When two compressors are run in parallel, their load is usually increased by a common ramp up controller to maintain them in balance and prevent surging of one or both compressors.
LNG1032-140 :
A :
What is the problem when two compressors are run in parallel? What is the solution? Wrong or Missed Data? Click
During initial cargo loading the excess LNG vapour is free flowed ashore and the HD compressors are started in turn as required.
LNG1032-141 :
A :
What is the use of the HD compressor(s) at the initial phase of cargo loading? Wrong or Missed Data? Click
No
LNG1032-142 :
A :
Is it better to run two compressors on reduced load than one compressor on full load? Wrong or Missed Data? Click
The alarm in the cargo control room is accepted there but then it must also be accepted and reset locally in the compressor house.
LNG1032-143 :
A :
From where can alarms on the HD compressor be accepted and reset? Wrong or Missed Data? Click
In the engine control room.
LNG1032-146 :
A :
Where are the remote controllers for the LD compressors situated? Wrong or Missed Data? Click
Cargo tank pressure low. Low Low gas seal pressure. Low Low bulkhead seal pressure. High High gas discharge temperature.
LNG1032-147 :
A :
Can you state 4 conditions that will trip the LD compressor? Wrong or Missed Data? Click
Two
LNG1032-158 :
A :
How many main cargo pumps are normally fitted in each tank of both Moss and Membrane type vessels? Wrong or Missed Data? Click
Four times in one hour but after the third time a 30 minute waiting period is required before the next start.
LNG1032-161 :
A :
What is the maximum number of consecutive starts that can be carried out for a main cargo pump? Wrong or Missed Data? Click
It is more efficient and good operating practise to operate one main cargo pump at design flow rate rather than two pumps at 50% flow rate.
LNG1032-162 :
A :
What is the difference between operating one main cargo pump at 100% flow rate and two pumps at 50% flow rate? Wrong or Missed Data? Click
Videotel CBT LNG Vers 1.0.32 (QUESTIONS & CORRECT ANSWERS)
2.Equipment (Module 2) - test for Electrician
Fluctuations in the discharge pressure and ammeter readings are an indication that the pump is starting to cavitate so the discharge valve should be shut in to stabilise conditions.
LNG1032-163 :
A :
How do you know that a cargo pump is cavitating? What would be your action in this case? Wrong or Missed Data? Click
Main cargo pumps can be test run when the pump is fully submerged in liquid.
LNG1032-164 :
A :
When can you test run a cargo pump? Wrong or Missed Data? Click
Low motor current. Motor single phase failure. Motor over current. Tank Low Low level.
LNG1032-165 :
A :
Can you state 4 conditions that will trip a cargo pump? Wrong or Missed Data? Click
Hydraulic pressure low. Control air pressure low. Cargo tank pressure below or equal to primary insulation space pressure plus 0.5 kPa. Vapour header below or equal to atmospheric pressure plus 0.3 kPa.
LNG1032-166 :
A :
Can you state 4 situations that will give an ESD and stop all cargo pumps? Wrong or Missed Data? Click
It must be completely isolated.
LNG1032-167 :
A :
What is the key requirement before any inspection or maintenance is undertaken on electrical equipment? Wrong or Missed Data? Click
Keeping records of resistance and continuity readings can help providing early indications of possible faults.
LNG1032-168 :
A :
What can help to provide early indications of possible electrical faults? Wrong or Missed Data? Click
Insulation resistance testing and recording of the pump cables and motors on all loaded voyages. Recording of pump amps, position of discharge valve, discharge pressure during bulk discharge to establish any trend. Routine inspection/cleaning of starter boxes, all connections to be clean and tight. Routine testing of all associated trips and alarm functions, using current injection and pressure calibrator test equipment as required.
LNG1032-169 :
A :
Can you give 4 procedures that would be considered good practice for in service maintenance and monitoring of pump performance? Wrong or Missed Data? Click
To cool down the cargo tanks by pumping LNG through the spray rails at the top of the tank. To cool down the liquid header prior to discharge. To pump LNG to the forcing vaporiser when additional gas is required for gas burning in the boilers.
LNG1032-170 :
A :
Can you give 3 procedures where stripping/spray pumps are used? Wrong or Missed Data? Click
One in each tank.
LNG1032-171 :
A :
How many stripping/spray pumps are normally fitted in an LNG carrier? Wrong or Missed Data? Click
2.Equipment (Module 2) - test for Electrician
10% open
LNG1032-173 :
A :
What state should the discharge valve be in prior to starting a stripping/spray pump? Wrong or Missed Data? Click
After the first main pump in the tank has been stopped and the liquid level is above the height of the stripping pump.
LNG1032-174 :
A :
When are stripping/spray pumps normally started if the tanks are going to be "heeled out" (i.e. the maximum amount of cargo is to be discharged ashore)?
Wrong or Missed Data? Click
The pump must never be run dry because the flow of LNG through it cools the motor windings and cools and lubricates the motor bearings.
LNG1032-175 :
A :
What happens if a main cargo pump runs dry? Wrong or Missed Data? Click
On starting, when the discharge pressure is seen to increase and the motor amps are seen to decrease, this indicates that the pump is operating satisfactorily and flow has been established.
LNG1032-176 :
A :
On starting, how do you know that the pump is operating satisfactorily and flow has been established? Wrong or Missed Data? Click
No.
LNG1032-177 :
A :
Can stripping/spray pumps be started normally at any tank level? Wrong or Missed Data? Click
Cargo tank pressure below or equal to primary insulation space pressure plus 0.5 kPa. Vapour header below or equal to atmospheric pressure plus 0.3 kPa. Control air pressure Low Low.
LNG1032-178 :
A :
Can you state 3 situations that will trip the stripping/spray pumps? Wrong or Missed Data? Click
A soft starter is a reduced voltage starter for AC induction motors replacing mechanical contacts with solid state devices (thyristors) to control the current flow and therefore the voltage applied to the motor. The most common thyristors are known as silicon controlled rectifiers (SCRs) and triacs.
LNG1032-179 :
A :
What is a AC induction motor soft starter? Wrong or Missed Data? Click
Soft starters designed to control only one phase will reduce the torque but not the motor current on two phases. Soft starters designed to control two phases will reduce the torque but the current will not be optimally reduced or balanced. Soft starters designed to control three phases will reduce the current and the torque.
LNG1032-180 :
A :
A soft starter controls the current flow and therefore the voltage applied to the motor. What is happening in the motor if a soft starter is applied to 1, 2 or all the 3 phases of the motor?
Wrong or Missed Data? Click
Maintenance of cabling connections/junction boxes, pump motors and pumps is normally carried out only at refit.
LNG1032-181 :
A :
When is carried out the maintenance of cabling connections/junction boxes, pump motors and pumps? Wrong or Missed Data? Click
Videotel CBT LNG Vers 1.0.32 (QUESTIONS & CORRECT ANSWERS)
2.Equipment (Module 2) - test for Electrician
When a pump is opened up for inspection the motor bearings are always renewed irrespective of their condition.
LNG1032-182 :
A :
In which cases are you changing the bearings of a pump when it is opened up for inspection? Wrong or Missed Data? Click
A regular record is kept of pump and cable insulation resistance to earth, usually taken once every round voyage.
LNG1032-183 :
A :
What kind of record will keep the electrican about the cargo pumps? Wrong or Missed Data? Click
30-169mm
LNG1032-91 :
A :
What is the wall thickness of the aluminium spherical tanks in a Moss type vessel? Wrong or Missed Data? Click
IGC max. filling limit is 98% volume of the tank. Higher filling limits are permitted with Flag State and Class approval. Moss type vessels CANNOT normally load to a level of 99.8% of tank volume.
LNG1032-92 :
A :
What is the maximum filling limit according to the IGC code? Are higher filling limits possible? Can Moss type vessels normally load to a level of 99.8% of tank volume?
Wrong or Missed Data? Click
0.0015
LNG1032-93 :
A :
What is the normal guaranteed boil-off rate per day in a modern Moss type vessel? Wrong or Missed Data? Click
0.7mm
LNG1032-97 :
A :
What is the thickness of the Invar primary and secondary membranes of the Gas Transport NO 96 System? Wrong or Missed Data? Click
250mm
LNG1032-98 :
A :
What is the approximate thickness of the insulation in the Technigaz Mark III system to allow a boil-off rate of 0.15% per day? Wrong or Missed Data? Click
530mm
LNG1032-99 :
A :
What is the approximate thickness of the insulation in the Gas Transport NO 96 System to allow a boil-off rate of 0.15% per day? Wrong or Missed Data? Click