27 September 2016

MARINE BOILER QUESTIONS AND ANSWERS-ETO


1. What is boiler?
It is a pressure vessel in which the water is heated to evaporate and generate the steam and the unit is so arranged that the generated steam accumulated in it.

2. Types of boiler:
          A. Water Tube Boiler
          B. Fire Tube Boiler.

3.Types of boiler by pressure:
Low pressure boiler up to 10 kg/cm2.
Medium pressure boiler 10 to25 kg/cm2.
High pressure boiler over  25 kg/cm2.

4. Explain the difference between fire tube & water tube boiler.
                          Difference between water tube & fire tube boiler
Water tube boiler                   
Fire tube boiler
1. Water flows through the tube.
1. Water flows around the outside of the tube.
2. Hot gasses pass around the outside of the tube
2. Hot gas passes through the tube.
3. Lighter in comparison with capacity
3. Robust 8 heavier.
4. High pressure & high capacity
4. Less pressure & less capacity.
5. Complex, cleaning difficult
5. Simple, easy maintenance
6. More efficient
6. Less efficient.
7. Distilled water to be used.
7. Normal water to be used.

5. What are the advantages & disadvantages of water tube boiler?

Advantage of water tube boiler
·         Lighter.
·         Simple to construction
·         Safer.
·         Efficient over 85%, Hence reduce fuel consumption.
·         Steam can be produced within shorter time.
·         Greater evaporation rate.
·         High pressure and temp. steam is produce.

Disadvantage:
           1) Little reserve of water and steam in the boiler, so efficient control of water level is required.
           2) the high rate of heat transfer across those tube walls together with small bores required positive circulation of water.
          3)The small bore tubes demand  pure feed condition to prevent scale formation which could lead to blow and over heating.
          4)The thin tubes give little resistance for corrosion, Cleaning difficult.

6. What are the functions of steam drum?
    (a) steam separation, 
    (b) steam-water circulation and 
    (c) purifying steam.

7. What is the function of super-heater?
Super-heater is used to super heat the steam and get higher thermal Efficiency of the plant.

8. Why large boilers are top supported?
        (a) avoid buckling of furnace walls, 
       (b) allow thermal expansion and 
       (c) reduce thermal loads.


Q. Name of Aux. boiler Mounting & major parts:
1) Main steam stop v/v (non return type)
2) Two safe v/vs.
3) Two gauge glass
4) Air vent cock.
5) Feed check v/v (non return type)
6) Automatic feed water regulator. (Not mounting)
7) Scum blow down v/v.
8) Blow down v/v (non return type).
9) Salinometer cock / sampling cock.
10) Man-hole door.
11) Mud-hole door
12) Pressure gauge connector.
13) Root v/v for level indicator.
14) Root v/v for pressure gauge glass.
15) Circulating p/p suction v/v
16) Soot blower.  (Not mounting)

9. Sketch a vertical auxiliary boiler






10. Feed check v/v: (Short Note) 
Pair of non return valves, one main and other auxiliary v/v fitted with stop/close indicator. Double shut off reduces the risk of boiler water leakage into the feed water line and if the feed water line fractures or a joint in the line blows then boiler contents will not be discharged out.

11.Main steam stop v/v: (Short Note) 
Main steam stop v/v is fitted on top of the boiler and connected with the main steam pipe-line. It is usually screw down non return type v/v. Its purpose is to isolate the boiler from the main steam line.

12. Safety v/vs :  (Short Note) 
Safety v/vs are fitted to a boiler to prevent boiler over pressure. At least two safeties must be fitted to a boiler. Safety values should be capable to release all steam, the boiler can produce without raising the pressure by more the 10% over a set valve.

13. Where air vent cock is located and its purpose?
The air vent cock is fitted at the top of the steam space of the boiler.
Its purposes are-
1. To release air from the boiler either filling the boiler water or raising the steam.
2. To allow air to enter in the event of boiler cooling down or blowing down .( to prevent vacuum effect)

14.Boiler safety devices :
·         1} Safety valves (Two)
·         2} Low / high water level alarm
·         3} Too low water level alarm and shut down
·         4} Water level indicators
·         5} Pressure gauge 
·         6} Low fuel oil pressure alarm
·         7} Low / high fuel oil temperature alarm
·         8} Flame failure alarm
·         9} Smoke density alarm
·         10} Easing gear arrangement
·         11} Air vent
·         12} Force drought fan stop alarm
·         13} Low / high steam pressure alarm

15. Why we need to blow down the gauge glass?
Gauge glass blow down is made to know the boiler and gauge glass connection is clear or not. And to give the exact water level in the boiler.

16. Boiler gauge glass blow down procedure:
·         1} Shut steam and water cocks than open the drain cock.
·         2} After draining water from the sight glass,if nothing comes out, both steam and water cocks are good in order.
·         3} Open the steam cock side, blow out the steam.
·         4} Close the steam cock side, the steam connection is clear.
·         5} Open the water cock side, blow out the water.
·         6} Close the water cock side, the water connection is clear.
·         7} Close the drain cock.                          
·         8} Open the water cock, water should then gradually come rise up to the top of the gauge glass.
·         9} Open the steam cock, the water in the glass should fall to the level of the water in the boiler.
Note: Working position - all cocks handle are in downward position.

17. Why we need to blow down the boiler water?
Boiler blow down is made to reduce the density of salt and to remove the dissolved and suspended solids, also the floating solid impurities in the boiler system.
If these are not removed from the boiler water system, foaming, priming, corrosion will occur in the boiler steam space and feed water system.

18. What check should be carried out on a boiler during watch?
o    1.Steam pressure & temperature.
2. Boiler water level.
3. Blow down gauge glass.
5. F.O. Pressure and temp.
6. Check the flow gas temp.
7. Check the flame shape.
9. Feed water press and temp.
10. Feed water regulator
11. Check safety level devices.
12. Cascade tank water level and temp.
13. Observation tank check for oil.
14. Condenser sea water outlet temp.
15. Check any leakage of valves.
16. Blow down the boiler
17. Soot blow

19. Alarm fitted in boiler system.
o    1.Steam press, high / low.
2. Boiler water level high/low.
3. Flame failure
4. High salinity.
5. Fuel temp. high or low

20. Indication of soot blow is done.
o    1.Shoot will come out through the funnel.
2. If steam is used for soot blowing steam press. Will suddenly comedown.
3. Exhaust back press will reduce.
4. Exhaust gas outlet temp at the uptake (after the EGB) will reduce because of boiler heat transfer.
5. After soot blow is finished within short time steam press will come up.

                                                                                         
21. Why do you perform scum blow down and bottom blow down?
Scum blow down ( surface blow down):
To remove accumulated, suspended and floating solids, impurities and also remove dissolved solid concentration, they hinder the formation of steam.
Bottom blow down: 
To remove suspended solids and residual sludge that have settled at the bottom.
If these contaminants are not removed regularly they will build up until they hinder the
circulation patterns.                                                                 

22. Explain why water testing is essential in boiler water management?
1. To prevent scale formation in the boiler & feed water system. 
2. To prevent corrosion in the boiler & feed water system.
3. To control the sludge formation & prevention of carry over with the steam.
4. To prevent entry of foreign matter such as oil, waste, sand copper particles, iron oxide in the boiler.


23. Test carried out on feed water of a low pressure aux boiler: 

Ph Test: 
Reason:
To determine the ph value i.e. the degree of acidity or alkalinity of the water.
Procedure:
· A litmus strip is submerged in the sample water.
· Color of the strip change accordingly to the condition of the water.
· Blue color indicates alkaline & Red means acidic.
· The degree coloration compared against the datasheet to indicate the possible range of ph value.

Alkalinity test:
Reason: To ensure about alkaline condition of the sample.
Test for P-alkalinity:
100 ml of boiler water is taken as a sample.
10 drops of phenolphthalein is added, then sample will twin in pink color.
N/50 sulfuric acid is added to clear the sample.
Calculation: ml of N/50 acid used X 10 = PPM CaCO3.

Test for total alkalinity:
P-alkalinity test is taken. 
10 drops of methyl orange is added, result yellow coloration. 
N/50 sulfuric acid is added until it turn to pink. 
Calculation: ml of N/50 acid used for both test x 10 = PPM CaCO3.

Chloride test:
Reason: To measure the chloride value to make an indication of sea water leakage in feed water system.
Test:
100 ml of boiler water taken as sample. 
10 drops of phenolphthalein is added sample will turn into pink 
N/50 H2SO4 is added to clear the sample. 
2ml of H2SO4 is taken again. 
20 drops of potassium chromate indicator is added. 
N/35.5 Silver nitrate solution is added until a brown coloration results.
Calculation: ml of N/35.5 solution used x 10 = P.P.M. Cl.

Phosphate test:
Reason: To determine the amount of phosphate content as a reserve. 
Test:
· 25 ml filtered boiler water is taken as a sample.
· 25 ml vanadomolybdate reagent is added.
· Comparator tube is fitted with this solution z is placed in night hand compartment of the comparator.
· A blank prepared by mixing equal volume of vanadomolybdate reagent and demonized water is placed in left hand compartment
· At least three minutes is allowed to develop the color then compared with disc.

Calculation: Phosphate reserve in P.P.M from the disc reading. 


24. How feed water treatment keeps the boiler scale free?
1) By using distilled water.
2) By keeping the hardness salts in suspension in the solution, to prevent scale formation.
3) By stopping the suspension salt and impurities from sticking on the heat transfer surface.
4) By providing anti foam to prevent water carry over.
5) By eliminating dissolved gases and providing some degree of alkalinity to prevent corrosion.

25.Enumerate the boiler water test
Alkalinity test
a. Phenolphthalein ( p) alkalinity test
b.Total ( T ) alkalinity test (2 x P)
Chloride test
Condensate PH test
Amerzine test ( Hydrazine test)
Excess phosphate test
Conductivity test (Total dissolve solids test)
Hardness test

26.Purpose of Boiler water test?

1. Alkalinity test:
This is to ensure that the boiler water prevents corrosion by neutralization of acidic gases.
(a) Phenolphthalein ( p) alkalinity
This test is carried out to prevent acidic corrosion.
(b) Total ( T ) alkalinity test
To determine the amount all of hydroxide, all of the carbonate, and two thirds of the phosphates.
Note: Hydroxides and carbonates can co-exist together in a solution but hydroxides
and bi-carbonates can not.

2. Chloride test
To know the amount of salt in boiler water.
To minimize chloride level and to adjust the blow down.

3.Condensate PH test
To control condensate PH value within a limit. 
To minimize corrosion in steam and condensate system.

4. Amerzine test ( Hydrazine test)
To test for dissolved Oxygen content ****
To know reserve hydrazine (N2H4) ppm and to prevent corrosion and aeration.
To minimize oxygen pitting and corrosion in boiler, steam and condensate system.

5. Phosphate test
To control the scale formation due to hardness (presence of Phosphate in sample means no hardness salts).
A reserve of phosphate should be maintained in the boiler water ready to neutralize any hardness salts which may enter.

6. Conductivity test
Measure of the total amount of dissolved solids (T.D.S) including the treatment chemicals. (Excessive density leads to priming and or deposits)
To remove dissolved and suspended solid by blowing down.

7. Hardness test
To check for salt causing "hardness"
Hardness test of boiler water are not necessary when the phosphate is above the lower limit of the control range.

27. Describe the correct procedure of blowing down boiler water (partial blow down).
Blowing down procedure of boiler (partial blow down)
·         Put notice
·         Take permission from the port authority if the ship at port.
·         At first close all the steam requirement v/v to purifier, F.O tanks etc.
·         Wear proper clothing.
·         Blow down the gauge glass by taking feed water in the boiler.
·         Stop the water p/p and keep it to normal mode.
·         Maintain sufficient pressure in the boiler.
·         Stop firing of the boiler.   
·         Cutoff the F.O system of the boiler.
·         Keep one person standby near the gauge glass.
·         Ensure that the ship side v/v outside of the ship nobody is working or no fishing boat is there.
·         First open the ship side v/v fully.
·         Remove the scum by scumming.
·         Finally crack open the boiler blow down v/v to avoid thermal shock & water hammering.
·         Keep eye on gauge glass.
·         Close the blow down v/v & then ship side v/v before low water level of the boiler.

28. Significance of regular blow down:
1) To reduce the water level in the boiler to prevent carry over or priming.
2) To reduce corrosion.
3) To remove sludge or mud from the boiler.
4) To reduce solid particles.
5) To reduce the dissolved solid.
6) To reduce oil by scum blow down.
7) To reduce chloride.


29. What is foaming in boiler and how to prevent it ?
It is the formation of thick layer of steam bubbles on the top of the water surface inside the boiler due to:
High concentration of impurities.
By the animal or vegetable fats in feed water carryover from the oil heaters.
Increase in level of dissolved & suspended solid TDS level.
Increase in water level.
To prevent foaming , surface or scum blow down should done frequently to expel any floating impurities for the boiler and no lube oil should be allowed to enter the boiler.

30. What is boiler priming and how to prevent it ? 
It is condition in which large amount of water are carried along with the steam into the steam line.
It is caused by:
1. Excessive foaming 
2. Improper amount of steam space 
3. By a sudden rush of steam such as is produced when steam stop valve is suddenly opened.
To prevent priming: 
Never keep the water level too high.
Open steam stop valve slowly.

31. Why are boiler manholes elliptical in shape?
The boiler manhole-lids are mounted from the inside of the boiler so that the boiler pressure will help to keep them tight. Hence the manholes have to be elliptical in shape to make it possible to take the lid out from the boiler.

32. Describe the procedure followed to raise steam from a cold boiler.
Procedure to raise steam from a cold boiler:
§  Wear proper clothing.
§  Ensure all piping involving water; steam and fuel are in order.
§  Make sure that uptake cover is removed safety v/vs are in order.
§  Ensure boiler plant in operational order.
§  Shut main steam stop v/v.
§  Take water to the boiler at 1/4 rd of the gauge glass.
§  Blow down the gauge glass to check it.
§  Check the F. O. tank temp & system.
§  Make sure that air vent of steam drum and super heaters are open.
§  Start the blower to make the combustion chamber gas free.
§  Start the boiler F.O. circulating p/p/ booster p/p.
§  Inject the fuel and light up the burner.
§  According to the manufacturer warm up the boiler by continue firing for 5 minutes every half an hour.
§  Take personal safety from back fire.
§  Shut the vent of steam drum when white steam come out.
§  Ensure the sufficient quantity of water is available in boiler.
§  Take normally 18-24 hours for complete operation.
§  Thus the boiler is ready for work. 

32. What action will you take in case of foaming and priming?
o    Scum blow down.
o    Reduce boiler fire rate.
o    Check whether boiler chemicals added are in excess.
o    Detect the source of contamination.
o    In case of bad priming the boiler may have to be taken out of service, shut down.
o    For contamination due to oil have to be chemically cleaned.

33. Boiler blow down procedure ( cool down):
·         Change the fuel oil burning system from HO to DO and then shut down the burning system.
·         Stop feed pump close feed check valve.
·         Drain down the boiler after allowing it to cool down.
·         If no sufficient time to do this, lower the boiler pressure to 3 to 4 bar.
·         Shut the main steam stop valve.
·         Open the ship side valve then open the blow down valve.
·         Banging noise will appear when boiler is empty.
·         Close the boiler blow down valve and ship side valve.
·         Then release the steam pressure through safety vlv by means of easing gear.
·         When pressure is off, open the air vent and the boiler to cool down.

34.Describe the maintenance procedure of a cascade tank.
Maintenance procedure of cascade:
Changing the filter periodically which protects the boiler system from any                   contamination.
Maintaining the cascade tank water level.
Maintain the water temp. around 600C.
Maintaining the correct operation of flat v/v.
Keeping clean the tank and sight glass.
Always supply clean drain return to the cascade tank.
Always drain the tank for scum out.
Tank should be covered to prevent entry of any dirt or foreign matters.
Tank surface should be scale and deposit free.

35. Prevention of oxidation: 
Oxidation which is responsible for metal corrosion can be prevented by preventing any ingress of dissolved oxygen.
This can be done by two ways.
Mechanically 
Chemically. 
Mechanically it is done by de-aerating equipment. 
Chemically add chemical to boiler water such as sodium sulphite or hydrazine. 2Na2SO3+O2 = 2Na2SO4 
        N2H4 + O2 = 2H2O + N2

36. Prevention of acid corrosion: 
Acid corrosion occurs due to magnesium chloride & carbon dioxide with continuous supply of dissolved oxygen (MgCl2, CO2) in the boiler water.
This can be prevented by lime (Ca(OH)2) and soda ash (Na2CO3) & scavenging the oxygen. 
MgCl2 + Ca(OH)2 = Mg(OH)2+CaCl2 
CaCl2 + Na2CO3 = CaCO3 + 2NaCl

37. Opening up and Inspection Procedure
After making sure no vacuum in it, Then---
1. To remove top man hole door, slacken the dog holding nuts but do not remove them until first broken the joint.
2. Remove nuts and dogs and take out the door.
3. The bottom door can be removed after warning personnel to keep clear of the top door.
4. Make ventilation before entering. Do not allow naked light near the boiler.
5. Preliminary internal inspection carried out before cleaning, to check scale deposits and any special points.
6. Plug orifice to blow down valve to prevent choke, place guards over the manholes landings to prevent damage.
7. Carried out cleaning and internal works.
When all works completed, a full internal examination must be carried out:
·         Cleanliness, all openings are clear, water level gauge connection clears from deposits.
·         All internal pipes and fittings have been replaced correctly and securely attached.
·         Remove plug from the blow down valve orifice.
·         The face of manhole doors and landings inspect to clean and undamaged).
·         Replace manhole doors by using new joints.
·         Operate all boiler mountings. Open air vent cock and fill the boiler with water to sufficient level.

38. How external and internal treatment of boiler feed helps to reduce the scale formation inside the boiler? 
Scale is formed inside the boiler due to presence of salts in the feed water. This scale formation can be reduced by reducing the content of salt. 
This is achieved externally by:
- Using evaporated fresh water or evaporated sea water.
- Proper filtering of feed water.
- Maintaining the correct feed temp.
- De-aeration.
Internally this is done by:
- Ensuring a chemicals reserve dissolved in the feed water in the boiler.

39. How do take action if gauge glass showing low water level?
If water level has not yet dropped completely out the sight glass, water may be put into the boiler.
If water drops completely out of sight glass, check another sight glass, if both disappear water; do not add water until the boiler is cool enough to prevent any possible damage due to rapid cooling of over heated plate.
1. The fire must be immediately stopped.
2. The main steam stop valve must be closed.
3. Blow down and cool down the boiler.
4. Check leakage, drum outside, Located the cause of trouble and make necessary repair.
5. Enter the boiler after it has cooled and examined any possible damage.
6. After repair, water fill up slowly and restore to normal operation.
7. If no damage occurred, inject the water slowly into the boiler and restore it to operation.

40. What are the possible causes if gauge glass shows no water?
·         One gauge glass defective.
·         Boiler tube crack and leaking.
·         Feed regulator jammed.
·         Fail feed pump (Air in feed water line or pump).
·         Level controller malfunction.         
·         Steam consumption is too much.


41.
Boilers Alarm and Trip Functions

The most important alarm and trip functions on marine boilers

Function
Audible and visual
Action
Low water level
Alarm
Low Low water level *
Alarm
Burner stop
High water level
Alarm
High High water level
Alarm
Feedwater pump stop
Low steam pressure
Alarm  (overridden on slave boiler?)
High steam pressure
Alarm
Burner stop
Low feedwater pressure
Alarm
Stand-by pump start
Low fuel oil pressure
Alarm
Stand-by pump start
Low fuel oil temperature
Alarm
High fuel oil temperature
Alarm
Low combustion air pressure
Alarm
Burner stop
Low atomizing steam pressure
Alarm
Burner stop
Flame failure **
Alarm  (overridden during light-up)
Burner stop
Burner not in firing position
Alarm
Burner stop


42. Significance of regular blow down:
§  To reduce the water level in the boiler to prevent carry over or priming.
§  To reduce corrosion.        
§  To remove sludge or mud from the boiler.
§  To reduce solid particles.
§  To reduce the dissolved solid.
§  To reduce oil by scum blow down.
§  To reduce chloride.

43.How regular partial below down of a boiler helps to reduce the boiler water problem?
Boiler water problem means presence of various salts, oil, gas, oxygen, scum & even priming.
Regular partial blow down reduce the boiler water level as well as total dissolved solid which are precipitated from salt by using chemical & chloride. 
It also removes sludge & prevents priming. Thus regular partial below down of boiler helps to reduce boiler water problem.

44. With respect to contamination of boiler water by fuel oil explain why the presence of oil is hazardous?
Oil will effect to the heating surface & causes:
    - Over heating
    - Poor heat transmission.
    - Efficiency loss.
    - Oil may cause acid corrosion.
    - It may causes priming. 

45. Source of oil contamination:
1. Leaky steam heating coil of heater.
2. Leaky heating line of fuel oil tank.
3. Excess lubrication of machinery
4. Condenser (steam leakage sea water gets entry.
5. If the cascade tank is not covered properly dirt’s, debris get entry.

46. Step to be taken after identification the contamination (Oil) :
1) Boiler load is to be reduced.                      
2) If boiler pressure can not be maintained then open the exhaust by pass v/v
3) Identify and isolate the leaky component.
4) Cascade tank scum blow down should be done.
5) Also boiler scum blow don should be done.
6) Continuously add coagulants & potentially
7) Alkaline chemical should be added to maintain alkalinity for protection from acid corrosion.
8) Anti-foam should be added to prevent carry over of water.
9) Check for any more, any more oil spot is visible or not.
10) Then carry out other tests of boiler water to ensure that other parameters are within the limit.
One short system / single short system:
Na2CO3 + H2O ->NaOH + H2O
NaOH + Na2HPO4 –> Na2PO4+H2O
Na2PO4+CaSO4 -> Ca3(PO4)2+Na2SO4
The chemical is added to make the boiler water more alkaline known as BNT corn starch is used to combine the sludge together.
No other treatment is required. 

47.What is caustic embrittlement? How to prevent it ?
It is inter crystalline fracture. It is cause by high concentration of caustic soda and the material under stress. The stress corrosion cracks follow the grain or crystal boundaries of the material and failure.
Sodium sulphate or sodium nitrate is used for the prevention of caustic embrittlement.
It can be found in highly stress area in boiler. Such as tube and tube plate connection, riveted head, seam and boiler mountings.

48. Erosion
It is a mechanical attack on the metal surface which may be due to a disturbance in the flow of the fluid over the metal surfaces, resulting in a loss of metal. Suspended abrasive matters in the fluid can increase the rate of metal losses.

49. Corrosion:
It is the deterioration of metals due to oxidation. The present of water in an acidic condition provides the electrolyte required for corrosion action.
Two forms of corrosion:
Direct chemical attack:
It occurs when metal at high temperature comes into contact with air or other gases, resulting in oxidation or sulphidation of the metal.
Electro-chemical action:
Galvanic action, this being set up when two dissimilar metals are placed in an electrolyte. The noble of the two metals form a cathode to the base metal which , forming the anode, is wasted away.


50. Caustic embrittlement.
Caustic embrittlement is a form of inter crystalline cracking, which results from a solution of sodium hydroxide or caustic soda, becoming more and more concentrated at the bottom of a crack or fissure (narrow opening) which may be the result of fatigue, in the boiler plate or furnace.
The plate must be stressed intention (Wi fNi f x et eto u 117m b n f, so that wastage take place at the bottom of crack, the plate weakens, the crack extends to expose new metal to the caustic action and thus it proceed.
Caustic embrittlement will only occur when there is a high caustic alkalinity that is when the ratio of NaOH to the alkalinity is high. To keep this ratio at the safe level the sodium sulfate to sodium hydroxide should be maintained above 2:5. The sodium sulfate comes out of solution in high sodium hydroxide concentration and by doing forms a protective layer on the surface of the plate.
Also keep the lowest T.D.S level. (Total dissolved suspended & solid).

51. What do you do for preventing of oxygen?
The oxygen-scavenging chemical which is used for DE-aeration the water are usually sodium sulphate or hydrazine.
Excessive dosage of hydrazine could lead to steam and condensate line corrosion due to ammonia being produced as the excess hydrazine decomposed.
In high pressure boiler, by using the sodium sulphite, the sulphite can break down to give hydrogen sulphide which can attack steel brass and copper.

52.Why water testing is essential in water management?
1) To ensure efficient steam production.
2) To get better efficiently of boiler.
3) To minimize heat loss through expensive blow down from boiler.
4) To maintain clean & scale free heat transfer surface.
5) To prevent metal loss due to corrosion.
6) To reduce the total dissolves solid.
7) To prevent formation of deposit in steam condenser system. 8) TO keep the water in alkaline condition.

53. Safety device of boiler gauge glass: 
1) Two gauge glass.
2) Glass is very thick.
3) Guard protect from accidents damage.
4) A board painted white with diagram block.
5) Water side ball, steam side orifice.
6) Drain cock.
7) All handle must be pointed vertically down ward in normal working condition.
8) Remote operation is provided with gauge glass.

54. If boiler water level low, what are the reasons?
The reasons are-
1) Evaporation & consumption rate is higher than the feed rate.
2) Cascade tank empty.
3) Regulator not functioning properly.
4) Safety valve blowing.
5) Blow down v/v leaking.
6) Boiler tubes leaking.
7) Boiler feed p/p is not building / vapour lock.
8) Heating coil is leaking.
9) Faulty gauge glass.                         

55. If the boiler water is low, what to do?
At port:
1. Stop firing.
2. Blow through the gauge glass to check the water level.
3. If the water level is low then
4. Inform C/E
5. Stop feed p/p running.
6. Shut main steam stop v/v
7. Stop T/A by consulting with duty officer.
8. Stop C. O. P by informing duty officer.
9. Stop purifier if running
10. Go for a check.
At sea:
It water level is below the gauge glass, it is unsafe to put water.
1) Inform C/E.
2) Stop feed p/p if running.
3) Inform bridge & reduce engine RPM.
4) Shut main steam stop v/v.
5) Stop purifier if running.
6) Go for a check.

56. Indication of tube leaking:
1) White smoke.
2) Boiler water low level alarm due to excessive leakage, if the feed P/P cannot cover.
3) cascade tank water level low.
4) Feed P/P running continuously.
5) Change flame shape.
6) Noise.

57. Purpose of blowing down a boiler.
1) Reduce water level to prevent carryover or priming.
2) Reduce total dissolved solid.
3) Reduce chloride.
4) Remove sludge.
5) Remove oil by scum blow down.
6) Boiler empty.

58. If chloride is found too much in your boiler water what will you do?
Blow down frequently
Reduce the boiler load to minimum.
If highly contaminant shut down completely and wash out.
Trace and find out the fault and remedies.

59. What do you understand by composite, alternative, and economizer boiler?
Composite boiler:
If exhaust gas and oil fired can be used the same time, it is termed the composite boiler. In this type a separate nest of tube for exhaust gas is provided, situated above the return tubes from the fire furnace. Uptake from the tube nest are separated.
Alternative boiler: 
If the exhaust gas and the oil fire are arranged to be used only at a time, the exhaust gas boiler term as the alternative boiler. This unit can be oil fire heated by the exhaust gases alternatively. It required only one uptake.
Economizer:
In this system a separate exhaust gas economizer is connected to an oil fired auxiliary boiler or an accumulator by means of piping and a set of circulation pump. Exhaust gas is used as heating medium and it has no steam space.

60. What is meant of accumulation pressure?
Accumulation pressure is the rise in boiler pressure which take place when the spring loaded safety valve lift due to the increase loading caused by further compression of the spring.


Reference : marineengineeringonline

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