By Evan Williams, Cambridge Companies

January 31, 2019


Upgrading your facility? For example, some central considerations include safety, code compliance, and cost-effectiveness.

When you Convert your fleet to compressed natural gas, it can help reduce fuel costs. Typically, considerations include the cost of the new vehicles and fueling infrastructure. An overlooked yet essential component is the cost to modify the existing shop facility and ensure the new vehicles are serviced in a safe and code-compliant environment.

Existing Shop Improvements

Ask yourself what requires the maintenance shop to be CNG compliant. Naturally, engage a qualified engineer or consultant to perform the detailed analysis. Thus, include the following in the analysis:

  1. Ventilation: Upgrade the existing ventilation system to afford more air changes per hour. Shops are usually heated with a gas-fired unit or radiant tube heaters. However, these are typically not compatible with a CNG shop.
  2. Shop Height: The height of the shop directly impacts the ventilation requirements. If the shop is shorter than 20′-0″, it may not be viable for a CNG retrofit.
  3. Gas Detection: The local Authority Having Jurisdiction (AHJ) sometimes requires a gas detection system.
  4. Fire Separation: The walls that separate the shop from the administration offices are required to be two-hour rated for a CNG Shop.
  5. Electric: Look up at the ceiling and down at the floor. Is there any wiring or conduit in the areas within 18″ of the roof or the floor?  Upgrade to Class 1, Division 2 rated.

This is not an exhaustive list of all the changes, however it shows how the CNG retrofit work impacts areas of the shop.

Existing Shop Classification

Start the shop conversion analysis with a review of the existing shop and of performed activities.

Determine if the facility will be classified as a Minor Repair Shop or Major Repair Shop. Those terms are designations in the code that determine the standards the shop needs to meet, depending on the work performed:

Minor Repair Shop: Includes service activities that do not impact the fuel system or generate heat over 750° F. It includes brake repairs, tire work, and PM activities.

Major Repair Shop: Includes areas where there will be welding, vehicle bodywork, or engine overhauls. Work to the fuel system may also be performed.

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