Stop the overfill before containment has to catch it

Buyer impact

What federal SPCC actually requires

For covered onshore facilities, 40 CFR 112.8(c)(8) requires the installation to be engineered or updated using good engineering practice to avoid discharges. The rule requires at least one acceptable safeguard and requires regular testing of liquid-level sensing devices.

Do not turn one percentage into a universal rule

The federal SPCC language above does not prescribe one universal alarm percentage or shutoff percentage. Project specifications, adopted fire code, insurers, manufacturer instructions, and other industry standards can be more specific. Use the requirement that actually governs the installation rather than copying a generic 90/95 rule into every project.

Where PEI RP600-24 fits

PEI's current RP600-24 is the recommended practice dedicated to overfill prevention for shop-fabricated, stationary, atmospheric aboveground tanks. PEI states that it covers the installation, operation, inspection, maintenance, and testing of overfill-prevention equipment used on tanks serving bulk storage, motor-fuel dispensing, emergency generators, heating-oil systems, used-oil storage, and similar petroleum or alternative-fuel applications.

That makes RP600 especially relevant to the kind of packaged AST systems used at fleet yards, job sites, facilities, and standby-power installations. It is a better starting point for those systems than assuming every tank falls under a terminal-scale overfill standard.

Build the fill process around failure prevention

• Know the usable fill limit. Tank nominal capacity is not a license to fill until product reaches the top fitting.
• Give the delivery driver a reliable level signal. Local gauge, alarm, automatic stop, or another approved method needs to work during the actual delivery.
• Test critical devices. An alarm that has never been function-tested is not much of a safeguard.
• Plan the fill connection and truck position. The driver needs safe access, hose routing, and a practical way to respond if the transfer must stop.
• Document the response. Operators should know what the alarm means, who stops the transfer, and what happens when equipment is out of service.
• Keep containment independent. Assume the prevention system can fail and preserve the secondary-containment layer.

Overfill prevention is not interstitial monitoring

Overfill equipment acts during the transfer, before too much fuel enters the tank. Interstitial monitoring checks the space between containment barriers after product has crossed the primary wall. Remote telemetry may report level off-site. An AST can have one of these functions without having the others.

Primary sources

• eCFR: 40 CFR 112.8(c)(8), bulk-storage overfill safeguards
• Petroleum Equipment Institute: RP600-24 Overfill Prevention for ASTs
• U.S. EPA: Tank inspections and SPCC integrity-testing context