Data transmission in pipeline systems

A method of data transmission in which metallic structure of a pipeline system is used as a signal channel and earth is used as return of comprising the steps of:

• arranging a current loop path for use in applying signals to the signal channel and earth return circuit, the loop having first and second conducting portions electrically connected to one another at a first location and electrically connected to one another at a second location, the second location being spaced from the first location, and the metallic structure comprising at least one of the conducting portions;
• applying a signal to one of the conduction portions using an inductive coupling arrangement disposed around the respective conducting portion to generate a potential difference between earth and the metallic structure in the region of the loop and cause a signal to be propagated along the signal channel provided by the metallic structure away from the loop;
• and
• ensuring that the spaced locations are separated by at least a minimum distance selected to give desired transmission characteristics.

A data transmission system for use in pipeline systems which transmission system comprises:

• apparatus for forming a current loop path comprising a portion of an inner conductive member and a corresponding portion of an outer conductive member electrically connected to one another at two spaced locations, the outer conductive member surrounding the inner conductive member and being part of the metallic structure of a pipeline system;
• an internal unit disposed within the outer member and having a transmitter for injecting a signal into the loop;
• and
• an external unit disposed outside the outer member and comprising an inductive coupling arrangement arranged to be linked by flux generated by current in the loop, the arrangement being such that in use the current flowing in said portion of the inner member does not match the current flowing in the corresponding portion of the outer member whereby signals are generated in the inductive coupling arrangement so allowing communication from the internal unit to the external unit.

A method of data transmission for use in pipeline systems which method comprises the steps of:

• forming a current loop path comprising a portion of an inner conductive member and a corresponding portion of an outer conductive member electrically connected to one another at two spaced locations, the outer conductive member surrounding the inner conductive member and being part of the metallic structure of a pipeline system;
• injecting a signal into the loop form an internal unit disposed within the outer member;
• and
• disposing an external unit outside the outer member which unit comprises an inductive coupling arrangement arranged to be linked by flux generated by current flowing the loop,
• and the arrangement being such that the current flowing in said portion of the inner member does not match the current flowing in the corresponding portion of the outer member whereby signals are generated in the inductive coupling arrangement so allowing communication from the internal unit to the external unit.

A method of data transmission in which metallic structure of a pipeline system is used as a signal channel and earth is used as return comprising the steps of:

• arranging a signal coupling loop having first and second conducting portions electrically connected to one another at spaced locations, the metallic structure comprising the first conducting portion, and a portion of an elongate deploying member which is arranged to move within and relative to a surrounding portion of metallic structure comprising the second conducting portion;
• applying a signal to one of the conducting portions to generate a potential difference between earth and the metallic structure in the region of the loop and cause a signal to be propagated along the metallic structure away from the loop;
• and
• ensuring that the spaced locations are separated by at least a minimum distance selected to give desired transmission characteristic.