Petroleum Storage Tank Facilities – Part three
by Brenna ShumbamhiniJune 9, 2022
In previous installments of this series we talked about the kinds of petroleum storage tanks, their areas, common hearth hazards, described the kinds of fires, and hearth suppression systems that storage tanks might have.
In this third and last article we are going to talk about firefighting methods and techniques as nicely as pre-incident response planning basics.
Firefighting Strategies and Tactics
Firefighting methods and tactics begins with a properly deliberate and tested pre-incident response plan. This will be discussed later within the article. Storage tank fires are complicated occasions. These fires would require the implementation of plans, preparation, proper utilization of assets, and an extensive logistics part to ensure the assets can be found and arrive on scene in a coordinated and timely trend. The following strategies and tactics 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 solely be achieved when based on planning and preparation, with all associated taking part in all elements of the process in addition to the exercising of the plan. Exercising the plan can be conducted with desk top scenarios as well as periodic full scale exercises.
As soon as a fire division receives notification of an incident, size up and intelligence gathering should be started. Information should be gathered shortly to begin the development of firefighting methods. The following ought to be thought-about:
Rescue of personnel within the instant area
Life security hazards to web site personnel
After the instant issues are addressed, we have to determine the type of hearth current:
Full floor involvement fire
Once we’ve examined the above information we are able to then begin to develop our resource listing and incident action plan (IAP). Remember that the kind of product concerned may also impression our resource needs and techniques. The following are various forms of fires and firefighting techniques:
Ground Spill or Dike Fires
These fires can be considered as simple pool or spill fires. Calculate the world (length x width) and use the proper utility rate primarily based on NFPA 11, Standard for Low-, Medium-, and High-Expansion Foam. Knowing the product may also give you the appropriate type of foam concentrate and software methodology. Alcohol merchandise will require a gentle software technique. Firefighters shouldn’t enter the dike space unless secure to do so and approved by the Incident Commander in consultation with the incident’s Safety Officer. Atmospheric testing must be performed prior to and through entry. Exposures such as tanks, associated piping, and pumps should be protected with water through ground or mounted screens. Ground fires must be extinguished first, then using dry-chemical equipment, valves and flanges extinguished. The most effective gear for these mixed fires can be hydro-chem™ technology whereby foam/water answer as well as dry-chemical may be delivered concurrently via the same nozzle.
Specialized portable monitor placed on lip of storage tank.
Rim Seal Fires
Rim seal fires can normally be extinguished utilizing the fixed or semi-fixed foam systems if put in and correctly maintained. On external floating roof tanks, if the fixed or semi-fixed fire protection methods aren’t current, manual firefighting will need to be carried out. Under the protection of a water spray, a firefighting crew will ascend to the gauging platform with hand-held foam tools. The major method ought to be the use of foam wands to capture the hearth (Photo 1- Foam Wand) which permits the position of specialised monitors to be placed on the lip of the tank. (Photo 2- Specialized moveable monitor) The monitors can then be used to extinguish the rim seal fire using the reach of the monitor in order that hoselines and personnel usually are not working from the wind girder away from the ladder. If this gear just isn’t obtainable, then foam hoselines could be used from the wind girder. This is a hazardous operation, and only undertaken if there is a structurally secure wind girder with handrails. (Photo 3- Foam chamber and Wind Girder) Personnel must be secured to prevent falling.
In some instances, elevated streams from fireplace autos have been used. This is not a main method of extinguishment. It has been noted that there’s all the time an opportunity of sinking or tilting the roof under the excess water/foam resolution, thus creating a bigger downside, which may include an obstructed /unobstructed full floor fire.
On tanks fitted with internal floating roofs, these fires could additionally be thought of rare, but they do happen. They will be extremely tough to extinguish unless fixed or semi-fixed fireplace safety systems are put in. Foam chambers and foam dams are the simplest, and the design of the system must be calculated on a full surface hearth, particularly if the pan under is aluminum.
The most troublesome method of extinguishment in a coated floating roof tank will be to shoot foam water resolution by way of the eyebrow vents. Using hydro-chem™ into these vents has proven effective up to now.
Full Surface Fires
Staffing requirements for a major tank fire will differ relying on the kind of tank, location, water provides, nature of the incident and the provision of educated personnel. Attacks on these fires will predominantly use the Type III “Over the Top” methodology of extinguishing agent delivery. The product involved will decide the required foam utility fee and share of concentrate to water flowed. The measurement of the tank may even determine the application fee. For bigger tank diameters a bigger application rate is required. The chart beneath is accepted by business specialists to be the minimal software rates primarily based on the tank diameter:
Table 1– Application rates
Foam answer (foam concentrate + water) circulate charges to be established are based on the next method:
Foam solution flow price = Tank floor area x application fee (as noted in table 1)
Tank floor area = 3.14 x radius2
Application fee = as per table under
Foam Concentration Flow Rate (lpm [gpm] of froth concentrate)
Foam concentrate circulate rate = Foam solution move fee x foam %
Foam percent = 1%, 3%, 6% depending on kind of froth, product on hearth and manufacturer’s recommendations
Foam Concentrate Quantities
Foam concentrate circulate price (lpm or gpm) x period
Duration = sixty five minutes for Type III (over the top) functions
Please observe that these quantities are for extinguishment purposes. For vapor suppression after extinguishment it is an accepted follow to double our extinguishment supplies to take care of the suppression of vapors and stop the possible reignition of the product.
Some of the above flows could also be properly in extra of 37,854 lpm (10,000 gpm) and would require large capacity delivery devices similar to giant trailer mounted displays and enormous portable pumps.
Now that we know our flow charges and foam concentrates required we need to also look at different components such as:
Position and condition 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 in the tank to just accept the total foam solution without inflicting an overfill
What different tanks, piping, or constructions may be exposed
Weather conditions (present and expected)
Foam chamber on tank. Note the wind girder with acceptable handrail. If the foam chamber was not current or did not function properly, the wind girder could be used to advance foam hoselines for seal hearth extinguishment.
In any fireplace scenario we wish to involve the native facility personnel in our planning section as technical specialists. They can also be at the command publish advising the Incident Commander immediately. These fires aren’t our ordinary ‘bread and butter’ operations and must be treated as an incident that may change quickly and unexpectedly, often with extreme penalties. Do not try to extinguish a full floor hearth without all necessary sources on the scene. Cooling of adjoining tanks can be a tactic for use previous to all foam delivery and personnel sources are on the scene. The cooling of the tank that is on fireplace isn’t recommended unless full 360 diploma cooling could be accomplished, which is uncommon. Also, when cooling a tank, use solely the quantity of water needed. When the cooling water stops turning to steam, you might shut down the streams and begin them up again when necessary. This will conserve water supplies for extinguishment and scale back the water flowing into the dike areas. Generally between 1,893 lpm (500 gpm) and 3,785 lpm (1,000 gpm) shall be required for every tank cooled. In addition to the proper supply units and foam provides, we want to be certain that our foam answer delivery zone on the surface will have the power to spread out once it hits the floor and canopy the complete surface space. According to the National Fire Protection Association (NFPA) foam can travel effectively across a minimal of 30m (100 ft) of burning liquid. We imagine that for calculating foam runs, this number must be reduced to 24m (80 ft), guaranteeing that our landing zones journey and overlap each other. Firefighters ought to be conscious of the space a grasp stream can attain in addition to the touchdown zone size and width. These could be obtained from the producer of the screens and nozzles and verified in the subject during drills and exercises. By figuring out this information we will pre-plan the positioning of our grasp streams. Range finders can be used throughout operations to gauge distances to the tank to assist with monitor positioning. There are a few occurrences that may occur at a storage tank fire that the fire service should be conscious of. These are:
This occasion can occur when a water stream is applied to the hot surface of burning oil, supplied that the oil is viscous and the temperature exceeds the boiling level of water. It causes a brief duration of slopping of froth over the rim of the tank with a minimum of depth.
Frothover is a steady, gradual shifting froth over the rim of a tank and not using a sudden and violent response. Frothover might occur when the tank just isn’t on hearth and water already inside the tank is out there in contact with scorching viscous oil which is being loaded. An example is when scorching asphalt is loaded into a tank automotive and comes into contact with water in the tank, inflicting the product to froth over the top. During a hearth with crude oil it could also occur when the warmth wave created by the burning crude oil reaches the water layers (stratums) within the crude oil. This warmth wave will convert the water to steam, causing a frothover.
This occasion is a sudden and violent ejection of crude oil from the tank because of the reaction of the hot-layer and the buildup of water at the bottom of the tank. The gentle fractions of crude oil burn off, producing a heat wave in the residue. The residues with their related heat wave sink in course of the underside of the tank. This heat wave will ultimately reach the water that usually accumulates at the backside of the tank, and when the 2 meet the water is superheated and subsequently boils, expanding explosively causing a violent ejection of the tank contents and fireplace. The increasing contents being expelled can travel the space equal of ten tank diameters. เพรสเชอร์เกจ should be given throughout pre-incident response planning of the placement of the command post, staging areas, rehab, gear placement, etc.
Pre-Incident Response Planning
When planning for a response to a petroleum storage tank facility it’s best that the information gathered is finished on-site and with the assist of facility personnel. While on web site, entry roads that you can be use to entry the world and position hearth equipment (appliances) must be pushed by the autos that might be used throughout an incident. Many times the turning radius of equipment is too nice to make the turns needed within the facility. Swales or culverts can also impede apparatus. If the apparatus chassis is simply too long and or low, it may hang up or ground while traversing a swale or culvert. Bridges on website may not allow the burden restrict of recent apparatus, preventing its use at an incident.
During pre-incident response planning information that ought to be gathered consists of the next:
Tank sorts, dimensions, contents and capacities
Pipe isolation valves, places, and operating mechanism
Fixed hearth protection techniques out there
Access factors to facility and tank
Contact phone numbers
Locations and operation of emergency shutdown gadgets (ESD’s)
Availability of firefighting assets
Foam focus requirements
Mutual/automatic help available
Other information may be obtained primarily based on the wants and necessities of your department. While these articles aren’t completely inclusive of all info that a fire department needs to know, it is a good start. Other assets are listed at the end of this article. It is essential that firefighters attend courses on this specialized firefighting, pre-plan these services, and exercise the pre-plans. Don’t allow these facilities to turn into a half of the panorama. Visit these facilities and ask questions!
For extra information, go to www.worldsafeinternational.com
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 during training. Note the protecting hose stream in place.