Using Variable Frequency Drives in Class 1 Division 2 Enclosures

Class 1 Division 2

In the demanding manufacturing and production environments of today, using a VFD (Variable Frequency Drive) to adjust the motor speed and the speed of other process equipment can help in cutting down on energy consumption, giving tighter control over processes, and extending the life of equipment. Though using VFDs has so many benefits, industries had been using the fundamental on/off motor controllers till recently in specific areas (Class I Division 2 enclosures) of their facilities. Let’s get into the roots of this topic.

Evaluating Class I Division 2 Enclosure

Class I locations refer to those locations where flammable vapors and gases may be present in the air in adequate quantities to generate ignitable or explosive mixtures. This class is further divided into two divisions. In the context of this topic, let’s understand what Division 2 refers to. 

An area can be evaluated as Class 1 Div 2 enclosure in one of the below situations: 

  • Volatile flammable gases or liquids are used, handled or processed, but the dangerous vapors, gases or liquids are usually confined inside closed systems or containers from which they can escape only if there’s a breakdown or rupture of the system or due to abnormal container operation. 
  • Ignitable gas or vapor concentration is usually stopped by positive mechanical ventilation. This might turn out to be hazardous through the ventilating equipment’s abnormal operation or failure. 
  • Beside a Class I, Division 1 location, to which ignitable vapor or gas concentration might sometimes be communicated until such communication is stopped by sufficient positive pressure ventilation from a clean air source. 

Using VFDs in Class 1 Division 2 Enclosures

Many engineers have tried placing VFDs in a Class 1 Div 2 enclosure, but the heat generated within the enclosure had resulted in the failure of these VFDs. The solution was to develop explosion-proof enclosures with heavy-duty blowers to ensure constant airflow inside. This allows the VFD placed inside to function without any issues even at temperatures of up to 50-degree Celsius. The blower can be coupled with advanced pre-filter and filter screens to ensure this airflow without posing any risk to the enclosure’s explosion-proof integrity. 

In the recent past, flame-proof enclosures are available, which can be integrated with VFDs. They come with special fan and filter assemblies, explosion-proof keypads, and operators for common functions like, speed control, start, stop, fault status indicators and run. These panels are generally used on portable skids for specific areas where the control panel can be installed far away from location of system operation.

Benefits of Placing VFDs in Class 1 Division 2 Enclosures

Mounting a variable frequency drive next to motors in Class I, Division 2 enclosures has many benefits:

  • A consideration reduction in installation, construction and maintenance costs
  • Elimination of engineering and logistical issues
  • Enhanced uptime
  • Reduced energy consumption

In a nutshell, it’s now simpler to use VFDs in an explosion-proof Class 1 Div 2 enclosure in industries like oil & gas, petrochemical, food & beverage manufacturing, waste water or water, pharmaceutical, and OEM skid builders.