1. Primary Inner Tank
- Holds used diesel, contaminated fuel, oily water, and sludge.
- Usually made from carbon steel or stainless steel.
- Designed as an atmospheric storage vessel.
- Shell, heads, bottom plate, and welds must resist internal corrosion and sediment accumulation.
2. Secondary Outer Containment
- Provides secondary containment if the inner tank leaks.
- In double‑wall designs, the outer shell captures released liquid and prevents it from reaching soil or drainage.
- Many factory‑built waste diesel tanks are manufactured to UL 142.
- Outer tank forms an integral bund, removing the need for a separate concrete dike.
3. Interstitial Space & Leak Detection
- Interstitial space between inner and outer walls for leak monitoring.
- May be fitted with inspection ports, monitoring tubes, vacuum gauges, or liquid sensors.
- When inner wall fails, the detection system gives early warning.
- Allows operators to intervene before a large spill occurs.
4. Vents, Fittings & Support Structure
- Equipped with normal vents, emergency vents, fill ports, drain valves, level gauges, suction connections, and grounding points.
- Support feet, skids, or lifting lugs keep the tank stable and allow safe handling.
- For fire‑protected models, lightweight fireproofing materials may be placed in the interstitial space.
- Improves fire resistance and overall safety.