Pumping Pipeline

Dear all piping specialists,

I visited a pump house yesterday. From my observation, I found that the contractor was using a flexible union instead of eccentric reducer and concentric reducer for the suction line and discharge line respectively. In my opinion, the reason that flexible union was chose was because they want to avoid vibration from the pump to the pipeline. But, the flexible union might become a place for trapping the air in the suction line because it can't maintain its diameter between the pump bore and the pipeline. As a result, this may cause unstable flow and cavitation. Finally, it will damage the pump components. Due to unequal diameter of the flexible union, the water, which pumped to the discharge line will undergo a rapid change of velocity at the flexible union and also resulted an unstable flow at the discharge line.

1. Is my analysis correct on this matter ?
2. What is union usually used for ?
3. Should we install strainer in suction line or discharge line ? In my opinion, we shouldn't install it in the suction line because it will create a great friction loss to the system. Am I right ?

Please guide me.

Thanks.

Regards,

cckla

[Non-text portions of this message have been removed] Received on Thu Jun 10 20:42:00 2004