Mouldy Navy

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JK
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Mouldy Navy

Postby JK » Thu Jul 20, 2017 1:22 am


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JollyJack
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Re: Mouldy Navy

Postby JollyJack » Thu Jul 20, 2017 5:00 am

He was on Iroquois and Algonquin, both razor blades now.
Discourage incest, ban country "music".

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Big Pete
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Re: Mouldy Navy

Postby Big Pete » Thu Jul 20, 2017 5:55 am

Very interesting, my Web browse can't find the link, do we have Political Censorship in Canada yet?
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JK
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Re: Mouldy Navy

Postby JK » Thu Jul 20, 2017 5:26 pm

Thanks BP, link is fixed. I stuck a couple of extra letters on the end of the first attempt.

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Big Pete
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Re: Mouldy Navy

Postby Big Pete » Fri Jul 21, 2017 8:09 am

It Makes me wonder how good the Engineers onboard are, it sounds as if the condensate drains in the AC units were unable to handle the flow of condensate and it was overflowing out of the air ducts! Or at least that is what the "first stage of the 2 stage Engineering fix" implies.
The Mould on the stanchions attached to the A/C trunking appears to indicate that the cold conducted into them from the trunking was sufficient to take the brackets below the Dew Point, causing condensation on them and hence Mould growth on the constantly wet surface. That in turn sounds as if it is caused by having too small an air flow at too low a Temperature through the A/C system. I wonder if somebody deliberately restricted the air flow in order to lower the outlet temperature at the blowers? For optimum air conditioning you don't want to freeze your b**** off, just reduce the humidity so that your body can cool itself naturally by evaporating your own perspiration. That is the point of the "Comfort Zone" chart of Relative Humidity against Temperature that you get with every Air Conditioning Plant manual.
When was a Cadet we were told that every A/C plant should have a re heater after the cooling unit, because air leaving the cooling unit was 100% humid ( it rains in side the A/C unit, right) and would be intolerable to live in. Haven't seen that done on many ships, usually the air absorbs enough heat through the insulation on the trunking to warm it up and reduce the humidity to comfortable levels. I have certainly seen the air trunking and back end of the A/C unit rot out because of condensation on several older ships.
Air Conditioning and Refrigeration are probably the two most mis- understood topics at Sea.

Next time you have time, take a look at your Air Con and read the manuals, check if it is set up correctly, and read what it says in SOLAS about Legionnaires and other airborne Diseases..

BP
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D Winsor
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Re: Mouldy Navy

Postby D Winsor » Fri Jul 21, 2017 9:49 am

You would be surprised how little a restriction in the air flow into suction of a ventilation fan would cause the fan to suck the condensate off A/C coils and sometimes out of the condensate catch tray under the coil. So on a Naval vessel designed to be operated primarily in the North Atlantic, combined with the occasional trip into tropical climates and with all outside air to crew areas sealed. It should not be surprising that there would be an issue with condensate being drawn into the ventilation system causing mold.

I ran into major issues with condensate being drawn off A/C coils in a sealed fan room with a separate air intake room and blown into into ventilation ducts especially when the dampers for the air re-circulation and fresh air supply system were not properly setup to compensate for air being drawn out by exhaust fans, or by plugged air filters. On one particular class of ships I worked on the Chief's office and Crew's Rec room were at the ends of the main ventilation ducts and if something wasn't quite right water would come out of the vents in my office or in the rec room. This was a real good indicator that the filters were getting dirty or the dampers were out of position.

We must also remember that the primary purpose of the A/C systems is to remove the heat generated by the sophisticated electronics and computer systems, not for the comfort of the crew. Mold in the vents may be a problem for the crew but not necessarily for the electronics.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

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Big Pete
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Re: Mouldy Navy

Postby Big Pete » Sat Jul 22, 2017 12:08 am

Interesting what Dave is saying, but most A/C units I have seen had baffles after the cooling battery to try and strip droplets of water out of the air flow. Regarding balancing the the recirculation, I have usually set this up with the Fresh Air Damper 100% open, and the recirculation damper open 100% then, assuming that the ship is properly "battened down" for A/C operation, any air not drawn out by the various exhaust / extraction fans will create a positive pressure in the accommodation and push back into the A/C fan suction in preference to fresh air from outside. The system should be self regulating automatically drawing in enough fresh air to replace any drawn out by the exhaust fans. It was my understanding the recirculating % is determined by the capacity of the exhaust fans compared to the supply fans. This has of course changed over the years, I think at one time 80% air re circulation was acceptable, I think it is only 40% now, that is another thing to check in SOLAS, which also lays down the number of air changes per hour in in each type of space, and special rules for Hospitals and smoking areas etc.
Obviously all external doors and windows have to be kept sealed for the A/C to be effective, The main role of the A/C is to strip out water from out of the air and condensing all that steam takes a lot of power, recirculated air from the accommodation has a lower humidity and therefore takes less power to cool down enabling a lower air temperature to be achieved with a lower power consumption.

I think that most Naval ships, built in the last 20 or 30 years have chilled water systems to cool their electronics, the same way as Diesel Electric ships do, with water cooled propulsion motors, Alternators, rectifiers and inverters.

Hope some more people can add their thoughts on thsi, Refrigeration and A?C are not well understood at Sea, and a good discussion on this would be very beneficial to all our readers.

BP
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Merlyn
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Re: Mouldy Navy

Postby Merlyn » Sat Jul 22, 2017 4:25 am

Bring back NH3 , HP bursting discs, brine coolers and deck mounted water cooled condensers.
Minimum probs.
Easy leak location.
Way down temps.
Good hang over cure.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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JK
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Re: Mouldy Navy

Postby JK » Sat Jul 22, 2017 7:44 am

Their system would be designed for full recirculation, I would think, in case of some types of attacks.
If it is not designed correctly or run routinely in full recirc, I could see this kind of problem. The system needs to have a certain % of fresh air to renew the air inside the ship.

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Big Pete
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Re: Mouldy Navy

Postby Big Pete » Sat Jul 22, 2017 11:41 pm

I believe Warships use activated Carbon Filters to remove Nuclear, Biological. and Chemical Agents from the Fresh Air drawn into their "Citadels" which are the protected areas inside warships. Even the engines and boilers have combustion air ducted in from the Deck, so at that only a small supply of clean filtered air is required for the machinery spaces. As JK says, I would imagine that under these conditions air recirculation would be at a higher % than normal, but we all need Oxygen to breathe, you can't go on 100% recirculation.
It is always better to ask a stupid question than to do a stupid thing.

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JK
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Re: Mouldy Navy

Postby JK » Fri Aug 04, 2017 6:49 am

I honestly know little of a navy ships HVAC, but I'd bet it's overly complicated :)

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Merlyn
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Re: Mouldy Navy

Postby Merlyn » Fri Aug 04, 2017 7:43 am

Old English Saying for Warships.

" Keep The Powder Dry "
Way before A/C
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Re: Mouldy Navy

Postby Sea Rover » Fri Aug 04, 2017 10:55 am

it's interesting how a thread about mold on a Navy ship gets more attention than the new licensing requirements.................

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JK
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Re: Mouldy Navy

Postby JK » Fri Aug 04, 2017 12:18 pm

i have no axes in that fire because I'm pretty well done with the career. I feel bad for the younger guys though.
Everyone that answered here are retired.

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JollyJack
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Re: Mouldy Navy

Postby JollyJack » Fri Aug 04, 2017 9:10 pm

I'm not! 11 months to go!
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