Alternative Material for Carbon Steel Fire Water Lines

Ductile Iron, as is used extensively throughout the UK for factory hydrant applications, perhaps?

Polypropylene, as used extensively throughout the UK for potable water distribution, perhaps?

304 grade corrosion resistant steel.

Check "protective wrapping" for burried pipelines.

Wrapping of pipes stops the movement of reactive groundwater that degrades pipes and reaches an oxygen deprived situation where pipes no longer corrode.

This is used for underground pipes in many places, also bridge and pier pylons etc.

Since it's a petrochemical plant I suspec there will be expectations on the materials used and suspect that "plastic" would not be suitable due to potential chemical softening and degradation due to heat during fires that it's meant to stop. (Even the conducted heat from metalic above ground pipes to their connections witht he underground items.

You don't say where you are located but if you are in the USA, check with your local fire marshall or fire prevention office. If they don't know they can look it up in their copy of the National Fire Protection Association (NFPA) standards. If they are not helpful you could contact a fire prevention consultant. This would probably hold true in most countries also.

Theoretically, any material that is approved for underground water piping would be suitable for the hydrant system, such as PVC, PPE, CPVC, ST STL 304 or 316, etc. I don't know what your local codes are so this information is of limited value. Check the local codes because it is extremely frustrating to have to rip out a newly installed system because it does not meet codes.

Have you considered the in-place installation of a liner within the carbon steel? This is often done for leakage in buried drinking water and sewer piping? It is a possibility. If the leaks are not substantial the liner would provide the physical strength where the leaks are till the corrosion made them of substantial size, probably many years from now.

Good Luck, Old Salt

We are in the Middle East, Kingdom of Bahrain. Liners are our current method of repair. Thanks very much for the comments.

You probably have current leakage from an imposed current CP on a pipeline coming into the plant. that can CAUSE corrosion, even in "stainless" steels. I'd consult a corrosion engineer to try to solve the problem the right way instead of thrashing around trying different things in the hope of getting lucky. you'll probably save money in the long run. I don't know about underground fire water mains, but above ground ones have to be metallic.

• Carbon steel is the most material used for buried piping system for fire fighting water networks. Taking into consideration to carry out:

- Surface preparation to Sa 2-1/2 followed by inorganic zinc silicate primer, and cold wrapping insulation.

- Cathodic protection.

The prescribed system can work safely for about 30 years, and then can be replaced by a new system.

Note. For carbon steel buried piping systems, we do our best to eliminate flanged connections to avoid corrosion of stud bolts and flanges and to minimize electric current resistance required for cathodic protection.

• Or you can use galvanized carbon steel for above ground piping systems and use fiberglass in buried sections of fire fighting networks, which becomes the most recently used all over the world, where it doesn't need any cathodic protection.

Are you sure the corrosion is external? My experience with sprinkler water systems is they rot from the inside out due to the water not being moved. I realize there are two systems one non and the other a circulating system. Other than that switch to a stainless or plastic feed pipe as permitted by law or code.

Google "C900DR14" and you will see an acceptable underground piping system for Fire Mains. This is approved for use virtually anywhere in the USA when employed with mechanical joints. It also will not degrade over time.

Regardless of what some minimum local codes, specifications, or opinions might say, or how they are interpreted, one thing that should probably not be lost in this discussion, and selection of piping materials, is understanding basic nature of fire fighting (or for that matter testing) itself. In this regard, it is generally understood that large quantities of extinguishing water should be delivered, and rapidly(to save as many lives and as much property as possible).

Exactly what this means to a piping system is perhaps less understood or obvious, unless of course one does accurate calculations of the demand/flow vs pipe velocity sizing and potential surge event calculations etc. Flow velocities that are considered risky or extreme for some types of weaker piping materials (sometimes chanced in fire fighting or combined water supply/fire fighting service) in examination of various specifications and literature showing velocity limitations or concerns, may be more common than many realize.

Another possible reality in fire fighting events (at times maybe understandably involving a lot of "rear ends and elbows" in well-meaning effort to save lives, as opposed to a lot of thinking, deliberation, and general utility training), is that valves and hydrants may get opened and closed quite quickly(in less than "critical time"), exacerbating surge magnitude and events. It is most reassuring when the available piping and its restraints etc. have been demonstrated to be tough and dependable enough to handle the transient pressures created by such changes in flow velocities, and in such service.