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Installation of Bottom Loading Systems

Bottom loading

Bottom loading - is a safe and modern technology for filling petrol truck tank with petroleum products through a system of valves and fittings.

The bottom loading system reduces environmental and economic losses from evaporation and spillage, increases the loading speed and unloading operations, and allows for more accurate recording of oil  product shipments.

BONUM plant installs a DIXON bottom loading system, produced by a company with more than 100 years of experience in the market.

Преимущества систем нижнего налива Bonum

Benefits of bottom loading systems:

Protection of oil products from the ingress of impurities;

Accelerated loading of tanks;

Recyclable up to 95% of fumes;

Enhanced fire protection;

Driver and operator safety. Poisoning protection;

Environmental protection;

Overfilling prevention

Overfill prevention systems are part of the API recommendations and are mandatory when using lower filling systems.

The system functions as an emergency stopover measure in case of mechanical and other unforeseen circumstances that have potential to lead to a catastrophic oil products spill.

Possible malfunctions that could result in a spill:

  • Meter malfunction;
  • In rare cases, a malfunction of the oil products supply module meter may occur;
  • Human factor;
  • The operator can specify the wrong amount of oil products.
  • There are data on operator errors, trying to fill the compartment twice;
  • Error in operation;
  • Oil products residues from previous filling.

While filling the tanker compartment with bottom filling, the hatches remain closed to prevent oil products from spilling over the top of the tank. The complexity of the method is that it is not possible to visually control the level of the compartment filling and therefore prevent overfilling. The overflow prevention system is designed to eliminate this threat.

While filling the tanker compartment with bottom filling, the hatches remain closed to prevent oil products from spilling over the top of the tank. The complexity of the method is that it is not possible to visually control the level of the compartment filling and therefore prevent overfilling. The overflow prevention system is designed to eliminate this threat.

Optical overflow prevention systems

The most effective tool to ensure safety during bottom filling. Optical sensors are activated if the pre-set level of petroleum products in the compartment  is exceeded  and automatically switch the pump. According to API standarts, spill prevention systems must have a self-diagnostic function. 

This wat, the operator can be sure that the system is functioning correctly before loading.

Bottom filling equipment

The terminal equipment and tanker trucks for bottom filling system usage are installed under API standards. The standards were developed by the American Petroleum Institute, a non-profit organisation in the USA, in order to streamline oil production and refining processes. Due to a single standard, all producers manufacture systems of a compatible type and the consumer has a wide choice of bottom filling systems. 

The bottom filling terminal is equipped with two components - the installation itself and the API coupling, which is used to fill the tank..




There are two types of systems: systems with fixed metal pipes and combined systems that include API couplings, flexible hoses, swivel mechanisms, which in turn simplify the docking process and allow the hoses to be crossed and poured through several compartments simultaneously. 





API coupler - is the second component of the terminal, which is located at the end of the filling unit. Its shape is comparable to all the adapters on API low-fill tanks. 


Advantages of the bottom loading systems:

Air switching valve

The air switching valve is used in a set with API adapters and performs an important function: when connected, it activates the trailer parking brake or blocks the engine from starting.

Air switching valves are used together with PVS recirculation adapters. During the installation, the PVS recirculation adapter and the PVS outlet coupler press the air switching valve piston in the same way as the gravity adapter.

API adapter

The API adapter is the main component of the bottom filling system and its dimensions are strictly regulated for exact compatibility. The adapter is designed in two versions - open type and gravitational.

On the open adapter, the joint is done manually. On the gravitational one, an adapter is required for the connection, which includes the squeezing device.

Pneumatic bottom valves

Pneumatic bottom valves - exclude the risk of spillage, they have a special duct through which the lower part of the valve is cut in case of an accident. This means that only part of the fuel in the pipe will be lost.

The bottom valve control unit is designed to open the PVS recycling valves and pneumatic bottom valves.

Dust protection caps

Dust protection caps - are specially designed to protect adapters from harmful substances and damage during operation, design of the cover prevents accidental opening.

Advantages of the bottom loading systems:


In the first case, all PVS recirculation valves are initially unlocked, after which power is supplied to the pneumatic control line for the bottom valves.


In the second case, power is supplied to the bottom valve control line by a control button on the control unit, after that the PVS recirculation valve with the bottom valve is opened.

The control units are separated by their functionality, with or without an indication of the bottom valves opening. The use of pneumatic control units with indication of the opening of the bottom valves allows the operator to verify that the bottom valve has triggered and that oil products have started to drain.

There are numerous modifications of the filler caps, the simplest version is dead-ended. However, there is a need for ventilation, washing and other manipulations that require occasional access to the compartment. The filler cap may contain openings for: top filling, recirculation valve, small hole air release valve, overflow prevention sensor and various control devices. This equipment is mainly factory installed on the filler caps, in other cases it is installed individually.

The PVS recirculation valve opens when the tank compartments are being filled or unloaded. The valves flow capacity is determined by API recommendations. When an oil product is being filled, PVA is forced out of the tanker upper part. When the tank is unloaded, air or PVA from underground tanks at the filling station enters the tank. Prior to the invention of the bottom filling method, this function was performed by simply opening the lid on the tanker top hatch, which resulted in significant fuel and environmental pollution and additional time expenditure. A compensation valve is mounted on the diverter line of the tanker and provides ventilation of the line during the transportation of petroleum products. When the ATS is being loaded or unloaded, the compensation valve ensures that the PVC recirculation line is airtight.

A PVS recirculation adapter is installed at the end of the PVS ROW to connect the recirculation hose through the PVS ROW coupler. They are piston adapters that release pairs after the PVS ring coupler is connected. Basically, the PVS ring adapter is equipped with an air switching valve, sight glass and a drain hole.

The PVS ring coupler is a device for connecting the PVS ring adapter and PVS recycling line adapter of underground tanks at filling stations. It may contain a piston or cooper and must ensure tight connection. Similarly, when the PVC outlet coupler is connected to the PVC outlet adapter at the PWS (tank semi-trailer), the pneumatic switch installed on this adapter is activated.

The PVC outlet line is used to connect the recirculation valves to the PVC outlet adapter installed on board of the PWS. All recirculation valves must be connected to a single PVS line (manifold). The size and capacity of the PVC outlet lines are described in API recommendations.

Recuperation of petroleum air-vapour mixture in the process of bottom filling.

The process of collecting PVC oil products usually takes place in 2 cases:


at the filling terminal, when loading a tanker truck;


at the filling station, when unloading a tanker truck. .

At the PVS loading terminal, instead of releasing the vapour mixture into the atmosphere, the fuel is forced out of the tanker container for further processing under pressure. Vapours can be collected by both the upper and lower fuel filling methods, but lower filling is the most efficient way of recirculating PVC. During the lower filling process, product is loaded through a pipe system, API adapters and bottom valves located at the bottom of the tanker truck.

During the entire filling process, the manhole cover on the tanker neck remains closed and thus the PVA is removed through a PVA recycling valve. The PVS recirculation valves in each compartment are connected to a single collector that leads the PVS to the PVS outlet adapter. A PVS recovery hose or PVS outlet unit is connected to the PVS outlet adapter, bringing the PVS vapour from the AC to the processing site. In most cases, the capacity of the tanker truck arriving at the filling terminal is fully filled with PVA collected at the filling station and the PVA outlet hose is released at full load.

Collection of PVS at filling stations

When fuel is unloaded at filling stations, the process of collecting PVS is carried out simultaneously with the discharge of petroleum products into an underground tank. If the collection system is not used, oil product vapours are removed from the underground fuel storage tank through a breather valve system, getting into the atmosphere. Due to the recirculation system, PVS reaches the tanker reservoir.

When used correctly, this system works very efficiently. It should be noted that the same PVC recirculation system installed at the station is used for both loading and unloading PVC.

The purpose of the PVS recirculation system is:

  • Environmental protection from harmful emissions of poisonous compounds;
  • Protection of oil products from evaporation during loading and unloading.
  • Protection against overfilling in case of emergency situations

The BONUM Machine Building Plant manufactures low-fill equipment as well as refurbishing upper-fill tanks. Learn more about lower fill!

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