Painting of Flange Faces

[yasernoman]

I know this topic has been address in several forums, but none of the answers helped me too much.

I have a vessel that requires internal painting/coating. The senior engineer on the project insists that flange faces must be painted as well. Spiral wound gaskets have been specified for this vessel, with an option to use Grafoil gaskets. Vessel operates at 1000 kPa(g) and 150C.

1) Is there any document, guideline, code, standard, or specification that will clearly state whether painting on flange faces is permitted, not permitted, or subject to agreement between manufacturer and client?

2) Has anyone here had experiences with painted flange faces that were successfully operated with no leakage issues in the oil field / refinery environment?

3) Has anyone had any other experiences with this issue.

Your response is very much appreciated. Thanks in advance.

 

[unclesyd]

The only time I've seen paint on flanges when they were shipped in with the black mill coating or a wax based coating. These coatings were always removed prior to installation. Some times when pipe spool was primed or painted there could be paint on the flange face but not on the raised face.
Be real careful with spiral wound gaskets as anything that will form a radial path across the spirals can cause a leak.
A case in point was we had a leak on a 24" manway several hours after installation and the spiral wound gasket was replaced and within hours we had another leak. I was called in at 2:00 in the morning to assist in resolving the problem. They had thrown the first gasket away, but it was quite obvious what was causing the problem. The mechanics had used some 1" wide tape to hold the gasket while they maneuvered the flange into position. The tape had burnt leaving a very small indention, path, across the spirals.
No more taping spiral wound gaskets gskets.

 

[moltenmetal]

If the service conditions are 150 C, I fail to see what the paint will be doing. Even a solid teflon lining is reaching its limits of mechanical durability at around 150 C.

A tank with an internal lining for corrosion resistance, if properly specified, will have all its flange faces and the ID of all nozzle necks coated. However, it will NOT use spiral-wound gaskets! A gasket compatible with the process and whcih will not damage the lining is selected, and what type that will be depends on the type of lining, temperature and pressure etc.

There are numerous other requirements of design and fabrication for internal lining beyond merely coating the flange faces, and these vary by service and type of lining material used.

 

[gr2vessels]

The Australian standard AS 4458 - Pressure Equipment;- Manufacture says:

21.3.2 Protection of threaded components and machined surfaces;- Threaded components and machined surfaces shall be protected against corrosion and damage in transit and during pre-erection storage.
21.3.3 Protection of flanges;- Before despatch, flange faces should be protected against damage. Raised and similar sealing faces should be fitted with protectors, which should be removed only immediately before erection.

The reality is the wording is not the smartest one, since is not accounting for inexperienced junior/senior engineers over zealous interpretation (painting of flange face!!??). Obviously your senior engineer hasn't seen many specifications related to the flanges in fabrication, protective coating and anything about gaskets and flange face relation.
There is literature about the flange face quality for gasket sealing purposes. Perhaps if you get him to read some of those, he'll give up asking for painting the flange face or give up engineering. Either way, you win.

 

[jamesl]

You may ask the senior engineer how to satisfy the requirement in B16.5 that flange face shall have a serrated concentric or serrated spiral finish from 125 to 250 roughness if the flange face is painted. I guess the senior engineer does not really understand why the Code has such requirements.

 

[moltenmetal]

jamesl: PLENTY of pressure vessels are constructed with internal lining which extends beyond the nozzle neck to cover the entire flange face. Lining and gaskets are selected together to provide a system that works.

125-250 microinch 40-55 grooves per inch is only one of many flange facings used on ANSI flanges.

 

[yasernoman]

It seems there has been a few examples where vessels with internal coating had their flange facings painted. Flexitallic (gasket manufacturer) and painting contractors seem to consider this a typical practice specially for low pressure applications. That's where the senior engineer is coming from, and that's why he raised the question regarding painting.

The problem is there is no documented code or standard or specification that clearly states "do NOT paint on flange faces" or "Painting on flange facing is NOT permitted". The question was actually raised when I specified no painting on flange faces.

moltenmetal: if you have come across applications where painting was applied on the flange faces, do you know what range of pressures you have seen it being used for? Please let me know.

Thanks

 

[doct9960]

yasernoman,

I suggest you talk to your project's material/corrosion engineer. Your vessel is internally lined for a reason...corrosion. And I agree with your senior engineer about extending the coating/lining to the flange face because they are exposed to the corrosive process. For the gasket, you will have to use a non-metallic flat gasket. Ask your material engineer for the material. You may also want to question the applicability of lining/coating for 150 °C. Lining/Coating are usually limited to 120 °C.

 

[moltenmetal]

I have seen internal nonmetallic linings used to the limits of 300# class, but as both doct 9960 and myself have indicated, there are temperature limits.

 

[TJOrlowski]

Painting of your flange faces will work fine, as long as you select a gasket constructed with materials compatible with your fluids/pressures/temperatures, and that will have excellent sealability.

Solid Grafoil, or Kammprofile seem like good places to start the discussion.

Consult a gasket manufacturer. Fully describe your application.

-TJ Orlowski