Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1985-07-24
1987-09-01
Rowland, James L.
Communications: electrical
Condition responsive indicating system
Specific condition
361215, 361217, G08B 2100, H02H 1100, B67D 532, H05F 300
Patent
active
046911987
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a control system for diverting and equalizing electrical potentials between two objects, for example the shell of a storage tank installation and the body of a tank truck/vessel, when loading flammable/explosive fluids, of the type recited in the preamble of the appurtenant, independent claim 1.
When loading a tank truck with explosive substances, the explosives control board in Norway requires, inter alia, that the main switch in the truck's electrical system must be in the "off" position, and that eletrical connection must be established between the body of the tank truck and the shell of the storage tank.
Many systems are currently in use for establishing eletrical connection of the above type, but they all lack a means for controlling that electrical connection actually has been established with the tank truck. Moreover, there is always a possibility that a busy driver could begin the loading process by starting the storage tank's fluid pump without first having switched off the truck's electrical system, thus endangering his own and his colleagues' safety. It is up to the driver to remember to turn off the main switch for the truck's electrical system.
On their inspection rounds, the explosives control authority have withdrawn the driver's licenses of tank truck drivers who have failed to observe the regulations.
In the modern systems a "crocodile"-type clamps or similar type arrangements are usually used to establish an electrical connection with the tank-truck or a delivery tank of transporting means. If the driver forgets to break the connection by removing the crocodile clamp when he has finished loading, no catastrophe results, because the contacts on the crocodile clamp will be torn loose when the truck drives away. Prior art systems can be delivered with electronic control of the truck's connection to the storage tank's "rack connection", but it is not known on the systems currently in use in Norway to provide a similar safeguard at the other end of the cable that establishes the electrical connection for equalizing electrical potentials.
However, U.S. Pat. No. 3,290,668 discloses a grounding and indicator means for checking that adequate connection has been established with the tank truck by means of a clamp with electrically insulated clamping members which are attached, e.g., to a flange or screw on the tank truck body. The two halves of the clamping means are connected to a control circuit comprising a voltage source, a resistor and an indicator which shows that current is flowing in the circuit when the clamp has been satisfactorily connected to the tank truck. This control circuit is connected to ground, but the circuit has no means for simultaneously controlling that grounding has actually been established. Said indicator will flash a green light and actuate or energize relays for starting the fluid pump when the connection is found to be in order, and will flash a red light and stop the pump if the connection has not been made and no current is flowing through the control circuit.
The object of the present invention is to provide a control system for diverting/equalizing electrical potentials between two objects, for example a tank truck and a storage tank, wherein the electrical equalizer connection is continuously monitored, and which is adapted to ensure that the tank truck's electrical system will automatically fail to receive electrical current when said electrical equalizer connection has been established.
This will make it impossible for a tank truck driver, perhaps through forgetfulness or carelessness, to place himself or his colleagues in danger during the loading of explosive substances.
The control system also includes fault indicator means which issue a warning if a plug connector is short-circuited or the contact is poor.
Since the current flowing through the electrical system of the tank truck is automatically cut off when the electrical equalizing connection is established, the truck cannot be started during the loading operation. The ele
REFERENCES:
patent: 1524423 (1925-01-01), Chapman
patent: 1564855 (1925-12-01), Jurs
patent: 4220951 (1980-09-01), Bash et al.
Myer Daniel
Rowland James L.
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