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A PL A I N - L A N G U AG E B O O K O N PET RO L STAT I O N S A FETY DANGER BENEATH THEPUMP How ageing underground fuel tanks put petrol stations and their neighbours at risk, and a simple three-step health check that can catch a leak before it becomes a fire. Mohd Shamsuri Khalid, PhD Based on doctoral research at the Malaysia-Japan International Institute of Technology, Universiti Teknologi MalaysiaB EF O R E YO U B E G I N A NOTE TOTHE READER Every day, millions of Malaysians stop at a petrol station, fill up and drive away. Almost nobody thinks about what sits a metre or two under their tyres: steel tanks holding tens of thousands of litres of fuel. This book is about those tanks. Many of them have been underground for more than 15 years. Nobody has looked inside most of them since the day they were buried. Steel rusts, and rust eats away at a tank wall slowly and out of sight. When the wall gets too thin, fuel can escape. Petrol that escapes can catch fire. The book is drawn from a PhD study that measured one of these old tanks at a real petrol station in Banting, Selangor, and then worked out what would happen to the people nearby if it leaked and caught fire. The findings are serious. The good news is that the study also shows a practical, affordable way to check a tank before anything goes wrong. You do not need an engineering background to read this. Technical words are explained when they first appear, and there is a glossary at the end. 4,124 petrol stations in Malaysia in 2016 1,050 single-wall steel tanks already more than 15 years old 6.15mm thinnest wall measured in the case-study tank, below the 6.42 mm safe minimum 10m radius where a fire from that tank could kill about 9 in 10 people exposed for one minute 20–40m distance from the station to the nearest homes RM5–6k cost of the three-step health check, done in about two weeks What is inside01 A Nation on Wheels Why there are so many petrol stations, and so many old tanks 02 What Lies Beneath How a petrol station is laid out and how its tanks are built 03 The Slow Enemy How rust weakens a buried tank 04 When Things Go Wrong Fires and explosions at fuel tanks and petrol stations 05 The Gaps Nobody Watches Laws, habits and blind spots that leave old tanks unchecked 06 A Three-Step Health Check The method this book is about, explained simply 07 Inside an Old Tank The case study at a petrol station in Banting 08 How Risky Is It? Turning measurements into a risk rating 09 If It Leaks and Burns How far the danger would reach 10 The Cost of Checking Why prevention is the cheapest option 11 What We Can All Do Lessons for operators, companies, authorities, workers and neighbours — Glossary and About the Author Key terms in plain words 0101 C H A PTE R O N E A NATIONON WHEELS Malaysia runs on cars, and cars run on fuel. That simple fact explains why petrol stations now sit at the edge of so many neighbourhoods. In 2010 there were about 20.2 million vehicles registered in Malaysia. By 2016 there were about 27.6 million. Every one of them needs somewhere to refuel. The oil and gas sector has long been one of the pillars of the economy, and fuel retail alone brought in about RM4.8 billion in 2008. To keep up with demand, oil companies built more stations, many of them inside or right next to housing areas. By 2016 the Department of Occupational Safety and Health (DOSH) counted 4,124 petrol stations in the country. PET RO L STAT I O N S B Y B R A N D, M A L AYSI A ( D O S H , 2 0 1 6 ) BRAND 2007 2014 2016 Petronas 865 978 1,070 Shell 904 920 956 Petron (formerly Esso, Mobil) 490 510 580 Caltex 397 410 437 BHPetrol 284 303 337 Others (Buroq, Petro Teguh, Smart Stream, Haz Capital and others) – – 744 Each station keeps its fuel in tanks buried under the forecourt. A typical modern station has four tanks of about 23,000 litres each, around 92,000 litres in all. Older stations often had just two: one for petrol, one for diesel. Here is the part that worries safety experts. DOSH surveyed the tanks across the country. Of the 2,100 single-wall tanks holding RON95 petrol, about half, roughly 1,050 tanks, had been in service for more than 15 years. Nobody could say for certain whether they were still sound.y The part everyone sees. Pumps, canopy and shop. The fuel itself is stored out of sight, in steel tanks beneath the ground. I N S H O RT More cars meant more petrol stations, often close to homes. Many of the tanks under those stations are now old, and their condition is largely unknown. 02 C H A PTE R T WO WHAT LIES BENEATH A petrol station looks simple from the road. Underneath, it is a small fuel depot. Every station has three main parts:Every station has three main parts: The dispensing area. The pumps, or dispensers, under a steel or concrete canopy. The tank area. Usually an empty or fenced patch of ground. The only clues are manhole covers and tall vent pipes. Below are the underground storage tanks, often shortened to USTs. The service building. The shop, office and sometimes a café or restaurant. Of the three, the tanks carry the greatest risk of fire and explosion, because that is where most of the fuel is. Three kinds of tank Malaysian stations use three types of underground tank: 1. Single-wall steel tanks. One layer of bare carbon steel. Cheapest, and the most common type among older stations. This book focuses on these. 2. Double-wall tanks. A steel tank with an outer skin of fibreglass (FRP, fibrereinforced plastic). The second layer gives extra protection. 3. Fully fibreglass tanks. Made entirely of plastic composite, so they cannot rust. New steel tanks waiting to be installed. A coated tank being handled at the factory. How a tank is made and buried A steel tank is built from flat steel plates The plates are rolled into a cylinder andA steel tank is built from flat steel plates. The plates are rolled into a cylinder and welded to two curved end caps, called dish ends. The steel used is a pressure-vessel grade such as SA 516, chosen to cope with fuel, temperature and pressure. A new tank wall is about 12.7 mm thick, roughly the thickness of a stack of seven coins. Before it leaves the factory, every tank should be filled with water under pressure to prove it does not leak. This is the hydrostatic test. The manufacturer also keeps a file of records: material certificates, inspection and test plans, design drawings and test results. This file is called the Manufacturing Data Report. Later in this book you will see why those papers matter. At the station, a pit is dug, the tank is lowered in by crane, connected to pipes and vents, and buried. Going underground. A tank is craned into its pit. Once the soil and concrete go back on top, nobody sees it again.Tanks in the pit just before they are covered. The round fittings on top become the manholes you see on the forecourt. T H E C O R E P RO B LE M Once a tank is buried, it is almost never inspected again. The study found no regular inspection, visual check or maintenance of the tank body at the stations it looked at. Most operators only notice a problem after a large amount of fuel has already gone missing. 03 C H A PTE R T H R EE THE SLOW ENEMY Steel tanks rarely fail suddenly. They are eaten away, little by little, by corrosion. Corrosion is the everyday word "rust" in its scientific form. It is a chemical reaction between metal and its surroundings. On a buried fuel tank, it attacks from two sides at once. From the outside. Groundwater and wet soil touch the steel. Rainwater drains, poor drainage and sinking foundations let water collect around the tank andpoor drainage and sinking foundations let water collect around the tank and speed things up. From the inside. Fuel carries small amounts of water, sludge and corrosive impurities such as sulphur compounds. These settle at the bottom of the tank, right on the steel. Inside corrosion is very hard to detect once a tank is buried. What years underground can do. An old steel tank after removal, its surface covered in rust. The kinds of corrosion TYPE WHAT HAPPENS, IN PLAIN WORDS General corrosion The whole surface thins out evenly over time, like soap wearing down. Pitting Small, deep holes form in one spot while the rest of the wall looks fine. Crevice corrosion Rust grows in corners and gaps where liquid sits still. Galvanic corrosion Two different metals touching in a wet place make one of them rust faster. Stress corrosion Constant load plus a corrosive liquid opens cracks that keep growing.The pattern usually goes like this. Corrosion starts as a small pit. Over 15 years or more, the pit deepens. It can turn into a crack and then a hole. At that point fuel can seep into the soil, and vapour can reach the surface. The bathtub curve Engineers describe the life of equipment with a shape called the bathtub curve. Failures are common at the start, when there are hidden manufacturing faults. They are rare in the long middle stretch of normal life. Then they rise again as the equipment wears out. A tank that has passed 15 years is moving onto the rising right-hand edge. Early faults Normal working life Wear-out tanks past 15 years Age of the tank → C h a n c e of failure → The bathtub curve. Failure is more likely at the very start and again near the end of a tank's life. Redrawn from the study, after Tan Cheng (2006). Data from DOSH show how far along that curve Malaysia's stations are. Of the stations investigated, 91% were built more than 15 years earlier, and 27% were more than 30 years old. All the tanks in that sample were steel. Corrosion is not just a theory. A record of 285 leaks from underground tank systems in New York State (2013–2014) found that the tank itself was the source in about one leak in four, and corrosion of the tank was named as a cause in about 8% of all cases. In nearly half of all cases, the cause was never found.