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The volume of sea chest
- Thread starter myvo
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- #3
Compositepro
Chemical
IR, a sea chest is where a ship draws sea water from for whatever needs it has like cooling water of fire fighting.
"a sea chest is where a ship draws sea water from for whatever needs it has like cooling water of fire fighting."
There's part of you answer. Another part is what are your needs? I presume the sea chest acts as a reservoir to allow timed release for cooling or firefighting or whatever. Figger the time of need and the rate of use for that need and compute the volume from there, with a reserve. Like Civils do with detention/retention ponds. Or air receivers on compressors.
Am I anywhere near understanding what you are talking about? Should there be rum involved?
There's part of you answer. Another part is what are your needs? I presume the sea chest acts as a reservoir to allow timed release for cooling or firefighting or whatever. Figger the time of need and the rate of use for that need and compute the volume from there, with a reserve. Like Civils do with detention/retention ponds. Or air receivers on compressors.
Am I anywhere near understanding what you are talking about? Should there be rum involved?
MikeHalloran
Mechanical
The sea chest is also where the engine cooling pumps draw their 'raw' water from.
They are typically pretty big pumps.
At the hull surface, the sea chest typically has some sort of grillage to keep out sea monsters and subsurface junk.
At its upper end, the sea chest typically has a removable (often transparent) cover and a gasket. The top plane of the sea chest should be a little above the static waterline, so that one can stop the engines, stop the boat, remove the covers, and observe and hopefully remove whatever has clogged the inlet grillage, like seaweed, fishing line, fishing nets, scraps of canvas, body parts, whatever.
The sea chest itself should be large enough to supply the raw water pumps for at least a few seconds while the hull surface grillage is temporarily obscured by something sliding along the hull surface while being run over, like an inflatable dinghy, or anything else you can imagine. I do not recall seeing a rule about this; it just seems like common sense.
You should, however, double check the requirements, for instance by scanning the various Rules For Classing Ships, downloadable for free from eagle.org. Allow considerable time, and do use automated tools like the multiple file search function in Acrobat Reader; there is an awful lot of text to look at.
As for the calculation itself, it should be as simple as cross sectional area x vertical dimension, roughly.
Mike Halloran
Pembroke Pines, FL, USA
They are typically pretty big pumps.
At the hull surface, the sea chest typically has some sort of grillage to keep out sea monsters and subsurface junk.
At its upper end, the sea chest typically has a removable (often transparent) cover and a gasket. The top plane of the sea chest should be a little above the static waterline, so that one can stop the engines, stop the boat, remove the covers, and observe and hopefully remove whatever has clogged the inlet grillage, like seaweed, fishing line, fishing nets, scraps of canvas, body parts, whatever.
The sea chest itself should be large enough to supply the raw water pumps for at least a few seconds while the hull surface grillage is temporarily obscured by something sliding along the hull surface while being run over, like an inflatable dinghy, or anything else you can imagine. I do not recall seeing a rule about this; it just seems like common sense.
You should, however, double check the requirements, for instance by scanning the various Rules For Classing Ships, downloadable for free from eagle.org. Allow considerable time, and do use automated tools like the multiple file search function in Acrobat Reader; there is an awful lot of text to look at.
As for the calculation itself, it should be as simple as cross sectional area x vertical dimension, roughly.
Mike Halloran
Pembroke Pines, FL, USA
To calculate a sea chest volume:
- calculate sea water consumption (sea water cooling, firewater, sea water service, watermaker systems) for each sea chest
- find sea chest nominal diameter from the consumption
- check Regulations. Should the unit comply with the latest EPA regulations? Some examples: 1.5 ft/s for common use, 1 m/s for ice class, 0.5 ft/s for EPA. find required open cross-sectional area
- calculate actual open cross-sectional area. Make sure to subtract the grill
- make adjustments and start over
- calculate sea water consumption (sea water cooling, firewater, sea water service, watermaker systems) for each sea chest
- find sea chest nominal diameter from the consumption
- check Regulations. Should the unit comply with the latest EPA regulations? Some examples: 1.5 ft/s for common use, 1 m/s for ice class, 0.5 ft/s for EPA. find required open cross-sectional area
- calculate actual open cross-sectional area. Make sure to subtract the grill
- make adjustments and start over
- Thread starter
- #11
we caculated the sum of flow of pumps use for cooling, fire fighting... And we caculated the dimension of grating in the sea chest and dimension of pipe joint with sea chest. But i can't calculate the volume of the sea chest. Can you give me the fomula to calculate it, please?
Thank you so much.
Thank you so much.
MikeHalloran
Mechanical
Can you tell us what Class Rules apply to your boat?
Mike Halloran
Pembroke Pines, FL, USA
Mike Halloran
Pembroke Pines, FL, USA
myvo, the volume should accommodate dimension of grating and dimension of pipe joint. Sea water velocity inside the sea chest should not exceed the allowable velocity (by Regulations and by requirements of piping systems). Usually the safety margin involved. Basically, it is not a volume calculation, but just a dimensioning. I do not use a formula, but draw a conclusion based on aforesaid.
- Thread starter
- #14
Myvo, there are regulations and rules to calculate the grating sizes and the seachest cross over pipe size. If you are looking at size of the chest, it has to be able to accommodate your pipe size. Suppose your cross over pipe is 12", you will need the chest of atleast 1 m x 1 m considering the stiffners and plates. It should also match with your frame spacing of the vessel.
For calculating the grating and cross over, it has been explained. Please note as per NK and LR, the area of the grating should be twice the area of the cross over pipe.
For calculating the grating and cross over, it has been explained. Please note as per NK and LR, the area of the grating should be twice the area of the cross over pipe.
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