2 replies to this topic

[akv_csl]

Hello,

 

I have a situation as follows.

 

1.       Three suction pipes connected to seachest (which is box type construction with openings to sea, with grills on sea side, to avoid contamination, from where sea water enter in to sea chest). Please See attached.

2.       One pipe is of DN1000 (18 mm thick). This will be connected to a pump of capacity 6000m3/hr.

3.       Other pipes are of DN250 and DN100.

4.       DN250 will be connected to a pump of 150 m3/hr and

5.       DN100 will be with (reduced pipe size after first valve) will be connected to a pump of 40m3/hr.

6.       Normal sea water level is 2 m.

 

Our aim is to verify whether negative pressure & the flow velocity generated within the sea chest due to high capacity pump will not affect the suction of small pumps (of 150 m3/hr and 40 m3/hr) when all thre working simultaneously.

 

How can we theoretically prove this.

 

Regards

Arun

Attached Files

•  seasuction.pdf   44.37KB   13 downloads

[curious_cat]

From your attached drawing is it correct to infer that the total C/S area of grill is approx. 10 m2? (2000 x 4963)

 

If so, your nominal velocity comes to ~0.16 m/sec. What is the NPSHr on these pumps? 

[akv_csl]

Hi,

 

Effective area is only 2.41 m2. The velocity through DN1000 pipe is 2.21 m/s , DN250 is ~1m/s and DN100 is 1.86 m/s. Please see attached.

 

Regards

Arun

Attached Files

•  seachest.png   47.11KB   7 downloads