Final Flashcards
What is FCI
Fixed Capital Investment
What is TCI
Total Capital Investment
What is Direct Production Cost part of?
Product Cost (C)
Do you get back the money associated to depreciation?
No
Can your cumulative cash position be negative?
Yes
The cost of installing a pump (not purchasing it) is
Part of Direct Investment Cost
The Marshall and Swift index is used to adjust
Capital Cost by time
A pump has a cost of $14,000 and a scrap value of $2,000. What is the total depreciation?
$14,000 - $2,000 = $12,000
Cost - scrap value = depreciation
A plant cost is $3,000,000 in 2007. What is the cost in 2018 if the M&S indices are 1452.3 in 2007 and 1955.8 in 2018?
$3,000,000(1955.8/1452.3)=$4,040,074
A plant has a cost of $300,000 for a capacity of 100 ton/day. What is the cost of the plant for a capacity of 230 ton/day if the power is x=0.6?
$300,000(230/100)^.6 = $494,490
What is depreciation?
Loss of equipment value
What is straight line depreciation?
Equal depreciation each year
Depreciation does not last for as long as the plant does what?
Operates
Depreciation does/does not last forever?
Does not
(T/F) Depreciation lasts only one or two year?
False
(T/F) Depreciation is mandatory?
False
MACRS depreciation is what?
Double decline followed by straight line depreciation
When the cost exponent of capacity is less than 1, two equipment of equal size will cost what?
More than one of twice the size
What is money spent today to take raw material and covert it to a unit of product called?
Product cost
A pump has a cost of $14,000 and a scrap value of $2000. What is the depreciation using straight line method over 10 years?
($14,000-$2,000)/10 = $1,200
A pump has a cost of $14,000 and a scrap value of $2,000. What is the first year depreciation using double decline method calculated for a total of 10 years?
$12,000(1-(2/10))^1 = $9,600
$12,000 - $9,600 = $2,400
What is return of investment?
Net annual profit divided by TCI
What is the value today of future money?
Present worth
What is POT?
Pay Out Time
What is the present value of all net profits in the future minus TCI?
Net Present Worth
Why is ROI a disadvantage?
It considers all future net profit being the same value
What depends heavily on the interest rate used?
Net Present Worth
What do we call the interest rate that makes NPW=0
Effective
What is the time needed to get the TCI back?
Payout time
What reduces energy consumption?
Heat integration
What converts many hot or cold stream curves into one hot and one cold, respectively?
Composite curves
What is Pinch?
The smallest delta T than can take place anywhere
What should not be transferred across the pinch?
Heat
What is obtained by overlapping hot and cold composite curves?
Minimum heating utility
What increases cold utility by the same amount?
Increasing heating utility
What is spread over the number of years the IRS determines?
Depreciation
A pump has a cost of $14,000 and a scrap value of $2,000. What is the second year depreciation using double decline method for a total of 10 years?
$12,000(1-(2/10))^2=$7,680 second year
$12,000(1-(2/10))^1=$9,600 first year
$9,600-$7,680=$1,920
The net profit of an investment is $200,000/year for 10 years. does the ROI change if the net profit is also $200,000/15 years?
ROI = Net Profit/ TCI
Net profit is $200,000/year for 10 years = $2,000,000
Net profit is $200,000/year for 15 years = $3,000,000
Yes it will increase
The net profit of an investment is $200,000 /year, the capital is $1,000,000. What is the POT?
$1,000,000/($200,000/year)=5 years
What have rotating gears, lobes, or screws?
Rotary pumps
What pump does not have a large pressure head?
Centrifugal pumps
What is defined as discharge pressure minus suction pressure?
Total Dynamic Head (TDH)
What is equal to the volumetric flowrate * the total dynamic head?
?=Q*TDH
Hydraulic power of a pump
What is the difference between suction head and vapor pressure head?
NPHSA
What is provided by the manufacturer of a pump?
NPHSR
NPHSR has to be (greater/smaller) than NPHSA.
Smaller
Two equal pumps in a series have what?
Double the head
What has smaller head than one pump?
Two equal pumps in parallel
What can happen if NPHSA is zero?
The pump can cavitate
What prevent flow reversal?
Check valves
What are usually not used for control?
Gate valves
What have large pressure drops?
Control valves
Closing a control valve (increases/decreases) the pressure drop in a system.
Increases
Do rotary pumps have reduced outlet pressure?
No
Do rotary pumps have rotating casings?
No
Do rotary pumps have cavitation problems?
No
Do Centrifugal pumps work well with viscous fluids?
No
Can centrifugal pumps only handle small flows?
No
Do centrifugal pumps cavitate when the flow is too large?
No
What is discharge pressure minus suction pressure?
Total dynamic head
NPHSA is define as what?
Suction head minus vapor pressure
In flash design, the balance of forces is considered what?
Gravity vs drag forces vs buoyancy vs viscosity
The velocity used to obtain a column diameter is smaller/larger than the flooding velocity?
Smaller
The formula g(delta z) + delta p/rho + (v2^2-v1^2)/2 = delta W - (sum of friction losses) is used for what?
Liquids
What is a rapid and uniform expansion?
Explosion
What is comprised of an initial system boundary and an expanding shock wave?
An explosion
When does the expansion end?
When the pressure of the final system is P = 1 atm
What is the limit for the expansion velocity?
The speed of sound
What can be achieved only when the initial pressure at detonation is sufficiently high?
The expanding shockwave reaches the speed of sound
The first law describes the rate change of what?
Total Energy (internal and external) of the system
What is the rate change of total energy of the system equal to?
Energy added/subtracted associated with mass entering/leaving the system \+ Heat added \+ Shaft work - Expansion work \+ Work done by fluid entering or leaving the system
The second law of thermodynamics is related to what?
Entropy change with time
In a closed system, the final mass is equal to what?
The initial mass
With closed systems, explosions are considered adiabatic and the heat terms go to what?
Zero
A closed and adiabatic system reduces the first law to what?
(DU/dt) + (M d/dt (v^2/2 + psi) = -P dV/dt
In closed and adiabatic systems the Second Law is reduced to what?
DS/dt = S gen
why does entropy generation only occur at the boundary?
Explosions are uniform
Because entropy only occurs at the boundary what can be neglected?
Entropy
Neglecting entropy reduces the second law to what?
DS/dt = 0
Because the speed of the system and its potential energy does not change, what term in the first law goes to zero?
D/dt (M(v^2/2 + psi))
The final representation of the first flaw when studying explosions is what?
DU/dt = -P dV/dt
If you integrate the final first law equation from t =0 to t = final time what happens?
First Law becomes
M( U at final pressure and temperature - U at initial pressure and temp) = W = - integral PdV
If you integrate the final second law obtained when studying explosions what do you get (from t=0 to t=tf)?
Entropy at initial pressure and temperature
=
0
What are some explosion and fire prevention methods used in design?
Explosion resistant equipment
Sprinkler Systems
Static electricity preventing materials
What are some explosion and fire prevention methods used in operation?
Inerting -Vaccum Purging -Pressure Purging -Sweep-Through Purging Static Electricity Control -Grounding -Increasing conductivity in joints with additives
Cracks in equipment are preferred where on a unit?
Top and bottom, not sides
Double walls may be used for what?
Corrosive materials
What can build up in pipes that have the potential to cause a fire or explosion?
static electricity
What is inerting?
using N2 or CO2 to reduce O2 concentrations in a vessel
Reducing oxygen levels reduces what?
the risk of explosions
If the vessel will contain gas, when should you perform inerting?
prior to loading the gas
If the vessel will contain liquid, when should you perform interting?
prior to filling with liquid and then continue to purge on vapor phase
What is needed during inerting?
an oxygen analyzer
What does LOC and MOC stand for?
Limiting Oxygen Concentration
Minimum Oxygen Concentration
Having too much oxygen can do what?
limit explosions
What oxygen concentration should you use as a rule of thumb if you do not have data?
10 mol%
What are the steps of vacuum purging?
1 Draw some vacuum to a pressure that will not make the vessel implode
2 Replenish with inert
3 Repeat until the oxygen is at the desired level
Does vacuum purging require the pressure to be zero?
No
What is inert is usually used in vacuum purging?
N2
What is usually the desired pressure level of the oxygen during vacuum purging?
atmospheric
During vacuum purging what do we assume to simplify calculations?
that temperature stays the same and Z=1
How do you calculate the moles of O2 at high pressure?
(n oxygen)H = (nH)(yO2) original
How do you calculate the moles of O2 at low pressure?
(n oxygen)L = (nL)(yO2) original
After N2 is added the pressure is (low/high).
high
How do you calculate the mole fraction of oxygen after nitrogen is added and the pressure is higher?
yO2 = (noxygen)L / nH
How do you calculate nH? (total number of moles at high pressure)
nH = (PH * V) / (ZH * R * T)
How do you calculate nL? (total number of moles at low pressure)?
nL = (PL * V) / (ZL * R * T)
for k times that vacuum purging is repeated what is the general equation?
yO2 = yO2 original * (nL/nH)^k
What are the steps for pressure pruging?
1 pressurize the vessel with inert to a value admissible
2 let the pressure go down
3 repeat until the oxygen is at the desired level
In what type of purging do we treat the original state as the high pressure one and PL is the initial pressure (usually atmospheric)?
Pressure purging
what formulas are used for pressure purging?
yO2 original = 0.21 PL/PH = 0.21 Patm/PH
(yO2 after being repeated k times)/yO2 original = (Patm/PH)^k
In what type of purging do you add inert into one opening and let the gas leave the vessel from another?
Sweep-through
What equation do you use for sweep-trough purging?
V dC/dt = Co (molecules going in) * Qv - C (molecules going out) *Qv
this is a mass balance
After integrating the sweep-through mass balance what equation do you get?
Q*t= V ln [(C (at t=0) -Co)/(C(t) - Co)]
Co needs to be what to avoid taking a long time to purge?
small
What is Q times t?
amount of mass
Piping and Instrument Diagrams show what?
all piping connecting equipment
all valves
all instrumentation (measuring, transmitters, controllers, actuators)
The first letter of an instrumentation indicator represents what?
the measured variable
the measured variable can be what?
Pressure
Level
Flow
Temperature
The letters following the first are used to what?
designate the function of the component or to modify the meaning of the first letter
Letters other than the first can represent what?
Indicator
Recorder
Controller
Transmitter
What is the meaning when there is no line on the instrumentation circle?
The instrument is mounted in the field near the process (close to the operator)
What is the meaning when there is a solid line on the instrumentation circle?
The instrument is mounted in the control room (accessible to the operator)
What does it mean when the is a dotted line on the instrumentation circle?
the instrument is mounted out of sight (not accessible to the operator)
Piping is indicated how on a PID?
thick line
A process is indicated how on a PID?
thinner line
electrical signals are indicated how?
dashed line
pneumatic signals are indicated how?
double slashes along the line
data links are indicated how?
open circles along the line
capillary tubing for filled systems are indicated how?
X’s along the line
hydraulic signal lines are indicated how?
L’s along the line
How are guided electromagnetic or sonic signals indicated?
hourglass like shapes (slanted)
What are angle valves used for?
high pressure drops
What kind of flare limits radiation effects?
vertical; tall
Why don’t we use horizontal flares?
take up too much space
plumes form on ground
Controls need relatively high what?
pressure drops
Pumps need what which should include all the necessary by-passes/on-off valves and check valves?
parallel spares
In heat exchangers leaks can are preferred from which tube?
tube side to shell side
Why would heat exchangers need a spare?
to be cleaned due to fouling during plant operation, all on-off valves need to be included for the spare
What is the purpose of a hazard and operability study?
1 identifies hazards systematically (based on malfunctions)
2 does not address risk (probability can be high or very low)
3 addresses consequences (harmless or harmful)
4 proposes actions (design and/or operational)
How many equipment are analyzed at a time?
1
How do HAZOP describe the consequences of malfunctions and propose actions?
by identifying deviations and their cause
Hazops are based on using what applied to parameters?
guide words
Give examples of Guide Words.
no or not more less as well as part of reverse other than/instead early late before after
Give examples of parameters.
Flow Pressure Temperature Level Time Agitation Reaction Start-Up / Shut-Down Draining / Venting Inertising Utility Failure DCS fairue Maintenance Vibrations
If a parameter does not apply you should do what?
check off and say does not apply if it doesn’t
What should be focused on first during a HAZOP study?
cause
How fast does sound travel?
343 m/s
