Flammable liquids ignite easily. They are bound to catch fire when exposed to the slightest form of an igniting agent. A liquid is considered flammable if its flashpoint is above 100.
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Although combustible liquids have an estimated flash point of 40, they are capable of catching fire. The ignition of a flammable or combustible fluid could cause a catastrophic fire.
It is significantly important to prevent such fluids in tanks from catching fire. The solution to protecting these fluids from igniting is designing appropriate storage facilities. The major storage facilities for flammable liquids are tanks (Long 55). The design and installation of flammable fluids storage tanks is specifically meant to avert the fluids’ possibility of catching fire.
In the US, the flammable and combustible liquids act was passed in 1988. There exists two major forms of storage. These are the underground storage tanks and floating roof tanks.
It has been noted that during incidences such as spills and overfills, a lot of unwanted and sometimes harmful content is released into the environment. In the past, many USTs were made of corrosive metals. Because of corrosion over time, several incidences of leakage occurred.
Consequently, the government found it necessary to establish laws that would mitigate these challenges especially regarding underground spillage. The law mandated underground storage tanks’ owners to upgrade their storage tanks. In this regard, owners were required to replace their faulty corrosive tanks with non-corrosive tanks.
The other form of flammable liquids storage is the floating roof tanks. These tanks satisfactorily handle the volatile and less dense liquids. In this regard, such tanks’ owners and operators must handle combustible and flammable liquids safely to prevent environmental hazards. The observance of these measures helps to prevent the dire consequences of such liquids’ ignition.
The floating roof tank is one of the main designs used for storage of flammable liquids. A specific floating roof tank has a special design and special installation procedures that cater for the safety of the stored liquids.
For a tank to store a certain flammable liquid safely, the liquid is pressurized to the rating of the tank and as per the nature of the fluid. Furthermore, some special tanks are needed to store cryogenic liquids. A floating roof tank has a covering that is not fixed. In addition, since the tank cannot withstand much pressure, it has a conical or flat roof.
The tank has a vent on top of the lid. The vent functions as an air outlet when the tank is filling to prevent the increasing pressure from lifting the lid off. Moreover, the vent is used for emergency purposes to keep the pressure constant in case of a rapid increase, which could damage the tank.
A rapid increase in pressure may occur due the rise in temperature as in the case of an accidental fire. The liquids stored in a floating roof tank should have low volatile tendency to prevent gradual loss (Myers 104).
Floating roof tanks do not have an airtight design that can hold back vapour in case of rapid evaporation. The vent used to release pressure during the filling process acts as a fireguard. It arrests the flame before it is sucked into the tank.
The vent should be designed in such a way that it is not obstructed in times of an emergency. The vapour pressure in a floating roof tank is measured at the top of the tank where there is vapour space. This measure helps to avoid the inclusion of the liquid pressure when the measurement is taken at the bottom.
Floating roof tanks are used to store liquids with high flash points to minimise their chances of igniting when there is an igniting agent in close proximity. Once ignited, the liquids could provide a lethal incendiary for a fire. Lubricating oil, among other petroleum products, is an example of the liquids that could be stored in a floating roof tank.
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If the roof of the tank is rigid, the liquid stored should have a significantly high flash point. Furthermore, the liquid should have low volatility so that the vapour concentration remains below the ignition level. If the tank is exposed to extremely high temperatures, the liquid vaporises quickly and the pressure inside the tank rises rapidly.
In case the vent designed for releasing the pressure fails, the resulting tension in the tank may cause an explosion. Such an explosion will damage the tank and spill out the stored liquid, which may accelerate the fire further. In some other instances, an improperly fixed lid may expose the stored fluid to the danger of catching fire.
In addition, the stored liquid could spill out and ignite a fire in close proximity. If a flame manages to ignite the fluid in the tank with the lid still in place, the tank may explode.
Another precautionary measure observed when manufacturing tanks with fixed roofs is the deliberate alteration of the tanks roofs’ strength (Myers 254). A tank is constructed with a roof of medium strength and a seam that can be easily broken between the roof and vertical walls.
This loosely bonded seam will unfold with the application of a sudden immense pressure such as the one that occurs on heating of the tank by a fire. In this regard, when the roof’s seam breaks during a fire, the pressure inside the tank cannot increase beyond the atmospheric pressure.
Furthermore, the content of the tank remains intact and free form ignition if the heating effect acts from below. Since the contents of the tank do not splash during an explosion, the chances of extensive fire damage are minimised.
The design of floating roof tanks does not involve any kind of a float chamber to cut out the liquid supply during the tank’s filling. In this regard, the tank has a plastic or rubber rim around the roof, which acts as a washer to prevent the liquid from overflowing through the rim onto the upper side of the tank’s lid.
The most common fire accident in a floating roof tank is the lighting up of the roof rim, which is often smeared with the overflowing content of the tank. Vertical tanks are used to store less inflammable liquids such as naphtha while horizontal tanks are used for the storage of highly flammable liquids such as motor gas. These tanks are designed to hold liquids at low pressure. Thus, they are used for highly volatile gases.
The design of a tank without a weak roof that can be blown away to release pressure makes the bottom of the tank vulnerable to pressure. The failure of the bottom seam may lead to a reaction that can cause the tank to be tossed away from the fire scene and cause fire elsewhere.
Tanks situated above the ground are vulnerable to collapse since an intense fire may compromise the integrity of their stilts, which are made of steel. In this regard, the most appropriate measure is to install the tanks in an underground vault and covering it.
For a tank installed in an underground location, corrosion of the tank’s material is inevitable. The tank can be protected through electrical means by attaching a charged cathode for deionisation purposes.
In addition, a tank installed in an underground location is vulnerable to the accumulation of vapours. In this regard, some form of aeration is necessary in order to contain the contamination of the stored liquid by condensed water.
Asphalt can be used for the construction of tanks because its flash point is above the ignition point of most of flammable materials. However, some asphalt tanks are reported to have ignited at temperatures significantly below asphalt’s flash point.
This has been attributed to the combined effects of the asphalt material and the flammable liquid in the tank. In addition, the fireproof design of a floating roof tank may fail when an electrostatic charge triggers the ignition of the liquids stored in the tank. The electrostatic charge is generated during the tank’s cleaning or when the process of filing the tank is not executed in an appropriate manner.
Therefore, to avoid the electrostatic charges, proper installation is critical so that the charges do not cause an ignition. Nevertheless, the flashpoint could be analysed to determine the compatibility with the tank used for storage.
The adoption of appropriate measures ensures that the storage of combustible and flammable liquids is handled properly with regard to the floating tank facilities. On this note, environmental hazards that result from spillage or ignition can be avoided.
Another significant method of storage of combustible and flammable liquid is the use of Underground storage tanks (USTs). USTs have a combination of connected pipes and are occasionally designed to occupy 10% of their size. Contrary to the common notion, USTs do not include other small volume tanks used in the farms for fuel storage. USTs are utilized by numerous businesses.
These tanks are usually used for the storage of petroleum related products and other flammable substances like oxygen and hydrogen. Due to the explosive nature of the substances stored in these tanks, it is significantly important to observe their proper and standardized ways of installation and maintenance.
Similarly, when transferring the content stored in these tanks, the appropriate precautionary mechanism should be employed to limit spillage. This ensures the safety of the operations (Long 224). In this regard, safety rules and storage tanks regulations have been developed to enhance secure storage and usage practices leading to economical and environmental benefits.
During installation, several measures should be observed because the effective use of USTs relies heavily on their installation procedures. There are two methods of installation.
These are existing new installation and new installation. An existing new installation entails the upgrading of earlier installations to ensure that the existing containers are in safe conditions and easy to monitor. Through these practices, tanks are upgraded enhancing corrosion protection, leak prevention and overfill detection.
During the upgrading process, the internal section of the tank is inspected to ensure that it is mechanically sound and free of leak holes. If a period of ten years has passed since the tank’s initial installation, the tank should be monitored on a monthly basis.
The presence of leakage holes in the tank can be established by using two procedures. The initial test is done before the lining of cathode elements while the second test is done five months afterwards. After the tests, the tank may be upgraded by combining two installation procedures of internal lining and cathode guarding.
For a new installation, the owner should inform the local authorities 30 days prior the date of the installation. This enables the review of the owner’s installation plans to ascertain their validity and counterchecked if they comply with the standards of the installation procedure.
In the proposal, the owner should provide details regarding the sites electricity or telecommunication lines, security, neighbouring buildings and water bodies such as wells in the vicinity. Afterwards an approval may be offered to the owner if he or she complies with the regulation standards.
USTs experts are then sent to the installation site for inspection purposes before the certificate of approval is awarded (Metelski 256). During installation, the owner is expected to obtain an insurance cover. Similarly, well-trained technicians should be employed to perform the installation. All the tanks and pipes should be installed in accordance with the manufacturer’s instructions.
In several countries, the standards of removal and disposal of USTs have been developed. Usually, the law requires all USTs owners to replace the tanks within a period of 10 years. In this undertaking, they are encouraged to use fibreglass tanks due to their ability to withstand corrosion.
Similarly, modern tanks have been reinforced with double fibreglass walls significantly reducing the issue of leaks in tanks. The tank replacement process demands the replacement of old pipes with new ones, which are stronger.
The new pipes have been reinforced with an additional double wall from a mixture of glass and plastic materials. During installation, tanks’ control systems are included to monitor and sense leaks. These measures are meant to observe and automatically report any leakages.
Due to the numerous demands from regulators and environmentalist, many owners of USTs have resorted to other methods of storage like above-the-ground tanks to reduce costs and for monitoring purposes.
However, some states do not permit this form of storage. In the U.S the Environmental Protection Agency’s (EPA) policies regarding USTs have been very strict. As a result, numerous achievements have been realized. More than half of the tanks’ owners have complied with the policies of upgrading their tanks and some have replaced theirs completely.
Despite these dramatic changes, some leakage incidences from fuel tanks are still being reported. To countercheck such occurrences, the US government through the EPA has provided resources for cleanup and prevention programs. These resources are provided to tribes, territories and local authorities to aid them in implementing their clean up and prevention programs.
Since the inception of the use of USTs, preventing leaks and spillages into the environment have always been a challenge. However, the EPA and other environmental organisations have significantly progressed in their bid to minimise and eventually halt the release of these substances into the environment.
Nevertheless, there have been major setbacks encountered by these organisations concerning the operation and maintenance of these tanks. When leakage of USTs occurs, the owners and the operators are required by law to report the matter to the relevant authorities. Thereafter, clean up of the spillage is done before 24 hours elapse.
In case of an underground leakage, operators should try as much as possible to minimise the contact between the tank’s contents and the air. This can be achieved by use of sorbents to limit the flow of the chemicals. In addition, an immediate excavation should be done. In some cases, the law mandates a secondary containment in cases of emergencies.
The secondary containment is supposed to be used at all times whenever humans’ health is at risk. This containment should be well fabricated to prevent the stored substance from seeping down the water table.
Furthermore, consideration of the volume of the containment is necessary. It must be stable enough to hold different pressures from different fluids. However, containments’ specifications vary from state to state and from one local authority to another.
To avoid incidences of leaks, owners and operators are required by law to monitor the volume of the stored substances regularly. The volume capacity of the tank should always be greater than the transferring tank’s capacity.
In this regard, owners should ensure that their operators comply with the required USTs protocols. All operations on corrosive substances should be maintained to sustain the corrosion caused by the metal components. Similarly, the USTs facilities should be protected by the use of cathode elements. Frequent monitoring by qualified experts in cathode protection is vital.
Checkups and test should be carried out in a period of 5 months after installation and every 3 years thereafter. The criterion used by the cathode experts should be appropriate and up to date as per the regulations (Metelski 384). Thereafter, the USTs’ data regarding cathode protection should be stored in records for future reference.
Moreover, the owners are supposed to ensure that their UST lining material is appropriately matched with the storage substance hence avoiding cases of incompatibility (Long 384). In this regard, the repairs and maintenance practices should comply with the USTs protocols.
Despite the numerous regulations in place, the minimization of UST leakages still poses a great challenge due to the dangers exposed to the environment. Therefore, we should contribute significantly towards the mitigation of such challenges.
In the event of a spillage, the environment should be protected to reduce spillage hazards as stipulated by the law. In this regard, one is expected to put away all the flammable materials like cigarettes. The impacts of a fire outbreak are detrimental and sometimes fatal.
For any form of combustible and flammable liquids storage facility chosen, the safety of the stored liquid is a vital consideration. Knowing that the liquids stored are highly flammable, any material capable of causing an ignition should be kept away.
Nevertheless, these storage facilities should be continuously upgraded to improve their performance in handling the liquid. The realization of the appropriate storage system is very significant towards the safe handling of the liquid. Moreover, the owners or operators should consider the advantages and risks that they face in handling the liquid.
The location and the surrounding condition of the storage facility determine the choice of the storage facility. In this regard, underground storage tanks are viewed as less vulnerable to rampant fire risks than floating roof tanks.
Although these storage facilities are the most commonly used, there exist others such as the above-the-ground storage tanks. Each storage tank therefore suits each specific flammable liquid depending on its characteristics. Lastly, any flammable liquid should be kept safely for its utilisation and protection of biodiversity.
Long, Bob, and Bob Garner. Guide to storage tanks & equipment: the practical reference book and guide to storage tanks and ancillary equipment with a comprehensive buyers’ guide to worldwide manufacturers and suppliers. Bury St. Edmunds, U.K.: Professional Engineering, 2004. Print.
Metelski, John J., and Myra R. Anderson. Managing underground storage tanks. New York, N.Y.: Executive Enterprises Publications Co., 1989. Print.
Myers, Philip E.. Aboveground storage tank inspection guide. London: McGraw-Hill, 1999. Print.