Data transfer

Details Data transfer Data transfer

1994-12-13

1996-12-24

Hofsass, Jeffery

Communications: electrical

Continuously variable indicating

Combined

3408544, 166 651, G08B 1900, G08B 2100

Patent

active

055877079

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

This invention relates to a pipeline system comprising a metal pipeline having a coating of insulating material which, in conjuction with sacrificial anodes electrically connected to the pipe, provides cathodic protection, there being signal generating means adapted to he coupled to the pipeline and operable when so coupled to apply data to be transmitted in signal from to the pipeline for conveying along an electrically conducting channel formed by the metal pipeline.
U.S. Pat. No. 3,129,394 discloses the use of a pipeline to transmit alternating current signals. The pipeline is not used as a wire or conductor as such. It is used as the inner conductor of a coaxial cable. The insulating wrapping (provided for corrosion protection) provides the dielectric and the ground surrounding the pipe acts as the other conductor. By employing the pipe and ground as a co-axial cable, attenuation is substantially reduced and useful signals can be transmitted over substantial distances by amplification of the signal at one or more intermediate stations. Due to dissipation by leaks in the pipe wrapping, and other reasons, for most of the frequency ranges taught it was considered necessary to use higher output power than most communication systems. There is a fear that that will be undesirable because it will interfere with the normal direct current cathodic protection of the pipeline. However the possibility of using signals in the audio range is hinted at. It is said that the use of the pipe and surrounding earth as an alternating current transmission means will not interfere with the normal direct current cathodic protection of the pipeline but there is no disclosure of how this was achieved.
U.S. Pat. No. 3,551,890 discloses a system wherein a metal pipeline forms an electrically conducting channel for transmission of data, there being signal generating means adapted to be coupled to the pipeline and operable when so coupled to apply data to be transmitted in a signal form to the pipeline for conveying along the channel. In carrying out the teachings of that reference data is transmitted by modulating either the amplitude or the frequency of an AC carrier signal. We have found that no useful signal could be detected at the end of a pipeline which was 4 km long using such a technique. In practice it is desirable to transmit data over considerably greater distances than that in such pipeline installations.
An object of this invention is to provide a pipeline system with means for transmitting data over considerably greater distances without interference with the cathodic protection of the pipeline.
According to this invention there is provided a pipeline system comprising a metal pipeline having a coating of insulating material which, in conjunction with sacrificial anodes electrically connected to the pipe, provides cathodic protection, there being signal generating means adapted to be coupled to the pipeline and operable when so coupled to apply data to be transmitted in signal form to the pipeline for conveying along an electrically conducting channel, formed by the metal pipeline, wherein the signal generating means are operable to generate as the signal a pulsed electro-magnetic signal which comprises changes of voltage level in a very low frequency range (VLF and below), and wherein means are provided which are operable to use data transmitted via the channel provided by the pipeline to monitor the condition of the insulation of the pipeline. Preferably the signal generating means are operable to generate the electro-magnetic signal in the very low frequency range (VLF and below) so that it comprises changes of voltage level oscillating about the DC voltage level of the pipeline so that the mean level of the signal is substantially the DC voltage level of the pipeline. The longer the pipeline that forms the channel the lower the frequency that would be used. For the longer pipelines frequencies in the extremely low frequency (ELF) range (3 to 300 HZ) would be used whereas for short pipelines frequenci

REFERENCES:
patent: 3129394 (1964-04-01), Long
patent: 3551890 (1970-12-01), Silverman
patent: 3732534 (1973-05-01), Koomey et al.
patent: 3750096 (1973-07-01), Koomey et al.
patent: 4800385 (1989-01-01), Yamazaki
patent: 4901069 (1990-02-01), Veneruso
patent: 5256844 (1993-10-01), Grosvik et al.
patent: 5335730 (1994-08-01), Cotham, III
Combination of Corrosion-Survey Methods Improves Protection-M. D. Allen & N. R. Barnes-Oil & Gas Journal Feb. 29, 1988 pp. 59-64.

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