FIRE SUPPRESSION
Petroleum Storage Tank Facilities – Part 3
by Brenna ShumbamhiniJune 9, 2022
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In previous installments of this series we talked concerning the forms of petroleum storage tanks, their places, common fire hazards, described the forms of fires, and fire suppression systems that storage tanks could have.
In this third and last article we are going to talk about firefighting strategies and techniques in addition to pre-incident response planning basics.
Firefighting Strategies and Tactics
Firefighting strategies and ways begins with a well deliberate and examined pre-incident response plan. This might be mentioned later within the article. Storage tank fires are complex occasions. These fires will require the implementation of plans, preparation, correct utilization of assets, and an extensive logistics section to make sure the sources can be found and arrive on scene in a coordinated and timely fashion. The following methods and ways for firefighting presume that the planning and preparation stages have been carried out by plant and fireplace division personnel. Experience tells us that profitable and secure extinguishment of tank fires can only be achieved when based on planning and preparation, with all related collaborating in all elements of the process in addition to the exercising of the plan. Exercising the plan can be carried out with table prime situations in addition to periodic full scale workouts.
As soon as a fireplace department receives notification of an incident, size up and intelligence gathering should be began. Information must be gathered quickly to start the event of firefighting methods. The following should be thought of:
Rescue of personnel within the quick space
Life security hazards to site personnel
Extension
Confinement
Extinguishment
Environmental impression
Community influence
After the instant issues are addressed, we have to establish the type of fireplace present:
Vent hearth
Seal fire
Piping-connection fire
Full surface involvement fire
Once we have examined the above data we can then start to develop our useful resource list and incident motion plan (IAP). Remember that the sort of product concerned may even impact our resource wants and tactics. The following are numerous types of fires and firefighting tactics:
Ground Spill or Dike Fires
These fires can be considered as simple pool or spill fires. Calculate the area (length x width) and use the correct software rate based mostly on NFPA eleven, Standard for Low-, Medium-, and High-Expansion Foam. Knowing the product will also give you the right kind of foam concentrate and utility methodology. Alcohol products would require a gentle software technique. Firefighters should not enter the dike space except safe to do so and permitted by the Incident Commander in session with the incident’s Safety Officer. Atmospheric testing ought to be performed previous to and through entry. Exposures corresponding to tanks, related piping, and pumps must be protected with water via floor or mounted displays. Ground fires ought to be extinguished first, then utilizing dry-chemical equipment, valves and flanges extinguished. The best equipment for these combined fires can be hydro-chem™ technology whereby foam/water resolution as properly as dry-chemical could be delivered concurrently via the same nozzle.
Specialized transportable monitor placed on lip of storage tank.
Rim Seal Fires
Rim seal fires can often be extinguished utilizing the fixed or semi-fixed foam systems if put in and correctly maintained. On external floating roof tanks, if the mounted or semi-fixed hearth protection systems aren’t present, handbook firefighting will must be carried out. Under the safety of a water spray, a firefighting crew will ascend to the gauging platform with hand-held foam gear. The main method ought to be the usage of foam wands to capture the hearth (Photo 1- Foam Wand) which allows the position of specialised monitors to be placed on the lip of the tank. (Photo 2- Specialized moveable monitor) The displays can then be used to extinguish the rim seal fire utilizing the attain of the monitor in order that hoselines and personnel usually are not working from the wind girder away from the ladder. If this equipment just isn’t available, then foam hoselines could probably be used from the wind girder. This is a hazardous operation, and only undertaken if there’s a structurally safe wind girder with handrails. (Photo 3- Foam chamber and Wind Girder) Personnel must be secured to forestall falling.
In some cases, elevated streams from fireplace automobiles have been used. This is not a primary technique of extinguishment. It has been noted that there’s at all times an opportunity of sinking or tilting the roof underneath the surplus water/foam solution, thus creating a larger downside, which can embody an obstructed /unobstructed full floor fireplace.
On tanks fitted with inner floating roofs, these fires may be thought-about uncommon, but they do occur. They shall be extremely troublesome to extinguish except mounted or semi-fixed fireplace protection methods are put in. Foam chambers and foam dams are the simplest, and the design of the system should be calculated on a full surface fire, particularly if the pan under is aluminum.
The most troublesome method of extinguishment in a covered floating roof tank shall be to shoot foam water answer by way of the eyebrow vents. Using hydro-chem™ into these vents has confirmed effective up to now.
diaphragm seal
Staffing requirements for a major tank hearth will range relying on the type of tank, location, water provides, nature of the incident and the provision of skilled personnel. Attacks on these fires will predominantly use the Type III “Over the Top” technique of extinguishing agent delivery. The product concerned will decide the required foam software price and percentage of concentrate to water flowed. The dimension of the tank may also decide the application fee. For larger tank diameters a bigger application rate is required. The chart beneath is accepted by business experts to be the minimal software rates based on the tank diameter:
Table 1– Application charges
Foam resolution (foam focus + water) circulate charges to be established are based mostly on the following method:
Foam answer move price = Tank surface space x software fee (as noted in table 1)
Tank floor space = three.14 x radius2
Application price = as per table below
Foam Concentration Flow Rate (lpm [gpm] of foam concentrate)
Foam focus circulate fee = Foam solution move price x foam %
Foam percent = 1%, 3%, 6% relying on sort of foam, product on fire and manufacturer’s suggestions
Foam Concentrate Quantities
Foam focus move fee (lpm or gpm) x period
Duration = sixty five minutes for Type III (over the top) applications
Please observe that these portions are for extinguishment purposes. For vapor suppression after extinguishment it is an accepted apply to double our extinguishment supplies to keep up the suppression of vapors and prevent the potential reignition of the product.
Some of the above flows could additionally be nicely in extra of 37,854 lpm (10,000 gpm) and would require giant capability supply units corresponding to massive trailer mounted monitors and enormous moveable pumps.
Now that we know our circulate rates and foam concentrates required we want to also look at different components similar to:
Position and situation of roof drains
Volume of the product
Status of tanks and valves
Depth of water bottoms
Structural condition of tank
Product in tank and its physical properties
Is there room within the tank to simply accept the total foam solution with out inflicting an overfill
What different tanks, piping, or constructions may be uncovered
Wind course
Weather situations (present and expected)
Foam chamber on tank. Note the wind girder with acceptable handrail. If the foam chamber was not present or did not perform correctly, the wind girder could be used to advance foam hoselines for seal fire extinguishment.
In any fire state of affairs we need to contain the native facility personnel in our planning part as technical specialists. They can also be on the command submit advising the Incident Commander immediately. These fires are not our strange ‘bread and butter’ operations and must be handled as an incident that may change quickly and unexpectedly, usually with severe consequences. Do not try to extinguish a full floor fireplace with out all essential resources on the scene. Cooling of adjoining tanks would be a tactic to be used prior to all foam supply and personnel sources are on the scene. The cooling of the tank that’s on hearth isn’t really helpful unless complete 360 degree cooling may be accomplished, which is rare. Also, when cooling a tank, use solely the quantity of water essential. When the cooling water stops turning to steam, you might shut down the streams and start them up once more when needed. This will conserve water provides for extinguishment and reduce the water flowing into the dike areas. Generally between 1,893 lpm (500 gpm) and three,785 lpm (1,000 gpm) might be required for every tank cooled. In addition to the correct supply devices and foam provides, we have to make certain that our foam resolution delivery zone on the floor will be succesful of spread out as soon as it hits the floor and canopy the whole surface area. According to the National Fire Protection Association (NFPA) foam can journey effectively throughout no much less than 30m (100 ft) of burning liquid. We imagine that for calculating foam runs, this quantity should be lowered to 24m (80 ft), making certain that our landing zones travel and overlap each other. Firefighters should be conscious of the gap a grasp stream can attain as properly as the landing zone length and width. These could be obtained from the producer of the displays and nozzles and verified within the subject throughout drills and workouts. By knowing this info we will pre-plan the positioning of our master streams. Range finders can be utilized during operations to gauge distances to the tank to assist with monitor positioning. There are a few occurrences that may occur at a storage tank fireplace that the fire service ought to concentrate on. These are:
Slopover
This occasion can happen when a water stream is applied to the new surface of burning oil, supplied that the oil is viscous and the temperature exceeds the boiling level of water. It causes a short length of slopping of froth over the rim of the tank with a minimum of depth.
Frothover
Frothover is a gradual, sluggish moving froth over the rim of a tank with no sudden and violent response. Frothover may happen when the tank is not on hearth and water already inside the tank comes in contact with hot viscous oil which is being loaded. An instance is when sizzling asphalt is loaded right into a tank automotive and comes into contact with water within the tank, causing the product to froth over the top. During a fireplace with crude oil it may also happen when the heat wave created by the burning crude oil reaches the water layers (stratums) in the crude oil. This heat wave will convert the water to steam, inflicting a frothover.
Boilover
This event is a sudden and violent ejection of crude oil from the tank due to the response of the hot-layer and the accumulation of water at the backside of the tank. The mild fractions of crude oil burn off, producing a heat wave in the residue. The residues with their related heat wave sink towards the underside of the tank. This warmth wave will finally reach the water that usually accumulates on the bottom of the tank, and when the two meet the water is superheated and subsequently boils, increasing explosively causing a violent ejection of the tank contents and fireplace. The expanding contents being expelled can travel the distance equivalent of ten tank diameters. Careful consideration must be given throughout pre-incident response planning of the situation of the command post, staging areas, rehab, gear placement, and so on.
Pre-Incident Response Planning
When planning for a response to a petroleum storage tank facility it’s best that the knowledge gathered is completed on-site and with the assist of facility personnel. While on website, entry roads that you may use to access the area and place fireplace equipment (appliances) should be driven by the automobiles that will be used throughout an incident. Many instances the turning radius of equipment is just too nice to make the turns wanted within the facility. Swales or culverts may impede equipment. If the apparatus chassis is just too long and or low, it could hold up or ground while traversing a swale or culvert. Bridges on website might not enable the burden restrict of new apparatus, preventing its use at an incident.
During pre-incident response planning info that must be gathered contains the following:
Tank varieties, dimensions, contents and capacities
Pipe isolation valves, areas, and working mechanism
Fixed fire safety methods obtainable
Access factors to facility and tank
Contact phone numbers
Locations and operation of emergency shutdown units (ESD’s)
Availability of firefighting assets
Water supplies
Pumping necessities
Foam focus necessities
Mutual/automatic aid available
Other info could be obtained primarily based on the needs and necessities of your department. While these articles usually are not totally inclusive of all info that a fireplace division needs to know, it is a good begin. Other sources are listed on the finish of this text. It is essential that firefighters attend courses on this specialised firefighting, pre-plan these services, and exercise the pre-plans. Don’t enable these amenities to become part of the panorama. Visit these facilities and ask questions!
For extra data, go to www.worldsafeinternational.com
[su_note]Resources
American Petroleum Institute [API]. API Recommended Practice 2021: Management of Atmospheric Storage Tank Fires. Washington, DC: API, 2001, Reaffirmed 2006 Hildebrand, M. S. & Noll, G. G. Storage Tank Emergencies: Guidelines and Procedures. Annapolis, MD: Red Hat Publishing, 1997 Institution of Chemical Engineers [IChemE]. BP Process Safety Series: Liquid Hydrocarbon Tank Fires: Prevention and Response. Rugby, UK: IChemE, 2005 Shelley, C. H., Cole, A. R. and Markley, T. E. Industrial Firefighting for Municipal Firefighters. Tulsa, OK: PennWell, 2007References 1.
Shelley, C. H., Cole, A. R. and Markley, T. E. Industrial Firefighting for Municipal Firefighters. Tulsa, OK: PennWell, 2007.[/su_note]
Top Image:- Foam wand being placed throughout coaching. Note the protecting hose stream in place.
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