News & Updates

ConVault Tank Maintenance: The Practical Guide for Long-Term Reliability and Compliance

At Core Engineered Solutions, we know that a ConVault Aboveground Storage Tank (AST) is an investment in peace of mind. Designed with a steel primary tank, a steel secondary containment layer, and six inches of reinforced concrete, ConVault is built for strength, containment, and code compliance. But even the toughest tanks require intentional maintenance to ensure longevity, warranty coverage, and safety.

Whether your tank supports a fleet fueling operation, backup power for a hospital, or aviation fuel at a municipal airfield, a strong maintenance program prevents costly issues before they arise.

This guide distills the essentials from the official maintenance manual, industry best practices, and our own field experience into one streamlined reference.

1. Visual Inspections: Weekly and Foundational

Weekly walk around inspections are the frontline defense against deterioration. Don’t overthink it — just walk the tank perimeter and look closely.

Key inspection points:
● Concrete Surface & Hairline Cracks: Examine the top surface and beveled edges. Minor hairline cracks are common from thermal expansion but can allow moisture intrusion if neglected. Early sealing prevents deeper structural damage and protects the interstitial space.
● Stains or Leaks: Look for wet spots, fuel smells, or dark streaks. Anything weeping from a crack or pooling underneath warrants attention.
● Labels & Placards: Ensure hazard decals and compartment labels (especially on multi-compartment tanks like diesel/gas split units) are visible and intact.
● Fittings, Nipples & Vents: Confirm that caps are tight, gaskets intact, and paint not chipped. Vent caps should be free from obstructions or debris.
● Foundation Area: Remove weeds, trash, or anything combustible. The tank pad must remain stable and accessible.

Pro tip: Schedule inspections the same day each week. Consistency helps you notice changes faster.

2. Leak Detection: Always Dry, Never Ignore

ConVault’s triple-layered containment offers best-in-class leak defense — but you’re responsible for monitoring it.

● Check the Leak Detector Tube: Open the cap weekly and confirm no fluid has accumulated. Any liquid — even clean water — means something’s wrong.
● Red Flag: Water in the interstice is usually from cracks at the top, not inner-tank failure. But both require action. Don’t just pump it out. Investigate and reseal.
● Electronic Monitoring: If equipped, test alarms regularly. Many fire marshals require documented leak sensor tests annually.

A dry interstice = a healthy tank. Moisture here can trigger alarms, void warranties, and signal real danger.

3. Corrosion Control: Focus on What’s Exposed

The concrete vault does the heavy lifting, shielding the steel tank from corrosion — but some components remain vulnerable.

● Seal and Reseal: Pressure wash and reseal the tank’s top every 2–3 years. In coastal or cold climates, consider 2-year intervals. Use elastomeric or rubberized coatings that flex with concrete movement.
● Hairline Crack Treatment: Clean, dry, and patch cracks early — especially near corners or fittings — to prevent long-term degradation.
● Fittings: Check for rust around nipples, gaskets, or penetrations. Wire-brush, prime, and repaint as needed with rust-inhibiting coatings.

4. Pump, Filter, and Hose Maintenance

Your fuel system is more than a tank. The surrounding equipment needs love too.

● Pump Health: Monitor motor heat, vibration, or noise. Replace filters every 6 months or sooner if flow slows.
● Hoses & Nozzles: Inspect for cracks, swelling, or leaking seals. Damaged hoses risk rupture. Shutoff nozzles must function correctly.
● Spill Buckets: After fuel deliveries, empty rainwater and drips from catch basins. Clean and reseal any cracked basins or gaskets.

Preventative maintenance here is about safety as much as uptime — don’t let a bad hose ruin a compliant system.

5. Vent and Overfill Systems: Safety Under Pressure

NFPA 30 and UL2085 require venting and overfill prevention — you need to keep them functional.

● Normal Vents: Inspect weekly to ensure pipes and screens aren’t clogged with debris or nests.
● Emergency Relief Vent: Lift and reseat annually. It should operate freely and reseal cleanly.
● Overfill Devices: Whether float-based or electronic, test annually and log the results.

Emergency vents must not be painted shut or tampered with. Let them function as intended — it could save lives.

6. Fuel Quality: Clean, Dry, and Additive-Ready

Water and microbes are the hidden killers of diesel fuel tanks.

● Water Monitoring: Use water-detecting paste on sticks or automated sensors monthly. If water is found, remove it with a thief pump.
● Microbial Growth: Water invites bacteria and algae, leading to sludge, filter clogs, and tank corrosion. Treat fuel with biocide additives if needed.
● Turnover & Stability: For tanks that see low usage (like generator backup), use stabilizers and rotate fuel when possible.

If your fuel fails, the tank suffers too. Good fuel = long life.

7. Documentation: Warranty Shield and Inspection Readiness

Documentation is part of the system — not an afterthought.

● Keep logs of all inspections, filter changes, tests, and repairs.
● Document who performed each task, what was found, and what was done.
● Store reports for 3–5 years or more, especially if required by your SPCC plan or local AHJ.

A documented maintenance history protects your warranty and shows regulators you’re in control.

Final Thoughts: Routine = Resilience

ConVault tanks are engineered for minimal upkeep — but not for neglect. A few minutes a week prevents leaks, protects your investment, and keeps you compliant with NFPA 30, UL2085, and local fire codes.

At Core Engineered Solutions, we support owners and facility managers with Sourcewell and GSA-compliant options, fuel system upgrades, and consultation for mission-critical operations.
Your tank was built to last 30 years. With proper care, it will.

News & Updates

Emergency Power Fuel Oil Systems and Tank Sizing

By Jeanne Murphy Murck, VP Operations
About the Author

In our industry, there have been many articles and studies published related to the changes to fuel composition and the resulting fuel maintenance headaches. By making cleaner fuels that are better for the environment, we have removed additives that killed destructive bugs (microbes). These reformulated fuels are more likely to take on water that boosts the growth of these bugs and accelerates corrosion.

The Challenge

In the case of fuel oil used in emergency power, microbe growth is further intensified by the lack of turnover and the EPA limits to burning fuel for the purposes of exercising generators. If we had storms twice a month and the fuel in these tanks was actually needed more regularly, then the fuel would be consumed more rapidly and the bugs wouldn’t have as much time to grow. But, alas (or shall I say thankfully), true weather-related emergency events necessitating the use of back-up generators are not that frequent. Undoubtedly, we could say that these events are on the uptick due to climate change, but the through-put of these systems never approaches the level of that of a gas station, for example.

Here’s what happens when fuel sits:

  • it gets stale
  • it takes on water from the atmosphere
  • it can become contaminated with microbes
  • it becomes more susceptible to the formation of asphaltene and wax residues
  • its cetane number may decrease

Solutions

Solutions to fuel quality issues that will arise in this setting typically include the following:

  • Periodically replacing fuel that has become stale due to lack of use. Most diesel in this country has some component of biodiesel in it and industry standards and engine manufacturers recommend storing any diesel that has biodiesel in it no more than six months.
  • Using a high quality fuel filtration system to remove water and particulate.
  • Cleaning the inside of the tank.
  • Using Biocide.

However, an important and often overlooked solution is the proper sizing of your fuel storage tanks to begin with! As stated in NFPA 110 (7.9.1.3), tanks should be sized so that the fuel is consumed within its storage life. The NFPA 110 Handbook also recommends several moderately sized tanks over one large tank.

Using several moderately sized tanks that meet the total fuel oil storage requirements of an emergency power fuel oil system can be very helpful on a couple of levels – first, you ensure fuel is consumed and turns over within its recommended storage life and second, you mitigate the risk of having your only fuel tank contaminated.

For example, let’s assume that an engineer has calculated the fuel oil capacity requirements for the back-up power system at a particular site to be 20,000 gallons. He then decides to specify that all the fuel (aside from that in the day or belly tanks) be stored in one 20,000 gallon main fuel oil storage tank. What happens if that one and only tank becomes contaminated by sitting unused and becoming affected as noted above, OR by the delivery of a bad batch of fuel from the terminal? Or, what if the pumping system tied to that one main storage tank fails? During an emergency event, the system would not be able to perform as needed.

A better strategy would be to specify two 10,000 gallon tanks including redundant fuel oil pumping systems for each tank to ensure fuel will be delivered when needed and that your risk of having an entire fuel system of contaminated fuel is greatly mitigated. In conclusion, specifying one large tank puts the entire back-up power system’s proper functioning during an emergency event in peril.

Core Engineered Solutions can help you size the fuel storage tanks with these issues in mind, as well as the redundancy requirements found in NFPA 110, NFPA 99, and NFPA 70.

For more information email [email protected] or call (703) 563-0320.