CP Interference Testing Scope and Criteria in Queensland

In Queensland, A registrable system is an impressed current cathodic protection system the converter of which is capable of delivering a current greater than 0.25A. However, a CP system, whether is registrable or non registrable, is required for initial start-up testing according to Queensland Electrical Safety Regulation 2013. Any ICCP system and SACP with total anode mass greater than 25 Kg will need further interference testing while anode is replaced.

Testing scope and criteria

  • Interference testing on all foreign structures,
  • Not greater than 3V/m voltage gradient in water or marine environment if anode is immersed in water or a marine environment,
  • Less than 100A total current in a 17.85m radius (surface area of 1000m2) with anode buried onshore or in nonsaline water,
  • Less than 500A total current for off shore,
  • -150 mV in 100m radially from an anode, -750 mV is allowed for short term testing
  • 10mV In soil resistivity greater than 1 Ω∙m from a buried structure, 50 mV is allowed for short term testing
  • 0 mV in soil resistivity less than 1 Ω∙m from a buried structure,
  • -500mV or up to -1000 mV with written agreement for non CP protected structure.

I do have the difficulty to understand the logic of interference test with sacrificial anode cathodic protection system, typically for the threshold of 25 kg  total anode mass. The nominal mass of common type of magnesium anode M54C is 12.5 Kg. Any pipeline with more than 2 such anode attached deems to be interference tested. However, the current output for SACP is very low, say, in 100~200 mA range. Therefore, the interference risk is very low and testing is meaningless and fully waste of time and resource.

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