Wiring and plumbing watertight compartments

Discussion in 'Boat Design' started by Annode, Aug 31, 2019.

  1. rxcomposite
    Joined: Jan 2005
    Posts: 1,924
    Likes: 151, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    As a rule, PVC pipe cannot be used to penetrate bulkheads in the engine room, only metal is allowed. Bulkheads containing sewage, corrosive cargo, fuel, or fresh water should also not be penetrated.
     
  2. Annode
    Joined: Aug 2019
    Posts: 17
    Likes: 0, Points: 1
    Location: Uk

    Annode Junior Member

    >I do not understand how a duct, that flows air, can not flow water.
    Exacaaaaactly...

    >As a rule, PVC pipe cannot be used to penetrate bulkheads in the engine room, only metal is allowed. Bulkheads containing sewage, corrosive cargo, fuel, or fresh water should also not be penetrated.
    Thank you for that definitive answer.

    By HVAC i mean 6" diam air piping, not 1" diam copper coolant tubes. I use HVAC and not DUCTING, becuase while I am sure you are correct, this is a generic term that could also imply pipes that duct outside air into the engine room for example.

    IN this instant case, I am trying to design a cable/water pipe/sewerpipe/hydraulics/control cables/HVAC air ducting run that runs the lengh of the boat and breaks out in each of the water tight compartments. Since all the power is engine room water tight compartment, and all the power sinks are in the other watertight compartments, the concept of watertight is meaningless unless this is propeerly addressed.

    This is a private boat that may do a little chartering, but I am less interested in the regulations that designing something that actually works... or not bother at all. I have looked at the oil/gas industry solutions. They are out of my budget. I am really asking how this is even possible in large ships becuase there are so manu ducts going everywhere.

    In fact, when you think about it, the conept of a water tight engine room is impossible because of the air flow requirements of the engines. Then there is the potential for fire to melt any pipes emergin through a watertight bulkhead system, thus allowing sea water to enter the rest of the boat via the ducting.

    If we are just talking about elec cables and hydraulic cables (which must run the full length of the boat to the windlass, then watertight is more likely to be achieved, but aa I look at the super yacht industy, I dont see how they can provide the level of creatur comforts they provide and have any watertight bulkheads.
     
  3. fallguy
    Joined: Dec 2016
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    This is good humor.

    A duct, however, passing through an enclosed box, of the same integrity of the box will not affect the integrity of the box. (other than the size of it) If the duct is damaged by a hull breach, then the duct becomes a liability if it runs all over the ship and it was placed in such a way to make it likely to be damaged.

    And, what I think is happening here is the OP has turned the basic concept of managing a hull breach or systems failure below waterline into the concept of why bother doing anything right if I have plumbing running.

    The idea is that things need to get above waterlines fast, or not allow ingress below waterlines, and to not have a catastrophic incident or failure of a raw water intake or single location hull breach sink the ship because they ran air ducts all over the place down the outsides of the hull...below waterlines, etc.

    The ideal example of my point is the dorade. Is it perfect, no. Does it allow engine room air exchange without ingress? Mostly. If the hull is sinking, the dorade will fail. If the vents were placed near the vessel centerline, only the most serious catastrophic damage would result in a breach of the vents. And then, if the dorade simply heads up from a below waterline engine room; if the engine room is watertight and shut, then even that horrible catastrophic impact might not sink the ship.

    It is all polemics at this point, because I have no answers for how to build superyachts, but just the general ideas.

    It does so remind me of the Star Wars movie where they go and fire a proton torpedo into the exhaust vent, though. That'll take out the engines of even a Death Star.
     
  4. Annode
    Joined: Aug 2019
    Posts: 17
    Likes: 0, Points: 1
    Location: Uk

    Annode Junior Member

    >The idea is that things need to get above waterlines fast, or not allow ingress below waterlines, and to not have a catastrophic incident or failure of a raw water intake or single location hull breach sink the ship because they ran air ducts all over the place down the outsides of the hull...below waterlines, etc.

    Well OK lets be more realistic. IN the movie "all is lost" the boat struck a partially submerged container that fell off a ship. That would probably breach the foward watertight compatments (berths). Assuming the watertight door is closed relatively quickly, the rest of the boat migh not get flooded, BUT if that forward compartment fills and starts leaking water into the next compartment or the engine room, even a small leak would cause sinking in 24hrs.

    Or lets say there is an engine room event. burst pipe, sea cock problem whatever and it starts to fill beyond the capacity of the pumps to cope with it (keeping in mind that the bilge pumps run onn elec from the generator all of which are essentially below the water line) then once it is filled with sea water, it will just pipe that to every other "water tight" compartment.

    So this is the point where I wonder *if* a wateright comaptment is even possible in modern motor boat design.
     
  5. fallguy
    Joined: Dec 2016
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I have built a small 10M powercat.

    It has about 8 watertights on each hull. They have inspection holes for the coasties. They are buoyancy boxes; not rooms.

    Not much help, but in your example, the key concept is time.

    What is coming from the engine room that would prevent the engine room from being sealed?

    Wouldn't it be wise to put air handling in a separate space from seawater intakes? Obviously not the dorade...
     
  6. Annode
    Joined: Aug 2019
    Posts: 17
    Likes: 0, Points: 1
    Location: Uk

    Annode Junior Member

    >Wouldn't it be wise to put air handling in a separate space from seawater intakes?
    Yes. and that is the plan, but still, short of individual heating and A/C units in each section, this is not practical.
    The heater runs on diesel and is in the engine room. It is designed to heat the whole boat.

    The Engine room seems like it would need fresh air plumbed to the air intakes of the motor so that if the boat was on its side or worse, updise down, the engine room would not flood. This seems to be contrary to the design in every boat I have seen.
     
  7. fallguy
    Joined: Dec 2016
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    The heater can be isolated from the engines.

    Engine room.

    Utility room.

    A diesel heater can also be hydronic which means plumbing lines go throughout the boat to hydronic heaters. Those would not be air ducts.

    A diesel forced air system probably needs locating above waterlines if it runs ducting all over.

    Again, all out of my league. I can only offer generalizations.

    The dorade box is the way to run air in. And yes it can flood if the boat lists that much.

    Basically, a radiant heating system will not allow flooding done right.
     
  8. rxcomposite
    Joined: Jan 2005
    Posts: 1,924
    Likes: 151, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Some notes following standard Marine engineering practice.

    1. The engine room can house the main engine and auxillary machineries like main bilge pump, Batteries and generators. It is fed combustion and cooling air from the uppermost deck and exhaust thru the sides or center of the boat. The exhaust must be located so that it does not flood when the boat list (downflooding). The minimum is 21 degree list. If the boats stability is greater than 21 degree, extended watertight air pipes are used so downflooding does not occur. Small boats can use flapper valve or ball valves for intermittent wave slopping. If not, a mechanical means of sealing should be provided. All air pipes for FO, FW, and spaces requiring ventilation should be treated the same.
    2. A second self contained bilge pump is used and housed in a separate watertight compartment. It has a control manifold that chooses intake water (sea water or fresh water). The self contained pump can either be powered by house battery, dedicated generator, or be of the portable kind stored elsewhere, usually in the main deck. The bilge pump can be dual purpose. For firefighting or simply supplying water to heads (comfort rooms).
    3. HVAC pipes should be fireproof (usually metal or metalized accordion ductings), with electric or manual control vents for each compartment. Each compartment can be isolated to prevent smoke or fire to spreading to other areas.

    These are applicable to small boats or yachts. Ships follows the SOLAS standards.
     
    fallguy likes this.
  9. Annode
    Joined: Aug 2019
    Posts: 17
    Likes: 0, Points: 1
    Location: Uk

    Annode Junior Member

    Some great answers..
    The what box? let me google that....



    SOLAS standards....

    SOLAS Convention - Wikipedia https://en.wikipedia.org/wiki/SOLAS_Convention
    The International Convention for the Safety of Life at Sea (SOLAS) is an international maritime treaty which sets minimum safety standards in the construction, equipment and operation of merchant ships. ... The current version of SOLAS is the 1974 version, known as SOLAS 1974, which came into force on 25 May 1980.

    >2. A second self...
    That was great info. thx
    >3. ... with electric or manual control vents..
    Where are these listed for sale please?
     

  10. rxcomposite
    Joined: Jan 2005
    Posts: 1,924
    Likes: 151, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Annode- 1.a dorade box traps water and drain it at the base. The inlet portion can be a rotatable scoop or mushroom and is usually decorative in shape. Hatch covers can also double as ventilation vents but does not trap water.
    2. A self contained bilge pump is nothing but a powerful water pump with a built in engine (diesel or electric). It must be sufficient to spray water with sufficient pressure after a long hose is attached, say the length of the boat. Or if located amidship, it must have enough pressure for the spray to reach the bow or stern of the boat. Used for deck washing and doubles as firefighting equipment. Some are portable that you can carry around as long as your design of the boat has fittings to suck water to the pump.
    3. Control vents are rectangular metal box with a means of closing and opening and have outlet to fit a suitable ducting diameter.

    You can buy this at any marine supply depot. Try Harbor Freight or West Marine or others depending on your area. Catalouges are available on line or printed versions for a dollar or two. Usually free.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.