Seawater Cooling system Network Balance
Seawater Cooling system Network Balance
(OP)
Gents,
At present we are working on an older plant with very little PID Information. We have two pumps, each with the following duty (Design Rate 387 m^3/Hr Head:90M of water (8.82 bar))
They are connected in parallel, with only one pump running at a time (second as standby). They discharge to a 10" Header which has the following lines coming off it :-
2 No. 8" Line
3 No. 6" Line
1 No. 4" Line
1 No. 3" Line
After these take-offs, the 10" Line eventually reduces down to 3" and runs as a partial ring main, feeding the plant and eventually being discharged into drains (The majority of plant on this main is now redundant)
Off of one of the 6" Lines comes another 3" Module Header, which is, effectively used to supply a 1/2" Heater feed. (Again,Due to various plant redundancies over the years)This Module Header has, according to Plant Line list the following operating conditions (Op Press 7.7 Bar,Op Temp Amb,Design Press 19 Bar, Design Temp 38°C)
We propose to run another 3" Header from this 3" Module Header, this line will supply a couple of 1" Connections.
Due to the fact that a lot of the branches are now,in effect,redundant , when I come to work out my mass flow rate at my new 3" Header, is it safe to assume that the mass flow of the pump discharge will be split (Proportionally) between all of the branches off the 10" Header, bearing in mind that the information for a full network balance is not readily available, and therefore loading equivalents for these branches isnt available.
Any guidance would be greatly appreciated
At present we are working on an older plant with very little PID Information. We have two pumps, each with the following duty (Design Rate 387 m^3/Hr Head:90M of water (8.82 bar))
They are connected in parallel, with only one pump running at a time (second as standby). They discharge to a 10" Header which has the following lines coming off it :-
2 No. 8" Line
3 No. 6" Line
1 No. 4" Line
1 No. 3" Line
After these take-offs, the 10" Line eventually reduces down to 3" and runs as a partial ring main, feeding the plant and eventually being discharged into drains (The majority of plant on this main is now redundant)
Off of one of the 6" Lines comes another 3" Module Header, which is, effectively used to supply a 1/2" Heater feed. (Again,Due to various plant redundancies over the years)This Module Header has, according to Plant Line list the following operating conditions (Op Press 7.7 Bar,Op Temp Amb,Design Press 19 Bar, Design Temp 38°C)
We propose to run another 3" Header from this 3" Module Header, this line will supply a couple of 1" Connections.
Due to the fact that a lot of the branches are now,in effect,redundant , when I come to work out my mass flow rate at my new 3" Header, is it safe to assume that the mass flow of the pump discharge will be split (Proportionally) between all of the branches off the 10" Header, bearing in mind that the information for a full network balance is not readily available, and therefore loading equivalents for these branches isnt available.
Any guidance would be greatly appreciated





RE: Seawater Cooling system Network Balance
An equivalent K value would need to be calculated for all the branches to determine how the flow will distribute.
RE: Seawater Cooling system Network Balance
I hope this helps.
RE: Seawater Cooling system Network Balance
We require this information for a 'first run' sizing of a new heat exchancher that we are installing.
So, if I was to assume an equivalent pipe length in each branch (Apart from the ring main which would be longer) a friction factor being the same for all lines (same material, age etc) would I be wrong in assuming the flow is proportional in each branch (to the diameter?)
Or, going at the proplem from another angle :-
Is there any way that I can deduce the mass flow from the operating conditions in the line I am tie-ing into ?
i.e. 7.7 Bar and Seawater running within a 3" pipe ?
I would have thought that knowing the pressure, size of line and the density of the fluid, I would be able to deduce the velocity of the fluid in the pipe (And hence work out my mass flow rate from that)?
To at least give me a ballpark figure for my available Seawater cooling rate ?
RE: Seawater Cooling system Network Balance
From flow data - Nozzles a 3" diam wiht 110 psi pressure will provide 2820 US Gallons per Minute. NFPA has a pocket guide with the same flow information in it.
Good Luck.... If you need furthere assistance email me at fjstanton@cs.com
RE: Seawater Cooling system Network Balance
See the Crane Handbook, page 3-2.