Dynamic loading on pipe supports 2

[sprinklerjim]

I am looking for information on how to determine the magnitude of additional loads (besides the dead load of water filled piping) that would be imparted to a normally dry piping network. Specifically, on a fire protection deluge system, how do you determine the loads that cause the piping to "jump" when suddenly charged with water?

 

[LSThill]

sprinklerjim (Mechanical)

Regards to the deluge system analysis look at the following engineering tools CAESAR II, FE-PIPE, BOS FLUIDS.

A detail Piping Classification Specification is required and verified calculation for the Pping Classification.

Have a real good look at the engineering manual on Ameron International for deluge system

http://www.ameron.com

contact Joil L. Folkers
Offshore/Maine and fuel Hndling
Fiberglass-Composit Pipe Division
The Americas
5301 Hollister, Suite 200
Houston, TX 77040

tel 713 690-7777 x 19


Leonard Thill

http://www.thill.biz

 

[bvi]

You can get a handle on the forces by considering the force developed by slug flow in a system, a slug of liquid moving down a vapor filled line). This is the fluid density times the velocity squared. However, in considering the velocity, note that the pump may be way out on its curve, with very little initial resistance downstream.

 

[bvi]

Actually, density times velocity squared is pressure. Multiply that times the pipe inside area to get the force.

 

[sprinklerjim]

OK, I'm getting more confused - maybe someone can help even more. Would the forces generated by slug flow be applied only in the same direction as the fluid flow? Specifically, when the fluid reaches an elbow, does the force only apply at the elbow inlet or does a force of equal magnitude develop at 90 degrees to the inlet?

Additionally, would the only force applied to an external support be due to slug flow? I am thinking that the stresses developed due to water hammer, etc. would be restrained by the piping walls and fittings and not transferred to supports. Am I totally off base?

The specific problem at hand is a fire protection deluge system ring header supported off pipe stanchions. We have designed several such systems where the ring header is located several feet above a floor. When the system discharges, the piping loop shakes initially (as expected), but no failure is experienced. However, when the approving authorities see the system shake, they want these shaking forces accounted for in a structural calculation.

Recent additions of NFPA 15 (National Fire Protection Associations Standard for Water Spray Systems) offer guidelines for sizing such pipe stands, but it appears as if they are only sized for the load due to water filled piping, not dynamic loads.

Being a sprinkler system designer, I don't have access to any of the pipe stress analysis software recommended earlier, but if slug flow is the only significant contributing force, I think I can do hand calcs to approximate such loading.

Any suggestions?

 

[bvi]

Slug flow is a momentum problem. When the slug hits the elbow, its direction has to change, the momentum of the fluid has to change. The force acts in the direction of flow, and it applies at every change in direction and change of cross-section (e.g. reducers). It acts on the elbow until the water hit the next one in the line, at which time the forces balance on the prior elbow. The force only acts on any straight run while there is liquid against one end and air against the other.

 

[LSThill]

sprinklerjim (Mechanical)

Time to have a VIDEO CLIP on this subject:

Paulin Research has put together some small video clips of the many capabilities of BOS Fluids.

http://www.paulin.com/

Videos available for download !!

Click Here to See Video Clips

BOS Fluids Steamline Example