It’s a gas
Published: 24 June, 2011
There are many benefits to installing a gaseous extinguishing system on a floating roof storage tank, yet it still feels like the industry's best-kept secret. Jose Sanchez de Muniain reports from StocExpo in Rotterdam.
Saval’s CFI rim seal solution has been protecting floating roof storage tanks throughout the world for over 50 years. The gaseous solution does not contaminate the stored product, is non toxic in the concentrations used on the floating roof, has the shortest atmospheric life of all chemical extinguishing systems – and works faster than Halon 1211. So why isn’t everybody using it? I caught up with Saval’s Rini van den Brand at this year’s StocExpo in Rotterdam, to find out more.
The idea for the gaseous rim seal protection system came when the risk of rim seal fires were discovered by Shell, upon the company’s introduction of floating roof tanks. Saval’s solution was an instant success due to its simplicity; a circular pipe with glass bulb-activated sprayers along the rim seal connects to a vessel that contains the fire suppression product. When the heat from a fire breaks the glass bulb, the superpressurised liquefied extinguishing agent is activated, instantly extinguishing the fire.
Today’s extinguishing agent is Trifluoroiodomethane – CF3I for short – a gas designed specifically as a fire extinguishing agent to replace Halon 1211 and (as it turned out) a solution with better extinguishing capabilities than Halon (even if slightly more expensive to produce).
When it comes to rim seal fire extinguishing agents, there are only two options – gas or foam, and in Rini’s opinion there is little competition between the two. Unfortunately, the fire industry is still in love with foam. ‘While the use of gaseous extinguishing systems is not new, it is very different to the tried and trusted technology used by firefighters, so they have to be fully convinced – seeing is believing and they have been brought up on foam.’
Looking at the cold hard facts makes interesting reading, however: CF3I will not degrade in its storage vessel as long as it does not come into contact with Oxygen or ultraviolet/infrared light; as well as putting out the fire in 2-5 seconds, it also cools the area of the fire so much that ice crystals form on the rim seal; CF3I makes no distinction when it comes to what type of fuel is being burnt – it will extinguish all fires, whether ethanol, crude, naphtha, diesel etc; CFI Rim is virtually maintenance-free, with no moving parts; it is VdS approved; and it is a fully automatic detection and extinguishing system.
So are there no disadvantages? What about the risk of secondary re-ignition fire? Rini points out that under normal circumstances a rim seal fire will be extinguished in 2-5 seconds, depending on the damage to the seal and how much vapour is released. ‘So let’s say detection takes two seconds, and extinguishment two or three seconds – within five to 10 seconds everything is gone. But CF3I will carry on being released for another 30-40 seconds – complete overkill both in extinguishment and cooling.’
Floating roof storage tank fires
Getting a handle on how many floating roof storage tank fires occur is not an easy task. The rule of thumb, says Rini, is that there are one or two storage tank fires somewhere in the world each month. But the last 24 months have been particularly disastrous, with multiple tank losses in events such as Puerto Rico (Caribbean Petroleum Corporation), Jaipur (Indian Oil), and Central Java (Pertamina). ‘Some areas of the world are more vulnerable than others, if for example there is a higher incidence of lightning strike.’ While the causes of some fires can be readily discovered eg hot work, electrical storms overfilling, others are not so obvious. ‘There is a mysterious one where a tank is loaded with diesel, and the next load is naptha. If the tank is not properly cleaned there is some kind of electrical discharge between the residues. It is a strange one but it does happen.’
How often Saval’s automatic solution does its job is hard to gauge, admits Rini, and more often than not his customers purchase refills saying that an operative has broken a glass bulb and thus released the agent accidentally (fires are not good for a company’s image). However, with over 50 years in the business, and between 4,000 - 4,500 floating roof storage tanks protected worldwide, not to mention VdS certification, Rini is quietly confident the CFI Rim is doing its job.