MEOclassIIexamnotes

  Advantages of CPP Improved Maneuverability. Full ahead to astern un 12 seconds. Lower ship speed can be obtained. Crash stop feature. Improved water flow into the rudder. Full engine power available for astern movements. Fewer engine starts. Low thermal.load on engine. Less engine wear. Less stern tube bearing wear. Lower starting air comsumption. No requirement for reversing gear. Higher engine efficiency Pitch adjustable for hull fouling and different sea conditions Engine power and speeds can be altered to stay clear of T/C surging zones Disadvantages of CPP Propellor heavier which will increase stress on tail shaft and stern tube bearings Survey period reduced by 1 year Additional cost during survey Lower propellor efficiency due to large dia hub versus propeller diameter Drop in efficiency range from 2 to 3 percent. Increased risk of breakdown due to system dependence and greater chance of cavitation damage on propellor blades

Schedule refers to the thickness of the pipe wall and therefore how much pressure it will hold . For a given schedule , the OD increases with NPS while the wall thickness stays constant or increases .Using equations and rules in ASME B31.3 process piping , it can be shown that pressure rating decreases with increasing NPS and constant schedule Schedule 40 is used because : It works for most applications and is readily available In small quantities , it is only slightly more expensive then tht thinner wall Schedule 120 The wall is thick enough so that it will not distort when walked on From half inch to 2 inch  it is rated no less than 140 psi at 73 degree fahein . The highest pressure typically found at any facility is 65 psi 

Shell and tube cooler The heat exchanger is first isolated from its systems and after draining the sea water and removing the end covers or headers to expose the tube plates and tube ends , an inspection is made for evidence of liquid flow or seepage from around tube ends from perforations in the tubes . The location of small leaks is aided if the surfaces are clean and dry  . The fixing arrangment for tube stack should be checked before removing covers or headers to ensure that the liquid inside will not dislodge the stack . This precaution also underlines the need for isolation of a cooler from the system. To aid the detection of leaks in large cooler such as main condenser , in which it is difficult to get the tubes dry enough to witness any seepage. It is usual to add a special fluorescent dye to the shell side of the cooler. When UV light is shown on to the tubes and tube plates leaks are made visible because the dye glows. Plate type cooler Leaks can be found by visu...

Fitted on electrically driven windlass Location between motor and gear box  It avoids the inertia of the driving motor being transmitted through the gear system in the event of shock loading on cable . Such shock can occur example when the anchor is pulled hard into thr hawser pipe when being hosed.

Control air dryer usually take the form of a refrigeration system to drop the temperature of the air below its dew point . The water droplets will collect on the surface of the fridge evaporator where they are led to an automatic drain. Further removal of water from the chilled air is effected by making the air swirl through a separating chamber where the water droplets collect on the outter surfaces. In some cases finallybthe air air can be led through dryers containing silica gel or activated alumina which will remove any remaining moisture from the air . This form of dryer must be fitted with means of refrigeration.

Free air holds moisture in suspension , when this air reaches the dew point in the coolers it comdenses.  If it were allowed to accumulate  , it would scrub the lub oil off the cylinder walls , present corrosion problems in the air storage tanks and any related equipment served Each cooler is equipped with a purge pot to collect the moisture where it is periodically blown off. Modern air systems are equipped with automatic drain valves located at strategic points including storage reserviors .

Low pressure steam is led to a sealing gland . The steam seals the gland , which may be a carbon ring or of labyrinth type , againsy air at the vacuum end of the shaft.