Duplex Configuration of Pumps Inside a Wet Well

Hazardous Spaces and the Class/Division System

Duplex Configuration of Pumps Inside a Wet Well

Romtec Utilities engineers, manufactures, and supplies packaged pump stations for many applications. Nearly all our pumping systems include wet wells and valve vaults that are considered confined spaces. All vault structures are confined spaces, but some pumping applications – like sewer – are also exposed to potentially flammable gases and vapors. These are classified as hazardous spaces and given a Class/Division/Group rating. These ratings further define the hazardous space and are used with guidelines set in place by the National Fire Protection Association (NFPA) and the National Electric Code (NEC) to determine what equipment is used and where it can be placed within the space.

Insulated Pump Cables Will Be Exposed to Flammable Gases or Vapors

The Class/Division system is used to identify the nature of a hazardous element and if a combustible concentration of this element is present. The wet well for a wastewater lift station, for example, can be exposed to hydrogen sulfide gas (H2S), an extremely flammable gas produced from storing raw sewage. Using the Class/Division system, the hazardous space of the wet well is classified as a Class 1 Division 1 space. This rating can never be completely removed, but some equipment can be installed to prevent ignitable conditions from being occurring within the space. When preventive measures are in place, the division rating of the space can change from Division 1 (ignitable) to Division 2 (not ignitable).

Preventive equipment is typically installed as some form of ventilation, but other methods can be used like chemical injection systems and other forms of odor control. The division rating within the space is used by the NFPA and NEC standards to determine where explosion-proof components must be used. Additionally, the area immediately outside the hazardous space is also given a division rating unless the hazardous space is airtight. Since flammable gas will pass through the top of a vault structure, any electrical panels must be intrinsically safe and incapable of producing sparks or other ignition sources if they are installed in the exterior classified space. The last classification given to these spaces is the Group rating. This value will rarely change in most water applications.

Open Top Hatch of Blowdown Lift Station at HRSG Plant

Group ratings in the Class/Division space are used to identify the type of hazardous elements present. This will typically only differ in pump stations within industrial settings, as they are used in many processes within power generation plants, chemical manufacturing, and even transporting flammable liquids. The group identifies the type of gas or vapor present in normal operating conditions within the space. They are defined as Group A – D (these are the only classifications that apply to pump stations). Using the Class/Division system and standards in place by the NFPA and NEC the pump station is much safer for owners & operators of the system and is always a requirement.

Romtec Utilities designs pump stations with hazardous and confined spaces every day. We can include any ventilation or odor control systems needed to prevent combustible concentrations of material from forming inside a hazardous space. All of our components and electrical wiring within these spaces meet or exceed all NFPA and NEC standards. Choosing an experienced partner with experience in the design and supply of pump stations is the best way to get a site-specific pumping solution in a single purchase. Contact our Sales Team for more information on hazardous spaces within your system!

Comments 4

  1. Hi I am an inspector with the San Diego City School District.

    I am in need of some technical information with Storm Water Wet well hazardous location classification i.e. Class 1 Div 2 per NFPA 820.

    Specifically when used in conjunction with a inline Modular Wetlands System (MWS).

    Can you provide me with some tech support on this?

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  2. We are looking for a Class A Division 1 ceiling hatch according to the engineering specs given. It will be installed to have access to electrical equipment on top of this vault where flammable products are stored.
    The dimensions required are 36″ X 36″ and should be downward opening.
    This is a Medical Plant recently established in Costa Rica.
    If you have the possibility to supply this product or give us a supplier of this item, it will be very much appreciated. Thanks in advance

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