T.S. Patriot State Engineering Manual

Patriot State was the training ship of the Massachusetts Maritime Academy from 1986 to 1998.

Evaporator Operation

The density of salt water is normally 1 pound of salt in 32 pounds of water. For the brine overboard, the ratio should be 1.5 to 32 pounds. Less than this means plant is not operating at full efficiency. More salt would mean excess salt is being carried over into the distillate. There are 1860 grains of salt in one gallon of sea water.

Salinity of make-up feed must not be more than 1 gpg and potable water not more than 10 gpg. Evaporators normally produce fresh water at or below .25 gpg.

Evaporators One and Two - Start-up

1. Open salt water feed pump suction valves.
2. Open overboard discharge valve.
3. Open salt water heater vent valve.
4. Start salt water feed pump.
5. Open feed control valve to establish a flow of water through the unit, when a water through the unit, when a water level appears in overboard gauge glass open pump sealing line, crack discharge valve and start brine overboard pump.
6. Energize the salinity indicator panel.
7. For unit one, pen air ejector drain to bilge and open steam supply valve to air ejector.
8. For unit number two, start the vacuum pump making sure drain is open to the bilge, open cooling line to condenser from the domestic glycol system. Check drain to bilge and if less than .25gpg, then drain to bilge can be closed and open valve to ADT.
9. When vacuum in second stage shell reaches 20" Hg, open steam supply valve to salt water heater.
10. Open salt water heater drain to bilge and test salinity, if less than .25 gpg, then close drain to bilge and open salt water heater drain regulator valve.
11. Open condensate supply valve to the salt water heater desuperheater.
12. Start chemical feed system.
13. Regulate the feed control valve to obtain an inlet temperature of 165° F.
14. When water appears in the distillate gauge glass, open sealing line, crack discharge valve and start pump making sure unit is dumping to bilge.
15. Check salinity of distillate at solenoid valve, if less than .25 gpg, the distillate can be pumped to a tank.
16. When purity is satisfactory, set all remaining alarm cutout switches to on.

Evaporators One and Two - Securing

1. Dump distillate to the bilge.
2. Close steam supply valve to salt water heater and close desuperheater water supply valve.
3. For unit number 1, close steam supply valve to air ejector.
4. For unit number two, shut off the vacuum pump and closing the cooling supply valves.
5. Close condensate drains from salt water heater and air ejector drains to system and open drains to bilge.
6. Secure distillate pump making certain the pump discharge valve is closed.
7. Deenergize salinity indicating system.
8. Close feed control valve after cooling unit to approximately 100° F.
9. Close salt water feed pump discharge valve and stop pump.
10. Close sea suction valve.
11. When second stage shell is pumped out, secure salt water overboard pump and close overboard sea chest valve.
12. Close distillate pump and brine overboard gland sealing valves and brine overboard valve.

Evaporators One and Two - Operaton

1. Maintain sea water heater outlet temperature at 165° F.
2. Maintain distillate and brine overboard levels within gauge glass.
3. Maintain correct level of chemical feed to evaporators for units output one ounce Ameroyal per ton of distillate produced.

Evaporator Three - Start-up

1. Start sea water supply, maintain 30-35 psi.
2. Open valve in the feed water line to admit sea water to the evaporator shell.
3. When water is visible in liquid level gauge in brine pump suction, start brine pump, and brine pump discharge valve.
4. Throttle open the sea water overboard valve to circulate sea water through the condenser to overboard.
5. Open steam supply valve to air ejector.
6. Turn on electrical power to the salinity panel.
7. When vacuum in shell is 24 to 27" Hg. slowly open the steam supply valve in the steam line to sea water heater.
8. Adjust the steam pressure control valve to maintain the required pressure.
9. Line up vacuum drag line to auxiliary condenser for condensate removal. Crack open the sea water heater vent valve to shell one half turn.
10. Regulate the sea water flow through the condenser with the overboard valve to maintain 157° F. +5° F. on the evaporator shell thermometer.
11. Start chemical feed pump to inject chemical into sea water feed supply line to the evaporator shell.
12. Slowly open valve in desuperheating line.
13. When distillate is visible in liquid level gauge in distillate pump suction, start distillate pump.
14. Open distillate pump discharge valve slowly and adjust so that water level is maintained in the gauge glass or below.
15. When the chloride content of the distillate leaving the distillate cooler is below .25 gpg as indicated on the salinity indicator, set the three-way solenoid to direct distillate to the ship's fresh water system through the fresh water meter.
16. Monitor unit carefully. Sea water supply pressure must be 30-35 psig to maintain 33-35 gpm sea water feed flow rate through the feed orifice. The shell temperature should be 157° F+/-5° F.

Evaporator Three - Securing

1. Deenergize the salinity indicator to trip the three-way valve.
2. Close valve in steam supply line to sea water heater.
3. Close valve in desuperheating line.
4. Secure the vacuum drag line from condensate system.
5. Close sea water heater vent line.
6. Close steam supply valve to air ejector.
7. Stop distillate pump.
8. Close distillate pump discharge valve.
9. Secure chemical feed system.
10. Close sea water feed supply valve to evaporator.
11. Secure sea water supply to condenser.
12. Stop brine pump.
13. Close brine pump discharge valve.

Evaporator Four - Start-up

1. Open suction and discharge valves of the ejector pump.
2. Open overboard discharge valve for the combined brine/air ejector.
3. Close vacuum relief valve on the separator.
4. Start ejector pump to create a minimum vacuum of 90% minimum (27" Hg.) Pressure at combined brine/air ejector inlet should be at least 300 kPa (43 psi), and the back pressure at the combined brine/air ejector outlet should be no more than 60 kPa (9 psi).
5. Check that no water is visible in the sight glass of the separator.
6. When the vacuum has been established, open hot water inlet and outlet valves and start the hot water pump. It should take no more than 10 minutes to establish vacuum.
7. Line up heat exchanger steam, atemporator, and condensate drains and admit steam to start evaporation. When evaporation has started, the boiling temperature rises, while the vacuum drops to 85% approximately. Shortly after normal vacuum has returned, water flow can be seen in the sight glass in the air extraction pipe..
8. Line up flow to the freshwater tank.
9. Switch on the salinometer.
10. Start the freshwater pump. After starting the freshwater pump the sight glass on the vacuum suction pipe must be empty. The freshwater pump discharge pressure must be between 120 and 160 kPa.

Evaporator Four - Securing

1. Secure heate excanger and stop the hot water supply to the distiller.
2. Stop the freshwater pump.
3. Switch off the salinometer.
4. Stop the ejector pump.
5. Open the vacuum relief valve.
6. Close inlet and outlet for the ejector pump.
7. Close the outlet valve for the combined brine/air ejector.

All valves - except for the drain valve - must be shut, while the distiller is out of operation.

Direct comments to William Haynes whaynes@maritime.edu
Mon, Jul 1, 1996
TSPS Engineering Manual ©1995 Massachusetts Maritime Academy