Fire water pipe support discrenpancy between NFPA 13 AND 15

[morgan.z]

A really confusing question about Fire water pipe support discrenpancy between NFPA 13 AND 15 has been bugging me , if someone can help me out ,it is highly appreciated, i guess , a lot people will benifit too:
NFPA13(2007)
9.2.6.1 Pipe stands shall be sized to support a minimum of
5 times the weight of the water-filled pipe, plus 250 lb (114 kg).
NFPA 14-2007 (standpipe ) refernces its pipe support design to NFPA13.
NFPA15: for hanger ,it clearly refernces it to NFPA13, NFPA 15 specifies some spacing requirement for support, but nothing special regarding pipe support design, i.e , 5 times the weight plus 250 lb does not apply.
This really puzzs me : the hose and standpipe system , water spinkler piping both need 5 times the weight of the water-filled pipe, plus 250 lb (114 kg)for its support design such as floor amounted or wall amounted, but not for water spay . why is that? sometime water spay and spinkler have no much diffrence.
For hanger , three piping system's design is consistent. it is OK.

 

[cdafd]

No water in the pipe?

 

[cdafd]

Nnnnnnn

 

[morgan.z]

Thanks for participating anyway, my questions are further clarified like:
1. For water spay pipe support per as NFPA15, 5 times the weight of the water-filled pipe, plus 250 lb (114 kg) is not required, is this understanding correct?
2. If question 1 confirmed, say there is a case where there are two fire water mains (two seprate fire water system) arranged - floor amounted support( one is for water spinkler and indoor hose station system , another is for water spay system for some vessels in other area. the support(pipe stand) for water spinkler has to be designed with 5 times the weight of the water-filled pipe, plus 250 lb (114 kg) load per as NFPA13 9.2.6.1 ,but the support load design is diffrent for the later one. It just does not make sense to me.

 

[cdafd]

I could infer from this it is needed:: Since the requirement is in NFPA 13 chapter 17 hangers.


6.3.2.6 *


Hangers shall be installed and located in accordance with NFPA 13.



6.3.2.7 *


Where the pipe support methods outlined in this standard or NFPA 13 cannot be used, water spray system piping shall be supported in a manner equivalent to the performance requirements of this standard or NFPA 13 and the design certified by a registered professional engineer.

 

[morgan.z]

Appreciated for your reply!
Seems that 6.3.2.7 of NFPA 15 is refering the support design to NFPA 13 besides hangers, which means not only hanger needs to follow NFPA 13, all other supports such as pipe stand nees to follow NFPA 13 too.
Since the water spay piping more often is attached to tank wall or equipment, 5 times the weight plus 250 lb is too much. should NFPA13 A.9.2.1.3 for building load apply to equipment?

NFPA13 A.9.2.1.3
The building structure is only required to handle the weightof the water-filled pipe and components, while the hangers are required to handle 5 times the weight of the water-filled pipe. In addition, a safety factor load of 250 lb (114 kg) is added in both cases.
Thanks !

 

[UFT12]

6.3.2.3 allows piping be attached to vessels such as tanks etc. It does not mention whether these are the vessels under protection but considering a fast detection system usually employed for such schemes, it would make sense the vessel is the one under protection. My understanding is, a registered engineer required to do the calculations can skip the x5 +250lb rule but he will have to include a safety factor at the end.

 

[morgan.z]

Thanks!
It is very common in chemical /oil industrial field the tanks /vessels are protected with water spray. Just to save manhour, projects often use standard suport drawings,instead of dedicated calculation,suport design etc.
Maybe similar to building, tank wall only needs to handle weight of the water-filled pipe and components, while suports (like brackets) to take on 5 times the weight plus 250 lb, it is a little streching of NFPA13 A.9.2.1.3 regarding hangers.