Black piping in a dry system

[DennisR4]

I believe this issue has been brought up on here before, but I can't find the thread. NFPA13 states that galvanized piping must be used in a dry system (NFPA13 2013ed. 8.4.7.2), however this is listed in the section 8.4.7 CMSA Sprinklers. So, if I read that correctly, this only applies if you are using CMSA sprinkelrs? And any other type, it is ok to use black piping? Thoughts?

To be clear, my company always uses galvanized piping in a dry system. A few of my co-workers and I were having a discussion, and one kept insisting that it is never ok to use black pipe in a dry system, per NFPA13.

 

[SprinklerDesigner2]

The galvanized requirement only applies to CMSA sprinklers.

From the handbook:

8.4.7.2.1 Where steel pipe is used in preaction and dry pipe systems, piping materials shall be
limited to internally galvanized steel.

8.4.7.2.2 Black steel pipe shall be permitted when the system is installed in freezers where the
air temperature is below 32°F (0°C) and the air supply is either nitrogen or a listed regenera-
tive air dryer.

FAQ

Does NFPA 13 require the use of internally galvanized steel pipe for all dry pipe
and preaction sprinkler systems?

Nongalvanized piping is allowed in freezers where the temperature is below 32°F (0°C), as the
rates of corrosion are greatly reduced as the temperature decreases. Nongalvanized fittings
are permitted by 8.4.7.2.3.

The use of internally galvanized steel piping materials applies only where CMSA sprin-
klers are used. Dry pipe systems using other types of sprinklers are not limited to a particular
piping material but must comply with the requirements of Sections 6.3 and 6.4.
The use of nitrogen in lieu of compressed air has been shown to help to reduce corrosion
in dry pipe and preaction systems.

8.4.7.2.3 Nongalvanized fittings shall be permitted

 

[TravisMack]

This points to an issue that many have with understanding NFPA 13. We must remember when reading and interpreting NFPA 13 that location has meaning.

This particular issue is above galvanized pipe and dry systems. As Art noted, it only applies to CMSA (formerly large drop) sprinklers. I've run into AHJs that have tried to make this apply to all dry systems.



Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[DennisR4]

That was part of my point Travis. I was arguing with my co-worker that it did not apply to all dry systems. He argued otherwise.

 

[SprinklerDesigner2]

For decades the idea that galvanized pipe was superior for use in fire sprinkler systems, especially dry pipe systems, was simply accepted as a fact but recently there has been a rethinking of this.

Changes have begun and as an example the UNIFIED FACILITIES CRITERIA (UFC) for the Department of Defense [URL unfurl="true"]https://www.wbdg.org/FFC/DOD/UFC/ufc_3_600_01_2016_c2.pdf[/url] now prohibits the use of galvanized pipe on all standard wet and dry pipe systems found on page 98:

9-7.6 Piping.
9-7.6.1.1 Galvanized piping is only permitted for deluge sprinkler systems, valve trim
piping and drain piping exposed to the Facility exterior.
9-7.6.1.2 Black steel pipe must be used for the addition, repair or relocation of
existing galvanized pipe in wet pipe, dry pipe or preaction systems.\2\

What I ask AHJ's who want to see galvanized is why do they suppose the Department of Defense would specifically prohibit its use if it was so superior to black steel pipe?

By paying attention to it I am discovering the systems we have the most trouble with are dry systems where we used galvanized pipe. We're replaced a lot more galvanized than black in parking garage and cotton storage warehouses.

Galvanized is not best.

 

[UFT12]

Agree with SD2. I m pretty confused as to what is best for dry/preaction and any open system. I ve read studies that prove in various cases that galvanized is not always better. In fact, they do not recommend it. Black steel also has issues but it is difficult to compare as each installation is different depending not only to what is happening on the inside but also what kind of corrosive atmospheres may prevail on the outside etc. An other factor is, what kind of gas medium is pressurized in the piping? Air of N2 or other inert gas? The two latter options are always advantageous (but increase costs). Here are some articles for consideration.

https://www.sfpe.org/page/FPEExtraIssue6

https://cdn2.hubspot.net/hubfs/4773...on-Fire-Sprinkler-Systems.pdf?t=1541109511013

https://cdn2.hubspot.net/hubfs/4773...ry-Pipe-Sprinkler-Systems.pdf?t=1541109511013

 

[sl3656]

I was thinking about this the other day and glad I found this thread.

An "experienced" fire protection engineer within our team basically gave the following anecdotal advice (I'm stressing the word anecdotal here!):

- Use black steel with nitrogen compressed gas systems
- Use galavanized steel with air compressed gas systems

It's interesting to hear that galvanised piping appears to cause more issues. I'm actually in the process of specc'ing up our dry pipe system job and in the many reference specs I have been given, I see galvanized pipe always required as part of any dry pipe system.

 

[chicopee]

So what is the main issue with internally galvanized piping? Any paper on the subject?

 

[MGXFP]

https://www.sfpe.org/page/FPEExtraIssue6/FPE-Extra-Issue-6-June-2016.htm

I have been offering schedule 40 black steel on dry and preaction along with nitrogen systems. I make sure I communicate in writing to a potential customer that galvanized pipe in dry and preaction systems is not recommended.

 

[cdafd]

Ok I have not seen any galvanized pipe in years, until maybe today, waiting on spec sheet.

So if I read right, on a dry pipe system, galvanized pipe is still allowed.

 

[TravisMack]

It is still allowed. You must still use a C-100 with galvanized piping (this change occurred around the 2010 edition).

It is definitely no longer preferred. I believe that FM Global has several restrictions against using galvanized.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[stookeyfpe]

The issue with a galvanized pipe is galvanizing is only a surface coating after the steel pipe is chemically treated. The chemical treatment is known as pickling, which is the chemical removal of the scale. The problem is that after galvanizing the steel pipe, the threads were exposed and corrosion returned. This in turn attacked and further corroded the inside of the pipe, which equals a lower surface coefficient for the friction of flowing water to a fire sprinkler. That's how I understand this issue.