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Bracelet Anode Length 2

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ek4putr4

ek4putr4

Mechanical
Joined
May 2, 2008
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43
Location
MY
Hi,

Is there any limitation or minimum length of Half bracelet Anode?

FYI, we have one calculation that shows 180 mm of the anode length. The thickness of the anode (Aluminium Alloy) is 55 mm for 24" pipeline OD + 5.5 mm AE coating.
 
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Sounds pretty short. What spacing?

Did you assume any holes in the coating?


**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)
 
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The spacing is one anode every 9 joints. No holes in the coating, only coating breakdown factor.
 
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Seems very very light weight.
If its not fresh water, something's wrong. Can you post your calcs?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)
 
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It was done by our consultant using their inhouse software. Pls see the attachment.
 
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Guess I was thinking of a 36". I compared the mean current density values to DNV and it looks OK.

The DNV spec is here. Have a look yourself.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)
 
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Tx big inch
Now back to my question, is 180 mm for the anode length too short? Will it become problem during fabrication? The CPR is well below 5.
 
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It might be a bit short versus anode suppliers' standard anode sizes for 24-inch pipe. Try getting the designer to reiterate the design to fit your nominated supplier's standard half shell length if possible. It's only a short line and there is scope for optimisation of the design dependent upon what standard you use. For example, ISO 15589-2 will give you a lower coating breakdown factor. Conversely, it wouldn't allow the optimistic anode capacity at 40 deg C either. If you can buy standard, even if it's more alloy than you need, it may still work out cheaper. Try asking anode suppliers.

Steve Jones
Materials & Corrosion Engineer
 
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Actually the total pipeline length is about 50 km, only the first 2 km have spacing every 7 joints, the remaining spacing is every 10 joints with the same anode length. I think this spacing is already maximum, or is it possible to make the spacing become every 15 or 20 joints to make the anode dimension longer?
 
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ek4putr4,

PLEASE READ the DNV code I gave you.,
SEE section 5.4.1, 5.6.1, 5.6.9

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)
 
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The answer should be in the applicable CP design standard! Anode spacing can be verified by an attenuation calculation. Take your pipeline design and the CP design standard and work through it. It's not so difficult.

Steve Jones
Materials & Corrosion Engineer
 
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Thanks Big Inch, actually our CP spec is still based on DNV RP B401 1993, and not yet using DNV RP F103. Quite old you know, but our Principal Eng still prefer this one, don't know why. Based on our spec also, the spacing is limited to 10 joints max, thats why we got such short anode.

I think I'll just give excess mass to the anode to get the minimum length that can be fabricated.
 
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Maybe he doesn't know there is a new one.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)
 
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He surely know that new practice exist, but still resist to change his mind.
 
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hope you mean like, "in the sand", rather than someplace dark and dirty.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)
 
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Contact the manufacturer for his tolerances, CP Tech & Alico will produce with a minimum of 300mm for bracelet anodes.

The insert dimension and the anode thickness will govern the minimum length of anode with due consideration for shrinkage and cracking.

If you are using DnV RP F103, you can actually increase the spacing more than 120mts [old requirement in RPB401].


Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit
 
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