What is Pressure Vessel?

Pressure vessels are probably the most widespread “machines” within the different industrial sectors. In fact, there is no factory without pressure vessels, steam boilers, tanks, autoclaves, collectors, heat exchangers, pipes, etc.
More specifically, pressure vessels represent components in sectors of enormous industrial importance, such as the nuclear, oil, petrochemical, and chemical sectors.
There are numerous Codes & Laws present in each country to control the usage of this 'machines'! its useful but its dangerous!
What one need to design a Pressure Vessel?
● good workmanship with regard to the tools used,
● knowledge of the basic engineering principles and the phenomena involved,
● fantasy and creativity with regard to the selection of the models used,
● fair knowledge of the legal requirements pertaining to design,
● fair knowledge of manufacturing and testing procedures, and especially
● extreme carefulness in each step, from the design specification to the design
report.

Pressure Vessel mostly are made-up of 'Steel' Steel behaves in an elastic fashion even beyond the proportional limit, as long as another characteristic point corresponding to stress called elastic limit is not exceeded.In practice, we typically equate the proportional limit to the elastic limit.

we always discuss the steel’s behavior at room temperature. It is, however, of the greatest importance to be aware of the influence of temperature on the mechanical characteristics of the material. As we shall see, not only temperature but also time may have a strong influence.

Next we will discuss some "TERMS"

What Next?

Now, let us start new topic, on design of pressure vessel!

I think this one of the interesting subject, and we find lots of data over here and their defining how to design pressure vessel.

Some people take advantage of this and confuse you some time.. end result you may get over size vessel (high cost) or under size vessel (Dangerous!)

Solution.. buy High end software!! Sure. thats the last thing I'll recommend!

Hence onward, for few more post we will discuss this subject, and I'm open for suggestions and lengthy discussions over this :)

So next post.. Over view on Pressure Vessel (Simplified :)

Drinktec Photos

I'm attaching few pictures of Drinktec exhibition..

Visit to Drinktec

Hello All from Munich!
Right now I'm at drinktec,and sharing my experience with you all.
Drinktec (website : www.drinktec.com) Drinktec is an exhibition which happen at Munich germany after each 4 year! Its for people from Brewery & Beverages.

The exhibitors are manufacturers & supplier from/ for same Industry.
Its a good experience for new bee like me, who is very new to this industry. you will find here huge stalls from all equipments around the world. I've seen huge bottling plant made alive in Stall at exhibition.

I'll share few pictures from exhibitions soon.

Chao!

Material Properties

The differences have to be taken into consideration by both designer and welder. The high thermal expansionand low thermal conductivity of the austenitic steels lead to higher shrinkage stresses in the weld thanwhen carbon and ferritic steels are used. Thin sections of austenitic steels may therefore be deformed when an abnormally high heat input is used




These steels are mainly used in wet environments. Withincreasing chromium and molybdenum contents, the steels become increasingly resistant to aggressive solutions. The higher nickel content reduces the risk of stress corrosion cracking. Austenitic steels are more or less resistant to general corrosion, crevice corrosion
and pitting, depending on the quantity of alloying elements.
Resistance to pitting and crevice corrosion is very important if the steel is to be used in chloride-containing environments. Resistance to pitting and crevice corrosion increases with increasing contents of chromium, molybdenum and nitrogen.

Material of Construction

In pressure Part Industry we use various type of material.

Typically in industry like this, we mainly classify material as Mild Steel also known as Carbon Steel, we also use low & high alloy steel & yes stainless steel!

What diffrentiate staineless steel from Carbon steel is its corrosion resistance properties, whcih comes because of its alloy elements.

In my blog hence onward, we will discuss about the material of constrution that we use in this industry.

I'll come back soon.

Good Websites

Hello friends,

After long time I'm updating my blog.
Please find here some shortcut to useful websites.
http://www.cleavebooks.co.uk/scol/ccpress.htm For Conversion
http://www.unitconversion.org/ for Conversion
http://mrnathan.munichre.com/ For World Sesmic/Wind Chart!
http://www.nicee.org/IITK-GSDMA_Codes.php Great india IIT website for earthquake and wind load calculations
http://www.allstainlessltd.co.uk/otherproducts.asp Good site for pipe fittings details

I'll update more links soon..

Left Thermax & Joined Ziemann

On 1st May I joined Ziemann, My Previous company is Boilers and my new company is in Brewing. and Now my job profile has changed.. Now i'll learn how to make beer.. As i'm learnign I'll share some good thing in steam with you after a while

Till then take care..

VALVES FUNDA

Lets start this session with some overview on Control Valves.


A power operated device, which modifies the fluid flow rate in a process control system. It consists of a valve connected to an actuator mechanism that is capable of changing the position of a flow controlling element in the valve in response to a signal from the controlling system.

Mainly control valves, which are used for the flow control (with some turn down) are Globe valve

Before we start on valve sizing part, lates start with the main terminology used for the Control Valves

TRIM: The internal parts of a valve which are in flowing contact with the controlled fluid.
Examples are the plug, seat ring, cage, stem and the parts used to attach the stem to the plug.
The body, bonnet, bottom flange, guide means and gaskets are not considered as part of the
trim.

Closure member: A movable part of the valve which is positioned in the flow path to modify the rate of flow through the valve.

Plug: A cylindrical part which moves In the flow stream with linear motion to modify the flow rate and which may or may not have a contoured portion to provide flow characterization.

Seat ring: A part that is assembled in the valve body and may provide part of the
flow control orifice. Seat Ring also can be an integral part of the body or cage material or may be
constructed from material added to the body or cage.

Cage: A part in a globe valve surrounding the closure member to provide alignment and
facilitate assembly of other parts of the valve trim. The cage may also provide flow
characterization and/or a seating surface for globe valves and flow characterization for some
plug valves.

Globe valve plug guides: The means by which the plug is aligned with the seat and held stable throughout its travel. The guide Is held rigidly in the body or bonnet.

Stem guide: A guide bushing closely fitted to the valve stem and aligned with the seat.
Disadvantage: Higher pressure drops and minor cavitation can excite vibrational modes that are
very destructive and can result in valve failure.

Post guide: Guide bushing or bushings fitted to posts or extensions larger than the valve stem
and aligned with the seat.

Boiler Design Life

Most of the cases.. Custumer ask for expected boiler life & we tend to say approx 10 years..

How one arrive at this figure? I've asked this question so many time to may expert inthis field but not able to get any satisfactory answer.

Recently i went thru ASME VIII Division1 , where the Fatigue requirements are discussed.

If the boiler pressure variation is less than 20% then we need not to consider those variation in fluctuating load. Only boiler cold stat-up & shut down need to be considred while calculating the fluctuating cycle.

i.e for 12 bar(g) design pressure boiler, the maximum operating pressure is 90% of design pressure i,e 10.8 bar(g) 20% of pressure variation means , pressure below 8.6 bar(g) will be counted for fluctuating load.

also delta temperature is important while calculating the fluctuation temperature.
for Delta of 200 (Star-up condition) the equivalent cycle is 4 per star-up & for
delta of 100 (Shut-down condition) the equivalent cycle is 1 per shut down, i.e if boiler is closing 15 time per month, it 12 per year, the cycle it will go thru is (4+1) x 15 x 12 = 900 cycles.

Approx, 10000 cycle boiler can take by design, i.e boiler design life will be = 10000/900 = 11.11 year approx.

Convection Continuied..

OK..
Now the big question.. the flow parameter Re & thermal parameter Pr, how they connects to HEAT TRANSFER???

So for our help.. Mr. Nusselt has created Nusselt Number!!

The traditional dimensionless form Nusselt number Nu, which may be defined as the ratio of convection heat transfer to fluid conduction heat transfer under the same conditions.

Nusselt number Nu can be calculated as

Nu = X . Re^y.Pr^z

Where X , y, z parameters are depends upon geometry, nature of flow, flow regime etc

Nusselt Number can also calculated as

So equating these two equation.. one can find heat transfer co-efficient on fluid side.

Hope you have understood the above co-relations..

Heat Transfer : CONVECTION At Glance

Lets See.. "CONVECTION HEAT TRANSFER"
Heat transfer occur when there is Delta T Across the two bodies.. heat always flow from hot side to cold side. Heat transfer may occur under natural draft or under forced circulation.

Industrial heat transfer equipment are mostly occur under forced condition.

As discussed above, one can conclude that the flow characteristics of the fluid on any side will pay an important role!!

We may recall our old books and some jargon like ' boundary layer', 'Lamina Flow' , 'Turbulent Flow' etc.

Lay-Mann says: As we break the boundary layer.. more new fluid molecule come in contact with the surface & more heat they will carry.. So in Laminar flow the heat transfer will be less as fluid wall touching the heating surface is not leaving the place & core will remain unaffected! while in turbulent flow the boundary wall will brake & better heat transfer will occur.

This 'Turbulent' thing can be identified scientifically using Reynolds analogy . Same is represented with Reynold's Number.

Reynold's number can be calculated as:

While there is one more parameter which plays an important role in heat transfer which is 'Prandtl number', which shows how heat will diffuse in fluid during convectio heat transfer..

Prandtl Number can be calculates as

Where v is Kinematic Viscosity & k is thermal conductivity of fluid

As you have noticed, Reynold's number is depends on carrier geometry & fluid properties, while Prandle number is depends on fluid property only.

Now how to use these number to evaluate heat transfer??

Wait for my next Scrap..

About Shell & Tube heat Exchangers

The discussion is IS 4503 Oriented.
IS 4503 is the code for heat exchanger ..

Type of heat exchanger

1. Fixed Tube Plate
2. U Tube
3. Floating head

Classification on Pressure

1. 2.5 kg/cm²(g)
2. 6.3 kg/cm²(g)
3. 10 kg/cm²(g)
4. 16 kg/cm²(g)
5. 25 kg/cm²(g)
6. 40 kg/cm²(g)

Classification on Temperature
Max. Allowable Metal Temperature

• Carbon Steel : 250ºC
• SS : 120ºC
• Non-ferrous : 65ºC

Max. Fluid Temperature

• Carbon Steel : 540ºC
• SS : 590ºC
• Non-ferrous : 200ºC

Corrosion allowance : 3mm minimum

Tube Pitch : 1.25 times the diameter of the tube

Tube Plate thickness is depend on the Tube outside diameter

Spacing of tube plate support (baffle) : minimum 50mm (varies from 0.6m to 2.5m)

Baffle distance to be decided to avoid any flow induced vibration which will lead to tube to tube plate cracking. TEMA has very indepth calculation to avoid these kind of ' harmonic' vibrations.

Something About Pressure Vessel/Heat Exchanger Codes

In day to day life we have to deal with Pressure vessel / heat exchanger manufacturing code.
These codes are not performance oriented code, these are safety oriented code. The basic approach of the code is from user point of view.. more the hazard stringent will be the code.

The Category of the pressure vessel are depends upon hazard the pressure vessel failure will lead to..

The classification depends upon pressure/volume/ liquid category (lethal or normal) .

European directive for the Pressure vessel is PED 97/23 EC (Pressure equipment directive)

Famous Code of construction used world wide are
EN 12953 : SHELL BOILER
EN 12952 : COIL / TUBE BOILER
EN 13445 : UNFIRED Pressure Vessel
BS 5500/ PD 5500 : UNFIRED Pressure Vessel
IS 2825 : UNFIRED Pressure Vessel
IS 4503 : Heat Exchanger
ASME VIII Div1 : UNFIRED Pressure vessel
BS 2790 : SHELL BOILER (replace with EN code)
BS 1113 : COIL / TUBE BOILER (replace with EN Code)
TEMA : Heat exchanger code
TRD : German Code for Fired Vessel / BOILER
GOST : Russian Code for Fired/ unfired vessel / BOILER

Feed Pump Selection

Lets do the Quick Caclulation
Inputs
Actul Flow in m3/hr ?
Design head MWC ?
Operating head MWC ?

Minimum Flow required for safer operating of the pump ?
How the by pass is maintained, using Orifice or control Valve ?
Let Boiler Steam flow rate is 31000 kg/hr

Flow
32.488 m3/hr X 1.05 (design factor) + Min. bypass flow via orifice = 40.87 m3/hr
Head
(Boiler pressure + pr. drop in system ) x 1.05 (design factor) = 207.38 MLC

				SIZING PARAMETERS
			Pr. Drop	Flow	Head	Density
Flow Rate		31000		m3/hr	MLC	kg/m3
Working pr		18	1.75	40.87	207.38	955.317
Design Pr		20	1.75	40.87	228.38	995.331
Temp		105
Rated Flow		34
% Bypass		20

Select the pump for 40.87 m3/hr & 207MLC & 228MLC Condition

Superheater - Gas Flow

Design of any heat exchanger is manly depend upon the flow configuration.
As discussed before the configuration could be of three type (majourly)

1. Parallel Flow
2. Counter Flow
3. Cross Flow

The compactness increases from Parallel flow to Counter Flow to Cross Flow

While complexity increases in reverse direction.

The superheater has flue gas on one side & Ideal gas on other. As steam has less capacity of carring the heat than water, we have to give more area.

The velocity of steam & flue gas plays a majour role in deciding the compact ness of heat exchanger.
More the velocity, more will be reynold's number, higher will be nusselt number, higher will be heat transfer co-efficient which leads to higher over all heat transfer co-efficient & hence
lesser Area.

Superheater - Performance Optimization

One thing we must remember while designing super heater.. Better the steam dryness compact will be the super heater.

One must always ensure that dry steam (99%) is coming in the superheater.
Just to give you the picture..

• for 98% Dry steam.. the unit energy required to make steam 100% dry+70ºC superheat

is : 61.5kcal/kg

• for 99% Dry steam.. the unit energy required to make steam 100% dry +70ºC superheat

is : 56.1kcal/kg

i.e if you give 99% dry.. 61.5-56.1 = 5.4Kcal/kg i.e for 6000kg/hr its 40KW less energy is required.

Lower heat demand.. means lower heat transfer area.

"Higher dryness fraction, lower heat load, lower heat transfer area, compact heat exchanger"

Now Dryness can be improved by giving dimister pad or giving external equipment to improve steam dryness.

Superheater Program

See the attached screen shot of the program.
It includes all possible configuration of the Super-hater.
The program is for Convective super-heater.

Main Window

The Super heater module

Superheater Design

A Major component of the Boiler

Superheater are of Two Type
1. Convective type
2. Radiant type


Convective super heater gives maximum of 80ºC of Superheat while, Radiant Superheat can give 150-300ºC Superheat. Former is more prone to thermal failure & rarely used in 'flue gas boiler'.

I'll discuss the convective type super heater.
The basic criterion for the design are
1. Degree of superheat required
2. Steam Dryness available at inlet of super heater
3. Heat duty available.
4. Maximum pressure drop allowed in the system.
5. Flue gas maximum temperature.
6. Type of heat exchanger configuration flow, Cross/Parallel/counter etc.
Flue gas maximum temperature is required to select the MOC of the super heater tubes

for Heat duty following equation shall be validated
M Cp DT = m. (Unit enthalpy of steam)
Where
M = Mass of flue gas
cp = Heat capacity of the flue gas
DT = Temp. drop across super heater
m = mass of Steam

NOx of the Boiler

Nox is majourly a function of Burner & then a Boiler.

Mainly in retrofit market Nox commitment can be achieved by changing burner design & Burner refractory.

Type of Nox
1. Thermal Nox Contributes to 80% of Total Nox
2. Instant Nox Contributes to 15% of Total Nox
3. Fuel Nox Contributes to 5% of Total Nox


I'll write in details later..

Burner Design

Burner Design

Three parameters decides performances of the burner
1. Turbulence,
May be created by 'Swearler' & high velocities, which results in better fuel atomization. optimum size of fuel droplet is 50 microns
2. Time,
Time of residence, residence time of the fuel during combustion, for gas its low, for LDO its high & for FO its highest
3. Temperature,
Right & high temperature at core, wil yield better combustion.

O2%

O2% gives excess air level, excess air decides fuel qty, more excess air, more the fuel gases, more stack temperature & hence more stack losses, as more air is carrying the heat with it.

Heat is carried away with the N2 in the flue gases, which can't be recovered & hence carried away in stack.

Fast Burner Funda!!

Hi I'm making this live again.. lets start with Burner!!

The Flame Visibility
1. Low Luminous flame causes, Non uniform Temperature & heat flux distribution
2.Low Luminous flame causes Poor radiant heat transfer & hence lower thermax efficiency
3. While More luminous flame gives Good radiant heat transfer, Low flame temperature & low NOx

Flame Geometry & O2
Blue Whitish flame,7.5% O2 Whisling Noise
At high excess air & velocity, molecules of the fuel start burning in fractions. on-off in this manner they produce small explosion along the length.
Hence flame will be bright & fluctuating in nature

Blueish pinkish flame
Less blue, more pink gives less NOx, higher blue flame suggest excess air & higher NOx

Critical Heat Flux for Any Flue gas Tube Steam Genrator

CHF (Critical Heat Flux)

During the brainstorming session, we have come with a critical question on 'Furnace life' due to higher heat loading in the furnace. during the 'research', I came across a term, Critical heat flux(CHF) or the 'burn out point'.

The past decade has witnessed unprecedented improvements in the performance of packaged boiler which were brought about, for the most part, by a restless pursuit of reducing the foot print of boiler. These advances have led to increases in the amount of heat that is dissipated and has to be removed from these furnaces to keep its life up & good heat transfer, large increase in heat dissipation per unit surface area is now the benchmark for designing of the furnace.

The CHF is a very interesting and important phenomenon from both fundamental and practical points of view. From the fundamental point of view, CHF accompanies tremendous changes in heat transfer, pressure drop and flow regime.

The critical heat flux (CHF) condition is characterized by a sharp reduction of the local heat transfer coefficient that results from the replacement of liquid by vapor adjacent to the heat transfer surface (Collier & Thome, 1994). The occurrence of CHF is accompanied by an inordinate increase in the surface temperature for heat-flux-controlled systems, and an inordinate decrease in the heat transfer rate for temperature-controlled systems. The CHF condition is generally more important in the heat-flux-controlled systems, since the temperature increase can threaten the physical integrity of the heated surface.

Dissipation of large heat fluxes at relatively small temperature differences is possible in systems utilizing boiling phenomenon as long as the heated wall remains wetted with the liquid. With the wetted wall condition at the heated surface, heat is transferred by a combination of two mechanisms:
(i) bubbles are formed at the active nucleation cavities on the heated surface, and heat is transferred by the nucleate boiling mechanism, and
(ii) heat is transferred from the wall to the liquid film by convection and goes into the bulk liquid or causes evaporation at the liquid-vapor interface. The large amount of energy associated with the latent heat transfer (compared to the sensible energy change in the liquid corresponding to the available temperature potential in the system) in the case of nucleate boiling, or the efficient heat transfer due to liquid convection at the wall, both lead to very high heat transfer coefficients in flow boiling systems. Removal or depletion of liquid from the heated wall therefore leads to a sudden degradation in the heat transfer rate.

The way in which the heated surface arrives at the liquid starved condition in a flow boiling system determines whether it is termed as Critical Heat Flux

At atmospheric pressure, The critical heat flux is slightly above 1MW/m². The formula for calculation of heat flux is given below.

This formula is derived by Zuber,N and its more in line with the practical values

Heart of Thermal Engineering

Q = M x cp x DT

Yes Dear,
The heart of thermal engineering is this.. Go any where & this formula will follow you :)

In any heat exchanger you must balance following equations

Mh x cph x DT h = Mc x cpc x DTc = U A LMTD

Where , h & c are for Hot & Cold fluid।

I'm attaching a Paper for your reference, You can study it & answer them all.

http://www.sendmefile.com/00540546

About the Tools!

Day In day out I've to do Thermal Calculation, the fuel combustion analysis, mass balance or design of heat exchanger, Why not to formulate them & use it as a GUI based program.. I'm great fan ov Visual Basic 6.. & all my applications are stand alone.. means no set up required just save it & run it :)
Here I'll share about the tools I'm developing

If you are intrested please mail me @ papasumit@gmail.com for a FREE COPY

You can see the Screen shots of the programs.. I'll add details soon

Boiler Engineers Tool


Fuel Combustion Tool




Heat Exchanger Design




Finned Tube Heat Exchanger Design



More to come....

About Me...

Hi all..
Hope you all are enjoying the life to the fullest..

Let me take pleasure to introduce myself, I'm Sumit Y Waghmare (BE Mechanical) residence of Pune, India.
Currently I'm working in reputed Boiler Manufacturer in pune as Asst, Manager Design. Now guess the kind of work a design engineer is doing in a Steam Insustry.. yes lots of thermal, mass & heat balance!
Thou thermal was not my major in my engineering.. it was now bread & butter for me. I've learn a lot many things in my stay in company & all creadit goes to my learnign capacity ;) and off-course to the company.
I'm looking forward your discussion on the topic.. the Queries, the Troubleshooting, Your on site design experience..
I also developed small package software which i think is be very useful tool for any thermal engineer..
What I'll share?
I'll share my knowledge, I'll introduce you with my small soft tools! You may ask for a trial copy :) till date I've not thought of making it commersial but it all start if there is a good response!