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 TM 55-1925-273-10-1
0028 00
disinfect the water (ensure than the water supplied to the potable water tanks is bacteriologically safe for human consump-
tion) as the water is being discharged from the reverse osmosis water purification units (figure 1, item 1) to the potable water
storage tanks (figure 2, item 1). The quantity of bromine added depends on the raw water intake to the reverse osmosis water
purification units (figure 2, item 2). If the raw water is considered non-contaminated, a low feed rate is used. If the raw water
is considered contaminated, a high feed rate is used. The feed rate is manually selected. The bromine feeder also injects
bromine as water recirculates to and from the potable water tanks.
HYDROPNEUMATIC TANK
The hydropneumatic tank is a pressurized potable water tank; it maintains potable water supply pressure for the potable
water system. Pressurized potable water is supplied from the hydropneumatic tank to the potable water heaters and various
areas throughout the vessel. The initial charging of the hydropneumatic tank to 60 PSI (4.1 bar) is accomplished using the
compressed air system. Once charged, the pressure switch activates the potable water pumps (figure 1, item 4) to maintain
water pressure.
HOT WATER HEATER
Two hot water heaters (figure 1, item 1) are provided to supply hot water to the galley, all faucets, showers, and the laundry
compartment. The hot water heaters heat the potable water supply and maintain a setpoint temperature. Power for the hot
water heaters is supplied from the main switchboard.
HOT WATER RECIRCULATING PUMP
A hot water recirculating pump (figure 1, item 2) operates continuously to recirculate hot water throughout the potable water
system. The pump is rated for 10 gal/min (45.5 L/minute) at 20 PSI (1.4 bar), and is driven by a 440 Vac, 2 hp motor.
ROWPU THEORY OF OPERATION
PRINCIPLES OF REVERSE OSMOSIS
The specific process through which osmosis occurs is called ion exclusion. A concentration of ions at the membrane surface
forms a barrier that allows pure water molecules to pass while excluding molecules of foreign materials.
OSMOSIS
Osmosis is the diffusion of two mixable solutions through a semi-permeable membrane in such a manner as to equalize their
concentrations. Natural osmosis occurs when a substance of lesser salinity naturally diffuses through a membrane into a
higher concentration salinity. Cellular functions in the human body function in this manner. The process is very energy
efficient in that it requires very little heat or pressure. However, the warmer the liquids, the more efficient the process due
to the activity of the molecules. It is a natural function for liquids of unequal density to try to equalize themselves with one
another when they are in molecular contact. In natural osmosis, liquids that are less saline attempt to equalize pressure by
becoming more saline. The membrane of a living cell (figure 4, item 1) passes lower density saline solution (figure 4, item
2) into higher density saline solutions (figure 4, item 3). This happens because the lower density solution (figure 5, item 1)
inside the cell naturally moves to equilibrium with the higher density solution (figure 5, item 2) the cell is located in. The cell
membrane (figure 5, item 3) allows liquid to pass, but it prevents particles (figure 5, item 4) from passing.
REVERSE OSMOSIS
Osmosis is an important process to life, but it does not produce water that is palatable to humans. In order to produce water,
the osmosis process must be reversed. The same principles apply, but some form of energy is necessary to force osmosis
reversal. Thus, the process called `reverse osmosis' was engineered to overcome the natural phenomenon of osmosis.
Reverse osmosis works by forcing water of a higher salinity content through some type of semi-permeable membrane in an
effort to remove the impurities. Salt is one of the impurities that is removed during the reverse osmosis process, and this
makes it possible to create potable drinking water from undrinkable water sources.
0028 00-4
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