3 replies to this topic

[GMU]

Gentlemen

 

I have a problem with the pumping system has been installed .

The pumping system in the discharge line of the pump to about 8m away from the pump discharge , there is a tee where the flow is divided into two .

The left side of the flow is going to a tank 500m3/hy to 2.4km 140m distance and height difference . The pipeline is 12 " diameter carbon steel is STD .

On the right side according to design flow is going to 300m3/hy a tank that is at the same level of the station and pumping 16m away. This line has 8 " diameter carbon steel is STD in this dial are two orifice plates one after the other , then downstream there is a pressure control valve and finally a pressure sustaining

The pump works stable in the entire flow pressure when the tank is sent out to 2.4km away.

The problem that arises is when the throttle valve on the right side is hunger, nor to send 300m3 / h to the nearby tank, pump gauge begins to oscillate strongly and the discharge starts to vibrate but no pump cavitation and no the flow rate of 300m3 / h is obtained as due to vibration valve closes in the line of 8 "diameter .

It is a bit odd since the habrir the 8 "pipe , the pump should give more flow as part of the flow is sent to another tank which is very close muty having low friction losses .

 

I 'd appreciate your comments.

 

 

 

 

Edited by GMU, 27 March 2014 - 07:15 PM.

[TS1979]

Very difficult to follow. Drawing a flow diagram may help to understand your problem

[katmar]

I guess that when you are pumping to the distant tank at 500 m³/h the delivery pressure on the pump will be around 15 barg, mainly due to the high static head.  When you are pumping to the closer tank you need to dissipate all this pressure over your collection of orifices and valves. This could be resulting in cavitation in the orifices and/or valves and some very high local velocities.  You should try to get the design calculations for the orifices and valves in the short line - I expect the problem is in there.

[sukanta87]

Hi GMU,

There are several possibilities for the vibration in the above situation. The things can be checked

1. Pipe sizes for 300 m3/h and 500 m3/h ( it seems the mentioned sizes are OK).

2. Restriction Orifices size, thickness and their respective DP ( But its required to check if the 8" line is on flow. You refereed that vibration happening when this
line is closed)

3. Stress analysis and sufficient pipe supports.

4. Recommended Operating pressure for the pump (see vendor's document for performance curves) and shut off pressure.

5. Pressure relief valve and/or VFD and/or VSD can be considered on the discharge line to have the desired operating condition.

6. Must be sure about cavitation.