Essay: OPTIMIZATION OF STEAM SYSTEM

 
INTRODUCTION TO INDUSTRY CHAPTER-1
We wanted to get detail knowledge of the actual working condition of dying mills.
For the same purpose, we have visited the RUNGTA MILL. It is situated at UDHANA.
We analyzed the whole plant and its operation.
During this analysis, we find that there is need of some efficiency and safety improving equipment in the plant.
They have not installed safety relief at steam header,
Proper conditioning of steam is required to process grey clothes hence the steam required desuperheating and they don’t have any desuperheater for this purpose.
The flow nozzle installation will be recommended in main steam line to measure exact mass flow rate of steam.
Hence we decided to recommend few equipments and also check the design of few available equipments.
So our area of working are :
Recommendation of safety valve in steam header.
Recommendation of desuperheater after PCV.
Recommendation of flow nozzle at main steam line.
Recommendation of proper steam line size.
Fig. 1.1 Block diagram of project
Grey Clothes: It is a raw material for textile industry. This grey clothes are passed through different processes and make a cloth as per need of textile industry.
Drum Machine: This machine is used for dyeing purpose. In this machine raw material is processed at temperature 1300 C and time required for it is 3 hours.
Jet Machine: This machine is also used for dyeing purpose. This machine is operated at temp. 1300C and time required for this 45 min. The difference between the drum machine and jet machine is that the raw material used in this machine is of same quality but the output from these both machines has different quality.
Centre Machine: This machine is used to dry and straitening the clothes. In this machine hot oil at temp.1800 C passes from radiator is used for drying. The hot oil required is heated in Thermo pack.
 
INTRODUCTION TO PROJECT CHAPTER-2
This project is about designing various equipments that are necessary for proper functioning of the steam system
A steam system should have a desuperheater to increase the degree of desuperheat of the steam required at the low pressure side of the gland sealing, a safety valve that can release the steam if working pressure increases than the set pressure and a flow nozzle at appropriate position to measure the mass flow of the steam
When we visited the rungta mill, we analyzed the whole plant and then came to know that they do not have any desuperheater, safety relief valve at header.
So we decided to recommend them the design and position of desuperheater, safety relief valve and flow nozzle.
We also studied crank book for the further information required as per our project.
According to P K NAG book, a flow nozzle is used to measure the mass flow rate of steam by creating intentional pressure drop
FIG. 2.1
COAL TYPE B – grade ( pulverized coal )
WATER BOILLING TEMP. 80 ℃
BOILER TYPE Water tube boiler
STEAM SUPPLY CAPACITY 5½ tone/hour
COAL USED PER DAY 23 tone/day
WATER FEED PER DAY 100000 litter /day
WATER TYPE R.O water
Ph SCALE OF WATER 6.0 approx
I.D SPEED 1113 rpm
F.D SPEED 2143 rpm
PIPE MATREIAL Carbon steel
STEAM APPLICATION Decca
Jigger
Jet dying
Roll press machine
washer
dryer
2.1 INPUT DATA FOR PROJECT
Table 2.1
INPUT DATA FOR BOILER
DESIGN PRESSURE 155 PSI
DESIGN TEMPERATURE 186℃
MAX. WORKING PRESSURE 160 PSI
MAX. WORKING TEMP. 186℃
CLASSIFICATION CLASS-1
HYDRAULIC TEST PRESSURE 232.5 PSI
HEATING SURFACE 230 M²
EVOPORATIVE CAPACITY
FROM & AT 100℃ 5000 KG/HR
Table 2.2
MATERIAL CLASSIFIED
TUBES PLATES ASTM 516 GR.-70 31.25 TEN/IN² E-7018
SHELL ASTM 516 GR.-70 31.25 TEN/IN² E-7018
MATREIAL GRADE TENSILE ELECTROD
Table 2.3
OBJECTIVE CHAPTER-3
The main objective of this project is to design the various equipment of the steam system in such a way that the optimization of stream can be done.
After complete analysis of plant we get to an idea to:
Design the steam piping according to the IBR & ASME 31.1 for design steam piping correct or wrong.
Design safety relief valves for the Header.
Design a desuperheater so that steam at required condition can be supplied to Jigger, Decca, Jet Dying, Dryer, Roll press m/c.
Recommendation as well as design of flow nozzle at main steam line.
 
LITERATURE REVIEW CHAPTER-4
As per a technical paper published by RS publication, According to experimental work of Sallet (1981), the flow inside a typical safety valve was studied by visualization of the flow in a 2D valve model.
Pressure distributions and discharge capacities were investigated in tests with choked air flow, water and choked two-phase flow.
It can be recognized that the physical effects of flow separation, capitation, choking and valve disk vibrations are significant flow phenomena that complicate the prediction of the characteristic valve coefficients.
Sallet also observed that vertical flows near the valve disk (periodic flow oscillations due to flow past a cavity) cause valve disk vibrations.
This effect is larger for incompressible flows. Also in a safety valve the interaction between shock waves and flow separation can cause self-sustaining oscillating flow fields.
In Whitworth CJ, Gray GM Desuperheaters is considered to be relatively reliable devices. But if on admission to the steam pipe, attemperating water is atomized to increase its surface/mass ratio for rapid vaporization by the passing flow of superheated steam – the temperature of which is reduced as a consequence of providing sensible and latent heat for this process.
According to crane book, a flow nozzle is used to measure the mass flow rate of steam by creating intentional pressure drop.
Indian Boiler Regulation (IBR) :
The Indian Boilers Act was instituted to consolidate and amend the law relating to steam boilers. Indian Boilers Regulation (IBR) was made in activity of the powers conferred by section 28 & 29 of the Indian Boilers Act.
IBR Steam Boilers implies any closed vessel exceeding 22.75 liters in capacity and which is used expressively for generate steam under pressure and includes any mounting or other fitting attached to such vessel, which is wholly, or partly under pressure when the steam is stop.
IBR Steam Pipe implies any pipe through which steam goes from a boiler to a prime mover or other client or both, if pressure at which steam passes through such pipes exceeds 2.5 kg/cm2 above environmental pressure or such pipe exceeds 254 mm in internal diameter and includes in either case any connected fitting of a steam pipe.
POWER PIPING – ASME CODE FOR PRESSURE PIPING, B31 :
The ASME B31 Code for Pressure Piping consists of a various individually published Sections, each an American National Standard, under the direction of ASME Committee B31, Code for Pressure Piping. Rules for each Section have been created considering the requirement for application of particular requirements for different types of pressure piping. Applications considered for each Code Section include.
B31.1) Power Piping: piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems.
B31.3) Process Piping: piping typically found in petroleum refineries; chemical,
Pharmaceutical, textile, paper, semiconductor, and cryogenic plants and related processing plants and terminals
B31.4) Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids: piping transporting products that are predominately liquid between plants and terminals and within terminals, pumping, regulating, and metering stations
B31.5) Refrigeration Piping: piping for refrigerants and secondary coolants
B31.8) Gas Transportation and Distribution Piping Systems: piping transporting products that are predominately gas between sources and terminals, including compressor, regulating, and metering stations; and gas gathering pipelines
B31.9) Building Services Piping: piping typically found in industrial, institutional,
Commercial, and public buildings, and in multi-unit residences, which does not require the range of sizes, pressures, and temperatures covered in B31.1
B31.11) Slurry Transportation Piping Systems: piping transporting aqueous slurries between plants and terminals and within terminals, pumping, and regulating stations
B31.12) Hydrogen Piping and Pipelines: piping in gaseous and liquid hydrogen service, and pipelines in gaseous hydrogen service
This is the B31.1 Power Piping Code Section. Hereafter, in this Introduction and in the text of this Code Section B31.1, where the word Code is used without specific identification, it means this Code Section.
Hot wastewater, produced in textile dyeing plats, can be a significant source of heat energy. In many instances, this valuable resource is discharged to wastewater treatment facilities without employing the heat it acquired during processing. The waste water quantity has been calculated by the equation,
Q=m_Water C_P ∆t
 
DESIGN OF STEAM PIPING CHAPTER-5
5.1. INTRODUCTION
The basic concept of a piping design is to safely and economically transport steam, brine, or two- phase flow to the destination with acceptable pressure loss. The piping associated with plant can be divided in piping inside the plant and the piping in the steam field.
Water pipe sizing is based on velocity, pressure drop and capital cost. Low fluid velocity is usually correlated to low pressure drop, however, this results to large diameter pipes which are generally expensive. High fluid velocity usually travels to small diameter pipes, which reduces capital cost but results to unacceptable high pressure losses. Within the limit of acceptable velocity range for a given service, a compromise needs to be made between pressure drop and capital cost. This is often termed as “sizing the pipe by economic pressure drop”.
Factors needed to be considered for water pipe design are scrubbing the water, velocity of water, corrosion allowances, pressure drop, pressure and temperature.
5.2 DESIGN PRACTICE:
The problem of design procedure is to find a pipeline configuration and size within the constraints, which is safe and economical.
5.2.1 The steps in pipeline design are as follows:
I. The determination of the problem, which includes:
a. The characteristics of the fluid to be carried, including the flow rate and the allowable head loss;
b. The location of the pipelines: its source and destination, and the terrain over which it will pass, the location of separator station and the power plant;
c. The design code to be followed; and
d. The material to be used.
II. The determination of a preliminary pipe route, the line length and static head difference.
III. Pipe diameter based on allowable head loss;
IV. Structural analysis:
a. Pipe wall thickness; and
b. Stress analysis.
V. The stress analysis is performed in pipe configuration until compliance with the code is achieved.
VI. Support and anchor design based on reaction found in the structural analysis.
VII. Preparation of drawings, specification and the design report.
5.3 TYPES OF LINE SIZING:
Fluid velocity.
Pressure drop
5.3.1 PIPELINE SIZING ON STEAM VELOCITY:
If pipe work is sized on the basis of velocity, then calculations are based on the volume of steam being carried in relation to the cross sectional area of the pipe.
Even these velocities can be high in terms of their effect on pressure drop. In longer supply lines, it is often necessary to restrict velocities to 15 m/s if high pressure drops are to be avoided.
Alternatively the pipe size can be calculated by following the mathematical procedure as outlined below. In order to do this, we need to define the following information:
Flow velocity (m/s) C
Specific volume (m3/kg) v
Mass flow rate (kg/s) m
Now as per continuity equation
m=(A*C)/v
&
A=π/4 d^2
d=√((4*m*v)/(π*C))
5.3.2 STRUCTURAL ANALYSIS:
Circumferential stress or Hoop stress due to pressure and vacuum is considered for sizing and selecting the pipe with suitable wall thickness.
Equations for pipe stress analysis are given in the design code. The first step is the determination of wall thickness required by ASME B31.1 (Power Piping):
Tm= PDo/(2(σ+Py)) + A
Where Tm = Wall thickness in millimeters;
P = Design pressure in kilopascals;
Do = Pipe outside diameter in millimeters;
= Allowable stress in kilopascals;
y = 0.4, for most geothermal application it based on temperature range and steel type;
A = 1 mm corrosion and erosion allowance.
Stress analysis should be carried out for the following load cases for compliance with the code requirement and support load calculation. ASME B31.1 POWER PIPING requires that a pipeline shall be analyzed between anchors for the effects of:
1. Sustained loads, Gravity + Pressure;
2. Operation loads, thermal expansion stress alone or thermal expansion stress + sustained loads;
3. Occasional loads, sustained loads + seismic load or wind load perpendicular to the general alignment of the pipe;
4. Occasional loads, sustained loads + seismic loads along the general direction of the pipe;
5. Reverse the direction of seismic or wind loads;
6. Modes of thermal operation need to be considered in the analysis.
In addition to this, an analysis should be carried out for zero friction to determine the maximum load on the anchors in the event of an earthquake. Other dynamic loads that can be considered are fluid hammer effects, thrusts from safety valves, and slugging flow.
5.3.3 SELECTION OF THE PIPE MATERIAL TEMPERATURE BASIS:
Table 5.1
ANSI B36.10 CARBON STEEL SEAMLESS PIPE WEIGHT PER KG/MTR
5.3.4 INITIAL ASSUMPTION OF VELOCITY OF STEAM IN PIPES:
Nominal pipe size in mm Average velocity in m/s
Table 5.2 Allowable velocity for sizing of pipe
SAFETY VALVE CHAPTER-6
6.1 Introduction:
According to ASME standards Safety valves are defined as the pressure relief valves actuated by inlet static pressure and characterized by rapid opening or pop action.
The essential first function of a safety valve is to protect life and property.
It operates by releasing a volume of fluid from within the pressure vessel when a predetermined maximum pressure is reached, thereby reducing the excess pressure in a safe manner.
It should be installed wherever the maximum allowable working pressure of a system or pressure-containing vessel is likely to be exceeded.
In steam systems, safety valves are typically used for boiler overpressure protection and other applications such as downstream of pressure reducing controls.
Although their essential role is for safety valves are also used in process operations to prevent product damage due to excess pressure.
FIG 6.1 – 3-D MODEL OF SAFETY RELIEF VALVE
6.2 Construction:
The basic elements of the design consist of a right angle pattern valve body with the valve inlet connection, or nozzle, mounted on the pressure-containing system.
The outlet connection may be screwed or flanged for connection to a piped discharge system.
However, in some applications, such as compressed air systems, the safety valve will not have an outlet connection, and the fluid is vented directly to the atmosphere.
FIG 6.2 – CONSTRUCTIONAL DIAGRAM OF SAFETY VALVE
The valve inlet design can be either a full-nozzle or a semi-nozzle type.
A full-nozzle design has the entire ‘wetted’ inlet tract formed from one piece.
The methodology channel is the main part of the safety valve that is exposed to the process fluid during normal operation, other than the disc, unless the valve is discharging.
Full-nozzles are usually incorporated in safety valves designed for process and high pressure applications, particularly when the fluid is corrosive.
Conversely, the semi-nozzle design consists of a seating ring fitted into the body, the top of which forms the seat of the valve.
The plate is held against the nozzle seat (under normal working conditions) by the spring, which is housed in an open or closed spring housing arrangement mounted on top of the body.
The plate used in quick opening (pop type) safety valves are surrounded by a shroud, disc holder or huddling chamber which helps to produce the quick opening characteristic.
6.3 Basic Operation of Safety Valve:
Lifting:
When the inlet static pressure rises above the set pressure of the safety valve, the disc will begin to lift off its seat.
However, as soon as the spring starts to compress, the spring force will increase; this means that the pressure would have to continue to rise before any further lift can occur, and for there to be any significant flow through the valve.
The additional pressure rise required before the safety valve will discharge at its rated capacity is called the overpressure.
The allowable overpressure depends on the standards being followed and the particular application. For compressible fluids, this is normally between 3% and 10%, and for liquids between 10% and 25%.
Reseating:
Once normal operating conditions have been restored, the valve is required to close again, but since the larger area of the disc is still exposed to the fluid, the valve will not close until the pressure has dropped below the original set pressure.
The difference between the set pressure and this reseating pressure is known as the ‘blow down’, and it is usually specified as a percentage of the set pressure.
For compressible fluids, the blow down is usually less than 10%, and for liquids, it can be up to 20%.
FIG 6.3 LIFT V/S PRESSURE
6.4 Types Of Safety Valves:
Conventional Safety Valves
Balanced Safety Valves
Piston Type Balanced Safety Valve
Pilot Operated Safety Valve
Full Lift Safety Valves
Low Lift Safety Valves
High Lift Safety Valves
6.5 Design Procedure of Safety Valves:
6.5.1 Design Procedure of Safety Valve for Header:
Operating pressure, Po = 10.54 bar
Mass flow rate, ms = 5 tph
Set pressure, Ps = 1.25*10.54
=13.175 bar
Relief capacity, E = 0.3*5*103
= 1500 kg/hr
Area, A = (100*E)/(C*(P+1.013))*F = 378.575 mm2
So, Diameter, d = 21.95 mm
Now taking d= 22 mm A^’= 380.13 mm2
Actual relief capacity E = (C*(P+1.013))/(100*F)*A^’ = 1506.158 kg/hr
Actual release in percentage = 30.12 %
6.5.2 Noise Emission:
L_w=17*log⁡〖(〖q_m〗^’/1000)+50*log⁡〖(T)-15〗 〗
= 110.35 dB
L_a=L_W⁡〖-10*log⁡(A) 〗
=101.33 dB
FIG 6.4 SAFETY VALVE AT STEAM HEADER
6.6 Design Material for Safety Relief Valve:
TABLE 6.1
 
SILENCER CHAPTER-7
7.1 Introduction:
A vent silencer or a blow off silencer is a device used to reduce unwanted noise created by gas or steam flow in a pipeline discharging directly into the atmosphere.
This noise can be generated due to the high velocity flow through the valve and turbulence created around any obstacle in the line that suddenly restricts or changes the direction of flow such as valve or an orifice.
Vent and blow down noise is a function of upstream pressure and temperature, type of gas being vented, the valve size and type, plus the effect of downstream piping.
Each vent silencer is designed to attenuate the noise level to the required sound pressure level criteria at a given distance from the silencer.
In any steam or gas venting / blow off system, the primary release of noise energy occurs at the open stack exit.
The blow off silencer is installed either within the stack or at the stack outlet to intercept this noise before it escapes into the environment.
7.2 Application of Vent Silencers:
High Pressure Vents
Steam Vents
Safety Relief Valve Outlets
System Blow Downs
Purge Outlets
7.3 Noise Reduction Principles Used In A Vent Silencer:
Absorption of the high frequency audible noise into a sound absorbing material.
Reactive section to attenuate the low frequencies and provide broad band noise reduction.
FIG 7.1 3-D MODEL OF SILENCER
7.4 Design Characteristics:
Try to keep low pressure at exit.
Stay away from sonic flow and have a moderate speed.
Having the possibility of increasing the number of orifices in the plate.
Value of β should be between 0.75 and 0.20 & value of flow coefficient, C, should be between 0.78 and 0.60. As if orifice are too small the speed will be increased and system may collapse, on the other hand if the orifices are too big there will be no pressure drop.
7.5 Data Required To Design Vent Silencer:
Application (Vent, Blow down, Relief Valve etc.).
Fluid Composition (Steam, Gas, Air).
Molecular Weight or Specific Gravity.
Process conditions upstream of valve i.e. Flow rate (W) and units (lb/hr, SCFM, ACFM)
Temperature (T1)
Pressure (P1)
Atmospheric pressure (Pa) and downstream temperature (T2) if known.
Line size between valve and silencer and connection type.
Line size from silencer discharge.
Attenuation required (silencer performance).
Allowable pressure drop.
7.6 Design of Silencer:
7.6.1 Orifice Diameter Calculation :
Data given:
Outer Diameter of pipe, Do = 114 mm
Thickness of pipe, t = 6.02 mm
Inner Diameter of pipe, Di = 100 mm
Temperature at inlet of silencer, T = 459 K
Pressure at inlet of silencer, P = 10.54 bar
Mass flow rate of steam, Ms = 5 tph
Viscosity of fluid, µ = 0.01526*10-3 Ns/m2
Specific volume, ʋ = 0.18701 m3/kg
Pressure drop, Δp = 5.25 bar
Density, ρ = 5.34 kg/m3
Length of pipe, L = 3 m
Ratio of specific heat, k = 1.3
7.6.2 Design Steps:
Select the pipe diameter , Di = 100 mm
Determine the pressure drop required in terms of water column.
Δp (in terms of water column) = 53.588 m
Calculate the critical velocity i.e. sonic velocity.
Vs = √kRT = √(1.3*287*459)
= 413.82 m/s
Calculate velocity of steam in pipe.
V = m/ρ”A” = (5*〖10〗^3)/(5.34*3600*0.785*〖0.1〗^2 )
= 33.132 m/s
Calculate the Reynolds number, Re in the pipe.
Re = ρV”D” /μ = (5.34*33.132*0.17)/(0.01526*〖10〗^(-3) )
= 1.1594 * 106
Calculate Darcy coefficient, f
f = 0.316/〖Re〗^0.25 = 9.63 * 10-3
Calculate the pressure drop due to friction.
h = (flV^2)/2gD = 16.180 m
Calculate Krequired that is the sum of all pressure drops including ΔP.
Krequired = h + ΔP = 16.180 + 53.588
= 69.768 m
Assumption of the no holes.
No of orifice = 5
Calculate the flow through single orifice, q.
Discharge through pipe, Q = 0.26009 m3/s
Discharge through single orifice, q = Q/5
= 0.052018 m3/s
Assume the diameter of orifice plate, d
Assumed diameter of orifice, d = 20 mm
Calculate orifice relation β, with the pipe and proposed orifice diameter
β = 0.30
Obtain the flow coefficient, C for square edge orifices from tables of orifices plates
Flow coefficient, C = 0.6
Calculate K of the orifice
K_Orifice = (1-β^2)/〖C^2 β〗^4 = 183.83 m
Calculate the speed in the orifices to determine if sonic speed is reached.
Velocity through each orifice, Vo = q/Ao
=165.57 m/s
Since the velocity of steam is less than the sonic velocity, hence the design is safe.
7.7 Calculation of Sound Intensity:
Sound intensity at inlet of silencer = 17* log (m/1000) + 50* log T -15
= 129.97 dB
Sound intensity at outlet of silencer = 17* log (m/1000) + 50* log T -15
= 110.70 dB
7.8 Design Material For Vent Silencer
COMPONENT MATERIALS
Table 7.1
FIG 7.2 DESIGNED STEAM SILENCER
 
DESUPERHEATERS CHAPTER-8
8.1 Introduction:
Desuperheaters are critical component used in management of steam from power generation sources to industrial uses of steam.
Desuperheating is also known as ATTEMPERATION.
Desuperheating is the process of reduction of temperature in steam line through the direct contact and evaporating of water within the steam flow stream.
8.2 Principle:
The principle function of any Desuperheater is to accelerate the phenomenon of absorption of the spray water by the steam so that steady conditions of steam temperature are reached within a short distance from the outlet.
8.3 Desuperheaters Essential Design Characteristics:
Temperature control:
Fast response to change in steam flow and temperature.
Accurate steam temperature control.
Ability to desuperheat to near steam saturation temperature.
Turn down / range ability:
High ratio of maximum to minimum controllable flow.
Excellent temperature control for full range of flow.
Prevent overspray or water accumulation:
Prevent excess water from being injected into flow stream.
Avoid thermal shock to steam pipe.
Eliminate water droplet impact:
Minimize water droplet size – good atomization.
Ensure desuperheating do not impact steam pipe wall.
8.4 Types of Desuperheater:
Tube bundle type desuperheater
Water bath type desuperheater
Water spray desuperheater
Single point radial injection spray desuperheater
Multiple nozzle radial injection spray desuperheater
Single point axial injection spray desuperheater
Multiple nozzle axial injection spray desuperheater
Variable orifice desuperheater
Steam atomizing desuperheater
Venture type desuperheater
FIG 8.1 – INSTALLED DESUPERHEATER
8.5 Single Nozzle Axial Injection Water Spray Desuperheater:
This type of superheater represents the vast majority of desuperheating applications.
In water spray desuperheaters, superheated steam is passed through a section of pipe fitted with one or more spray nozzles.
This injects a fine spray of cooling water into superheated steam, which causes the water to be converted into steam, reducing the quantity of superheat.
Water is more evenly distributed through the superheated steam.
FIG 8.2 – Single Nozzle Axial Injection Water Spray Desuperheater
8.5.1 Factors Affecting the Water Spray Desuperheaters:
Particle size: Since water is directly injected on the superheated steam, so smaller the size of water particle, distance required is smaller for heat exchange take place.
Turbulence: With increase in turbulence of flow, heat transfer increases and proper mixing of cooling water and superheated steam takes place.
Thermal sleeves: Careful control of spray is required to guarantee that water does not drop out of suspension as this outcome in thermal stresses being generated in the pipeline and breaking may occur.
Cooling water flow rate: required amount of cooling water should always be present in order to get the desired quality of steam at the outlet of desuperheater.
8.5.2 Advantages & Disadvantages:
Advantages:.
Minimum steam pressure drop.
Cost effective.
Simple in operation.
Disadvantages:
Desuperheated steam temperature can only be reduced unto 10oC above saturation temperature.
Limited pipe sizes.
Most inclined to bring erosion damage to the internal pipe work.
8.6 Design Procedure Of Desuperheater:
8.6.1 Design Procedure of Single Nozzle Axial Injection Desuperheater:
Design 1 :- For 40NB line
Diameter of inlet pipe, Di = 40.94 mm
Diameter of outlet pipe, Do = 40.94 mm
Length of inlet pipe, Li = 5Di
= 204.7 mm
= 205 mm
Length of outlet pipe, Lo = 15Di
= 614.1 mm
=615 mm
Diameter of nozzle, dn = 25 mm
Diameter of cooling water pipe, dc = 26.64 mm
Height of flange from steam pipe, hf = 60 mm
Distance of drain pipe from nozzle, Ld = 2000 mm
Length of thermal sleeve, Lts = 800 mm
FIG 8.3 DESIGN OF DESUPERHEATER
8.6.2 Drain Calculation:
Outer diameter of drain pipe, Do = 33.4 mm
Thickness of drain pipe, t = 3.38 mm
Inner diameter of drain pipe, Di = 26.64 mm
Orifice diameter, do = 10 mm
Orifice relation, β d_(o orifice)/d_(i drain line) = 0.3753
Pressure drop, ∆P = 3 – 1.01325
= 1.98675 bar
= 20.26439 m
Density of fluid, ρ = 980 kg / m3
Area of orifice, A = (πdi2)/4
=3.6745*10-5 mm2
Coefficient of discharge, Cd = 0.6
Mass flow of drain, m4 = (C_d ρA)/√(1-β^(4 ) ) √(2∆P/ρ)
= 4.438 g /s
= 15.978 kg/hr
8.6.3 Calculation Of Cooling Water Required:
Case 1
Inlet of steam at 150 ℃
Mass flow of steam at inlet of desuperheater, m1 = 0.65 tph
= 650 kg/hr
Mass flow of drain from desuperheater, m4 = 15.978 kg/hr
Enthalpy of steam at inlet of desuperheater, h1 (at 150℃) = 2755.026 kJ/kg
Enthalpy of cooling water at inlet, h2 (at 30℃) = 126.1973 kJ/kg
Enthalpy of steam at outlet of desuperheater, h3 (at 130℃) = 2720.8 kJ/kg
Enthalpy of drain water, h4 (at 105℃) = 440.086 kJ/kg
According to Mass Balance
m1 + m2 = m3 + m4
650 + m2 = m3 + 15.978
Therefore m3 = m2 + 634.022 kg/hr
Now, According to Enthalpy Balance Equation:
Enthalpy before process = enthalpy after process
m1h1 + m2h2 = m3h3 + m4h4
650* 2755.026 + m2*2720.18 = (m2 + 634.022)*2720.8 + 15.978 * 440.086
m2 = 22.7993 kg/hr
Mass flow of cooling water required m2 = 22.7993 kg/hr
Mass flow of steam m3 = 656.8213 kg/hr
Case 2
Inlet of steam at 143 ℃
Mass flow of steam at inlet of desuperheater, m1 = 0.65 tph
= 650 kg/hr
Mass flow of drain from desuperheater, m4 = 15.978 kg/hr
Enthalpy of steam at inlet of desuperheater, h1 =2737.69 kJ/kg
Enthalpy of cooling water at inlet, h2 = 126.1973 kJ/kg
Enthalpy of steam at outlet of desuperheater, h3 = 2720.8 kJ/kg
Enthalpy of drain water, h4 = 440.086 kJ/kg
According to Mass Balance
m1 + m2 = m3 + m4
650 + m2 = m3 + 15.978
Therefore m3 = m2 + 634.022 kg/hr
Now, According to Enthalpy Balance Equation:
Enthalpy before process = enthalpy after process
m1h1 + m2h2 = m3h3 + m4h4
650* 2737.69 + m2*2720.18 = (m2 + 634.022)*2720.8 + 15.978 * 440.086
m2 = 18.49 kg/hr
Mass flow of cooling water required m2 = 18.49 kg/hr
Mass flow of steam m3= 652.712 kg/hr
Design 2 :- For 80NB line
Diameter of inlet pipe, Di =77.9 mm
Diameter of outlet pipe, Do = 77.9 mm
Length of inlet pipe, Li = 5Di
= 389.5 mm
= 390 mm
Length of outlet pipe, Lo = 15Di
= 1168.5 mm
=1170 mm
Diameter of nozzle, dn = 40 mm
Diameter of cooling water pipe, dc = 40.94 mm
Height of flange from steam pipe, hf =100 mm
Distance of drain pipe from nozzle, Ld = 2500 mm
Length of thermal sleeve, Lts =1000 mm
8.6.4 Drain Calculation:
Outer diameter of drain pipe, Do = 60.3 mm
Thickness of drain pipe, t = 3.9 mm
Inner diameter of drain pipe, Di = 22.5 mm
Orifice diameter, do = 20 mm
Orifice relation, β d_(o orifice)/d_(i drain line) = 0.3809
Pressure drop, ∆P = 3 – 1.01325
= 1.98675 bar
= 20.26439 m
Density of fluid, ρ = 980 kg / m3
Area of orifice, A = (πdi2)/4
=8.4931*〖10〗^(-5) mm2
Coefficient of discharge, Cd = 0.6
Mass flow of drain, m4 = (C_d ρA)/√(1-β^(4 ) ) √(2∆P/ρ)
= 10.26 g /s
= 36.95 kg/hr
8.7 Design Material for Desuperheater:
TABLE 8.1
FLOW NOZZLES CHAPTER-9
9.1 Introduction:
It is used to measure the flow rate of the steam system.
The flow nozzles create an intentional pressure drop, ΔP for calculating the flow rate.
The flow of any compressible fluid neglecting the velocity approach factor is given by the following equation.
Q = “Y” C_d “A” √(2∆P/ρ)
The velocity of approach has a significant effect on the quantity discharged through a nozzle
The factor correcting the velocity of approach is given by following equation. √(1-β^4 )
Flow coefficient, C which is a function of both velocity approach factor and discharge coefficient is given as follow:
Flow coefficient, C = C_d/√(1-β^4 )
Hence the corrected equation for calculating flow rate considering the velocity of approach is as follow:
Q = “YCA” √(2∆P/ρ)
FIG 9.1 – FLOW NOZZLE ASSEMBLY
9.2 Design Procedure of Flow Nozzle:
Orifice relation, β = 0.75
Discharge coefficient, Cd = 0.95
Flow coefficient, C = C_d/√(1-β^4 )
= 1.1732
Pipe inner diameter, D = 100 mm
Nozzle diameter, d =0.75*100
=0.075 mm
Area of nozzle = 0.004417 mm2
Flow rate, Q = 0.260 mm3/s
Density, ρ = 5.34 kg/m3
FIG 9.2 – DESIGN PROCDURE OF FLOW NOZZLE
Case 1
Flow rate, Q1 = Q
= 0.260 m3/s
Pressure drop, ΔP = 2250 mm of water column
= 22072.5 pa
Finding net expansion factor, Y from the table given in Crane technical paper 410.
Q = “YCA” √(2∆P/ρ)
Y=0.55
Case 2
Flow rate, Q2 =1.1 Q
= 0.286 m3/s
Pressure drop, ΔP = 2500 mm of water column
= 24525 pa
Finding net expansion factor, Y from the equation
Q = “YCA” √(2∆P/ρ)
Y = 0.57
Case 3
Flow rate, Q3 = 0.5Q
= 0.13 m3/s
Pressure drop, ΔP = 1000 mm of water column
= 9810 pa
Finding net expansion factor, Y from the equation
Q = “YCA” √(2∆P/ρ)
Y = 0.41
Case 4
Flow rate, Q4 = 0.75Q
= 0.195 m3/s
Pressure drop, ΔP = 1625 mm of water column
= 15941.25 pa
Finding net expansion factor, Y from the equation
Q = “YCA” √(2∆P/ρ)
Y = 0.48
FIG 9.3 – EXPANSION FACTOR V/S PRESSURE DROP
9.3 Design Material for Flow Nozzle:
TABLE – 9.1
 
FUTURE SCOPE CHAPTER-10
Existing steam pipe line size will be checked as per IBR/ASME 31.1.
Optimum pipe size shall be recommended to industry to reduce pressure losses
And to increase life of pipe.
New Design of steam safety valve shall be completed for steam header.
The efficiency of silencer can be increase further.
Desuperheater design will be done according to IBR for proper conditioning of steam.
To measure exact mass flow rate of steam flow nozzle will be designed for main steam line.
REFERENCE CHAPTER-11
Crane book for flow nozzle design.
Technical paper by Fainger lesser for sound attenuation calculation.
A module paper by SPIRAX SARCO to design the desuperheater.
R.K. BANSAL book for fluid mechanics.
R.F.Stearns, R.M. Jackson ,R.R. JOHNSON, and C.A. Larson, “Flow Measurement with Orifice Meters”; D.Van Nostrand Company , Inc., New York, 1951.
Mohinder L. Nayyar, Piping Handbook, 7th ed., New York, McGraw-Hill, 2000.
M.I. Carlos A. Miranda Herrera, “steam silencer, noise reduction, pressure relief” Carretera Pascualitos-Pescaderos Km. 26.5, Delegacion Cerro Prieto, Mexicali B.C., Mexico.
http://www2.spiraxsarco.com/resources/steam-engineering-tutorials/desuperheating/basicdesuperheater-
types.asp
http://www2.spiraxsarco.com/resources/steam-engineering-tutorials/safety-valves/introduction-tosafety-valves.asp
http://www.osti.gov/scitech/biblio/329226