Question

Question 1.

a) Sketch and describe in detail a simple single pass composite boiler.

b) Explain its operation and state two advantages.

Question 2.

a) Sketch a biological sewage treatment plant, label it and explain its operation. 

b) State five conditions under which oily water can be discharged overboard.

Question 3.

a) Sketch a rotary vane steering gear, label the parts and explain how it functions 

b) List five (5) vital checks to carry out prior to the ship sailing out of port.

Question 4.

a) Draw a basic direct expansion refrigeration cycle and describe its operation 

b) In Heating Ventilation and Air Conditioning (HVAC), explain what operation is carried out to achieve comfort (in terms of humidity) during summer and in winter. 

Question 5.

a) Describe the principle of operation of both the positive displacement and roto-dynamic pumps.

b) List three (3) characteristics each of the above pumps.

c) Sketch a gear pump and label it. 

Answer 1

A operation -

Ansciens a water Terol → exhaust gos uptake. ttubes exhaust gos inier vefactory oil fired uprace formace. burner fire brief

The Cochran boiler whose working pressure is normally of the order of 7 bar is available in various types and arrangements, some of which are:

Simple pass composite boilers, i.e., one pass of the exhaust gases and two uptakes, one for the oil fired system and one for exhaust system. Double pass composite boilers, i.e., two passes for the exhaust gases and two uptakes, one for the oil fired system and one for the exhaust system. Double pass exhaust gas, no oil fired furnace and a single uptake. Double pass alternatively fired, two passes from the furnace for either exhaust gases or oil fired system with one common uptake.

The material used is good quality low carbon boiler steel plate. The furnace is pressed out of a single plate and is seamless.

Advantages -

• Low floor area required for the boiler installation.
• Low initialization cost.
• It is easy to operate.
• Less manpower requirement for the operation.
• It is easy to transport from one place to another

operation -

watafu. oney iniet C Vent black wator intet vent: sludge & retum line lo Soneen filter HL Hoodt Sellement Chamber Chlorinanon collection Chamber AEranon chamber primary chamber: froat TO PUBB biocors overboard discharge pumip

The basic principle of the working of a biological treatment plant is decomposition of the raw sewage. This process is done by aerating the sewage chamber with fresh air. The aerobic bacteria survive on this fresh air and decompose the raw sewage which can be disposed of in the sea. Air is a very important criterion in the functioning of the biological sewage plant because if air is not present, it will lead to the growth of anaerobic bacteria, which produces toxic gasses that are hazardous to health. Also, after decomposition of the sewage with anaerobic bacteria, a dark black liquid causes discolouration of water which is not accepted for discharging. Thus in a biological sewage treatment plant, the main aim is to maintain the flow of fresh air.

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