1. It Is Mainly an Atmospheric Storage Tank
- Normally designed as an atmospheric tank, not a pressure vessel.
- Stores waste oil, used lubricants, solvents, antifreeze, and similar liquids at near atmospheric pressure.
- Under UL 142, atmospheric steel aboveground tanks are typically designed for a small pressure range between −0.5 psig and 1 psig.
- This range mainly covers venting and thermal breathing.
2. Low Pressure Versions Exist but Are Not Typical
- Some tanks may be designed for low pressure operation, but this is not the common configuration for waste oil storage.
- Low pressure tanks usually operate above 1 psig and below 6 psig.
- They require stronger shells, tighter vent control, and more careful pump and piping design.
- If higher pressure capability is needed, specify a low pressure or special purpose design.
3. Pressure Testing Is Not the Same as Operating Pressure
- Factory leak tests and hydrostatic tests may use higher pressures than normal operation.
- These values do not mean the tank should be used under continuous pressure.
- UL 142 production testing has historically used pressures around 1 to 5 psi for certain tank types.
- Fire‑protected or special double‑wall tanks may be tested at higher values.
- Operating pressure must always follow the manufacturer nameplate and local code.
4. Venting & Pump Control Determine Real Safety
- Biggest pressure risk: overfilling, blocked vents, or pumps discharging directly into the tank.
- Normal vents, emergency vents, level alarms, and interstitial leak detection must remain functional.
- Before purchase, confirm design pressure, test pressure, vent sizing, and applicable standard with the supplier.