Storage tanks shall not be and are not exempt from trending economic processes aiming at improving business economics by improving the quality of service provided to clients and by cutting cost preferably by applying innovations contributing to the sustainability of the company and its operations. Linerbag products is one of such innovations which are to be applied in fixed roof storage tanks.
Research into the possibilities of applying an sort of enclosure inside existing (or new built) tanks, with opening provisions for liquid in-/outflow, metering and safeguarding, made out of rubber or thermoplastic materials was initiated and the results were subsequently patented by the Dutch Pvt. Ltd company “Accede b.v.”. Such enclosures were named Linerbag® products.
The research and development confirmed that subject enclosures for application inside fixed roof storage tanks can be manufactured and can be made operational for the storage of liquids including liquid hydrocarbons, chemicals and even food products.
The first full scale Linerbag product has been tested, by Accede b.v., extensively (with water) and has been made operational for an initial, small scale , liquid hydrocarbon storage field applications (Euro 95 at Avia Marees in Kolhorn, North-Holland. A first full scale Linerbag product was also tested in a small scale (three cubic meter) diesel storage tanks at Hamer, Apeldoorn). A new dedicated directive named BRL-K21028 [ I ]* has been made official by Kiwa for last mentioned application in the Netherlands. The first Linerbag application at Avia, Kolhorn is currently being “life cycle” monitored and lessons learnt so far have been incorporated in this revision of the TDDR.
As a Linerbag product, by design basis, encloses all stored liquid (including possible water and sediments, etc), there is no longer any contact between the stored liquid and the (steel) tank wall. Such Linerbag products therefore have an impact on corrosion processes of the steel tank driven by the contact between the steel of the tank and the stored liquid. As corrosion processes are multiple and complex, the specific gain in terms of corrosion reduction caused by a Linerbag are subject of the particular circumstances of every single application and can only be determined on a case by case basis.
The Linerbag product, being made of non-rigid thermoplastic or rubber material, will contain very little (virtually no) air. (Virtually) all air in the tank remains outside the Linerbag. The Linerbag material will maintain contact with the liquid top surface during emptying as a result of the gravity of the Linerbag material and of the pressure difference between the air outside the Linerbag product inside the tank and the (under-) pressure of the discharged liquid. These features of a Linerbag application have an impact on the vaporization of the liquid hence on the emissions of such vapors to the tank environment. As with corrosion, vaporization and emission processes are equally complex and vary for each component of the liquid composition. The specific gains in terms of vaporization and emission reduction can only be determined on a case by case basis.
As the Linerbag enclosure separates the stored liquid from both the tank wall as well as from the air inside the tank, it reduces the exposure to fire and explosion risks. Subject to the thermal resistivity i.e. conductivity and fire retardant values of the applied Linerbag material, the resulting risk reduction may be quantified.
The Linerbag being an enclosure holding all liquids, becomes by its application the first containment of the liquids while the traditional (steel) tank thereby becomes the second containment. The risk of a spill from such double containment created by the Linerbag application and the steel tank is less then when no Linerbag is applied. A leak detection system, installed in between the Linerbag and the tank floor furthermore caters for an early first containment leakage warning system.
Linerbag applications may reduce or even eliminate the requirement to apply lining inside a tank, thereby reducing the number of man hours which have to be worked inside the tank over the life time of a tank. Tank walls and floors without lining will furthermore be easier to inspect while the quality of the inspection may improve. Linerbag may be designed such that they allow for non-cleaned, safe, removal from the tank which contributes to further reduction of the required man hours to be worked inside a tank over its (extended) life time.
Linerbag products and their applications may well result in possible new standards in terms of “Best Available Technology (BAT)” and in reduction of risks to new “As Low As Reasonably Possible (ALARP)” levels for storage tanks.