Question 1. What Is The Affect Of Sulfur In Coal When Used In Boiler?
Sulfur gets oxidized to SO2 and fraction of SO3 and could react with water to shape sulfuric acid and this happens at a temperature called the acid dew point which normally is ready 120 oC. The sulfuric acid so formed corrodes the metallic when it comes in contact with it.
Question 2. What Do You Mean By Ibr Steam Boiler?
IBR Steam Boilers means any closed vessel exceeding 22.75 liters in ability and which is used expressively for generating steam beneath pressure and includes any mounting or different becoming connected to such vessel, that is entirely or in part under stress whilst the steam is close off.
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Question three. What Do You Understand By ‘water Tube Boilers’ And ‘fireplace Tube Boilers’?
In water tube boilers the water passes via the tubes and the recent gases passes out aspect the tubes wherein as in case of hearth tube boiler the recent gases passes via the tubes and the water passes over the tubes.
Question four. What Is The Parameters Required To Estimate The Boiler Efficiency By ‘direct Method’?
Steam drift charge
GCV of gas
Fuel glide fee
Steam situations ( stress and temperature)
Feed water temperature
Question five. Why Boiler Blow-down Is Required?
As the feed water evaporate into steam, dissolved solids pay attention in the boiler. Above sure level of awareness, these solids encourage carryover of water into steam. This results in scale formation within the boiler, resulting in localized overheating and ending eventually in tube failure. Hence blow-down could be very a lot required for boilers.
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Question 6. What Is The Principle Of Mechanical Deaeration (stress Type) Of Boiler Feed Water?
The stress-type de-aerators operates by permitting steam into the feed water via a pressure manage valve to maintain the preferred operating stress, and hence temperature at at the least a hundred and five °C. The steam raises the water temperature inflicting the release of O2 and CO2 gases which are then vented from the system. This type can lessen the oxygen content material to zero.0.5 mg/litre.
Question 7. What Is The Effect Of Boiler Loading On Boiler Efficiency?
The maximum performance of the boiler does no longer arise at full load, but at approximately two-thirds of the total load. If the weight at the boiler decreases in addition, performance also tends to lower.
As the load falls, so does the price of the mass glide rate of the flue gases thru the tubes. This discount in waft rate for the identical heat switch area decreased the exit flue fuel temperatures with the aid of a small quantity, lowering the sensible warmness loss.
Below 1/2 load, maximum combustion home equipment need more excess air to burn the fuel completely. This will increase the practical heat loss.
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Question eight. What Is The Principle Heat Losses That Occur In A Boiler?
The principle warmness losses that arise in a boiler are:
Loss of heat because of dry flue gasoline
Loss of warmth because of moisture in gasoline and combustion air
Loss of heat because of combustion of hydrogen
Loss of heat because of radiation
Loss of warmth due to unburned gas
Question 9. What Does You Meant By Tangential Firing With Respect To Pulverized Coal Fired Boiler?
The approach of firing used for coal firing in pulverized fuel fired boiler is the tangential firing. In this sort of firing four burners are used on the nook to corner to create a fireplace ball at the center of the furnace.
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Question 10. What Are The Disadvantages Of ‘direct Method’ Of Boiler Efficiency Evaluation Over ‘oblique Method’?
Do no longer provide clues to the operator as to why efficiency of device is lower.
Do not calculate diverse losses answerable for various efficiency ranges.
Question 11. List Out The Data Required For Calculation Of Boiler Efficiency Using ‘oblique Method’?
The facts required for calculation of boiler efficiency the usage of indirect approach are:
Ultimate analysis of gasoline (H2, O2, S, C, moisture content, ash content)
Percentage of Oxygen or CO2 within the flue fuel
Flue fuel temperature in 0C (Tf)
Ambient temperature in 0C (Ta) & humidity of air in kg/kg of dry air.
GCV of fuel in kcal/kg
Percentage combustible in ash (in case of solid fuels)
GCV of ash in kcal/kg (in case of strong fuels)
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Question 12. Explain The Different External Water Treatment Methods?
External remedy is used to do away with suspended solids, dissolved solids (specifically the Calcium and Magnesium ions which is a primary purpose of scale formation) and dissolved gases (oxygen and carbon dioxide). The strategies include Precipitation methods, wherein chemical substances are delivered to precipitate calcium and magnesium as compounds of low solubility.
The lime-soda process is usual of this elegance, but other precipitating agents such as caustic soda and sodium phosphate can be used whilst the composition of the raw water permits.
Ion-change progresses, in which the hardness is eliminated because the water passes via mattress of natural zeolite or synthetic resin and without the formation of any precipitate. Ion change tactics may be used for almost overall demineralization if required, as is the case in massive electric powered power plant boilers.
De-aeration, wherein gases are expelled by means of preheating the water earlier than getting into the boiler system. Water commonly contains about 10 mg/1 of dissolved oxygen at ambient temperature Filtration, to remove suspended solids.
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Question 13. What Are The Salient Features Of A ‘packaged Boiler’?
The features of package boilers are:
Small combustion space and excessive heat release fee ensuing in faster evaporation.
Large range of small diameter tubes leading to suitable convective heat switch.
Forced or prompted draft structures ensuing in correct combustion performance.
Number of passes ensuing in higher universal warmness transfer.
Higher thermal performance at decrease potential (say beneath 1 ton) levels compared with other boilers.
Question 14. What Are The Two Main Classification Of A Stoker Fired Boiler?
Chain grate or traveling grate stoker.
Question 15. Briefly Explain The Principle Involved In ‘reverse Osmosis’?
When solutions of differing concentrations are separated by means of a semi-permeable membrane, water from less focused answer passes via the membrane to dilute the liquid of excessive awareness.
If the solution of excessive concentration is pressurized, the process is reversed and the water from the answer of high awareness flows to the weaker answer.
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Question sixteen. What Are The Various Methods Available To Control The ‘extra Air’ In A Boiler?
Various strategies are available to control the extra air:
Portable oxygen analysers and draft gauges may be used to make periodic readings to manual the operator to manually alter the glide of air for maximum operation. Excess air discount up to 20% is viable.
The most not unusual method is the non-stop oxygen analyzer with a local readout established draft gauge, by means of which the operator can regulate air glide. A similarly discount of 10-15% can be done over the preceding gadget.
The equal continuous oxygen analyzer can have a far flung managed pneumatic damper positioner, by means of which the readouts are available in a manage room. This allows an operator to remotely manipulate a number of firing systems simultaneously.
Question 17. Describe ‘chain Grate’ And ‘spreader Stoker’ Type Boiler?
Chain-Grate or Travelling-Grate Stoker Boiler:
Coal is fed onto one quit of a transferring metal grate. As grate moves along the duration of the furnace, the coal burns earlier than dropping off on the stop as ash. Some diploma of ability is needed.
Especially when putting in place the grate, air dampers and baffles, to make sure clean combustion leaving the minimal of unburnt carbon within the ash. The coal-feed hopper runs along the whole coal-feed end of the furnace. A coal grate is used to control the charge at which coal is fed into the furnace by way of controlling the thickness of the gasoline mattress. Coal need to be uniform in size as huge lumps will not burn out completely by the time they reach the cease of the grate.
Spreader Stoker Boiler:
Spreader stokers utilize a combination of suspension burning and grate burning. The coal is always fed into the furnace above a burning bed of coal. The coal fines are burned in suspension; the bigger particles fall to the grate, wherein they're burned in a skinny, speedy-burning coal mattress. This technique of firing gives right flexibility to satisfy load fluctuations, considering the fact that ignition is sort of immediately whilst firing rate is accelerated. Hence, the spreader stoker is preferred over different types of stokers in lots of industrial applications.
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Question 18. Write Short Notes On ‘intermittent Blow Down’ And ‘non-stop Blow Down’ With Respect To Boilers?
The ‘intermittent blown down’ is given with the aid of manually operating a valve suited to discharge pipe at the bottom factor of boiler shell to reduce parameters (TDS or conductivity, pH, Silica and Phosphates awareness) within prescribed limits in order that steam fine is not probable to be affected. In intermittent blow down, a huge diameter line is opened for a quick time frame, the time being based totally on a thumb rule consisting of “once a shift for two minutes”. ‘Intermittent blow down’ calls for big short-term will increase in the quantity of feed water placed into the boiler, and hence may additionally necessitate larger feed water pumps than if non-stop blow down is used. Also, TDS degree will be various, thereby inflicting fluctuations of the water level within the boiler due to modifications in steam bubble size and distribution which accompany changes in awareness of solids. Also extensive quantity of heat strength is lost with intermittent blow down.
There is a steady and constant dispatch of small circulate of focused boiler water, and alternative by means of consistent and regular inflow of feed water. This ensures regular TDS and steam purity at given steam load. Once blow down valve is ready for a given situations, there may be no want for everyday operator intervention. Even even though big portions of warmth are wasted, possibility exits for convalescing this warmth by using blowing right into a flash tank and generating flash steam. This flash steam may be used for pre-heating boiler feed water or for some other purpose. This sort of blow down is commonplace in high-strain boilers.
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Question 19. Explain The Reasons For Carrying Out “blow Down” In A Boiler?
Water carries sure percentage of dissolved solids. The percentage of impurities located in boiler water relies upon on the untreated feed water pleasant, the remedy system used and the boiler operating approaches. As a popular rule, the higher the boiler operates pressure, the extra can be the sensitivity to impurities. As the feed water materials evaporate into steam, dissolved solids concentrate in the boiler both in a dissolved or suspended state. Above a sure stage of attention, these solids encourage foaming and motive carryover of water into the steam. This results in scale formation in the boiler, resulting in localized overheating and ending eventually in tube failure. It is therefore necessary to govern the level of concentration of the solids and that is executed via the process of ‘blowing down’, wherein a sure extent of water is blown off and is mechanically changed by using feed water – as a result keeping the top-rated level of total dissolved solids (TDS) in the water. Blow down is necessary to shield the surfaces of the heat exchanger inside the boiler.