type A spark-resistant design requires all components of fans and blowers within the airstream to be made of nonferrous material. This includes the housing, inlet cones, wheel, and fasteners. Besides being low weight and corrosion-resistant, nonferrous materials are also less likely to create sparks upon friction and temperature rises. Aluminum is the most preferred nonferrous material used in a type A spark-resistant design.

Apart from nonferrous materials, type A spark-resistant design involves the fan assembly that reduces the likelihood of any physical contact between its stationary and rotating components. Moreover, the fan shaft of a type A spark-resistant fan is made of Monel (a nickel alloy). If it is made of steel, it must be covered with a nonferrous sheath. The pedestal & housing uprights can be carbon steel or stainless steel but can only be bolted to the aluminum housing, because you cannot weld aluminum to steel.

Type A is the most effective spark-resistant design for industrial fans and blowers.

2.      Type B Spark-Resistant Design, Mid-Range Price

Type B design offers medium-level spark resistance. This design doesn’t entail the use of nonferrous material through and through. The design only requires the impeller and the shaft seal to be made of aluminum, but this must be welded aluminum. Everything else can be carbon or stainless steel.

Like type A, type B spark-resistant fan also requires an assembly where stationary parts don’t come into contact with moving parts.

3.      Type C Spark-Resistant Design, Low Price

A steel-on-steel strike is prevented by using an aluminum inlet cone (referring to IATC products, such as BI, Airfoil, RTS, or BCHS type), coupled w/aluminum “rub rings” inside the housing. For a fan type that does not have an inlet cone, the 2 sets of rub rings on each interior side of the housing are bolted through the housing & these can be replaceable “wear liners.” Aluminum shaft seal cover plate also for AMCA Spark C.

Type C fans and blowers also have assemblies where the possibility of moving and stationary parts coming into contact is negligible.

One caution about AMCA A&B – if used in a material handling application, an aluminum wheel exposed to any kind of dust will abrade very quickly. The lifespan of an aluminum wheel that might see any kind of dust can be measured in weeks or 6 months at the most.

Application of Spark-Resistant Fans and Blowers

Spark-resistant fans should be used in every industrial setting where combustible dust present in the airstream. However, the following facilities and areas must have spark-resistant fan/blower in their air movement and ventilation systems.

  • Chemical plants and storage facilities
  • Paint booths
  • Lab fume exhaust system
  • Woodworking facilities

Centaxia Industrial Air Solutions provides air movement solutions to a host of industries with its industrial fan and blower line. We also provide AMCA-standardized fans and blowers designed to reduce the risk of explosions caused by combustible dust and gases in the airstream.

At Centaxia, you can find top-quality equipment (axial, centrifugal fans, their expansion joints, and motors/drives) from trusted US and Canadian manufacturers at reasonable price points.