Water hammer effect on anchor

[davidlabbe998]

Hey everyone,

I have an issue with a pumping system for ÉC-1, see in attachment. Yes, sorry it is in french, you might use google transl...

Velocity calculated : 4.41 m/s.
Steel galvanized 4" A53 B pipe
Pump is Flygt NP 3153.462

What will be the water Hammer effect?

Will the air chamber extension of 1.5 meters will be enough?

We want to change the pumps and be sur the system can take the new pressure. (old Velocity 2.06 m/s)

 

[davidlabbe998]

With this plan, you can see the general arrangment at the top (Vue agrandie "C").

I've used EPANET to get the flow/Velocity/head pressure data right.

 

[georgeverghese]

Would suggest fitting a mechanical brake or latch for this pump to prevent reverse rotation on pump stop, and also a damped check valve to prevent water hammer. Alternative to damped check valve would be to drill a small hole in one of the dual plates of the check valve, but there is a risk this hole may get blocked with microbial growth.

 

[davidlabbe998]

Thank you for the recommendation.

Here is what I've done :

Velocity reduced by pipe elasticity :

V reduced =(1477.8 m/s)/(1+(102mm/6mm)*(2.18*10^6 kN/m^2/207*10^6 kN/m^2))^0.5 = 1361 m/s

Water Hammer pressure :

DeltaP = 1000 kg/m^3*1361 m/s*(4.41-0)m/s = 6 002 kPa

Water Hammer absorber capacity :

Volume : 0.010889 m^3

Abs. capacity = 0.010889 m^3*1000 kg/m^3*9.81 kN/kg= 106.82 kN/0.00817 m^2 = 13 074.66 kPa

So it'll be good… anyone correct me if i'm wrong!

 

[fel3]

Is there any opportunity to increase the size of the discharge pipe and fittings? Your velocity of 4.41 m/s (14.5 ft/s in my world) is very high for this application. If you could use 150-mm (6") pipe and fittings, the velocity would be a much more reasonable 2.0 m/s (6.4 ft/s).

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[davidlabbe998]

It's not possible.

As you can see in section "E-E" in attachment the discharge pipe is inside a concrete monoliths of 5.9 m wide from the wall of the lock.