Firewater piping, Underground vs. Above ground?

[panteo]

Hope someone could provide me some advice on this.
I'm working at a large chemical complex in Korea.
Our 27years old firewater system consists of two main pumps, motor driven/engine driven and small jockey pump with total of 3miles underground waterpipe(Pipe dia: 8inch). Our firewater pressure is kept at 10BAR. But the firewater piping is very leaky and the amount of water loss is some 50tons per hour.
To save the water loss, we plan to replace the loops.
The disputed topic is whether the piping installed at above ground or at underground.
Mechanical engineer is opt for above ground installation because of easy maintenance. But I think the pipelines at the above ground can be damaged by strong flame in the event of severe fire or explosion.

Many thanks in advance

 

[kjbsze]

Very expensive to keep above grade firewater piping from freezing. For existing facility, the pipe rack may not be able to support the added weight of pipe. Since you mention excessive leaking, I assume you have a wet system.

 

[TravisMack]

From an installation standpoint, there are many variables that will affect the cost. However, you described an existing chemical facility. I can envision a nightmare trying to route a new 8" supply loop overhead through the facility. The installation costs will likely be quite a bit higher to run overhead. True, maintenance is easier, but if you use sectional valves wisely in the underground, the maintenance costs can be reduced.

I would not worry about a large fire damaging the pipe. If the fire gets that bad, the building is going as well.