ARV valve in GRP fire water piping system 3

[PAN]

In the GRP (glass-reinforced plastic) fire water piping system for seawater service, GRP pipe manufacturer recommended to install automatic air release valve at each high pipe in the system. I understand that Ni-Al bronze is suitable body material for seawater application. However, I'm in doubt whether we can use other material for competitive price with the equivalent corrosion resistance or not? Are there any manufacturers of ARV who can supply GRP body material? Please comment.

 

[gerhardl]

Yes, for instance

http://www.arivalves.com/Water_Supply_Screen.htm

but you skipped the size you wanted. Please remember that air valves has to be dimensioned according to the real amount of air (in and out).

 

[MortenA]

Be carefull about this. High points in a fire water system can be really dangerous with regards to water hammer.

Assuming that its a wet system heres what can happen:

U have deluge valves (and downstream dry deluge arrays and you have some fire water monitors at fairly high elevations with standpipes (wet).

The pressure in the ring main is maintained using jockey pumps with bleeds and the fire water pumps start on low pressure alarms.

When the deluge valves open then the pressure will drop and you may get collumn separation in the risers. When the pressure starts to increase when the fire water pumps gets up and running - bang!

You may argue that this is just what the air release valves will avoid - because the air that sucked into the system will not collaps when the pressure goes up - and this is correct. But then somy opens the monitor (while the system is pressurized) - and a valve has a very high capacity for air compared to water and you will get the same effect!

I have resently done surge studies just into this problem.

Best regards

Morten

 

[stanier]

Ventomat can manufacture air valves in polypropylene or SAF 2507.

MortenA is quite right. You need to consider the surge of the system. AFT Impulse can model these three stage air release valves that are deigned to mitigate waterhammer.

Another key device is the pump check valve. Suggest you consult

http://www.noreva.de

and seek their advice on deceleration vs max return velocity.

A good text on the issue is Fluid Transients in Pipeline Systems ARD Thorley.

http://www.ventomat.com

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[MortenA]

AFT and many other similar packages

Best regards

Morten

 

[PAN]

Thanks for your suggestion. My process engineers informed me that they have checked transient analysis with PIPENET Vision (firewater network simulation program). I will confirm with them again for the result.

In parallel, the GRE pipe manufacturer commented me to add automatic ARV valves in the system. The locations were suggested from their experience (high point). The additional quantities are more than 10 points. It seems the large numbers of addtional ARV for an existing system. I will try to confirm the specific locations after contact ARV's suppliers.

If you have further comment, please let me know.

 

[stanier]

PAN,

Air valve supplies sell valves. Of course they will agree with a higher quantity than you need. ARV software always over predicts the needs of a system.

Check out Haestad Methods Advanced Water Distribution Modelling and Management. The book is worthwhile. Haestad were giving away CDs of the book at recent exhibitions.

Prof ARD Thorley councils engineers that air valves can cause more problems than they solve. refer Fluid transients in Pipeline Systems. Check out

http://www.ventomat.com

for some article son their deployment.



Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[PAN]

stanier,

Vent-O-Mat suggested me to install additional 29 air valves in the existing system.

You are right. "Air valve suppiers sell valves"