While the NEC permits the use of a Cl 1 Division 1 approved thermal mass flow meter in Class 1 Div 2 location, the flowmeter’s installation expense is significantly higher and often overlooked when selecting the appropriate device for the location.

Class 1 Div 2 and 1 Refresher

Class 1 Div 2 has edge over Cl 1 Division 1
When selecting a thermal mass flow meter for a Class 1 Division 2 Hazardous Area, using a flowmeter with Class 1 Division 1 approvals increases installation costs, giving Sage Prime an edge.

The Sage Prime® is rated for use in Class 1 Division 2 areas.  For a quick refresher on hazardous areas,

Class 1  means the presence of hazardous (hydrocarbon) vapors or gases.

Division 1 means that hazardous vapors are frequently present.

Division 2 means that the hazardous condition infrequently occurs (such as in an emergency).

Many industrial facilities have classified their plant areas as Div. 2, which has been done primarily for two reasons:

  1. Environmental—A Division 1 area frequently has hydrocarbon vapors present, which is not desirable given the EPA requirements for fugitive emissions, greenhouse gases, and potential fines.
  2. Expense – The installation cost is less expensive in a Div. 2 area because flexible conduit can be used, and conduit seals are not required.

Determine the Classification of Your Thermal Flow Mass Meter

A Division 1 area requires the use of an explosion-proof enclosure to contain any explosion. In contrast, a Division 2 device requires a circuit that will not ignite the vapor/air mixture under normal operating conditions. Some of the leading thermal mass flow meter manufacturers are only categorized as Class 1 Division 1, unlike the Sage Prime®, which has a Division 2 rating.

Division 1 Device Increases Installation Costs

According to the National Electric Code Section 500.8(B) (2), explosion-proof instruments rated for Class 1 Division 1 can be used in Division 2 areas; however, the device must be installed following Division 1 requirements. This means that the conduit seals and rigid conduit will need to be installed up to the seal. Doing so can significantly increase the installation cost, and, likely, many customers do not consider this until installation time.

When selecting a thermal flow meter for installation in a Div 2 location, remember that using a meter approved for Cl 1 Div 2 will save on your installation costs.

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