Answer MEP Question 66

Q. (a) Explain in detail how you would isolate the High-Pressure Water Mist (Hyper Mist) System intended for fire protection of the engine room’s machinery and equipment for routine maintenance.
(b) Describe all tests and inspections you would make and how you would return the system to service.
(c) On a U.M.S vessel, how does a High-Pressure Water Mist ( Hyper Mist) System function when it is kept in auto mode?

(a) Explain in detail how you would isolate the Hyper Mist System for routine maintenance.

The system is needed to be isolated when carrying out the system operation test without a pump operation. 

1. Remove the wiring of the water pump motor in the starter panel.
2. Remove the destruct plate of the "SYSTEM START" switch.
3. Make sure all indication lamps are lighting when push the "LAMP & BZ TEST" switch.
4. Make sure all water is drained from the line between the fresh water tank and the Hyper-Mist water pump.

(b) Describe all tests and inspections you would make and how you would return the system to service.

Following tests are to be carried out.
(1 ). Pressure tight test:  It is to be carried out if required by class rule requirement by the yard.  Do not apply pressure to the freshwater tank.

(2 ). Air blow test: It is to be carried out by shipyard,  5-9 bar air pressure to be applied for blowing pipelines. 

(3 ). System operation test: Carried out without water pump operation

3-1. Remote Manual Operation: 

Push the "SYSTEM START" switch on the main control panel or local control box. (The following condition is to be confirmed.)

1. The water pump suction valve is opened with an "OPEN" lamp on the main control panel. 
2. The distribution valve is opened. 
3. The water pump running with a "RUN" lamp on the main control panel. 
4. Indication of the "MIST DISCHARGE" lamp on the main control panel and AMS panel. 
5. Sounding of the alarm device in the protected area and AMS panel.

3-2. Automatic Operation: Apply the alarm signal from the Fire detecting system and the same confirmation as the above item 3-1 shall be carried out.

(4 ). Alarm tests:

4-1. Freshwater tank low level (if applicable) The electric wire of the level switch is by-pass, and the low-level alarm shall be Confirmed on the main control panel and AMS panel.

4-2 Electric source failure The non-fuse breaker is cut off, and the electric source failure alarm shall be confirmed on the AMS panel.

(5 ). Interlock test: 

5-1. Ventilation fan stop (if applicable) Push the "SYSTEM START" switch, and the stop of the ventilation fan is confirmed.

(6 ). Water discharge test (from the test piping):
Preparation 

Check wiring and piping around the water pump. Open the test valve.
Caution: Make sure the distribution valves are not to be opened otherwise water will be discharged into the Engine room.
Operate the water Pump and make sure its proper operation and proper water discharge from the test line.
A 30 seconds water mist discharge is to be carried out for at least one section.

Treatment after the test-Return the system to service:

The line from the freshwater tank through the Hyper-Mist water pump to the distribution valve must be filled with fresh water.

(c) On a U.M.S vessel, how does a High-Pressure Water Mist ( Hyper Mist) System function when it is kept in auto mode?

This system can be operated both automatically or manually. When the engine room is an unmanned condition, make sure to switch to be an AUTO position which enables an automatic starting function. 

To start 

1. Manual start 

(1) the system works when the "SYSTEM START SELECT" switch is on both the "AUTO" or "MANUAL" positions.

(2) in case of fire, press the "SYSTEM START" switch for the relevant protected area. 

Make sure that the water pump is started and the water mist is released with an indication lamp on the panel. 

2. Automatic start 

"SYSTEM START SELECT" Switch to be "AUTO" position. As this system is connected to the local fire alarm control panel, water mist is automatically released with visible and audible alarms when the fire detectors are activated. However and if necessary, press the "SYSTEM START" switch for the relevant protected area. 

To stop  

press "SYSTEM STOP" Switch after confirming that the fire has been extinguished.

Note: 

1. Press the "SYSTEM START" switch again when restarting the system. 

2. When the "MANUAL" position is selected, the system cannot be started automatically. 

3. Fill fresh water, if it is confirmed that freshwater is lacking to operate the system. 

4. Relevant ventilations will stop when the system starts.

Read the detailed article High-Pressure Water Mist system | Hyper-Mist System