Dry Sprinkler System Life with Galvanized and/or Nitrogen Inertion?

12/21/2020

Any thoughts or experience in system life expectancy for dry sprinkler systems with galvanized versus black steel pipe, and compressed air versus nitrogen?

Our firm (MEP/FP consultants) typically recommends nitrogen and galvanized pipe for dry sprinkler systems, and we often get the value engineer requests to accepts compressed air and/or black steel.

Any studies or data that support your experience? Approximate cost savings you might expect from each?

Thanks in advance!

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14 Comments

Jeremy James

12/21/2020 09:21:29 am

Typically, if you use nitrogen, you could lea in the side of using black pipe for a cost savings and an over redundancy. As an installation company, we've been told that galvanized is more susceptible to MIC due to the fact that microbes will attack one small spot (were the not coated or coating is broken) in the pipe and will become more concentrated, rather than a uniform and even distribution throughout the pipe. Obviously, nitrogen over an O2 compressor would be preferred as it will not add moisture or oxygen to then system, hopefully limiting the main components for corrosion. So, to answer your question, nitrogen and black pipe is the way to go. If cost is of concern, then industry standard leans towards galvanized and an air compressor. If you want a longer life system, then use Sch. 40 galvanized.

Jonathan Sullivan

12/23/2020 09:21:20 am

Accelerated corrosion has been a hot topic for our structural engineers lately; especially with epoxy coated rebar. I'm curious to see how it plays out.

James

12/21/2020 09:26:19 am

There was a game-changing white paper (almost ten years ago now) on this that completely changed my perspective on galvanized pipe in dry systems. The industry has (at least around here) very much gotten away from galvanized pipe in dry sprinkler systems, and for good reason.

If you still specify galvanized pipe, or see it specified, this paper would be very much worth your time: https://www.ecscorrosion.com/hubfs/ECS_August2018/PDF/White-Paper-Six-Reasons-Why-Galvanized-Steel-Piping-Should-NOT-be-Used-in-Dry-and-Preaction-Fire-Sprinkler-Systems.pdf

It's not that galvanized pipe doesn't protect the pipe - it does - but it also forces ALL of the corrosion to happen at the weakest point in the system and not across the entire system. As a result, systems leak EARLIER when galvanized pipe is used. Again, the white paper does a good job covering this one.

Dale

12/21/2020 10:29:39 am

James, thanks for sharing this link to the white paper. Very informative!

Patrick Drumm

12/22/2020 09:25:30 am

James,

Thanks for sharing the white paper. I'm looking forward to reading it.

Glenn Berger

12/21/2020 09:30:11 am

As James mentions above, the use of nitrogen has proven to be a game changer. The use of galvanized steel pipe is definitely not worth the money. Prior to nitrogen system being widely acceptable I was using the instrument-quality air with dessicant dryer configuration.

Sean Smither

12/21/2020 09:57:55 am

Im hesitant to support a group that promotes its own products while making claims based upon their own research. While its known about nitrogen, I feel the whole campaign against galvanized pipe by ECS has benefitted ECS greatly in terms of sales. Black steel in corrosive atmospheres will not last, even with aggressive measures being taken(painting, rust proofing . External corrosion situations must be considered. I suggest more studies be done on this subject matter . Read more into it than just trusting a study funded and performed by the same people who will benefit from it.

CJ Bonczyk

12/21/2020 10:03:36 am

Each type of system life expectancy will vary depending on the system type, quality of installation, and the owner maintenance. Even with nitrogen an improperly maintained and installed system can have issues thus depreciating the life of the system.

In dry systems:
The projected life for Schedule 10 black steel pipe can be increased from 20 (compressed air) to 60+ years with nitrogen. The projected life for Schedule 10 galvanized steel pipe can be increased from 10 (compressed air) to 150+ years with 98% nitrogen in a perfect scenario.

In wet systems:
The projected life for Schedule 10 black steel pipe can be increased from 15-25 without nitrogen inerting to 70+ years with nitrogen or deoxygenizing.

*Note the numbers above vary depending on the material, install and maintenance* (I.E. Is the piping lined with MIC shield, is the piping properly pitched, is there drains that are operated, is the nitrogen system properly maintained)

Absolute best practices for DRY SYSTEMS in my opinion is to utilize Sch 40 Galvanized, require all system piping to slope ½" per 10 feet regardless it's in a refrigerated space, and provide nitrogen with remote monitoring stations. We have done this for various high end global clients and have had great success.

**Note that we also do the service and inspections and provide the owner with proper training and maintenance to ensure membranes are checked, purity levels are recorded regularly, and so forth. Maintenance and service are critical as with any system.**

All owners will pay a premium for the galvanized Sch 40 and nitrogen systems up front obviously. However, the cost savings over time with a properly maintained system is huge. The constant cost to replace pipe and investigate leaks, system trips, burned up compressors, and maintenance fees add up quickly.

Many give the value engineering option of Sch 40 black steel with compressed air (and maybe desiccant dryers) to save project costs up front just to be awarded the job. The client believes that they can maintain the system on their own and they bank on the fact that the sprinkler contractor that they hired properly did their job on the install. I can't tell you how many times we have to come through and fix systems that are poor beyond imagination.

I was skeptical about nitrogen and even deoxygenizing wet systems when the technology was fairly new. I figured it was a marketing ploy. Then I did a job that was for a big client and it was an entire multi wet & dry system project that was properly installed. Within 2 years of install MIC in the system trashed the sprinkler systems and the client was furious at us saying we sold them a trash product.

Best places to get paper resources of cost analysis breakdowns would be from various Nitrogen vendors such as Potter, ECS, & South-Tek.

Brian Gerdwagen FPE

12/21/2020 10:06:12 am

Before moving to the South, I used black steel and compressed air for 10 years for all the Dry Systems my company installed in Los Angeles. We had a long history of those systems working for many years without complaint. The big difference is where the systems were installed.

In freezers and freezer buildings, you have the compressor intake air from the freezer. It is dry air. Any moisture is going to have been pulled out or it will freeze in the piping, or be in the drum drip.

When I moved to the south, there are dry systems at the exterior of the buildings due to winter. These systems are terrible. You need a nitrogen generator due to the normally humid air.

The big difference between black steel and galvanized is where the corrosion will occur. Black steel will corrode evenly. when it is time, the entire system will need to be replaced all at once. With galvanized, the corrosion will be localized. Individual pieces will fail and you will replace it piecemeal throughout.

Casey Milhorn

12/21/2020 10:08:58 am

I am no expert on this by any means, but multiple studies have found that what James said is true about the way corrosion attacks galvanized vs black steel pipe. The studies appear to be above board and were done in a controlled environment (which has its plusses and minuses). From a real world perspective we tend to see the same issues with galvanized and black steel the same. As expected, sch. 40 holds up a LOT better overtime, especially if roll grooved and not threaded. If I were a building owner that expected to own the building more than 5 to 10 years, I would opt for Nitrogen and black sch. 40 steel, at least on 2" and below. I would ask that roll grooving be used as much as possible on the branch lines. If I had an open air garage or loading dock or other type system exposed to the elements, I would opt for galv. sch. 40 2" and below along with Nitrogen. I would probably opt for nitrogen tank systems rather than generators due to cost, if I were dealing with just one or two smaller dry systems. Over that, the generators make more sense as the cost is spread out over several systems and many times one generator can service multiple systems. I always like to look at things from an owners point of view. That's my two cents anyway.

Lucas Kirn link

12/21/2020 03:56:26 pm

FULL DISCLOSURE: I am a co-author of the white paper referenced earlier.

First, I would like to address the claim that the "campaign against galvanized pipe by ECS has benefitted ECS greatly in terms of sales". This is false. We do not sell any sprinkler piping products and do not benefit financially when specific types of sprinkler pipe are installed. We identified a systemic problem with galvanized pipe and after researching the issue found that galvanized pipe was much more susceptible to corrosion in persistently moist (or wet) environments. It wasn't until several years after the paper was published that we saw our recommendations gain traction within the fire protection community.

On to the original question - I agree with what others have stated above. It can be difficult to assign specific numbers to life expectancy for a fire sprinkler system because there are many variables that come into play, such as: pipe type, pipe schedule, type of system, testing frequency, TI frequency, average temperature, etc. I think it's better to look at this as a hierarchy, where certain types of systems will outlast other types.

Based on my experience (almost 20 years in the sprinkler industry) here is how I would rank sprinkler systems in terms of their ability to resist corrosion over time:
1. Wet pipe system, sch 40 black steel
2. Wet pipe system, sch 10 black steel
3. Dry pipe system, sch 40 black steel
4. Dry pipe system, sch 10 black steel
5. Dry pipe system, sch 40 galvanized steel
6. Dry pipe system, sch 10 galvanized steel
7. Wet pipe system, sch 10/40 galvanized steel

Including nitrogen with any of the above options will significantly increase the lifespan of the sprinkler system and if cost is a factor tradeoffs can be made to help accommodate the higher upfront cost of a nitrogen generator - like using black steel instead of galvanized steel, or using schedule 10 pipe instead of schedule 40 pipe.

If you have a customer trying to make this decision the best question to ask is "how long do you plan on keeping the building?" If the answer is longer than 10 years I would recommend nitrogen with black steel every time.

Anyone who would like to contact me with additional questions (or criticisms) can reach me at lkirn@ecscorrosion.com

Brian Gerdwagen FPE

12/21/2020 04:03:36 pm

But you do sell corrosion consultation, so you do have a financial interest. It may not be in pipe, but to say that you have not benefitted is misleading.

Lucas Kirn link

12/22/2020 09:24:25 am

Brian - I believe I have been very forthcoming about my role/position on this subject matter. To suggest I'm being misleading is inappropriate.

Mark Harris

12/23/2020 03:41:38 pm

Regarding grooved schedule 40 pipe I have seen specifications that required cut verses roll grooves. Reasoning was moisture that would not readily drain at rolled grooves and the roll groove process can damage the galvanized coating onside pipe.

I am no longer with a sprinkler contractor but when I was our service fitters brought back many examples of the types of corrosion ECS references in white paper. Some were accelerated from installation quality (inadequate sloping of pipe on dry system) or threadable thinwall pipes but the term pay me now or pay me later applies. Pay for the nitrogen generator up front or shorter system life. And replacing system in a nursing home attic or data center is not cheap. Even a parking garage system replacement has logistics and end user revenue challenges.

FM Global does not make or sell nitrogen generators but section 3.2 of Loss Prevention Data Sheet Sheet 2-1 Corrosion in Automatic Sprinkler Systems talks about nitrogen reducing corrosion in in both carbon and galvanized steel.

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