Why Storage Tanks Deserve More Attention Than They Get

Storage tanks aren’t particularly interesting - or at least that’s what I thought at the start of my career.

One of my very first assignments as a graduate chemical engineer on an ICI site in the 1980s was to review every vent, overflow and relief system calculation on the site’s storage tanks. There were around 30 of them, some more than 40 years old, with minimal records and incomplete design data. It took months of digging through drawings, walking the site, and piecing together information.

At the time, I assumed I’d been given the job because nobody else wanted it. Perhaps that was true. But as my career progressed and as I became involved in investigating incidents, I realised that this “uninteresting” task was one of the most important learning experiences I could have had. Done properly, it would have prevented several of the incidents I later investigated.

What I didn’t appreciate back then was just how easy it is to lose containment from a storage tank, and how quickly things can escalate when large inventories are involved.

What I Didn’t Realise at the Start of My Career

1. Process & Mechanical Realities

• Tanks can be sucked in surprisingly easily, especially during commissioning or abnormal operations.

• Over‑pressurisation can happen faster than you expect.

• Vents and overflows must always be separate systems; combining them creates hidden failure paths.

• Overflow sizing must ensure self‑venting flow; if not, siphoning can occur and collapse the tank.

• Tank level changes with density, and ignoring this can lead to significant misjudgements.

• The tank bottom and its foundation are just as important as the tank itself.

  
  

2. Operational Realities

• Lute pots on flammable or toxic tank overflows must be checked regularly and protected from freezing or blockage.

• Bunding and spacing matter far more than most people think.

• Tanks can float when bunds fill with rainwater.

• Operators often crack bund drains open to stop them filling; a small action with big consequences.

• “Temporary” workarounds often become permanent without anyone noticing.

  
  

3. Organisational & Cultural Realities

• Storage tanks hold the largest inventories on site; when something goes wrong, escalation is rapid and unforgiving.

• Sites that were once part of refinery operations often lose scrutiny when the refinery closes, even though the risks remain.

• More than one site told me they didn’t need high‑level trips because they had “reliable operators”; then they demanned.

• Human reliability is not a substitute for engineered safeguards.

Why This Still Matters

I continue to learn, because new ways of losing containment keep emerging. Storage tanks may look simple, but they are often the most underestimated risk on a site. They sit quietly in the background, holding large inventories, waiting for someone to assume they are low‑hazard because they are “just storage”.

In reality, they demand the same level of rigour, scrutiny and respect as any other part of a high‑hazard operation.

What Lessons Have You Learned?

I’ve shared some of the insights that shaped my understanding of tank risks; many learned the hard way through incident investigation. I’d be interested to hear what others have seen, especially the patterns that only become obvious after an investigation.