Bituminous coatings 1

[749KDV]

Could anyone please explain the difference between a Coal Tar coating hot vs cold applied? Is it just that one is liquid, the other being like a tar? Is one better than the other for underground piping? Is specifying tape with the hot applied better than not specifying?
Are they equal to or better than each other? In other words, are the interchangeable?

 

[epoxybot]

Firstly, coal tar is a material derived from distilling coal. Bitumen is the residue from the fractionation of petroleum. They are two different materials.
Coal tar is a known carcinogen. Asphalt appears to be considerably less hazardous.

Coal tar coatings are usually coatings having a polymer as the coating matrix and the coal tar as the extender/flexiblizer. They are some of the best coatings for buried pipe.

Indene-coumarone resin based coatings are sometimes referred to as coal tar coatings. They are in fact the distilled Indene fraction of coal tar. They are better from a health and enviormental perspective. They are also more expensive and require a good chemist to achieve the mechanical properties and performance of a coal tar coating.

Asphalt/Bituminous coatings are, more or less, the substitute for coal tar coatings. They are usually less heat stable.

With any coating application, the base/primer coat is extremely important. It needs to be of a thin/low viscosity to prevent holidays and pinholes and create a tenacious bond. Low flash point solvents can be useful in primers. On the other hand solvents in intermediate and top coats may be a combination of high and low flash point solvents. High flash point solvents can migrate out of the coating overtime resulting in shrinkage, cracking and loss of flexibility. Low flash point solvents in the same coatings can be trapped in the coating if misapplied. Resulting in early coating failure.

Hot applied coatings, as I understand them, are asphalt/bituminous coatings which can have some very good performance properties but are none the less subject to the hazards of the construction phase and can have water intrusion problems. Even low levels of moisture at the substrate during application can be very detrimental to the water resistance of a bituminous coating.

Tape coatings used in conjunction with a coating or as a remedial field coating have some very good advantages where corriosion conditions have shown to be a problem. Tape coatings and joint tape are two different job materials.

The following two web links are very informative on this subject.

http://www.prci.com/publications/table_of_contents/L00036/L00036toc.pdf

http://www.prci.com/publications/FreeReports/L00037e.pdf

 

[749KDV]

Thank you epoxybot for that great explaination and link.
The reason why I asked the question is that I am trying to evaluate the difference between the "hot applied" and "cold applied" and also the difference between coal tar and bitumastic coatings.

The National Fire Protection Association Code (NFPA) 24 references the use of AWWA 203 (Coal Tar - Hot applied) coating for underground pipe. When asked, NFPA stated that if I do an eqyuivelancy evaluation for a coating other than what is referenced, then it is ok to use. I guess I am confused in your statement that if coal tar is a known carcinogen, why would AWWA still approve its use?

Anyway, I will read the report that you have linked. Again, I truely appreciate your help.

 

[749KDV]

Does anyone know of, or has performed an equivalency evaluation of AWWA C203 with AWWA C210?

 

[rconner]

I had noticed you had not gotten any response to your inquiry after many days, and I wondered if perhaps in part a reason for this could be some lack of understanding of exactly where you are coming from/what kind of at least some specific application and/or exposure "equivalency" you are talking about (I believe the two standards you referred to cover a scope of both internal linings and external coatings of steel water pipe. I was just curious is your specific interest is now with regard to external coatings (e.g. exposed to a soil environment), internal linings (and if so is this a potable water application), or what?

 

[749KDV]

OK,

Here's the deal: I am a design engineer at a nuclear plant. Our original design calls for underground fire protection piping to be coated in accordance with NFPA 24 which references AWWA C203. I am trying to find an acceptable substitute to hot applied coal tar, but in order for me to justify any other coating I have to perform an "equal to or better than analysis". This analysis MUST do a side by side comparison of attributes to prove that the new coating is at least equal to the original specified coating. This analysis must go to NFPA for their concurrance also.

With that said, It seems that some attributes of say bitumasic 300M coating with a Carboline Mastic Tape and overlap meets or exceeds the original design. However, there are some attributes that are hard to compare. For instance, service life seems to be shorter <15 years as opposed to Hot Applied Coal Tar service life of up to 20 to 30 years. Another good example is the minimum required coating thickness. For coal tar, the minimum thickness is 3/32" +/- 1/32 (per AWWA C203). For a bitumastic equivelant (per AWWA C210), the minimum thickness is 16mil. How do you prove that the difference in thickness is equivalent when comparing the two products? These are the type questions that I must answer. There are a slew of attributes that I must compare.
I was wondering if anyone else had performed this "comparison" evaluation and had some insight to how they have overcome the obstacles.

Thanks for responding rconner. I hope this sheds some light on the task at hand.

 

[unclesyd]

Since you didn't mention the material, steel, CI, or DI, for your pipe I would recommend that you get in touch with the manufacturer of the piping material to be used for information. You can get you pipe supplied about any way you want.

One that I'm familiar with is ACIPCO. They have very good technical support especially for water service.

Primers:

http://www.acipco.com/adip/linings/coatings.cfm

One thing to look at is using a polyethylene tube. I believe that we have it over some Bitumastic Coatings in some very bad ground.

 

[749KDV]

The U/G pipe is steel. This is not a new design or new run of pipe. This is repair to the coating of excavated Fire Service piping for corrosion and coating inspections. The pipe is 35 years old. Certain areas are shown to have sub-standard coating applications leading to backfill damage and corrosion of the pipe under the coating. These areas are cleaned, inspected, and re-coated. My job it to approve a substitute coating to AWWA C203.

 

[rconner]

I think the extra information you have provided may eventually result in some help to you. I suspect that while all manner of coatings and promoters of same are probably out there (a veritable "jungle out there"?) excavating, cleaning, and recoating/wrapping etc. of existing steel pipelines, and maybe particularly of such previously coated lines in a plant environment as it appears you are dealing with, is perhaps a quite specialized field.
While the experience of new pipe vendors is perhaps limited in this regard, I suspect particularly major pipeliners and energy/oil companies etc. probably deal with this much more often. I think some of these have literally thousands of miles of pipelines (and some of it quite aged or even installed originally without coatings!) in their systems and/or plants, and I think some of these are in various fashions monitoring these systems. It might thus be advisable to seek out and talk to some of these folks, as well as perhaps contractors and coating vendors who work with one or more of these operators, for their suggestions/recommendations/perspectives to weigh relative to this subject.

For whatever it is worth, I suspect a majority on a length basis of new steel water pipelines in at least say the 24” or 30" and larger sizes in the USA (that are most often now spiral-welded pipes) are probably now provided with a multi-layer system of special adhesives and polyethylene tapes per AWWA C214, with some lesser amounts of liquid coatings such as polyurethane coating e.g. per AWWA C222 on the exterior. At least the larger steel water pipelines are now generally cement mortar lined internally per AWWA C205. I believe the over-whelming majority of new steel pipelines for oil and gas (that are most often at least in the up to 24” sizes ERW and seamless pipes etc.) are now provided with fusion-bonded epoxy (FBE) coatings, as are sometimes even larger diameter spiral-weld steel pipe lines or sections for water or energy when they are installed by horizontal directional drilling (HDD). These trends in steel piping are generally away from formerly used technologies such as coal tar epoxies or enamels etc. Of course also for special applications, these coatings/wraps are even provided with some further mechanical protection in the form of armors, cement mortar, or weight coatings etc.

I have noticed also that many of the AWWA standards that cover steel pipe coatings and wraps (e.g. including AWWA C210 for liquid epoxies you have mentioned) at least also include some reference to field applications or repair in their scope or text. In this regard AWWA C209 for cold applied tape coatings for special sections… etc. even includes the statement, “Tape coatings conforming to this standard may be field or shop applied.” I have further noticed AWWA C218, describing I think now about nine generic coating systems for exposed steel piping, contains the guidance, “4.4.1.2 Previously coated piping. Where a pipeline is to be repainted, the existing type of paint and surface condition shall be determined and recommendations obtained from the manufacturers of new paint systems regarding the surface preparation requirements. Based on the paint system selected, the project specifications shall stipulate (1) how the surface of the old paint shall be prepared, (2) how much of the old paint must be removed, and (3) if repriming is required, the surface preparation necessary based on the adhesion and performance compatibilities of the manufacturer’s coating system.”

While I don’t know specifically about equivalency testing per your conditions, I suspect there are probably many reasons including performance for the gravitations reflected in these practices and standards.

 

[749KDV]

Thanks to all who have responded. We are wrapping up (no pun intended) our equivalency evaluation. We managed to contact manufactures of coatings and have provided MSDS, installation instructions, chemical compositions, thickness requirements, etc. We have compared the overall process of application including comparison of human performance factors involved in properly mixing the new epoxy based coatings. This introduces a possibility of inadequate coating compared to the original (AWWA C203) where no mixing was required. All of these variables and more were evaluated. Sometimes, you just have to do your best, and hope that your evaluation holds true. I would hate to be proven wrong in 5 years if the pipe deteriorates.

Thanks again.

 

[unclesyd]

Before you completely wrap up your pipe problem here is a material we used for wrapping repair of damaged coatings on pipe.

I would give them a call.

http://www.densona.com/index.htm