After successfully completing this lesson you should be able to describe
how aphromoo deep-well pump is designed and explained the function of the
principal components the student should have a basic understanding of tank
operations this chapter illustrates the hydraulic systems developed by Frank
moon AAS for the handling of liquid cargoes and briefly describes their
basic operating principles
the one pump per tank submerged cargo pumping system was developed by Frank
Mon AS in close cooperation with the major chemical tanker operators the
fram-o system satisfies requirements for safe and profitable cargo handling
efficient stripping and tank cleaning individual pump capacity is vary between
50 and 2000 cubic meters per hour and total discharge rates up to 15,000 cubic
metres per hour pumps are installed on chemical carriers
product tankers crude oil carriers floating production storage and
offloading and floating storage and offloading units FPSOs and F SOS and oil
/ bulk / or oboe carriers by January 2007 48,000 655 cargo pumps had been
delivered to or ordered for a total of 3030 three vessels the working principle
of a centrifugal pump can be seen here rotation of the impeller causes any
liquid contained in it to flow towards the periphery because of the centrifugal
force generated the center or eye of the impeller is thus evacuated and liquid
from the suction line then flows in to fill the void
the cargo pump is supported by a deck trunk welded to the deck all the
connections are on the top cover plate to which a capacity control valve is
also mounted for remote and local operation of the cargo pump this
specially developed control valve regulates hydraulic pressure and oil
flow to the motor according to the given discharge situation the pressure gauge
indicates the oil pressure to the motor the pipes that connects the pump unit to
the top cover plate
click on the components below to learn more about the pipes deck the return
from the cofferdam pipe if any leakages this will be discovered in the exhaust
trap on the top cover plate during purging
this is the supply line for the cargo pump it carries the oil from the Power
Packs to drive the hydraulic motor this is the return line for the cargo
pump it carries the oil back after it has been used to run the motor nitrogen
or air is introduced during purging in order to ensure that the cofferdam is
open and does not contain any cargo or oil
cargo is forced through this line when the motor and impeller are running when
emptying a tank nitrogen or air is introduced through the cargo discharge
pipe and any final remaining product is forced up this line and on through the
cargo manifold this is done to ensure that the tank and pump are cleared to
the maximum possible extent on completion of the discharge the cargo
pump is running during stripping the pump unit is mounted to the pipe
stack / casing with a compact hydraulic motor located inside the casing the
motor is surrounded by low pressure hydraulic oil a short independent shaft
supported by bearings lubricated by hydraulic oil is connected to a single
stage end suction centrifugal pump the hydraulic section is surrounded by a
cofferdam that completely segregates the hydraulic oil from the cargo with a
manual seal condition monitoring system this seal arrangement consists of a
mechanical oil seal single cofferdam lip seal and a double cargo lip seal the
cargo seal is exposed only to static head from the cargo any leakages in the
cofferdam chamber will by purging with compressed air or nitrogen be blown
through the cofferdam check pipe and collected in the exhaust trap a backstop
unit is fitted to the shaft enabling cargo to be loaded through the pump
Waring's are fitted between the impeller and the volute casing click on the
buttons to learn more about the pump unit
the hydraulic system is built as a central hydraulic main ring line system
in either a closed or open loop hydraulic pumps deliver oil to the main
pressure line from this named pressure line a number of hydraulic motors can be
run provided that a sufficient number of Power Packs have been started in order
not to over speed the hydraulic motors a speed control valve is installed
upstream of each motor it is important to understand that the Power Packs
deliver the oil and the cargo pumps our consumers
in an open-loop system the hydronic oil is gravitated from a hydraulic oil tank
to the Power Packs and further on via high-pressure lines to the cargo pumps
and other consumers in the system after use the oil is transported via the
return lines back into the hydraulic tank a pilot line is installed to each
capacity control valve in order to remotely operate the cargo pump from the
cargo control room an oil cooler is installed in the system in order to keep
the oil temperature within desired limits a jockey pump is installed inside
the hydraulic oil tank in order to maintain positive pressure in the
hydraulic system and to avoid contamination of the oil with cargo if a
leakage should occur in the cargo pump the jockey pump also serves as a cooling
/ lubrication pump for the main hydraulic pumps this system requires a
rather large hydraulic oil tank since all oil used is returned to this tank
before pumped back again to the consumers due to this the open-loop
arrangement is commonly used in small systems while the closed-loop
arrangement is preferred for large systems
advantages include simple air release procedure less piping leading to cost
reduction and lower risk of leakage and a reduced number of components
the disadvantage of this system is the size of the hydraulic tank in a
closed-loop system the hydraulic oil is fed by a feed pump to the Power Packs
and further on via high-pressure lines to the cargo pumps and other consumers
in the system after use the oil is transported by the return line in a
closed system only 10% of the oil goes back to the hydraulic tank while the
rest is used directly on the Power Packs and back to the consumers a pilot line
is installed to each capacity control valve in order to remotely operate the
cargo pump from the cargo control room an oil cooler is installed in the system
in order to keep the oil temperature within desired limits three feed pumps
are installed on the hydraulic tank one running constantly one in standby mode
and one in reserve when the cargo system is not in use the selected feed pump is
delivering low pressure sufficient to maintain positive pressure in the
hydraulic system and to avoid contamination of the oil with cargo if a
leakage should occur in the cargo pump when the system is in use the second
feed pump starts automatically increasing the pressure such that in
addition to leak prevention 10% of the total oil capacity is returned to the
hydraulic tank the third pump is brought online in the event of a problem with
one of the regular pumps since only 10% of the oil used is returned to the
hydraulic tank this system requires a much smaller hydraulic oil tank than the
open system the closed loop system is commonly used in big systems
the advantage of this system is the size of the hydraulic tank
disadvantages include a more complex air release procedure more piping and more
components note in the older systems to feed pumps were installed one was
running in standby and two during normal operation hydraulic pumps motors and
controls are devices requiring close tolerances controlled wear surfaces
accurate finish and an adequate supply of clean hydraulic fluid contaminated
oil will not provide proper lubrication and is a leading contributor to reduced
efficiency excessive downtime and increased maintenance cost the maximum
recommended water content is 300 parts per million or 0.03 percent and must
under no circumstances be above 500 parts per million or 0.05 percent
if in doubt please contact fram-o recommended cleanliness level is code 16
over 12 according to iso for 406 or c top PR 2016 over 12 means that the
number of particles above 5 micron in one milliliter is between 320 and 640
and the number of particles above 15 micron in one milliliter is between 20
and 40 the recommended operating temperature of
the hydraulic oil is between 30 and 55 degrees Celsius if the oil temperature
is below 20 degrees Celsius circulate the oil through the heating and venting
valve installed in the system for heating with only one power pack running
until the desired oil temperature is reached note do not exceed 100 bar
circulating pressure during heating even though most operations which happen
when you push the start button on a power pack are automatic it is important
to know what actually happens and which items need to be checked prior to
startup in order to perform an economical discharge and minimize wear
and tear on the equipment it is very important that the number of power packs
used corresponds to the number of hydraulic motors used as previously
mentioned it is important to understand that the various pumps used in the
system are consumers while the Power Packs are in the delivery business this
means that one pump requires an amount of oil in order to operate and the power
pack has to supply the amount needed in your manual onboard you will find a
table where you can find out how much oil flow each hydraulic motor needs and
how much oil flow each power pack delivers see under technical data in
your manual when planning a discharge just add the oil consumption of the
number of pumps to be used at the same time and choose number of Power Packs
so the flow delivered is a little above the flow required
for example during discharging you will use two SD 300 pumps and one ballast
pump how many power packs need to be run the
consumption of an SD 300 pump is 938 liters per minute two pumps will
therefore together require 1876 liters per minute the ballast pump consumes 246
liters per minute this gives a total oil consumption of two thousand one hundred
and twenty two liters per minute a small power pack delivers 697 liters per
minute to small packs will therefore together deliver 1394 liters per minute
one big power pack will deliver 831 litres per minute these units will
deliver a total of two thousand two hundred and twenty five litres per
minute we therefore need to run two small and one big power pack to meet the
demand before starting the main power packs
check the following hydraulic system tank oil level that the cooling pump for
hydraulic oil cooler is running that the cooling fan for Power Packs is running
that the necessary number of generators is running that the potentiometer for
system pressure is in minimum position that the speed control valves for all
consumers are in minimum position that the cargo pump cofferdams are purged
start the main Power Packs after an operation is completed all
consumers have been stopped in the main power packs are no longer required the
system should be stopped as follows reduce the hydraulic system pressure to
minimum stop the main Power Packs stop the cooling water pump and fan stopped
the excess generator sets stop the feed pump and restart in low speed this
happens automatically after approximately 10 minutes always leave
one of the feed or jockey pumps running in low speed to maintain over pressure
in the hydraulic system if by accident cargo should leak into the hydraulic oil
system when the Power Packs are stopped the mixture of oil and cargo would ruin
the plant to prevent this the hydraulic oil pressure must always be higher than
the cargo static pressure when the hydraulic system is not in operation one
of the feed pumps will keep a hydraulic pressure of approximately 4 bar 1 of the
feed or jockey pumps must always be running in low speed and all valves in
the main return line and in front of all cargo pumps and other consumers must be
open it is important that emergency stop
buttons are used in emergency situations only and not for routine operational
stopping of the system an emergency stop stresses the system and should be
avoided except in critical circumstances
emergency stop button should be activated when the following conditions
occur damage to the hydraulic pressure pipes or hoses that leads to leakage
critical pressure pulsation in the system known as hunting critical
vibration on the Power Packs damage to the cargo lines uncontrolled spill or
leakage during discharging the following conditions should lead to
automatic shutdown of the system low low oil level in tank closed valve in return
line in closed system low feed pressure in closed systems feed pump failure when
running at high speed after a shutdown the error must be located and repaired
before restart before restart reset system refill oil
if necessary in accordance with normal procedures event the system thoroughly
and startup in accordance with normal procedures