As a CP Engineer I would say it may be possible to carry out non-invasive surveys to establish the coating integrity. However, much information would be needed to make an informed decision on the best way forward. I am assuming the CP is an Impressed Current system and also protects the...
Hi zjam,
In order to calculate the number of rectifiers and groundbeds required for an underground pipe installations there is much information required before the calculations can be done. This information would include where is the pipe going to be installed (I.E. desert, temperate, coastal...
Ceasar,
DCVG is not normally done on sacrificial systems, the reason being is for a DCVG to be meaningful it is required to achieve a swing between the on potential (energised) and the off potential (polarised) in excess of 300mVDC (see NACE and ICORR specs). This is rarely achievable with a...
Ceasar, before making any sweeping comments, it would be useful to know what is being transported within the pipe, at what pressure and in which country the installation is being done.
Having seen the above information with regards to soil resistivity and cement coating it puts a whole new complextion on the issue. 1100 Ohm.cm or 11 Ohm.m is higher than is normally accepted as suitable for sacrificial anodes, consult NACE and ICORR standards as both recommend sacrificial anode...
As a CP engineer there are some documents that can give you guidance for test post distance I.E. BS EN 12954. However, as a general rule your list is quite comprehensive with the exception of 1000 feet, I would suggest 1000 meters is more normal.
It would be of great interest to know what type...
Hi IFixCameras,
Before coming over to the dark side of corrosion and cathodic protection engineering, I was a toolmaker, so I am very well versed with threads and how to repair them. I can't really give you much insight into the cause of not being able refit the threaded components, as this...
cap1a79,
I don't have any standards or case studies to hand on internal current drain through electrolyte past isolation. This is an experience thing with me as I only undertake field work on Cathodic Protection. However, I will ask a few of my contacts that are senior technologists with Nace...
Jela 123,
Both Insulated flanges and monoblock Isolation Joint, achieve exactly the same results in electrically isolating the sections of pipe. Without other influencing factor as in my previous post I can see no technical justification for the use of the much more expensive monblock system.
cap1a79,
I totally agree external CP systems do not effect the internal; structure of a pipeline as it is a seperate electrolyte and the normal requirments for a corrosion cell are not met. However an electrlitic substance within the pipe does have an effect on the amount of CP current...
Hi Jela123,
You don't mention what the pipes are carrying but I will try to help.
Firstly Insulated Flanges and Isolation joint have many applications, primarily to seperate pipework with active CP system and pipework without CP system. However, they can be used purly to prevent or reduce...
There are pro's and con's for the use of either type of fastner. As these are structures, where the aluminium is vastly larger than the fastners both in mass and surface area it could be argued that the aluminium structure should be anodic to the fastners, then any galvanic corrosion occurs on...
Yes Galvanic corrosion requires an electrolyte. You say the item is at 50-55 degrees centigrade, is this a constant temperature? What is the relative humidity and relative air temperature? Is the carbon steel coated? Is the bolt packed with grease?
It is wrong to think a structure in the...
Hydrogen is not a product produced that is normally associated with an anode, as hydrogen generation is normally associated with the protected structure (cathode). The Anode is more associated with the production of oxygen and oxides. In high current CP applications it is also possible to...
