Liquid Storage Tank Fires and Emergencies

Liquid Storage Tank Fires and Emergencies

Standard Operating Procedure – Op 12

1.  PURPOSE

To provide an operating procedure to all Fire Protection Department (FrPD) personnel when responding to and operating at liquid storage tank fires and non-fire emergencies and in accordance with FrPD Safety Management System Element 6 Safe Operations.

2.  SCOPE

This standard operating procedure will apply to all FrPD operations at storage tank emergency incidents both inside and outside plant areas as well as mutual aid responses.

3.  DEFINITIONS

3.1  Boilover: Occurs during a fire in an open-top tank containing crude petroleum. Boilover occurs when the residues from surface burning become denser than the unburned product and sink below the surface to form a hot layer which progresses downward much more quickly than the liquid surface. When this hot layer (heat wave) reaches freestanding water or water-in-oil emulsion in the bottom of the tank or on top of the sunken roof, the water is superheated and subsequently boils almost explosively, overflowing the tank.

3.2  Combustible liquid: A liquid having a flashpoint at or above 100 degrees F (38 degrees C)

3.3  Flammable liquid: A liquid having a flashpoint below 100 degrees F (38 degrees C)

3.4  Frothover: The overfilling of a tank that is not on fire when water or volatile hydrocarbons boil under the surface of viscous hot oil. (e.g., when hot asphalt is loaded into a tank car that contains some water.

3.5  FrPDICS: Fire Protection Department Incident Command System

3.6  PAS: Personal Accountability System

3.7  SCBA: Self Contained Breathing Apparatus

3.8  Slopover: Can result when a water stream is applied to the hot surface of burning oil, provided the oil is viscous and its temperature exceeds the boiling point of water.

4.  RESPONSIBILITIES

4.1  The Fire Commander shall:

4.1.1  Assume responsibilities for all FrPD operations.

4.1.2  Establish Incident Command and PAS.

4.1.3  Ensure SCBA entry control procedures are established as required.

4.1.4  Establish and maintain communications throughout the fire or non-fire operations.

4.1.5  Ensure all firefighters operating within an immediately dangerous to life and health (IDLH) atmospheres on the wind girder of or around storage tanks are wearing SCBA. Firefighters climbing a tank access ladder/stair may not be required to go “on air” until they reach the end of the clean air zone and enter the IDLH atmosphere. This needs to be determined by the OIC.

4.1.6  Ensure that all firefighters operating at the scene are in full firefighting personal protective equipment (PPE) i.e., fully bunkered, and that the PPE is appropriate for the contents of the tank and/or materials involved.

4.2  Unit Head shall:

4.2.1  Ensure pre-incident plans are available at the scene for all storage tank plant areas in accordance with SOP Ad 16 Pre-Incident Plans.

4.2.2  Ensure that all FrPD operational personnel are made familiar with the facilities by periodic risk visits and classroom sessions.

4.3  The Dispatcher shall:

4.3.1  Dispatch and mobilize fire apparatus and FrPD personnel in accordance with existing SOPs and Divisional intra-area mobilization plans.

4.3.2  Monitor and record all radio messages in logbook.

4.3.3  Use all available information as contained in SOPs, related General Instructions (GIs), and other reference materials to assist the fire commander at the scene.

4.3.4  Be properly trained and shall attend appropriate courses offered by the FrPD to increase their skills and knowledge.

5.  GENERAL

5.1  The type of storage tank used to store flammable and combustible liquids is determined by the physical characteristics of the product being stored and the location of the tank (e.g., tank farm vs. gasoline service station).

5.1.1  Combustible liquids are typically stored in large cone roof tanks, smaller low-pressure vertical or horizontal tanks, or in underground tanks.

5.1.2  Flammable liquids are usually stored in open-top or closed floating roof tanks in bulk quantities or in small low-pressure vertical or horizontal tanks, or in underground tanks.

5.2  Size-up

5.2.1  The selection and implementation of any strategic plan and its supporting tactics is dependent upon an accurate and ongoing size-up.

5.2.2  Size-up starts with the receipt of the alarm and continues until the last unit has left the scene.

5.2.3  The size-up process may be carried out many times and by many individuals during the course of an incident.

5.2.4  The responsibility for size-up initially lies with the first officer (or senior firefighter if no officer arrives with the first unit). However, all members must make a personal size-up of the fire situation.

5.2.5  As higher-ranking officers arrive, the responsibility for size-up is passed up the chain of command. This turnover of command should be done formally and announced to all units on the scene and to the dispatcher.

5.2.6  An accurate and complete size-up must include consideration of the following strategic factors:

·  Life hazard-Plant operations people that may be injured and overcome, Firefighters, Plant Emergency Response Team members, Reserve Fire Brigade members, other persons that may be on scene e.g., inspection groups, maintenance contractors, etc.

·  Types of hazards and risks present-Type of product present, combustible, flammable, corrosive, quantity of product present/exposed

·  Height of tank involved-Long hose lays, accessibility

·  Construction of tank-Open top floating roof, closed floating roof, cone roof, horizontal above ground, vertical above ground, underground

·  Plant type, areas numbers, and/or names, tank farm facility, offshore, loading facility

·  Location-Proximity to other plants, proximity to ignition sources

·  Water supply-Hydrant spacing, hydrant serviceability, pressures, water tanker required, drafting locations, use of high volume/capacity pumps e.g., super-pumps, adequacy

·  Street conditions, bridge construction, overhead obstructions, limited access, vehicles obstructing the road

·  Auxiliary fixed fire protection systems-Foam systems, Deluge systems for exposures

·  Weather-Wind direction and velocity, Heat stress on firefighters

·  Apparatus and equipment-Large caliber streams (LCS), Large diameter hose (LDH), Foam equipment and supplies, Super-pumps

·  Exposures-Six sides of the incident, all four sides, above (e.g., overhead pipe racks nearby, overhead wiring nearby), below (e.g., dike area), drainage provisions, dike area size

·  Time-Time of day, time fire started, may not be the time of the initial 110 call.

5.2.7  The person making the initial size-up will determine whether the resources in manpower, equipment, and mobile fire apparatus that are on the emergency scene are sufficient for him to reach his objectives in consideration of items in 5.2.8 below. These items will be evaluated and additional resources called for as necessary.

5.2.8  Incident objectives:

·  Life/rescue

·  Protection of exposures/prevent extension

·  Confining the fire and or spill if present

·  Extinguishment

·  Ventilation and damage mitigation

·  Product preservation

5.3  The Fire Commander having collected all the information available through the pre-incident plans, initial dispatch information and the on-scene size-up needs to develop a plan for control and mitigation of the incident and should:

5.3.1  Decide on the objective of the plan and develop the strategy and tactics to achieve the objective.

5.3.2  Decide if the tactics are to be offensive, defensive, or non-intervention.

5.3.3  Predict and anticipate, if possible, the fire behavior of the structure and contents involved.

5.3.4  Obtain feedback from the fire operations officer. The plan should remain flexible to allow for changes at the incident scene.

6.  TACTICS

6.1  Cone Roof Tanks

6.1.1 The following size-up items are specific to a cone roof vent fire incident:

·  Type of flammable liquid on fire (hydrocarbon or polar solvent)

·  Vapor air mixture in the tank and the potential for flashback through the tank pressure-vacuum vent.

·  Status of the tank. Is being pumped into or out of? Tanks being pumped into will intensify burning at the vent.

·  Flame impingement onto the tank shell or roof.

·  Safe access and emergency egress from roof.

·  Slope of the tank roof

·  Structural integrity of the tank roof.

6.1.2 The following tactics items are specific to a cone roof vent fire incident:

·  Lower the internal tank pressure by cooling the external tank shell with water so the pressure-vacuum vent reseats itself and extinguishes the vent fire.

·  Extinguish using hose streams. Apply a hose stream and discharge a dry-chemical into the stream or if possible use the Hydro-Chem system on the trucks. After extinguishment, air monitoring for flammable or toxic vapors should be performed until the area is safe and returned to a normal operation.

·  Use of hydro-chem nozzles.

·  Introduce an inert gas into the tank to create an oxygen deficient atmosphere; or

·  Close the pressure/vacuum snuffer plate if equipped; or

·  Use aerial apparatus to access and extinguish the fire using hand-held dry-chemical extinguishers. Note: If the pressure-vacuum vent has failed in the open position, it can enable flashback into the tank if the fire was initially extinguished with dry-chemical and re-ignites.

6.2 Cone Roof Partially or Completely Separated With Fire

6.2.1 The following size-up items are specific to a cone roof partially or completely separated with fire incident:

·  Type of flammable liquid on fire.

·  Flash point of the liquid.

·  Level of product in the tank.

·  Status of tank. Was it being pumped into or out of?

·  Probability that the fire will be confined to its original size. Has the roof damaged the tank shell?

·  Three-dimensional fires inside the dike area from flanges or pumps.

·  Flame impingement on the external shell, piping, valves, and flanges from a dike area.

·  Availability of sufficient foam supplies to extinguish the fire.

·  Position of the separated tank roof.

·  Status of dike drains or penetrations through the dike wall.

·  Exposures to adjacent tanks.

·  Weather conditions.

·  Status of suction/rundown lines. Are lines blinded in and exposed to fire creating an overpressure situation?

6.2.2 The following tactics items are specific to a cone roof partially or completely Separated With Fire:

·  Protect the structural integrity of the exposed tank shell and any fixed fire protection systems above the fire by using cooling water from master streams or hoselines.

·  Extinguish the tank fire using fixed systems or master streams and hoselines.

6.3 Open Top Floating Roof Tanks

6.3.1 The following size-up items are specific to a sunken floating roof incident:

·  Type of flammable liquid involved.

·  Flash point of the flammable liquid.

·  Product in the tank. How much of the upper shell is exposed?

·  Status of the tank. For example, is the tank being pumped into or out of?

·  Damage to the tank floor from the legs of the floating roof.

·  Is the roof partially or completely sunk?

·  Type of floating roof (e.g., pan, pontoon, or honeycomb roof).

·  Type, nature, and degree of roof damage, and the status of roof piping.

·  Status of dike drains or penetrations through the dike wall.

·  Possibility that other adjacent roofs will sink due to heavy rains.

6.3.2 The following tactics items are specific to a sunken floating roof incident:

·  Stop product flow into the tank and verify shutdown.

·  Apply foam to the fuel surface using fixed systems or portable/mobile fire apparatus.

·  Check for tank floor leaks caused by the cocked or slanted floating roof puncturing the bottom. Where present, control flammable liquid spills inside the dike area and apply foam as required.

·  Maintain vapor suppression using a foam blanket until the tank inventory has been pumped out. If available, a foam concentrate with a long drainage time should be used.

·  Before pumping, the tank contents consider the potential of the roof shifting and causing friction or spark between the roof and tank shell.

·  The primary objective should be to maintain vapor suppression, prevent ignition of the exposed flammable liquid, and maintain the integrity of the foam blanket for an extended period as the tank’s contents are being pumped out.

·  The method of foam application will depend on availability of application devices (e.g., fixed systems, portable devices, and mobile apparatus).

6.4 Full Surface Fire

6.4.1 The following size-up items are specific to a full surface fire incident:

·  Type of flammable liquid involved.

·  Flash point of the flammable liquid.

·  Product in the tank. How much of the upper shell is exposed?

·  Status of the tank. For example, is the tank being pumped into or out of?

·  Is the roof partially or completely sunk?

·  Type, nature, and degree of roof damage, and the status of roof piping.

·  Status of dike drains or penetrations through the dike wall.

·  Status of adjacent tanks e.g., full, empty, pumping, etc.

·  Contents of adjacent tanks.

·  Availability of sufficient foam supplies to extinguish the fire.

·  Exposures to adjacent tanks.

·  Weather conditions.

6.4.2 The following tactics items are specific to a sunken floating roof incident:

·  Protect exposures

·  Do not cool burning tank shell in an offensive mode unless it can be equally cooled for the entire circumference of the tank. If the tank is cooled unevenly, the shell will contract and fail, hindering firefighting operations.

·  During an offensive mode, cooling the tank shell above the product is useful in order to cool the inner tank shell to reduce it below the boiling point of the product.

·  Isolate the tank.

·  Calculate requirements (see below):

o  Water needed for attack,

o  Foam (see Attachment 1)

o  Hose needed,

o  Delivery devices needed,

o  Dike area,

o  Calculate approximate time to Boilover, if attack is on crude petroleum, by tracking and evaluating the transition of the heat wave down the tank and withdraw firefighters and operations personnel accordingly. The heat wave can travel down through the product at a rate of 1 to 4 feet an hour. A rule of thumb used to determine a minimum safe distance is 10 times the tank diameter

6.4.3  Do not attempt extinguishment until enough foam resources are on-scene to support extinguishment (120 minutes) and continued suppression. Foam for continued suppression is generally equal to the amount of foam required for extinguishment. [1]

·  Just prior to applying foam on a crude oil tank, cool the burning surface by passing over the fire with a fog stream several times. This will intensify the fire momentarily but will aid in the foam application.