Secondary oil containment around transformers is critical for capturing oil spills and protecting the environment. SPCC regulations provide guidance for containing oil-filled equipment. The rule specifies sizing oil containment systems to contain the contents of the largest vessel – or in this case, the transformer inside the containment area. Add 10 percent to the volume of oil to accommodate precipitation or snow.
How does this work practically for calculating secondary containment for transformers?
Calculating Transformer Oil Containment
Though calculating the required oil containment capacity for your substation is important, the total volume of oil is just one of many factors that influence the design of your secondary containment system. Additional considerations include:
- Number of vessels on site
- Total amount oil on site
- Site topography
- Physical encumbrances on the site
- Buildings, pilings, piers, cable runs
- Fences, roads, gates
- Depth of the grounding grids
- Size and depth of pads
- Available footprint
Meet SPCC Regulations for Oil Containment in 6 Simple Steps
We make it easy for engineers to figure out what size transformer oil containment is necessary to meet SPCC regulations. Calculate the secondary containment volume requirement for your transformer area by following these six steps:
1 cubic foot = 7.50 gallons of capacity
1 cubic foot of stone = 3 gallons of capacity at 40 percent void
- Find out the volume of oil for the largest transformer vessel in the area that needs containment. Add 10 percent freeboard to account for rain and snow.
- Determine the depth of the secondary containment area based on existing stone depth and the site layout. Calculate the capacity of oil for one square foot surface area. Note that different stone sizes have different void space for capacity calculations.
- Divide the 110 percent volume required by the capacity per square foot of stone. This reveals the square foot area of oil containment required.
- Calculate the square foot area of the transformer pad, plus any other piers in the containment area.
- Add the square foot of containment required (Step 3) to the square foot of the pads (Step 4) to find the total square foot area.
- Determine the length and width of sidewalls based on this square foot area and the physical constraints and barriers of the site (such as fencing, etc.)
Calculating Transformer Oil Containment: A Case Study
To comply with SPCC regulations, an electric utility wants to install secondary containment around its 600-gallon transformer. It sits on an 8-ft. by 10-ft concrete pad. A fence line lies 30 feet from the side of the transformer. Let’s follow the six steps above to calculate its secondary containment volume requirement:
- Oil containment volume needed = 600 gallons x 1.1 = 660 gallons.
- Existing stone depth is 12 inches. The stone has 40 percent void space, yielding a stone capacity of 3 gallons per square foot.
- Area of containment required = 660 / 3 = 220 square feet
- Area of transformer pad = 8 x 10 = 80 square feet
- Total area = 220 + 80 = 300 square feet
- To fit within the fence line in a symmetrical containment area, choose a width of 13 feet (6.5 feet in each direction). A length of 24 feet would provide a total area of 312 square feet to meet our oil containment needs.
Types of Transformer Oil Containment Systems
C.I.Agent Solutions supplies site-specific oil containment systems. For sites with clay or impervious subsoils, use our tried-and-true C.I.Agent Oil Filtration Walls. The system allows rainwater to flow out of the containment area during normal rain or snow events, but, in the case of an oil spill, will become an impervious barrier to hydrocarbons.
Also available is the Geomembrane Liner System with Oil Filtration Panels. This solution can be installed in all type subsoils. It is best suited for containment around the transformer, instead of the perimeter of the substation.
Additional Secondary Containment Resources
To help meet SPCC regulations for oil containment, the EPA provides some generic tools for calculating secondary containment volume requirements. If sizing a transformer oil containment system with C.I.Agent Oil Filtration Walls or Geomembrane Liner System with Oil Filtration Panels, check out this handy spreadsheet – it’s pre-programmed with the correct formula needed to calculate volume using our solutions. (Bonus: Does your oil containment area require a smaller footprint due to depth or space constraints? You can use ADS perforated pipes to create additional void space.)
Contact Us Today for More Info About Transformer Oil Containment
More than 10,000 substations worldwide use C.I.Agent Solutions oil containment systems. Contact us for your secondary containment needs.