Fixed tanks for agricultural diesel fuel storage

DM 22.11.2017 set out the rules for installing agricultural diesel fuel fixed tanks appropriately. From tank placement on the farm to maintenance, all regulations provisions to prevent fire or fuel spillage

Among the most significant production inputs affecting the financial budget of the farm is undoubtedly diesel fuel. It is used in substantial quantities for carrying out the work performed by self-propelled machines equipped with diesel engines. Since this fuel is highly flammable (in the presence of flame), a number of provisions pertaining to safety, especially fire safety, must be complied with for its safe storage on the farm. 

The procedure to be followed when installing a fuel tank depends mainly on its capacity. If it is larger than 6 m³, it is mandatory to comply with Presidential Decree 151/2011, which specifies which types of activities (including agricultural activities) are subject to fire prevention visits and inspections. If so, it will be necessary to display the Fire Prevention Certificate on the tank or its surrounding structure.

Besides these bureaucratic tasks, the farmer must comply with the provisions of the Ministerial Decree of 22.11.17, "Technical regulation of fire prevention for the installation and operation of containers-distributors, for private use, for the dispensing of liquid fuel category C, ."In this decree, the Ministry of the Interior, in agreement with those of the Economy and Economic Development, established provisions on the construction, installation and use of containers for agricultural diesel fuel or their retrofitting, if already installed. This decree repeals the pre-existing regulations on fixed fuel tanks (DM of 19.03.90 and 12.09.03) and defines on the occasion new rules for the dispensing of category C fuel, namely diesel fuel. Other fuels, such as gasoline, are not included in this list.

 DM 22.11.17, which officially came into effect on 5.1.18, covers diesel fuel tanks installed above ground, with a maximum capacity of up to 9 m³. It is worth mentioning that this limit does not apply to each individual container but rather refers to the sum of all those in the storage facility. In the case of multiple installations, the tanks must be placed at least 0.8 m apart, while the total holding capacity cannot exceed 45 m³ in any case.   Finally, the distance between different storage tanks must be at least five meters.

In addition, each tank must also be equipped with a CE declaration of conformity, an installation, operation and maintenance manual, and an identification plate prominently placed. 

 

Double or single wall with holding basin

Tanks for agricultural use are commonly cylindrical in shape and convex on the sides, with the central axis horizontal, although less frequently, vertical axis solutions are also available.

They are assessed for tightness by introducing pressurized air.

These tanks can then be either double or single-walled. In the case of double-walled, safety requirements are practically automatically met because, in that case, there is no risk of spillage into the environment. 

Conversely, single-walled tanks must be accompanied by a containment basin with a capacity of at least 110% of the tank's total content. Moreover, the whole assembly must be placed under a canopy for protection from the weather.

The containment basin is made of sheet steel, with a self-supporting frame and provision for fixing to the base. It is equipped with a lifting plate, grounding connection, sleeve with drain plug, and housings for attaching uprights and clamps. 

One of the main changes brought about by the most recent legislation is the capacity of the holding tank, which from a previous volume of 50% of the tank's volume has been increased precisely to 110% for better protection in case of emergencies. Indeed, it is essential to minimize both the risk of fire and the risk of possible harm to people or environmental pollution caused by accidental fuel spillage. Specifically, the ecological damage can be severe, with widespread die-offs of flora and fauna, particularly if the diesel fuel leaks into surface waters.   

The tank structure

Ensuring that the tank is firmly anchored to the ground is essential. Usually, anchor bolts are employed and placed at four sturdy points in the structure, where there are also housings for attaching the supporting posts of the weather shelter. As an alternative to a canopy, tanks may be housed in prefabricated boxes, provided they are made of fireproof material. However, they may not be placed in enclosed spaces or above enclosed places.

Moreover, they cannot be placed in transit areas, such as driveway ramps, terraces, and areas that, even if only occasionally, may be affected by the formation of explosive atmospheres. 

The placement of fixed tanks must meet specific requirements about distances from other artifacts, considering their overall size. Specifically, the following must be observed:  a distance of at least 5 m from buildings and deposits of flammable materials not subject to Presidential Decree 151; a distance of at least 10 m from buildings for residential use, public establishments or deposits of flammable materials subject to Presidential Decree 151; a distance of at least 3 m from company boundaries; a distance of more than 15 m from railway lines and 6 m in vertical projection from power lines with working voltages over 1000 V.

For safety purposes, some additional measures must be taken, such as placing fire-resistant elements near the tank, installing prohibition signs (smoking, open flames, dangerous behavior, etc.), installing grounding of the electrical system, and placing fire extinguishers near the tank. In addition to this, personnel capable of handling emergencies must be operating. 

 

Technical specifications

The regulations define some aspects of its design: First of all, there must mandatorily be a vent line equipped with a flame screen at its top, which must be placed at least 2.40 m above the ground.

Furthermore, a load-limiting valve must be installed to prevent the tank from being filled beyond 90 percent of its capacity and prevent harmful spills of diesel fuel. Lastly, there must also be an external suction pipe to allow the fuel to be decanted. A Ø 400 mm hinged circular hatch is usually installed for filling. The hatch is usually closed with a bolted lid equipped with a protective gasket.

For dispensing fuel, the tanks are equipped with a device contained in a metal cabinet placed on the supporting structure, with a key and/or padlock closure. Alternatively, a proper dispensing column can be chosen, although the most preferred is the first option.

The dispensing assembly includes a withdrawal pump, a flow meter, a level indicator, and the starting circuit, with an automatic shutoff established through a restrictor valve.

A discharge pipe with a safety shutoff must also be installed to allow appropriate periodic cleaning.

 

Dispensing cabinet or dispensing column

The metal dispensing cabinet includes several elements: a lock with a key to preventing misuse; an electrical panel with the main power switch, emergency button and management of pump blockage when the liquid level falls below the minimum; self-priming electric pump, equipped with a cleaning filter; flow meter and level indicator; rubber tubing with an automatic dispensing gun that can be hooked inside the cabinet.

Machinery tank filling pump generally has a flow rate of 50 to 90 l/min, a function of the capacity of the fixed tank.

Conversely, the dispensing unit comprises an approved dispenser and a dispensing pump, with flow rates as high as 120-130 l/min for fixed tank models for industrial use.

 

Software equipment and attachments

Emiliana Serbatoi of Campogalliano (MO) offers some models of fixed tanks equipped with dispensing storage software (up to 250 values) to automatically keep track of drawdowns in the medium to long term.

This is a useful function, for example, in the management of fleets of tractors and self-propelled operators in use at agromechanical companies. 

Available accessories include various fuel level gauges and hose reels (manual or spring-loaded) for the rubber terminal with a gun, a detail that provides more comfortable dispensing. Depending on the overall context, appropriate filters can be added at strategic points in the dispensing circuit for better purity of the diesel fuel concerning foreign elements (essential for feeding diesel engines with common rail injection).