The invention relates to a method for automatic disconnection of fuel supply, in particular of gas supply to a consumer at the moment of stopping the consumer, said supply being controlled by at least one cylinder valve being influenced by the pressure in a pilot line. Furthermore, the invention also relates to a system for automatic disconnection of fuel supply, in particular of gas supply, to a consumer at the moment of stopping the consumer, which system comprises one or more fuel cylinders in fuel connection with the consumer by a supply line having at least one cylinder valve, said cylinder valve or valves being activated by a pilot line.
In the field of fuel supply of consumers, such as combustion engines, there are rules for how to handle the fuel from the tank or cylinders up to the engine. Similar rules exist also with respect to other fields of fuel and gas handling. E.g. in plants for unloading or discharging of gas cylinders there are safety rules for how to connect the pipes and valves.
Specially in the field of the increasingly used systems for driving of motor vehicles and other systems where high pressures or large stocks of gas are involved, the authorities have issued regulations with respect to system design and handling. Thus, there are rules for safety systems necessary against pipe ruptures or excessive gas flows. Certain problems arise with equipment used in gas systems since the gas has varying density att different pressures.
Some of those problems mentioned have found their solution by the safety device described in US-A-6.044.863 of the same inventor. By such a device one has secured a prompt closing of the system in the event of rapture or excessive gas flows in the system.
A certain demand unsolved by systems known per se is that all the valves in the system have to be closed when the consumer is shut down.
The problems present for solving of such a demand have been overcome by a method as claimed in Claim 1 and by a system as claimed by Claim 3.
Thus, the pressure of the pilot line activating the valves in the system has to be lowered but the fuel or gas supply line must not be emptied due to the fact that a restart of the consumer is to be done in a smooth way, i.e. pressure shocks have to be eliminated in the system. If a restart is made with an empty supply line the risks are very high for having a pressure shock in the system resulting in more or less damages of the system.
Particularly advantageous embodiments have the features defined by the subclaims.
The invention will now be described in more detail with reference to the accompanying drawings, in which
In Fig. 1 a general arrangement of a multipel cylinder system is shown involving the method of automatic disconnection of the fuel supply to a consumer M according to the present invention. The system comprises a number of fuel tanks, in the present case in form of gas cylinders 1.
The gas cylinders 1 are arranged in blocks B of two or more cylinders each. A charging unit 2 is in communication with the gas cylinders 1 through an inlet line 3 having a branch line 3' for each gas cylinder 1. To each one of said gas cylinders 1 there is a cylinder valve 4 controlling the gas supply to the gas cylinder 1 when charged and from the gas cylinder 1 when used as a supply source for driving of the consumer M. The cylinder valve 4 may be either a manually activated or a solenoid activated valve with respect to starting up the system, but for closing the gas supply it is controlled by a pilot line 11.
Each one of the gas cylinders 1 is in communication with thermal relief outputs 5.
In the preferred embodiment of the present invention a section of the inlet line 3 is used also as a feed line 6 to the consumer M. Said feed line 6 involves a supply unit 7 having a manual stop valve 8, a fine filter 9, and a solenoid valve 10.
At the output end of the supply unit 7 a pilot line 11 is branched off downstream the valve 10. The gas pressure in the pilot line 11 is used for automatic control of the cylinder valves 4 in such a way that the cylinder valves 4 close the gas supply when the pressure of the pilot line 11 drops beyond a predetermined low threshold level.
For service reasons the system arrangement involves manual valves 12 and 13. The manual valve 12 being used for evacuation of the fuel tanks or gas cylinders 1, and the manual valve 13 being used for interruption of the automatic control of the cylinder valves 4.
The preferred embodiment of the system according to the present invention has a method of working as is shown in Fig. 2, which is self-explanatory. However, it is to be observed that the left hand side of Fig. 2 refers to the starting procedure of the consumer M and the right hand side thereof is the time schedule for automatic disconnection procedure of the gas (fuel) supply to the consumer M.
Thus, in the case of stopping the consumer M a stop activation is started, e.g. by pressing of an electric switch 14 (Fig. 3) in a control circuit for the gas (fuel) supply to the consumer M. By pressing the switch 14 the supply valve 10 is managed to its closed position by a solenoid 10' belonging thereto. Simultaneously a timer (I) is started for a delayed activation of a switch 15 controlling, e.g. the electric feeding of the consumer M.
By closing of the supply valve 10 the pressure in the pilot line 11, branched off from the output of the supply unit 7, starts sinking due to the fact that the consumer M still is working and consumes the gas in the pilot line 11. When passing a predetermined low pressure level in the pilot line 11 the cylinder valves 4 are closed.
Due to the fact that the timer (I) imply a delayed action of the consumer control switch 15, the consumer M is still activated for a time enough to consume the rest of the gas (fuel) in the pilot line 11 after the cylinder valves 4 are closed. When the timer (I) has run out the consumer M is shut down and is ready for a new start.
Starting of the consumer M involves another activation of the switch 14 to its start position, which gives the immediate result of opening of the supply valve 10 and of activation of a further timer (II) rendering an "on" function of a pilot valve 16.
The pilot valve 16 has taken the form of a by-pass pipe and a needle valve inside the cylinder valve 4 (being described in more detail in the US document mentioned above, e.g. with reference to Fig. 4 thereof). The pilot valve 16 is only working for a few seconds during the start up of the system to put the pilot line 11 under pressure for opening of the cylinder valve 4. Thus, when activating the pilot valve 16 the pressure in the pilot line 11 is raising, which means opening of the cylinder valves 4. The further timer (II) returns to its off position after a predetermined time resulting in closing of the pilot valve 16. However, since the pressure in the feed line 6 by now has obtained working level the consumer M is operating and the cylinder valve 4 remains open.
The description given above refers to a consumer M in form of a combustion engine driven by natural or bio gas. However, the very same method and system according to the invention may be applied also to other fuel or liquid or gas handling devices. Thus, the consumer M can be in form of a fuel cell, a plant for unloading or discharging of fuel tanks or gas cylinders transported by trucks or trains or being of an unmovable construction.
The feed or supply valve mentioned as a solenoid one may also take the shape of another type, such as e.g. a hydraulic or pneumatic valve function of two or three way type.
The different solenoids and timers described in connection with Fig. 3 above may be driven by one or more voltages U1 - U4.
Although an preferred embodiment of the invention has been given by way of illustration, it will be understood that the invention may be carried out with many variations, modifications and adaptions, such as hereinbefore mentioned or within the understanding and ability of skilled persons, without departing from its spirit or exceeding the scope of the claims.