Sunday, August 12, 2018
Thursday, August 9, 2018
What is dew point and why it is important in instrument air?
What is dew point and why it is important in instrument air?
The Dew Point is the temperature at which water vapor starts to condense out of the air (the temperature at which air becomes completely saturated). Above this temperature the moisture will stay in the air.
Electronic instruments uses instrument air received from instrument compressors must be free of any moisture. Because even a very small amount of moisture may condense and give enormous deviation between actual value and displayed value which would result in many problems. So the instrument air should be free of moisture. This is ensured by keeping the dew point below ‑400C or below.
The Dew Point is the temperature at which water vapor starts to condense out of the air (the temperature at which air becomes completely saturated). Above this temperature the moisture will stay in the air.
Electronic instruments uses instrument air received from instrument compressors must be free of any moisture. Because even a very small amount of moisture may condense and give enormous deviation between actual value and displayed value which would result in many problems. So the instrument air should be free of moisture. This is ensured by keeping the dew point below ‑400C or below.
What is dry bulb temperature, wet bulb temperature?
What is dry bulb temperature, wet bulb temperature?
Dry bulb is the temperature of ambient air measured by thermometer. It is called “Dry bulb temperature” because the temperature shown by thermometer is not affected by the moisture content of the air.
The Wet Bulb temperature is the temperature of adiabatic saturation. This is the temperature indicated by a moistened thermometer bulb exposed to the air flow.
Wet Bulb temperature can be measured by using a thermometer with the bulb wrapped in wet muslin. The adiabatic evaporation of water from the thermometer and the cooling effect is indicated by a “wet bulb temperature” lower than the “dry bulb temperature” in the air.
(Courtesy: h즈p://www.engineeringtoolbox.com/dry‑wet‑bulb‑dew‑point‑air‑d_682.html (h즈p://www.engineeringtoolbox.com/dry‑wetbulb‑dew‑point‑air‑d_
682.html))
Dry bulb is the temperature of ambient air measured by thermometer. It is called “Dry bulb temperature” because the temperature shown by thermometer is not affected by the moisture content of the air.
The Wet Bulb temperature is the temperature of adiabatic saturation. This is the temperature indicated by a moistened thermometer bulb exposed to the air flow.
Wet Bulb temperature can be measured by using a thermometer with the bulb wrapped in wet muslin. The adiabatic evaporation of water from the thermometer and the cooling effect is indicated by a “wet bulb temperature” lower than the “dry bulb temperature” in the air.
(Courtesy: h즈p://www.engineeringtoolbox.com/dry‑wet‑bulb‑dew‑point‑air‑d_682.html (h즈p://www.engineeringtoolbox.com/dry‑wetbulb‑dew‑point‑air‑d_
682.html))
What is the difference between fouling and scaling?
What is the difference between fouling and scaling?
Fouling is caused by the collection of loose debris over pump‑suction screens in sumps or growth of algae in sunlit areas while scaling is depositing of dissolved minerals on equipment surfaces
Fouling is caused by the collection of loose debris over pump‑suction screens in sumps or growth of algae in sunlit areas while scaling is depositing of dissolved minerals on equipment surfaces
Both the Nusselt number and the Biot number have the same form. What are the differences between them in terms of the variables employed and their physical significance?
Both the Nusselt number and the Biot number have the same form. What are the differences between them in terms of the variables employed and their physical significance?
Both the Biot number and the Nusselt number are of the form (hL/k). However, for the Biot number, the thermal conductivity k used is that for the solid; for calculating Nusselt number the k value as that of the fluid. The Biot number is a measure of the ratio of the temperature drop in the solid material and the temperature drop between the solid and the fluid.
The Nusselt number is a dimensionless version of the temperature gradient at the surface between the fluid and the solid, and it thus provides a measure of the convection occurring from the surface.
Courtesy:h즈p://research.me.udel.edu/advani/teaching/s98_me302_review.htm
(h즈p://research.me.udel.edu/advani/teaching/s98_me302_review.htm)
Both the Biot number and the Nusselt number are of the form (hL/k). However, for the Biot number, the thermal conductivity k used is that for the solid; for calculating Nusselt number the k value as that of the fluid. The Biot number is a measure of the ratio of the temperature drop in the solid material and the temperature drop between the solid and the fluid.
The Nusselt number is a dimensionless version of the temperature gradient at the surface between the fluid and the solid, and it thus provides a measure of the convection occurring from the surface.
Courtesy:h즈p://research.me.udel.edu/advani/teaching/s98_me302_review.htm
(h즈p://research.me.udel.edu/advani/teaching/s98_me302_review.htm)
Why baffles are used in reactors?
Why baffles are used in reactors?
The purpose of baffles in reactors ia s same as that of heat exchangers. Here also they increase turbulence thus causing higher rate of heat transfer, mixing thus ultimately reaction rate.
The purpose of baffles in reactors ia s same as that of heat exchangers. Here also they increase turbulence thus causing higher rate of heat transfer, mixing thus ultimately reaction rate.
What is the use of baffles in heat exchanges?
What is the use of baffles in heat exchanges?
Baffles installed in a heat exchanger acts as an obstruction in the flow path of shell side liquid. It reduces the effective cross section area through which the liquid travels. Due to this the velocity and turbulence of liquid is increased thus resulting in high heat transfer.
Baffles installed in a heat exchanger acts as an obstruction in the flow path of shell side liquid. It reduces the effective cross section area through which the liquid travels. Due to this the velocity and turbulence of liquid is increased thus resulting in high heat transfer.
In which type of condensation (Film type, drop wise) heat transfer would be higher?
In which type of condensation (Film type, drop wise) heat transfer would be higher?
In drop wise condensation the drops formed will fall and the new steam that enters will find a new surface to contact, and to transfer heat.
But in film type condensation a film will be formed on the tube wall which will prevent the fresh steam to contact the tube surface. So naturally drop wise heat transfer will be higher.
In drop wise condensation the drops formed will fall and the new steam that enters will find a new surface to contact, and to transfer heat.
But in film type condensation a film will be formed on the tube wall which will prevent the fresh steam to contact the tube surface. So naturally drop wise heat transfer will be higher.
How liquid nitrogen is saved in tanks?
How liquid nitrogen is saved in tanks?
Nitrogen is available in liquid form after compression. If it is exposed to atmosphere directly or comes in contact with heat it would flash (evaporate).
So we need to protect the nitrogen storage from the outside temperature. The boiling point of nitrogen is ‑195.8oC. To achieve that it is stored in an inside vessel with an outer vessel surrounding it.
The annular space between the two vessels is evacuated to ensure the outside temperature won’t enter inside as no medium is there. This method is similar to what we see in a thermos flask
Nitrogen is available in liquid form after compression. If it is exposed to atmosphere directly or comes in contact with heat it would flash (evaporate).
So we need to protect the nitrogen storage from the outside temperature. The boiling point of nitrogen is ‑195.8oC. To achieve that it is stored in an inside vessel with an outer vessel surrounding it.
The annular space between the two vessels is evacuated to ensure the outside temperature won’t enter inside as no medium is there. This method is similar to what we see in a thermos flask
When extended surface HE is required?
When extended surface HE is required?
When the temperature difference between two fluids is less to achieve higher heat transfer rate we may have to increase the external surface area. That’s why we need extended surface heat exchangers.
When the temperature difference between two fluids is less to achieve higher heat transfer rate we may have to increase the external surface area. That’s why we need extended surface heat exchangers.
When to use gate valve and globe, ball?
When to use gate valve and globe, ball?
Gate valve – On off purpose
Globe valve – Thro즈ling purpose
Ball valve – On off purpose with quicker action
Gate valve – On off purpose
Globe valve – Thro즈ling purpose
Ball valve – On off purpose with quicker action
Why tangential entry in cyclone separators?
Why tangential entry in cyclone separators?
If the dust laden gas enters straightly inside the cyclone separator it won’t acquire swirl motion. Only tangential entry sets up such swirl motion(centrifugal force) due to which separation of solid‑ gas is achieved.
If the dust laden gas enters straightly inside the cyclone separator it won’t acquire swirl motion. Only tangential entry sets up such swirl motion(centrifugal force) due to which separation of solid‑ gas is achieved.
What would be impact if we increase and decrease the size of packing in packed column?
What would be impact if we increase and decrease the size of packing in packed column?
Increase in size of packing will give lower mass transfer rate and lower pressure drop. Decrease in packing size will lead to higher Increase in size of packing will give lower mass transfer rate and lower pressure drop. Decrease in packing size will lead to higher pressure drop and high mass transfer rates.
Increase in size of packing will give lower mass transfer rate and lower pressure drop. Decrease in packing size will lead to higher Increase in size of packing will give lower mass transfer rate and lower pressure drop. Decrease in packing size will lead to higher pressure drop and high mass transfer rates.
What is the use of plate efficiency in distillation column?
What is the use of plate efficiency in distillation column?
Plate efficiency in plate column is used to convert the theoretical number of plates into actual number plates. As any plate can’t perform ideal we have to multiply its efficiency with theoretical no of plates to get actual plates required.
Plate efficiency in plate column is used to convert the theoretical number of plates into actual number plates. As any plate can’t perform ideal we have to multiply its efficiency with theoretical no of plates to get actual plates required.
When vacuum distillation is needed?
When vacuum distillation is needed?
In case if the substance being distilled may degrade before it reaches its boiling point we have to boil it a lower temperature than its boiling temperature. That’s why we need vacuum distillation.
In case if the substance being distilled may degrade before it reaches its boiling point we have to boil it a lower temperature than its boiling temperature. That’s why we need vacuum distillation.
Why SS are not corrosive?
Why SS are not corrosive?
The SS (stainless steel) contains some percentage of chromium. The chromium reacts with oxygen (which is present in air) to form Cr2O which prevents further oxygen to react with Iron (Fe) of SS to form rust.
The SS (stainless steel) contains some percentage of chromium. The chromium reacts with oxygen (which is present in air) to form Cr2O which prevents further oxygen to react with Iron (Fe) of SS to form rust.
What is the MOC of HE?
What is the MOC of HE?
The material of construction of heat exchanger depends upon the properties of the liquid / vapor being handled, pressure and temperature conditions etc. Normally used materials are carbon steel, stainless steel, nickel, nickel alloys or other special alloys.
The material of construction of heat exchanger depends upon the properties of the liquid / vapor being handled, pressure and temperature conditions etc. Normally used materials are carbon steel, stainless steel, nickel, nickel alloys or other special alloys.
What is the difference between PFD and PID?
What is the difference between PFD and PID?
The PFD (process flow diagram) gives us picture about stages of the process. But the PID (process instrumentation diagram) shows us the location of valves, pumps, compressors, utilities etc in the process.
The PFD (process flow diagram) gives us picture about stages of the process. But the PID (process instrumentation diagram) shows us the location of valves, pumps, compressors, utilities etc in the process.
What is the role of casing in centrifugal pumps?
What is the role of casing in centrifugal pumps?
The casing is designed in such manner its cross section area increases from the side of entry of liquid i.e. the liquid enters in a small cross section and moves along higher cross section. Due to that the part of its kinetic energy is converted into pressure energy.
The casing is designed in such manner its cross section area increases from the side of entry of liquid i.e. the liquid enters in a small cross section and moves along higher cross section. Due to that the part of its kinetic energy is converted into pressure energy.
What is MSDS?
What is MSDS?
A MSDS (material safety data sheet) is a sheet which gives all information such as physical, chemical properties of the chemical being handled, TLV, antidote, safety precautions, fire extinguisher type to be used etc. Everyone who handles a chemical substance should be well aware of the MSDS of that particular product.
A MSDS (material safety data sheet) is a sheet which gives all information such as physical, chemical properties of the chemical being handled, TLV, antidote, safety precautions, fire extinguisher type to be used etc. Everyone who handles a chemical substance should be well aware of the MSDS of that particular product.
Why Steam ejectors are used in series? Why an inter condenser is needed between two stages of ejectors?
Why Steam ejectors are used in series? Why an inter condenser is needed between two stages of ejectors?
If the system under which vacuum needed is large i.e. if we have to suck large volume of vapors from the system a single ejector can’t handle the entire load. So we need more ejectors in series.
In inter condenser the vapor from a particular stage is cooled and thus the load to the next stage is reduced. Only the inconsolable (the `part of vapor that can’t be condensed) move to the next stage which would leave the system along with next stage condensed vapor.
If the system under which vacuum needed is large i.e. if we have to suck large volume of vapors from the system a single ejector can’t handle the entire load. So we need more ejectors in series.
In inter condenser the vapor from a particular stage is cooled and thus the load to the next stage is reduced. Only the inconsolable (the `part of vapor that can’t be condensed) move to the next stage which would leave the system along with next stage condensed vapor.
What is the size of nozzle in steam ejectors?
What is the size of nozzle in steam ejectors?
One to three millimeters diameters.
One to three millimeters diameters.
Why steam ejectors are located above 10.33 meters only (or) What is Barometric leg ?
Why steam ejectors are located above 10.33 meters only (or) What is Barometric leg ?
When steam ejectors are in operation a higher vacuum is created inside the system. If the system comes in direct contact with atmosphere the atmospheric air would enter the system and break the vacuum.
So we use water as a seal. But water also will be sucked by the vacuum to a height of 10.33 meters which is known as Barometric leg. If the steam ejector is kept below 10.33 meters the
barometric leg would be unstable and water will enter the system. (10.33 Meters of water = 760 mm of Hg)
The barometric line should be straight to ensure a perfect vacuum.
When steam ejectors are in operation a higher vacuum is created inside the system. If the system comes in direct contact with atmosphere the atmospheric air would enter the system and break the vacuum.
So we use water as a seal. But water also will be sucked by the vacuum to a height of 10.33 meters which is known as Barometric leg. If the steam ejector is kept below 10.33 meters the
barometric leg would be unstable and water will enter the system. (10.33 Meters of water = 760 mm of Hg)
The barometric line should be straight to ensure a perfect vacuum.
Why PD pumps need safety valve at discharge side whereas a centrifugal pump doesn’t need it?
Why PD pumps need safety valve at discharge side whereas a centrifugal pump doesn’t need it?
Because the positive displacement pumps create a higher discharge pressure. (Even up to 200bars ) In case by mistake the discharge valve is closed the higher delivery side pressure will damage the discharge line and the pump itself. To avoid we need a safety valve which may recycle a portion of liquid from delivery side to the reservoir.
Because the positive displacement pumps create a higher discharge pressure. (Even up to 200bars ) In case by mistake the discharge valve is closed the higher delivery side pressure will damage the discharge line and the pump itself. To avoid we need a safety valve which may recycle a portion of liquid from delivery side to the reservoir.
What is priming in centrifugal pumps?
What is priming in centrifugal pumps?
Priming is a technique used to drive away the air entrapped in the suction line of a centrifugal pump. If the air present in the suction line are not removed the pump won’t be able to suck the liquid from the reservoir as air is lighter medium whereas liquid is heavier medium.
So the whole suction line and the part of casing is filled with water and the air is removed via the air vent. Also if air is allowed to enter to the impeller they will damage the impeller by flashing (cavitation).
Normally cavitation won’t occur in pump which is continuously in service as there is a li즈le chance for the air to get into the suction
line.
Unlike a positive displacement pump that can pump a liquid to any head as long as the pump body is strong enough, and there is enough horsepower available, the centrifugal pump can only pump a liquid to its rated head.
You’ll recall that this head was determined by, and limited to the diameter of the impeller and the impeller speed (rpm.) Since the weight of water is approximately 8000 times that of air (50 miles vs. 34 feet or 80 Km. vs. 10 meters) the centrifugal pump can produce only 1/8000 of its rated liquid pressure. In other words, for every one foot water has to be raised to prime the pump, the
centrifugal pump must produce a discharge head of approximately 8000 feet (each meter requires a head of 8000 meters) and that is impossible with conventional impeller diameters and speeds.
All of this means that if you intend to use a centrifugal pump you’re going to have to come up with some sensible method of priming it.
Your choices will include:
a) Install a foot valve in the suction piping to insure the liquid will not drain from the pump casing and suction piping when the pump stops. Keep in mind that these valves have a nasty habit of leaking.
b) Evacuate the air in the system with a positive displacement priming pump operating between the pump and a closed discharge valve.
c) Fill the pump with liquid prior to starting it.
d) Convert the application to a self priming pump that maintains a reservoir of liquid at its suction.
Priming is a technique used to drive away the air entrapped in the suction line of a centrifugal pump. If the air present in the suction line are not removed the pump won’t be able to suck the liquid from the reservoir as air is lighter medium whereas liquid is heavier medium.
So the whole suction line and the part of casing is filled with water and the air is removed via the air vent. Also if air is allowed to enter to the impeller they will damage the impeller by flashing (cavitation).
Normally cavitation won’t occur in pump which is continuously in service as there is a li즈le chance for the air to get into the suction
line.
Unlike a positive displacement pump that can pump a liquid to any head as long as the pump body is strong enough, and there is enough horsepower available, the centrifugal pump can only pump a liquid to its rated head.
You’ll recall that this head was determined by, and limited to the diameter of the impeller and the impeller speed (rpm.) Since the weight of water is approximately 8000 times that of air (50 miles vs. 34 feet or 80 Km. vs. 10 meters) the centrifugal pump can produce only 1/8000 of its rated liquid pressure. In other words, for every one foot water has to be raised to prime the pump, the
centrifugal pump must produce a discharge head of approximately 8000 feet (each meter requires a head of 8000 meters) and that is impossible with conventional impeller diameters and speeds.
All of this means that if you intend to use a centrifugal pump you’re going to have to come up with some sensible method of priming it.
Your choices will include:
a) Install a foot valve in the suction piping to insure the liquid will not drain from the pump casing and suction piping when the pump stops. Keep in mind that these valves have a nasty habit of leaking.
b) Evacuate the air in the system with a positive displacement priming pump operating between the pump and a closed discharge valve.
c) Fill the pump with liquid prior to starting it.
d) Convert the application to a self priming pump that maintains a reservoir of liquid at its suction.
What is critical insulation thickness for pipes?
What is critical insulation thickness for pipes?
We know that by adding more insulation to a wall always decreases heat transfer. The thicker the insulation, the lower the heat transfer rate. This is expected, since the heat transfer area A is constant, and adding insulation always increases the thermal resistance of the wall without affecting the convection resistance.
Adding insulation to a cylindrical piece or a spherical shell, however, is a different ma즈er. The additional insulation increases the conduction resistance of the insulation layer but decreases the convection resistance of the surface because of the increase in the outer surface area for convection. The heat transfer from the pipe may increase or decrease, depending on which effect dominates.
Consider a cylindrical pipe of outer radius r1 whose outer surface temperature T1 is maintained constant. The pipe is now insulated with a material whose thermal conductivity s k and outer radius is r2 .
Heat is lost from the pipe to the surrounding medium at temperature T∞ with a convection heat transfer coefficient h. The rate of heat transfer from the insulated pipe to the surrounding air
can be expressed as The value of r2 at which heat transfer rate reaches maximum is determined from the requirement that (zero slope). Performing the differentiation and solving for r2 yields the critical radius of insulation for a cylindrical body to be rcr,cylinder = k/h
Note that the critical radius of insulation depends on the thermal conductivity of the insulation k and the external convection heat transfer coefficient h.The rate of heat transfer from the cylinder increases with the addition of insulation for r2< rcr, reaches a maximum when r2= rcr, and starts to decrease for r2> rcr. Thus, insulating the pipe may actually increase the rate of heat transfer from the pipe
instead of decreasing it when r2< rcr.
Coutesy:IITB Source
(h즈 //www.cdeep.iitb.ac.in/nptel/Mechanical/Heat%20and%20Mass%20Transfer/Conduction/Module%202/main/2.6.4.html)
We know that by adding more insulation to a wall always decreases heat transfer. The thicker the insulation, the lower the heat transfer rate. This is expected, since the heat transfer area A is constant, and adding insulation always increases the thermal resistance of the wall without affecting the convection resistance.
Adding insulation to a cylindrical piece or a spherical shell, however, is a different ma즈er. The additional insulation increases the conduction resistance of the insulation layer but decreases the convection resistance of the surface because of the increase in the outer surface area for convection. The heat transfer from the pipe may increase or decrease, depending on which effect dominates.
Consider a cylindrical pipe of outer radius r1 whose outer surface temperature T1 is maintained constant. The pipe is now insulated with a material whose thermal conductivity s k and outer radius is r2 .
Heat is lost from the pipe to the surrounding medium at temperature T∞ with a convection heat transfer coefficient h. The rate of heat transfer from the insulated pipe to the surrounding air
can be expressed as The value of r2 at which heat transfer rate reaches maximum is determined from the requirement that (zero slope). Performing the differentiation and solving for r2 yields the critical radius of insulation for a cylindrical body to be rcr,cylinder = k/h
Note that the critical radius of insulation depends on the thermal conductivity of the insulation k and the external convection heat transfer coefficient h.The rate of heat transfer from the cylinder increases with the addition of insulation for r2< rcr, reaches a maximum when r2= rcr, and starts to decrease for r2> rcr. Thus, insulating the pipe may actually increase the rate of heat transfer from the pipe
instead of decreasing it when r2< rcr.
Coutesy:IITB Source
(h즈 //www.cdeep.iitb.ac.in/nptel/Mechanical/Heat%20and%20Mass%20Transfer/Conduction/Module%202/main/2.6.4.html)
What is TLV (threshold limit value)?
What is TLV (threshold limit value)?
The threshold limit value was set by American Conference of Governmental industrial Hygienists, Inc (ACGIH) which is defined as the level of concentration of a chemical substance in which a worker can work without an unreasonable risk of disease or injury. It can be expressed in ppm or mg/m3.
For example the TLV of chlorine for an 8 hrs work day is 0.5ppm or 1.5 mg/m3. Which indicates a worker can work without any unreasonable risk of disease or injury for 8 hours if and only the chlorine concentration in his/her vicinity is within 0.5ppm.
The threshold limit value was set by American Conference of Governmental industrial Hygienists, Inc (ACGIH) which is defined as the level of concentration of a chemical substance in which a worker can work without an unreasonable risk of disease or injury. It can be expressed in ppm or mg/m3.
For example the TLV of chlorine for an 8 hrs work day is 0.5ppm or 1.5 mg/m3. Which indicates a worker can work without any unreasonable risk of disease or injury for 8 hours if and only the chlorine concentration in his/her vicinity is within 0.5ppm.
How to convert ppm in to percentage?
How to convert ppm in to percentage?
We have to divide by 104 to for the ppm to get converted to percentage. To convert percentage to ppm we have to multiply by 104.
How to calculate?
ppm(parts per million) means out of million i.e. out of 106
Percentage means out of 100 ie out of 10^2
Let us assume we have to convert X ppm into percentage
10^6 parts of substance is having x parts of a component
10^2 parts of the substance would have (10^2 * X) / 10^6 = X/10^4
We have to divide by 104 to for the ppm to get converted to percentage. To convert percentage to ppm we have to multiply by 104.
How to calculate?
ppm(parts per million) means out of million i.e. out of 106
Percentage means out of 100 ie out of 10^2
Let us assume we have to convert X ppm into percentage
10^6 parts of substance is having x parts of a component
10^2 parts of the substance would have (10^2 * X) / 10^6 = X/10^4
When to use absorption factor method to calculate no of plates?
When to use absorption factor method to calculate no of plates?
If the operating data line and equilibrium line in the Mccabe thiele method runs parallel the no of theoretical plates would be infinite.
So it would be impossible to find the no of plates as the both won’t touch at any point. So we need absorption factor method wherein no of theoretical plates can be found by Fenske equation.
If the operating data line and equilibrium line in the Mccabe thiele method runs parallel the no of theoretical plates would be infinite.
So it would be impossible to find the no of plates as the both won’t touch at any point. So we need absorption factor method wherein no of theoretical plates can be found by Fenske equation.
What should be the packing size in packed columns?
What should be the packing size in packed columns?
The size of packing should be approximately 1/8th of the internal diameter of packed column for optimum pressure drop
The size of packing should be approximately 1/8th of the internal diameter of packed column for optimum pressure drop
Why we use LMTD to calculate overall heat transfer co efficient in shell and tube than arithmetic average?
Why we use LMTD to calculate overall heat transfer co efficient in shell and tube than arithmetic average?
In a heat exchanger the heat being lost by the hot fluid as well as the heat gained by the cold fluid is not linear. So we need to use logarithmic average than arithmetic average to calculate correct value of overall heat transfer co efficient.
In a heat exchanger the heat being lost by the hot fluid as well as the heat gained by the cold fluid is not linear. So we need to use logarithmic average than arithmetic average to calculate correct value of overall heat transfer co efficient.
What is the difference between HAZOP and HAZAN?
What is the difference between HAZOP and HAZAN?
HAZOP(hazard and operability studies)
HAZAN(hazard analysis)
Identifies hazards Assesses hazards
Preferred technique –used on every
project Selective technique‑ use when others fails
Qualitative Quantitative
Done by a team Done by one or two people
Also called “what if” Also calledRisk analysis,Risk assessmentProbabilistic risk ssessment(PRA)Quantitative risk assessment (QRA)
HAZOP(hazard and operability studies)
HAZAN(hazard analysis)
Identifies hazards Assesses hazards
Preferred technique –used on every
project Selective technique‑ use when others fails
Qualitative Quantitative
Done by a team Done by one or two people
Also called “what if” Also calledRisk analysis,Risk assessmentProbabilistic risk ssessment(PRA)Quantitative risk assessment (QRA)
Differentiate compressors, fans and blowers?
Differentiate compressors, fans and blowers?
Fans, blowers and compressors are differentiated based on the method used to move the air and specific ratio (specific ratio= discharge pressure/suction pressure). As per the American Society of Mechanical Engineers (ASME) the compression ration for fans is up to 1.11, blowers‑ 1.11 to 1.2 and for compressors above 1.2
Fans, blowers and compressors are differentiated based on the method used to move the air and specific ratio (specific ratio= discharge pressure/suction pressure). As per the American Society of Mechanical Engineers (ASME) the compression ration for fans is up to 1.11, blowers‑ 1.11 to 1.2 and for compressors above 1.2
What is surging in compressors and how it can be prevented?
What is surging in compressors and how it can be prevented?
In centrifugal and axial compressors when the suction volume falls below a certain limit i.e. when the compressor is not getting enough volume of gas to compress, the gas from discharge side will flow back to the compressor( which would reduce the speed of compressor )and join together with the suction side to increase the volume input.
Thereafter the speed of compressor picks and it come to normal operation. But meanwhile such revere in flow will cross huge pressure gradient across the compressor and vibration thus may damage the impeller. This momentary reverse flow lapses for very short time To prevent surging we need to install an anti surging system.
The anti surging system shall have a mechanism to measure the suction flow and discharge flow time to time along with a control valve. When the suction volume falls below a certain set value a part of discharge gas will be directed towards the suction to maintain the minimum suction volume. As normally compression leads to increase in temperature the gas recycle sis taken after the “after cooler” to ensure the discharge temperature is within control.
In centrifugal and axial compressors when the suction volume falls below a certain limit i.e. when the compressor is not getting enough volume of gas to compress, the gas from discharge side will flow back to the compressor( which would reduce the speed of compressor )and join together with the suction side to increase the volume input.
Thereafter the speed of compressor picks and it come to normal operation. But meanwhile such revere in flow will cross huge pressure gradient across the compressor and vibration thus may damage the impeller. This momentary reverse flow lapses for very short time To prevent surging we need to install an anti surging system.
The anti surging system shall have a mechanism to measure the suction flow and discharge flow time to time along with a control valve. When the suction volume falls below a certain set value a part of discharge gas will be directed towards the suction to maintain the minimum suction volume. As normally compression leads to increase in temperature the gas recycle sis taken after the “after cooler” to ensure the discharge temperature is within control.
Why centrifugal pumps are widely used in process industries than positive displacement pumps Centrifugal pumps ate widely used in process industries. Because 1) They are simple to construct and operate 2) Installation and maintenance are easy 3) Casing can be made of up variety of materials 4) Noise free operation 5) No need of safety valve at discharge side in case of single stage centrifugal pumps 6) Can handle variety of liquids. The impeller MOC can be altered accordingly.
Why centrifugal pumps are widely used in process industries than positive displacement pumps ?
Centrifugal pumps ate widely used in process industries. Because
1) They are simple to construct and operate
2) Installation and maintenance are easy
3) Casing can be made of up variety of materials
4) Noise free operation
5) No need of safety valve at discharge side in case of single stage centrifugal pumps
6) Can handle variety of liquids. The impeller MOC can be altered accordingly.
Centrifugal pumps ate widely used in process industries. Because
1) They are simple to construct and operate
2) Installation and maintenance are easy
3) Casing can be made of up variety of materials
4) Noise free operation
5) No need of safety valve at discharge side in case of single stage centrifugal pumps
6) Can handle variety of liquids. The impeller MOC can be altered accordingly.
Please give a comparison between orifice meter and venturi meter?
Please give a comparison between orifice meter and venturi meter?
1) The orifice plate can easily be changed to accommodate widely different flow rates, whereas the throat diameter of a venturi is fixed, so that its range of flow rates is circumscribed by the practical limits of Dp.
2) The orifice meter has a large permanent loss of pressure because of the presence of eddies on the downstream side of the orifice‑plate;
the shape of the venturi meter prevents the formation of these eddies and greatly reduces the permanent loss.
3) The orifice is cheap and easy to install. The venturi meter is expensive, as it must be carefully proportioned and fabricated. A home made orifice is often entirely satisfactory, whereas a venturi meter is practically always purchased from an instrument dealer.
4) On the other hand, the head lost in the orifice for the same conditions as in the venturi is many times greater. The power lost is proportionally greater, and, when an orifice is inserted in a line carrying fluid continuously over long periods of time, the cost of the power may be out of all proportion to the saving in first cost. Orifices are therefore best used for testing purposes or other cases where the power lost is not a factor, as in steam lines.
5) However, in spite of considerations of power loss, orifices are widely used, partly because of their greater flexibility, because installing a new orifice plate with a different opening is a simpler ma즈er. The venturi meter can not be so altered. Venturi meters are used only for permanent installations.
6)It should be noted that for a given pipe diameter and a given diameter of orifice opening or venturi throat, the reading of the venturi
meter for a given velocity is to the reading of the orifice as (0.61/0.98)2, or 1:2.58.(i.e. orifice meter will show higher manometer reading
for a given velocity than venturi meter).
1) The orifice plate can easily be changed to accommodate widely different flow rates, whereas the throat diameter of a venturi is fixed, so that its range of flow rates is circumscribed by the practical limits of Dp.
2) The orifice meter has a large permanent loss of pressure because of the presence of eddies on the downstream side of the orifice‑plate;
the shape of the venturi meter prevents the formation of these eddies and greatly reduces the permanent loss.
3) The orifice is cheap and easy to install. The venturi meter is expensive, as it must be carefully proportioned and fabricated. A home made orifice is often entirely satisfactory, whereas a venturi meter is practically always purchased from an instrument dealer.
4) On the other hand, the head lost in the orifice for the same conditions as in the venturi is many times greater. The power lost is proportionally greater, and, when an orifice is inserted in a line carrying fluid continuously over long periods of time, the cost of the power may be out of all proportion to the saving in first cost. Orifices are therefore best used for testing purposes or other cases where the power lost is not a factor, as in steam lines.
5) However, in spite of considerations of power loss, orifices are widely used, partly because of their greater flexibility, because installing a new orifice plate with a different opening is a simpler ma즈er. The venturi meter can not be so altered. Venturi meters are used only for permanent installations.
6)It should be noted that for a given pipe diameter and a given diameter of orifice opening or venturi throat, the reading of the venturi
meter for a given velocity is to the reading of the orifice as (0.61/0.98)2, or 1:2.58.(i.e. orifice meter will show higher manometer reading
for a given velocity than venturi meter).
When to use gear pumps?
When to use gear pumps?
When we need to handle high viscous liquids we need gear pumps as they deliver a higher discharge pressure (even up to 200bars) than centrifugal pumps. They are used to pump paints, resins, adhesives, pitch. diesel, crude oil etc. They are positive displacement pumps.
When we need to handle high viscous liquids we need gear pumps as they deliver a higher discharge pressure (even up to 200bars) than centrifugal pumps. They are used to pump paints, resins, adhesives, pitch. diesel, crude oil etc. They are positive displacement pumps.
When we need pumps in parallel and pumps in series?
When we need pumps in parallel and pumps in series?
If we need a higher discharge flow (Q) we have to go for pumps in parallel arrangement. If we need a higher head (H) we need to go for pumps in series. For more details please read the below article.
If we need a higher discharge flow (Q) we have to go for pumps in parallel arrangement. If we need a higher head (H) we need to go for pumps in series. For more details please read the below article.
Why steam enters top side of jacket in reactor?
Why steam enters top side of jacket in reactor?
If we pass the steam from bottom side the condensate that is formed after losing the heat won’t have a comfortable passage to get out of the system. In turn the entering steam will start to heat the returning condensate rather than heating the reactor surface. That’s why we have to pass it from the top.
If we pass the steam from bottom side the condensate that is formed after losing the heat won’t have a comfortable passage to get out of the system. In turn the entering steam will start to heat the returning condensate rather than heating the reactor surface. That’s why we have to pass it from the top.
Why the hot liquid in heat exchanger, reactor jacket should flow from bottom to top?
Why the hot liquid in heat exchanger, reactor jacket should flow from bottom to top?
If we pass the liquid from top to bottom, it will flow fast by gravity itself. So it will have less contact time with the heat exchanger/reactor surface which will result in poor heat transfer. That’s why the hot fluid should be passed from bottom to top to maximize the contact time. The same is applicable for cold fluid also in reactors
If we pass the liquid from top to bottom, it will flow fast by gravity itself. So it will have less contact time with the heat exchanger/reactor surface which will result in poor heat transfer. That’s why the hot fluid should be passed from bottom to top to maximize the contact time. The same is applicable for cold fluid also in reactors
What is the difference between evaporation and boiling?
What is the difference between evaporation and boiling?
Evaporation happens at any temperature whereas boiling occurs only at a single temperature for a single component like water. For example the water at sea surface evaporates everyday. It may happen either at 300C or 350C, whereas water boils only at 1000C when the vapor pressure becomes equal to atmospheric pressure.
Evaporation happens at any temperature whereas boiling occurs only at a single temperature for a single component like water. For example the water at sea surface evaporates everyday. It may happen either at 300C or 350C, whereas water boils only at 1000C when the vapor pressure becomes equal to atmospheric pressure.
What is the difference between vapor and gas?
What is the difference between vapor and gas?
A vapor is formed by heating any liquid and it can be condensed at atmospheric conditions either by reducing temperature or be increasing pressure. But a gas has already above the critical temperature and can’t be condensed by application of above methods. First it has to be brought below critical temperature. Then only it can be condensed.
A vapor is formed by heating any liquid and it can be condensed at atmospheric conditions either by reducing temperature or be increasing pressure. But a gas has already above the critical temperature and can’t be condensed by application of above methods. First it has to be brought below critical temperature. Then only it can be condensed.
How we can find leakage in any tube in shell and tube HE?
How we can find leakage in any tube in shell and tube HE?
We have to remove the bonnets of left and right side of the HE. We have to force a liquid thro’ the shell side with high pressure. It will penetrate the leaked tube and come out via the same tube. Thus we can find the leakage.
We have to remove the bonnets of left and right side of the HE. We have to force a liquid thro’ the shell side with high pressure. It will penetrate the leaked tube and come out via the same tube. Thus we can find the leakage.
Which liquid should be on shell side of a shell and tube HE and why?
Which liquid should be on shell side of a shell and tube HE and why?
Even though there are no strict conditions on this the following points are taken into consideration normally.
1)The corrosive fluid shall pass through the tube side as the replacement of tubes is easier and cheaper than shell side
2) The toxic, hazardous fluid shall pass through tube side. Because in case of any leakage it won’t get exposed to atmosphere.
Even though there are no strict conditions on this the following points are taken into consideration normally.
1)The corrosive fluid shall pass through the tube side as the replacement of tubes is easier and cheaper than shell side
2) The toxic, hazardous fluid shall pass through tube side. Because in case of any leakage it won’t get exposed to atmosphere.
What should be the pressure to be taken for pipe and reactor before put in service?
What should be the pressure to be taken for pipe and reactor before put in service?
For pipes the test pressure should be double the proposed application pressure and for reactors test pressure should be 1.5 times the reaction pressure. It means if we wish to subject a pipe to 10 bar we have to do pressure testing at 20 bars whereas for the reactor it would be 15 bars.
For pipes the test pressure should be double the proposed application pressure and for reactors test pressure should be 1.5 times the reaction pressure. It means if we wish to subject a pipe to 10 bar we have to do pressure testing at 20 bars whereas for the reactor it would be 15 bars.
What is Biot No?
What is Biot No?
Biot No is a dimensionless No defined as Bi= hL/kb (No unit). h= convective heat transfer co efficient (unit isW/m2 K)
L= characteristic length (Volume of the body/ surface area of the body” unit is metre)
kb= thermal conductivity of the body(W/mK)
It is the ratio between conductive heat transfer within a body to that of convective heat transfer away from the body. If it is above one means convection is more and less than one means conduction is more.
Biot No is a dimensionless No defined as Bi= hL/kb (No unit). h= convective heat transfer co efficient (unit isW/m2 K)
L= characteristic length (Volume of the body/ surface area of the body” unit is metre)
kb= thermal conductivity of the body(W/mK)
It is the ratio between conductive heat transfer within a body to that of convective heat transfer away from the body. If it is above one means convection is more and less than one means conduction is more.
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Why steam enters top side of jacket in reactor? If we pass the steam from bottom side the condensate that is formed after losing the heat...
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