Thank you for your comment.
I’m considering that this minimum line design by continuous bypass line with a fixed orifice.
Please refer to the attached file. (Attachment-1)
Continuous bypass (not require air or electricity) may be lower cost method of protecting a pump when I compare with the differential pressure switch and an on-off actuated gate valve.
Then, I design the capacity of CTP = 430 m3/h and TDH=50 meter of water
The maximum process flow: 290 m3/h
I estimate the minimum flow required of CTP(430m3/h)= 100 m3/h (~20 % of BEP)
CTP capacity design: 290m3/h + 100m3/h = 390 m3/h
Specific margin: 10%
CTP capacity design (include margin) = 390 m3/h x 1.1 = 429m3/h -> 430 m3/h
Base on my understanding below:
Continuous bypass system provide continuous flow whenever the pump in running, regardless the process demand. And I designed the flow rate of recirculation line is 100 m3/h. (equal to minimum flow requirement)
Recirculation line pipe diameter design
Nominal diameter = DN100 (4 inch)
Velocity in pipe (@100m3/h) = approx. 3.72 m/s
From above calculation, this conceptual design affect to the increment of CTP capacity.
I think, there is the possibility of decrease the above design flow (100m3/h) in recirculation line for reducing the capacity of CTP.
In my opinion, the way to decrease capacity of CTP
1.At CTP flow = 0 m3/h, I will design flow to orifice = 100 m3/h. The orifice is designed by inlet pressure = 78 meter @ (CTP flow=100m3)
2.At CTP normal operation, the operating pressure is ~58 meter of water. And water flow in recir. line will be less than 100 m3/h (= x m3/h)
3.I will design the capacity of CTP = 290 m3/h + x m3/h.
1.How to design the flow rate of recirculation line (continuous bypass) base on your experience?