Alfa SSN water intake

[woodstock74]

Does anyone have any good positional and shape information for the lower water intakes on the Alfa SSN 705?

Additionally, what exactely is it injesting water for? Would have thought water used to generate the steam would have been closed loop.

[hakkikt]

Probably cooling water for the

Probably cooling water for the reactor. I am not sure why the Liras (Alfas) have them while contemporary US subs dont, but I guess it has to do with the superior performance of the Alfas.

[aeroengineer1]

US subs use pumps to

US subs use pumps to force the water through the cooling system, and the Russian boats use forward speed to force the water through. It is quieter because it does not have the pump, but causes drag because the scoops have to be larger to accommodate for slow movement, hence they are oversized for most conditions. I am sure that they create turbulence and hene may negate the lack of noise from the pump.

Adam

[wlambing]

Adam,
We (USN) only use

Adam,
We (USN) only use pumps at certain power levels, as may be required to meet some steam plant demands. Otherwise, the systems operate on natural circulation. Haven't seen a Jane's for quite a while, but the "NC" feature was mentioned in the ship class data in those tomes, as well as many other documents
in the public domain. S5G (Narwhal)and S8G (Ohio)plants were discussed a lot.
We (Battlestar Narwhalica) discovered by happy accident (forgot to start the pumps!)after the 1974 overhaul, that even the small auxiliary seawater systems up forward worked just fine, without scoops, under moderately heavy heat loads, without problems to the serviced components. We just got even more quiet! We ran that way a good part of my time onboard 'til I left in early '78.
Scoops themselves make noise! Never had a Russian we couldn't track in my 22 yrs. service!! :^)
Take care,
Bill

[hakkikt]

I am not a nautical

I am not a nautical engineer, but I would assume that speeds of 40+ knots and maximum compactness as in the Alfa package call for different engineering solutions. Maybe you need the intakes at that speed anyway because pumps would become too large if dimensioned to supply enough cooling?

[woodstock74]

Ok, understand now. The water

Ok, understand now. The water is brought in to cool the condensor? Do we have any idea how long these intakes are on the Alfa?

[tom dougherty]

Wayne Frey's book has some

Wayne Frey's book has some good photos of the Alfa whihc should give you some guidance. Other Russian submarines also had scoops, which brought in seawater for cooling the condensors.

As far as US submarines, after the loss of Thresher, the SubSafe changes were instituted. Among them was to limit the size and length of seawater intakes and piping to the minimal size and lengths feasible, and to insure that these systems, under full sea pressure, were of the highest quality. Thresher was believed to have had a casualty to the failure of brazed joints in her seawater piping, along with poorly placed shut off valves. It is believed this may have been one contributing factor to her loss.

The use of scoops basically "invites" large quantities of high pressure water inside the pressure hull. The potential for catastrophic failures and major casualties are correspondingly greater.