The need for cathodic protection test stations? 2

[kacarrol]

Good afternoon,

I am working on a project that involves a buried water main. We will be installing magnesium anodes to protect the pipe.

Since this is a new subject for me I've been doing a lot of reading but the one thing I'm having difficulties with is the test stations. I have loads of information on how to install one but I can't find anything on how to determine when and where you need them.

Any help would be appreciated.

Regards,
K

 

[SJones]

Peabody's Control Of Pipeline Corrosion. The best person to tell you where you need test stations is an experienced CP designer who will use the pre-construction survey data, alignment sheets and knowledge of what the CP technicians will need for operational data gathering in allocating test post locations.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[brimmer]

Here are some best practice guidelines I use for placement of test posts. Generally spacing 1-2 miles as a rule of thumb in oil and gas transmission. It really depends how much monitoring you want to do. Place them at easy access locations such as road crossing etc. makes it easier to monitor in the future. I don't know how your anodes are spaced, but it is a good idea to put a post at an anode, that way it can help determine when your anodes are depleted, though if you have very short spacing it wouldn't be practical to put one at every anode.

Pipe casing installations
Foreign metallic structure crossings and tie-ins
Isolation joints
Waterway crossings
Bridge crossings
Valve, regulating and meter stations
Galvanic anode installations
Road and railroad crossings
Transitions between steel piping and non-metallic piping
At regular intervals (such as 2 km) or as required.
Isolated sections of metallic piping that do not come above ground at any point.

 

[SJones]

Might need a test post at every anode with magnesium to have a resistor control capability. Nevertheless, it demonstrates that a CP design shouldn't be undertaken by the inexperienced.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[kacarrol]

Thanks for the book reference. I'll see if I can dig up a copy around here. We have a big library but it's hard to navigate without a book title.

There is an experienced corrosion engineer who will be checking over all the documents when I'm done, but he's away on vacation this week. I like to do my own reading also, expedites the learning process.

Regards,
K

 

[kacarrol]

PS and thanks for the rules of thumb!

 

[HenryBiose]

CP test station location is design process, Normally for a sacrificial anode system for onshore. the test station is located for every anode location(say 1km) based on you design philosophy and need for monitoring.For Impressed Current, the conservative standard for Potential Test Post is usually every 1km.

But at Crossing and Insulating Joint there is need for a Test Post.The design for each test post varies.Please note

 

[LGS51]

Ms Carroll, you did not say if this water line will be coated, bare, what type of joint connection. Depending on the construction of the water line, you will have to design the CP Mg instatllation according to the pipeline. What is the soil resistance in the pipeline ROW? This will determine the Size Mg anode/anodes that you will need to install. Then depending on the coating and the current output from each installation of Mg, you can see how far the current will travel, this will depend on the coating Job of the pipeline. There are so many variables in this type of work, it is very difficult to pre-design a galvanic system. You need to do a lot of field work to get as much information as you can.