Effects of applying epoxi paint to a flanged piping joint 2

[engdrve]

In order to avoid corrosion is it possible to apply epoxi paint to the contacting faces of a water line FF flanged joint?. Will it has effects on the short or long term?.

 

[vpl]

yes and yes

Patricia Lougheed

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[FACS]

The thing about Epoxy paint, is that it chips. Compressing the paint on a flange will probably chip or crack it.

You can use a lead free galvanizing, which also has limited protection.

You can use a heavy NSF Grade grease, it also has limited protection.

Cathodic system is another option.

Stainless Steel is your best defense.

Charlie

http://www.facsco.com

 

[rconner]

Just a couple observations and opinions. I believe e.g. at least AWWA standards for many decades have required a (I think normally quite thin) "rust preventive" coating on machined faces of flanges, that can additionally be removed by the contractor if desired. While I was not around when this practice/these specifications started decades ago, I suspect this is due to the fact that this system essentially works, and of course this surface is eventually/virtually covered in most assemblies by a highly compressed/sealed rubber gasket. In fact, I have personally seen some presumeably experienced contractors wire brushing, or even power wire brushing, coating on flange faces on large projects (as perhaps they have found this maximizes the cleanliness/performance/consistency of such labor-reliant, critical bolted assemblies?)
Based on this history/practice at least for normal water applications, unless it comes as a feature of the coating/lining system of a new standardized product (e.g. fusion-bonded epoxy coated valves etc.), as another has stated it may not be the best idea to put heavier (and inevitably some more variable thickness?) coatings on flange faces.

 

[Ashereng]

There have been a recent introduction of HDPE pipe into our market here. I suppose that they can have SS flanges, but I think carbon steel is still fairly common.

Is your pipe CS. If it is, I don't think the rust contribution of the flange would be a significant portion. Or, are you concerned about leaks?

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Albert Einstein
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[11echo]

OK ...I have to ask, WHY would you want to "paint" the face of a flange to prevent corrosion? I've broken apart a number of flanged joints, and the ONLY time I've seen corrosion on the face is where the flange was leaking because of poor maintenance - not routinely re-torqued ...and if your dealing with a Flat Face flange it's probably cast iron, so alittle corrosion on a water line is no big deal. Exactly what are you trying to do?

 

[engdrve]

I am sorry guys,
it is cs. water piping line, 8" Dia. at 150 psi, aprox. 3000 m long.
it was also a proposal from the sucontractor in order to avoid corrosion on the faces of the fanges. because he wants to start to fabricate and paint the piping spools well ahead of the instalation time. But I was concerned if it could cause leakage effects later on during operation.
Sorry again for my englis grammar, but english is not my first language. But your comments are valuable.

 

[FACS]

When I worked in the Water Well industry; we coated all non protected steel surfaces with a heavy grease. It is very thick grease and has to be heated and applied with a paint brush. When it cools... it is like a soft wax and does not come off the part without heating and scraping it off.

This was mainly to prevent corrosion during storage and shipment.

We used it on spool surfaces because the Oring always needs to be lubricated, and it will stay on for 10-years, longer underground if not disrurbed.

Charlie

http://www.facsco.com

 

[joeswoes]

You always can dodge the problem totally and use composite flanges

 

[TangoCleveland]

Cosmoline

Larry

 

[rconner]

Seeing where this thread has gone I would like to voice one more, perhaps somewhat cautionary, observation/opinion. While not intending to counter any advice previously given, nor to start a grand debate on the issue, you may wish to check with the designer/manufacturer(s) of the specific flanged items involved, including sealing gasket, to see whether they feel flanged joint "lubrication" is a good idea. Of course it would appear the pressure peformance of simple flat-face flanges without o-ring grooves and e.g. simple flat or other rubber flanged gaskets used with same e.g. must be dependent on the rubber staying between same. It would appear in these particular cases this is basically by virtue of the friction developed between the surfaces in the bolting assembly process. It would also appear this friction, and therefore perhaps also at least very high pressure retention, of at least those sorts of gaskets/joints, might in theory be reduced due by the use of effective "lubrication". In other words, perhaps some unlike many other pipe joints where lubrication is undeniably invaluable for optimum perormance, lubrication could theoretically hasten "blow-out" of gaskets in some flanged joints (perhaps particularly with undependable bolting forces and/or very high pressures).