Pipeline mapping and interrupter therefor

• US 6,954,071 B2
• Filed: 07/01/2003
• Issued: 10/11/2005
• Est. Priority Date: 03/24/2000
• Status: Expired due to Term

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Flatt, David William, Worsely, Robert Ashworth, Petherick, Stephen John
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US10/609,504
• Publication Number:
  US 20040004479A1
• Time in Patent Office: 833 Days
• Field of Search: 324/326, 324/329, 324/220, 324/425, 324/72, 324/713, 324/263, 324/71.2, 324/551, 324/559, 702/64, 702/34, 702/33
• US Class Current: 324/326
• CPC Class Codes: C23F 13/04 Controlling or regulating desired parameters
• CPC Class Codes: G01N 17/02 Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement

Abstract

Cathodic protection voltages are used to resist the damage to pipes or cables from electrolytic effects. However, localized fields can lead to stray currents and may result in corrosion and it is therefore desirable to detect and analyse those stray currents. Frequently there are several pipes in the area of interest and so it is necessary to distinguish between those pipes. Therefore the cathodic voltage on the pipes is modulated, with different pipes having different modulations. This modulation may be applied using an interrupter. Orthogonal modulations with non-unitary aspect ratios improve the discrimination between the pipes while maximizing the energy content of the modulation pattern. The analysis is improved when the interrupters are synchronized with each other and so repeating on the same time-base. This synchronization may be achieved using an external time signal such as GPS. An interrupter which can be used in this regard is also proposed, and may be powered from the cathodic voltage itself.

Claims

1. An interrupter for controlling the negative protection voltage applied to an underground pipe or cable, the interrupter comprising:

a switch for controlling said protection voltage;

means for storing a predetermined fixed prior time;

means for storing a predetermined modulation cycle, the predetermined modulation cycle having its origin at the fixed prior time;

timing means for determining the time elapsed between said fixed prior time and the current time;

means for determining the location within said modulation cycle at the current time;

means for setting a signal to a value corresponding to the determined location with said modulation cycle, and subsequently modulating said signal according to said modulation cycle; and

control means for controlling said switch and modulating said negative protection voltage according to said modulated signal.

2. An interrupter according to claim 1, wherein said timing means comprises a GPS receiver.