FBE Tail protruding from 3L-PP anticorrosion coating on pipes

[bafometto81]

Hi guys,

I'm working as coating engineer and I have a question regarding the FBE tail protruding from a 3L-PP or 3L-PE anticorrosion coating on pipes.
In my opinion any residual FBE at the cutback area should be avoided as it could be detrimental for field joint coating and AUT operations...

Nevertheless I hear many people asking for a minimum 10 mm tail for example.

What's your opinion on that?

Regards,

NB

 

[BigInch]

The PE is there only for mechanical protection. The tail is because you don't want to have a possibility of a direct line of attack straight to the pipe, as you might have if it was cut flush and coating placed up against both FBE and PE edges in the same plane. Its more important to insure the quality of bonding of the joint coating to the FBE. Its not nearly so important to have mechanical protection. That's mainly for the long pipe length between joints. What joint coating system are you using?

"I think it would be a good idea."
- Mahatma Gandhi (1869-1948),
when asked about Western civilization

 

[bafometto81]

I'm using a heat shrinkable sleeve polypropylene based (the factory applied coating is polypropylene).
I agree that the main point is to ensure a proper bonding between the FBE and the PP, but I don't see how the tail could help that. when we preheat the pipe with induction coils in order to apply the HSS we pass the Tg of the FBE so we destroy the tail which in fact will be just residual FBE, not a proper protective tail. Furthermore during the blasting of the field joint area this tail can be damaged and again we will have just a damaged coating, not at all protective.
So it seems to me that this tail will not serve as a protective coating but will result just in a residual FBE wich in my opinion could cause some problems during the AUT test being seen as a defect.

NB

 

[BigInch]

You need a bigger overall cutback. You should be making enough of a cutback so that no part of any coating is damaged by the act of preparation for, or during the actual joining the pipe.

"I think it would be a good idea."
- Mahatma Gandhi (1869-1948),
when asked about Western civilization

 

[bafometto81]

ok, cheers for your help.

NB

 

[GregLamberson]

bafometto81

One caution, make sure your cutback corresponds to the width of your shrink sleeves.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[bafometto81]

Greg,

I do usually consider for the width of the sleeve 50 mm minimum (after shrinkage of the sleeve)overlap on the factory applied coating.

Cheers,

NB