The invention refers to a method for controlling the safe and correct transfer of liquid fuel from a tank vehicle to liquid fuel tanks, at a minimum cost, with simultaneous and continuous and in real-time control of the correct grounding of the Tank Vehicle and the secure and correct connection of the common flexible Vapour Recovery Rubber Hoses to the fuel vapour collection and return valves of the Tank Vehicle and the petrol station, with the use of an appropriate insulating device, which galvanically cuts off the tank vapour return valve from the grounded vapour recovery system of the petrol station’s tanks.

According to the applicable legislation on environmental protection, the release of hydrocarbon vapours to the environment while the tanks are being filled with liquid fuel is strictly forbidden. The remaining fumes covering their empty space are naturally pushed to the bleeding system of the tanks and they should be collected by the tank vehicle so that they can further be processed and liquified.

While the tanks are being filled, there is serious danger of fire or explosion in the area of the petrol station due to the increased inflammability and hazard of the liquid fuel and its vapours.

All the applicable safety regulations on the transfer of liquid fuel from the tank vehicle to the petrol station tanks should strictly be adhered to. In other words, at first the tank vehicle should be grounded and the flexible conductive vapour recovery rubber hose should be connected to the tank vehicle’s vapour collection valve and then to the vapour return valve of the petrol station tanks. The correct connection of the above should be safeguarded, either visually or through electronic control devices, and then the tanks of the petrol station shall be filled with fuel, either by opening the manual filling valve or by activating the pneumatic filling valve through the relevant order. According to the relevant legislation, all the necessary operations and controls taking place at the petrol station, while liquid fuel is transferred from the tank vehicle to the fuel tanks, should at the same time be monitored by a permanent integrated control device - Control Unit so that any human error or negligence can be avoided.

The existence of a permanent integrated control device safeguards the correct and safe vapour recovery process, the correct grounding of the tank vehicle, and prevents or interrupts the start of the fuel transfer unless all safety conditions and rules are fully met.

In the course of time, control systems have used three basic methods for detecting an interruption while a tank is being filled, although they fail to fully secure the correct vapour recovery process because they are deceived and are rather easily be bypassed, or exercise less control, or react slowly, or because they have a very high cost or they fail to meet the specified safety requirements.

In one method, the control of the correct connection of vapour recovery rubber hoses is carried out through two variable resistance thermistors: the reference thermistor, which is isolated from the flow of the returning gases, and the detection thermistor, which is installed in a series with the flow of the gases, inside the vapour recovery pipes.

While the tanks are being filled, when there is a gas flow, the detection thermistor is cooled and the difference in the resistances of the two thermistors can be detected, thus indicating the existence of gas flow in the recovery network. This method is quite effective, though very slow during implementation, because the monitoring system needs sufficient time, usually one to five minutes, in order to balance and perceive the flow of gases. This amount of time is considered quite long because in case the vapour recovery pipes have not been connected correctly, a significant amount of gases shall be released to the atmosphere.

In another method, the control is carried out by fitting the appropriate proximity switches to the tank vapour return valve and to the tank vehicle’s vapour collection valve, which detect the connection of the vapour recovery rubber hoses. Because these switches are usually externally installed and are easily bypassed by the operators with the use of metal, screwdriver, pincers, etc., the specific method is not considered sufficiently safe and reliable.

In a third method, the control is carried out by installing the appropriate pressure sensors, which continuously measure the pressure of gases in the tank vapour recovery network. This method is usually combined with a simultaneous installation, at the petrol station, of a liquefying unit for the recovery vapours that would escape to the atmosphere while they would be collected from the tank vehicle.

This method is quite effective, but the response and control time of the system is not instant and its implementation requires very costly equipment. U.S. Application Patent No. US201 1240136 (US8736622 B2) suggests controlling the correct connection of the flexible vapour recovery rubber hoses by installing the appropriate electronic circuits at the two metal end connectors of the vapour recovery pipe and a duct running inside the flexible hose. Special metal ends are required at the pipes as well as special and expensive equipment, unavailable and not compatible with all petrol stations and tank vehicles, which leads to a considerable increase of cost. There are electronic circuits and vicinity sensors that can be bypassed, incorporated into the specially manufactured end metal connectors of the vapour recovery rubber hoses (in movable elements), non-compatible with all tank vehicles. This special equipment is put to strain, knocked and damaged when it is used, thus increasing the possibilities for a control failure.

A major disadvantage of US2011240136 (US8736622 B2), as well as of all the above methods, is that the way of operation and control they offer does not secure, together with the secure connection of the vapour recovery pipes, the automatic control of the correct grounding of the tank vehicle delivering the fuel despite the use of special, sensitive or costly equipment. In other words, the entire set of the specified safety requirements is not met.

The purpose of this patent is, at a minimum cost and taking advantage of the conductivity specified for the flexible vapour recovery rubber hoses by the international standards and regulations, to simultaneously control in real time, the secure and correct connection of the flexible vapour recovery rubber hoses to the tank vehicle’s vapour collection valve and to the vapour return valve of the petrol station tanks, as well as the correct grounding of the tank vehicle to the grounding network of the petrol station.

All the above controls are carried out with the use of common flexible vapour recovery rubber hoses, familiar to persons skilled in the art, of low cost, which can be found in every petrol station and tank vehicle.

All low-cost devices used for carrying out the above controls according to the proposed method shall not include any movable or portable parts but shall be permanent and fixed equipment elements in the area of the petrol station, without no interventions in the usual equipment of the tank vehicle shall be required.

In this invention, an Insulating Device from any appropriate insulating material, which permanently and galvanically interrupts the conductive continuity of the Tank Vapour Return Valve from the grounded network of the tanks (permanently connected to the Ground Triangle of the fuel Tanks) and allows a Control Unit to identify the electric potential of the Tank Vapour Return Valve, is attached to the metal casing of the Tank Vapour Return Valve (camlock).

In real time throughout the delivery of the fuel, the Control Unit (interlock panel) shall control the electrical continuity of the conductive loop formed by the series connection of the Petrol Station’s Ground Clamp, the Tank Vehicle, the Tank Vehicle’s Vapour Collection Valve, the flexible Vapour Recovery Rubber Hose, the Tank Vapour Return Valve and the Equipotential Bonding Conductor, which is permanently and conductively attached to the metal body of the Tank Vapour Return Valve and permanently and conductively connects the Tank Vapour Return Valve with the Control Unit. The Control Unit, permanently and conductively connected to the Tank Vapour Return Valve through the Equipotential Bonding Conductor, can in a controllable manner apply and measure voltage on the Tank Vapour Return Valve. In the two cases, whether liquid fuel is transferred or not, the Equipotential Bonding Conductor carries out a different operation controlled by the Control Unit. When no liquid fuel transfer takes place, regardless whether the Control Unit is powered or not, the Equipotential Bonding Conductor restores the grounding of the Tank Vapour Return Valve to the Ground Triangle of the fuel Tanks.

When liquid fuel transfer takes place, the Equipotential Bonding Conductor interrupts the grounding of the Tank Vapour Return Valve.

The Tank Vapour Return Valve is grounded on the Ground Triangle of the fuel Tanks through the electrical continuity of the Vapour Recovery Rubber Hose, the Tank Vehicle’s Vapour Collection Valve, the Tank Vehicle and the Petrol Station’s Ground Clamp.

When liquid fuel is transferred, a voltage of 5VDC/1 mA, or any other electric signal known to persons skilled in the art, e.g. frequency, voltage, electric current, etc. that is measured and controlled by the Control Unit in real time, throughout the delivery of the fuel, is applied on the Equipotential Bonding Conductor. In case the continuously applied and measured voltage falls below the threshold of 2.5 VDC, the Control Unit perceives the conductive continuity of the loop that consists of the Petrol Station’s Ground Clamp, the Tank Vehicle, the Tank Vehicle’s Vapour Collection Valve, the flexible Vapour Recovery Rubber Hose, the Tank Vapour Return Valve and the Equipotential Bonding Conductor and activates the Pneumatic Filling Valve of the fuel tanks, which opens so that the fuel transfer can be completed.

Otherwise, when the voltage rises above the threshold of 2.5 VDC, the Pneumatic Filling Valve is deactivated, the fuel transfer is interrupted and the grounding of the Tank Vapour Return Valve is restored by the Equipotential Bonding Conductor to the Ground Triangle of the fuel Tanks.

Figure 1 shows the side view of the proposed configuration:

- the common and standardized, familiar to persons skilled in the art, Tank Vapour Return Valve (1 ),

- the Equipotential Bonding Conductor (2), permanently and conductively attached to the metal body of the Tank Vapour Return Valve (1 ),

- appropriate Insulating Device (3), installed between the metal body of the Tank Vapour Return Valve (1 ) and the Tank Vapour Recovery Hydraulic Network (15). - the Pressure Sensor (14), familiar to persons skilled in the art, permanently installed in the Tank Vapour Recovery Hydraulic Network (15) and its connection cable.

- The Proximity Switch (13), known to persons skilled in the art, permanently installed in the Tank Vapour Return Valve (1 ) and its connection cable.

Figure 2 shows:

- the Tank Vapour Return Valve (1 ),

- the Control Unit (4),

- the Equipotential Bonding Conductor (2), permanently and conductively attached to the metal body of the Tank Vapour Return Valve (1 ) and its electrical connection to the Control Unit (4),

- an appropriate Insulating Device (3), installed in a series with the metal body of the Tank Vapour Return Valve (1 ),

- the Petrol Station’s Ground Clamp (5) and its electrical connection to the Control Unit (4),

- the Tank Vehicle (6),

- the Tank Vehicle’s Vapour Collection Valve (7),

- the flexible Vapour Recovery Rubber Hose (8),

- the Pneumatic Filling Valve (9) and its pneumatic connection to the Control Unit (4),

- the Bleeding Network Safety Valve (10),

- the Ground Triangle of the fuel Tanks (1 1 ) and its electrical connection to the Control Unit (4) and the Liquid Fuel Tanks (16),

- the Ground Triangle of the Petrol Station’s switchgear (12) and its electrical connection to the Control Unit (4),

- the grounded Tank Vapour Recovery Hydraulic Network (15),

- the Pressure Sensor (14) and the Proximity Switch (13), known to persons skilled in the art, and their electrical connection to the Control Unit (4) and

- the rubber Fuel Transfer Hose (17).

In the proposed embodiment of the method, the Equipotential Bonding Conductor (2) is permanently and conductively attached to the metal body of the Tank Vapour Return Valve (1 ) in a way familiar to persons skilled in the art. When no fuel transfer takes place, regardless whether the Control Unit (4) is powered or not, the Equipotential Bonding Conductor (2), controlled by the Control Unit (4) through electrical-electronic devices familiar to persons skilled in the art, restores the grounding of the Tank Vapour Return Valve (1 ) to the Ground Triangle of the fuel Tanks (1 1 ).

In the proposed embodiment of the method, the below works should be carried out in the following order for the safe and correct transfer of the liquid fuel after the arrival of the Tank Vehicle (6) at the petrol station:

All works familiar to persons skilled in the art and related to the transfer of liquid fuel are carried out, e.g. connection of the Petrol Station’s Ground Clamp (5), connection of the flexible Fuel Transfer Rubber Hose (17), etc. Then the Control Unit (4) is provided with power. The Control Unit (4) controls the resistance values of the two independent ground triangles of the station, i.e. the Ground Triangle of the fuel Tanks (11 ) and the Ground Triangle of the station’s Switchgear (12), which should be within a predefined range, familiar to persons skilled in the art, continuously and for as long as the fuel is transferred. In this way, it is safeguarded that none of the independent ground triangles, i.e. the Ground Triangle of the fuel Tanks (1 1 ) and the Ground Triangle of the station’s Switchgear (12) have not been discontinued and that they remain correctly connected to the system.

In the proposed embodiment of the method, the permanently installed Insulating Device (3), which is made from a suitable insulating material, is interposed between the grounded Tank Vapour Recovery Hydraulic Network (15) and the Tank Vapour Return Valve (1 ). The Tank Vapour Return Valve (1 ), in a series with the Insulating Device (3), is the end of the Tank Vapour Recovery Hydraulic Network (15).

The Insulating Device (3) is manufactured from any insulating material familiar to persons skilled in the art, which can mechanically be processed, shaped, cut, etc., e.g. acetal plastic attached by thread or in any other way familiar to persons skilled in the art. The Tank Vapour Return Valve (1 ) is now permanently and galvanically isolated (ungrounded) from the rest of the Tank Vapour Recovery Hydraulic Network (15).

The Tank Vapour Return Valve (1 ) is equipped with a permanently fitted appropriate Proximity Switch (13) familiar to persons skilled in the art. The Proximity Switch (13) identifies the connection of the Vapour Recovery Rubber Hose (8) to the Tank Vapour Return Valve (1 ) and informs the Control Unit (4) through an electrical signal familiar to persons skilled in the art.

Ground the Tank Vehicle (6) in a way familiar to persons skilled in the art to the Ground Triangle of the fuel Tanks (11 ) by connecting the Petrol Station’s Ground Clamp (5).

The Control Unit (4) identifies the connection of the Petrol Station’s Ground Clamp (5) through an electrical signal familiar to persons skilled in the art, while, within a specified interval, the Vapour Recovery Rubber Hose (8) should be connected to the Tank Vehicle’s Vapour Collection Valve (7).

At first, the Vapour Recovery Rubber Hose (8) is connected to the Tank Vehicle’s Vapour Collection Valve (7) in a way familiar to persons skilled in the art.

Then, the Vapour Recovery Rubber Hose (8) is connected to the Tank Vapour Return Valve (1 ) and the Control Unit (4) identifies the correct connection of the Vapour Recovery Rubber Hose (8) to the Tank Vapour Return Valve (1 ), through an electrical signal familiar to persons skilled in the art from the Proximity Switch (13).

In the proposed embodiment of the method, the Proximity Switch (13) is used for maintaining the correct order of connections, while, in case it is bypassed or fails, the Control Unit (4) shall not activate the Pneumatic Filling Valve (9) and the fuel transfer process shall not be started.

The proposed order of connections of the Vapour Recovery Rubber Hose (8), which is continuously controlled by the Control Unit (4), safeguards its correct and secure connection, eliminates the release of hydrocarbons through the bleeding system of the tanks and the Tank Vapour Recovery Hydraulic Network (15) to the atmosphere from the unconnected end of the Vapour Recovery Rubber Hose (8), and removes any risks related to possibly released gases.

In the proposed method and following the correct and secure connections of the Petrol Station’ Ground Clamp (5) to the Vapour Recovery Rubber Hose (8), the Control Unit (4), through electronic devices familiar to persons skilled in the art, interrupts the grounding of the Tank Vapour Return Valve (1 ), which until then had been secured through the Equipotential Bonding Conductor (2), to the Ground Triangle of the fuel Tanks (1 1 ) and applies a voltage or any other electrical control signal familiar to persons skilled in the art, e.g. frequency, voltage, electric current, etc., to the Equipotential Bonding Conductor (2), in order to identify the electric potential of the Tank Vapour Return Valve (1 ) and, as a result, the electrical continuity of the Vapour Recovery Rubber Hose (8), the Tank Vehicle’s Vapour Collection Valve (7), the Tank Vehicle (6) and the Petrol Station’s Ground Clamp (5). In the proposed embodiment of the method, the voltage applied is 5VDC with 1 mA current limitation.

Throughout this period, the Tank Vapour Return Valve (1 ) is grounded to the Ground Triangle of the fuel Tanks (11 ) through the conductive continuity safeguarded by the Petrol Station’s Ground Clamp (5), the Tank Vehicle (6), the Tank Vehicle’s Vapour Collection Valve (7) and the Vapour Recovery Rubber Hose (8).

In case the voltage continuously applied and measured to the Equipotential Bonding Conductor (2) falls below the specified threshold of 2.5 VDC, the Control Unit (4) identifies the conductive continuity of the loop consisting of the Petrol Station’s Ground Clamp (5), the Tank Vehicle (6), the Tank Vehicle’s Vapour Collection Valve (7), the Vapour Recovery Rubber Hose (8), the Tank Vapour Return Valve (1 ) and the Equipotential Bonding Conductor (2) and activates the Pneumatic Filling Valve (9) and the fuel transfer process is started.

In case any part of the loop fails or the order of connections is wrong, the Control Unit (4) identifies that the voltage measured on the Equipotential Bonding Conductor (2) has risen above the threshold of 2.5 VDC, which means that it identifies the interruption of the conductive continuity of the loop that consists of the Petrol Station’s Ground Clamp (5), the Tank Vehicle (6), the Tank Vehicle’s Vapour Collection Valve (7), the Vapour Recovery Rubber Hose (8), the Tank Vapour Return Valve (1 ) and the Equipotential Bonding Conductor (2). Throughout this period, the Control Unit (4) deactivates the Pneumatic Filling Valve (9) and the fuel transfer process is interrupted or fails to start.

In this period, the grounding of the Tank Vapour Return Valve (1 ) is restored by the Equipotential Bonding Conductor (2) to the Ground Triangle of the fuel Tanks (1 1 ) and its electrical voltage is known to the Control Unit (4).

The Control Unit (4) continuously and uninterruptedly controls the voltage applied to the Equipotential Bonding Conductor (2) throughout the fuel transfer process.

The Pressure Sensor (14), which is familiar to persons skilled in the art, continuously informs the Control Unit (4) about the pressure value on the Tank Vapour Recovery Hydraulic Network (15), through an electrical signal familiar to persons skilled in the art.

The Control Unit (4) continuously and uninterruptedly controls the pressure and negative pressure values on the Tank Vapour Recovery Hydraulic Network (15), which, according to the safety regulations, should be within a specified range of pressure values so that no hydrocarbons can be released to the atmosphere through the Bleeding Network Safety Valves (10).

In case the pressure measured on the Tank Vapour Recovery Hydraulic Network (15) is outside the specified range of pressure values, the Control Unit (4) deactivates the Pneumatic Filling Valve (9) and the fuel transfer process is interrupted or fails to start.

In the proposed embodiment of the method, the Control Unit (4) uninterruptedly controls the electrical continuity of the loop that consists of the Petrol Station’s Ground Clamp (5), the Tank Vehicle (6), the Tank Vehicle’s Vapour Collection Valve (7), the Vapour Recovery Rubber Hose (8), the Tank Vapour Return Valve (1 ) and the Equipotential Bonding Conductor (2), thus securing that the specific Tank Vehicle (6) delivering fuel has been grounded and the control process cannot be bypassed (deceived) due to an error or negligence.

At the same time, it is safeguarded that the Petrol Station’s Ground Clamp (5) has not been connected to another vehicle or metal surface or that the Petrol Station’s Ground Clamp (5) has not been damaged by oxidization, dirt, etc., which could affect its electrical characteristics. It is also safeguarded that, in case the correct order of connections is not followed between the Petrol Station’s Ground Clamp (5) and the Vapour Recovery Rubber Hose (8), the Control Unit (4) shall not initiate the fuel transfer process. It is safeguarded that, in case the Petrol Station’s Ground Clamp (5) is removed from the Tank Vehicle (6), the Control Unit (4) deactivates the Pneumatic Filling Valve (9) and the fuel transfer process is interrupted or fails to start. It is safeguarded that, in any case the Vapour Recovery Rubber Hose (8) is removed from the Tank Vehicle’s Vapour Collection Valve (7) and the Tank Vapour Return Valve (1 ), the Control Unit (4) deactivates the Pneumatic Filling Valve (9) and the fuel transfer process is interrupted or fails to start.

The control of the electrical continuity-conductivity of the Vapour Recovery Rubber Hose (8) is secured in case it should be extended with the help of additional Vapour Recovery Rubber Hoses (8) between the two ends of the extended Vapour Recovery Rubber Hose (8).

In case of a possible interruption of the electrical continuity-conductivity of the extended Vapour Recovery Rubber Hose (8), or in case it is severed somewhere along the way, the Control Unit (4) deactivates the Pneumatic Filling Valve (9) and the fuel transfer process is interrupted or fails to start. For all the above-mentioned reasons, as per the proposed embodiment of the method, the Control Unit (4) is able to detect an error and react within an interval shorter than 100 msec, which is considered negligible.