All About Mechanical Engineering

Heads as per ASME : Quick overview

2011-10-16T22:13:00.001-07:00

I was studing some heads for a while, and thougth to summarise the variety in one go…

1. Flanged Head : Normally found in Vessel opertaing at low pressure, genrally water tanks, Boilers etc. They are also used in high pressure application where the diameter is small.

2. Hemispherical Head : Generally, the required thickness of the hemispherical head due to a given Pressure & temperature is half of cylindrical shell with equivalent diameter & Material.

3. Elliptical and Torispherical (ASME Flangged & Dished) heads : they are very popular in pressure vessel, their thickness is ususally same as the cylinder to which they are attached.

This is a quick heads up for variety of heads used in industry. The other type are

1. Conical or Toriconical head: they mostly form bottom end closure for the vessels, and act as hopper, or to give easy drainability. The important thing to consider while designing this heads are, a) they increase the overall height of the vessel. b) ASME need to do discontinuity analysis for half angle >30 deg, or else one need to go ahead with toriconical head to avoid the unbalanced force at the junction.

2. Miscellaneous head: Many chemical process requires unusual vessel configuration, the heads of such vessel can have unlimited configurations. The design of such head is very complicated, and there is no straight forward formula for that.

Keep reading!

Project Management Performance Analysis

2011-09-26T03:46:00.001-07:00

Good read for Project management performance analysis.

http://en.wikipedia.org/wiki/Earned_value_management

Keep reading!

Great Space Exploration Tool

2011-09-06T04:11:00.001-07:00

Wonderful website!

http://celestia.sourceforge.net/

Keep Watching!

Process Piping Pressure Calculation : B31-3

2011-09-06T02:29:00.001-07:00

B 31.3 is an ASME code for Process piping, Multiple time we come across situation, where we need to calculate the design pressure for a pipe.

In such cases, ASME VIII-Div-1 seems helpless, and B 31-3 comes for rescue.

Clause 304.1.2 talks about Straight pipe under internal pressure,

Where,

P > Internal design pressure

D > Outside diameter of pipe

S > Stress value of material as per table A-1

E > Quality factor from Table A-1A & -1B

Y > Coefficient from table 304.1.1

Compare equation 3a with ASME VIII-1 Formula (UG-27)

The formula is completely same, except factor PY against 0.6 P!

Y factor varies from material & Temperature, which varies from 0.4 to 0.7

As I’m working on one of the project, where I’m manually doing calculation, I thought this will be fastest way to share!

Keep reading!

Code Comparison : Discussion:1

2011-09-01T22:33:00.001-07:00

Scope & Responsibility:

Let’s start with comparing the scope & Responsibilities for various codes.

Following table will give an overview

Characteristics

ASME VIII-Div-1

EN 13445

GB-150

Scope

Ref ASME VIII-1 U-1

Pressure Not exceeding 20 MPa U-1(d)

Design by Formula

Minimum pressure 15 psi (g) [1 bar(g)]

Minimum -ve pressure 15 psi (g) [1bar(g)]

Refer EN 13445-1: 2009

No limit on pressure

Design by Formula & Design by Analysis

Minimum pressure 0.5 bar(g)

Minimum -ve pressure -0.5 bar(g)

Refer GB-150 : 1-1.1

Pressure not exceeding 35 MPa

Design by Formula

Minimum pressure 1 bar(g)

Minimum -ve pressure 0.2 bar(g)

Responsibility

Ref VIII-1 U-2 (b), UG-90

Responsibility of Manufacturer to design complete

vessel as per requirements of Code

19 responsibilities with Manufacturer, 14 with AI

Refer EN 13445-1: 2009

Responsibility of Manufacturer, counter signed by

notified body (Independent agency)

Annex - H to be filled & Signed

GB-150 : 3, Clause 3.2.2

Responsibility of Manufacturer & Designer to design

complete vessel as per requirements of Code

Next Topic Material & Properties!

Keep Watching!

Code Comparison : A Startup

2011-09-01T22:19:00.001-07:00

With my next feeds, I’ll be comparing following Code on various aspects

European Code : EN 13445

American Code : ASME Section VIII Div. 1

German Code: AD : 2000

Chinese Code: GB: 150

Keep watching!

Pressure Vessel Codes & Comparisons

2011-05-27T20:53:00.000-07:00

After getting my self stablaized in new company... now i'm evaluating the world around.

Filtration is the business, which is common to many needs, and hence it has been seen across the continent

Which brings me to todays discuss, short but sweet, and as usual with a promise to update you more as i learn more about this.

From Pressure vessel point of view, suddenly I'm exposed to number of Code of construction, which includes the old daddy ASME, PD-5500, AD-2000 and new comer like EN 134445. the new code i'm now exposed to is GB-150!

How many of you know this code? and importance?

GB-150 is Pressure vessel code for Pressure vessels in China! it very closely follows ASME, but has its own style! and its governed by Government.

In next few days, i;ll be sharing my finding as i'm all set to compare all these codes.

As an Indian, i like to as Indian Code for pressure vessel IS 2825. mostly its requirement by Gov. agency, but ASME is well accepted here in India, and IS 2825 closely follows PD 5500.

in my next post i'll be sharing more about the comparison of three codes, ASME, EN & GB

keep reading & Posting!

Weld - Defects

2011-02-10T01:23:00.000-08:00

We talk about type of welds & weld joints, the talk on welding will be incomplete if we don't talk about weld defect!

Some weld defects are visible, some are visible with aide & some are invisible and need extra process to reveal them.

Before we go into process of different methods to see those defect, one must first know what are those defects?

Let me show you some defects & with their names

Spatter

Incomplete Fusion

Incomplete Penetration

Overlap

Porosity

Undercut

Underfill

Some are Visiable in Radiography!

Burn Thru

Cluster Porosity

Excessive Reinforcement

External Undercut

Internal Undercut

lack of penetration

lack of fusion

Porosity

Suck Back

Tungsten Inclusion

in my next post, will discuss, i ndetail about the Methodology to see these cracks!

Good Informative Welding Site

2011-02-03T21:43:00.000-08:00

http://www.millerwelds.com/resources/dictionary.html
http://www.tpub.com/content/construction/14250/css/14250_55.htm
http://www.iiwindia.com/pdf/ASME_&_ISO_EN_Welding_Position_Comparison.pdf
http://www.gowelding.com/wp/asme.htm
http://www.arcraftplasma.com/welding.htm

weld Positions & Joints?

2011-02-03T21:30:00.000-08:00

Learning Welding doesn’t stop only at knowing welding process.
Followings are more important things selecting welding process :

1. What? What are we welding (Metal type, thickness, chemistry)
2. How ? How are we welding (Welding Position)
3. Where ? where are we welding (e.g in water, near sea shore, inside, outdoor)

We will discuss this in detail, but first we understand the definition & usage of these terms, to start with : Position

Position:
Generally as per ASME IX, following are the mentioned position for groove weld

Flat : 1G
Horizontal : 2G
Vertical Upward/Downward : 3G
Overhead : 4G
Pipe – Horizontal : 5G
Pipr 45º : 6G

For Fillet weld, replace G with F, and there is no 6F applicable!

Abbreviations used in Welding

2011-01-31T02:36:00.000-08:00

if you are new... visiting vendor's place or going for some technical discussion.
Following abbreviation will help you what "geek" talk they are doing :)

Welding Process

2011-01-31T02:29:00.000-08:00

Definition

welding noun /ˈwel.dɪŋ/ n [U] the activity of joining metal parts together
(Definition of welding noun from the Cambridge Advanced Learner's Dictionary)

Welding in industry has huge spectrum! it starts for arc welding, to fusion welding, to Laser and so on and so forth,

Generally, pressure vessel speaking, we use following three type of welding

- SMAW : Shielded Metal Arc Welding
- SAW : Submerged arc welding
- TIG : Tungsten Inert Gas welding
- GMAW : Gas Metal Arc Welding

Other types are
-Atomic Hydrogen Welding(AHW)

-Bare Metal ArcWelding(BMAW)
-Carbon ArcWelding(CAW)
-Electro Gas Welding(EGW)
-Electro Slag Welding(ESW)
-Plasma Arc Welding(PAW)
-Stud Arc Welding(SW)

Lets discuss Generall Welding Process in Brief
SMAW :

As you can see in picture, the arc is created between Parent material and electrode. The oxidation is avoided by the flux coated on electrode. Due to arc the weld metal start melting, and due to high temperature, the flux also get melted, due to density difference, the flux floats over weld pool, and thus by function makes a barrier between atmosphere & weld to avoid any oxidation.
The temperature found in arc is as high as 7000ºC, at which the gas/air get ionized, providing good electrical conductivity in the arc.
The actual transfer of metal from the electrode to the workpiece is in the form of molten globules of different sizes depending on the type of electrode used. Some electrodes produce globules that are so large that they actually shortcircuit the arc for a moment.
Electrodes for manual arc welding (sometimes referred to as stick welding) consist of a rod and a coating material. As a rule, the alloy in the rod will be similar to the material to be welded.

The most common types of electrodes are:
1. The Organic type (electrodes contain large quantities of organic substances such as cellulose)
2. The Rutile type (electrodes contain large quantities of the mineral rutile)
3. The Acid type (electrodes produce an Iron Oxide / Manganese Oxide / Silica type of slag, the metallurgical character which is an acid.)
4. The Basic type (Low Hydrogen)
5. LMA (Low moisture absorption electrode)

TIG Welding:

In Tungsten Inert Gas welding (TIG), an arc is struck between a Tungsten electrode and the workpiece. An inert gas flow (Argon) protects the electrode and pool from the surrounding air. The electrodes do not melt.The filler metal is inserted into the molten pool in the form of a separate rod. The process has a similar welding technique as gas welding but use electricity as energy source.

GMAW / FCAW Welding

In Wire welding an arc is struck between a continuously fed wire and the workpiece. An inert gas, active gas or a mixture of the two protects the pool from the surrounding air. The wire used can be solid or flux cored. In some cases the flux cored wire is self shielded and does not require any additional shielding gas.

What are not covered? Gas Welding (Oxy-acetelene) and Brazing!

Hope this will give you sufficient over view.

Pressure Vessel - A thought

2011-01-30T23:35:00.000-08:00

10 year ago after completing my degree in mechanical engineering , when i joined the industry, as a fresher Fabrication & Pressure vessel both were new to me. I took help of good old hand books from Dennis Moss and Megyesy. Thought they where great tool.. I understood one fact hard way, if you ignore basic, they are no good, as there are big mistakes in Dennis Moss book, which you never come across if you put your mind aside! on other had Megyesy, is too much orientated on ASME VIII Div-1, and will not help much if you want to look beyond horizontal vessel or less complicated vertical vessel.

ASME provide all tools & guidelines to analysis Failure (limits) but fails to help me understand how to implement it in actual practice (Additional loading, Conical head with angle >30º! etc. etc...)

Hence I started this Blog to help understand how to implement old engineering know how in Practical scenario!

currently I'm in phase of switching to a new Industry all together, may be i'll find more way to implement my know how their & learn new way to optimize things.

Take Care

Beer- Well Said

2010-11-11T23:42:00.000-08:00

Some where I've seen this image! we have 300+ variety of beer!

Beer in PET (Plastic Bottles)?

2010-11-10T20:01:00.000-08:00

Has any body ever thought why we don't get Beer in PET jar? or PET bottle.

Do you know, whole beer industry is as much intrested in giving beer in PET bottle than us, as this is the cheapest & easy way, though mother nature will not be happy :)

Beer in Plastic accounts only for 5-6% in world's beer package!

What is PET
its short form of Polyethylene Terephthalate, basically a polymer. its extensively used for packaging carbonated drinks.

Whats wrong with PET?

PET absorbs sizable amount of CO2 as the bottle tries to equilibrate with content inside, some study has shwon at 21ºC, PET bottle takes three weeks for 500ppb O2 to invade & four weeks for 10% of the CO2 to wave goodbye.

So what?

OK, Soft Drinks (Carbonated) can tolerate in grease of O2 upto 20ppm, before they change the flavors! so its perfectly on to store it for almost a year!

BUT, for beer, even 0.1 ppm O2 can spoil the itch on tongue! hence normal PET is no-no!

What Next?

People are trying to invent new Coatings to close this barrier or to minimize this sepage! its 'Work Under Progress'.

Whatever you say, beer look nice in Bottler & Test nice in Glass!

Three cheers to Glass!

Pressure Vessel Software-Solution

2010-10-24T06:48:00.000-07:00

I'm thinking of buying or developing software for pressure vessel.
I've searched lots of software from PVlite, Pressure Vessel Engineering, CEREBRO-mix etc. but end of the day, the customized solution that I need was always missing.
Let me list out what one expect from such software... atlease I do.. if i miss out something, let me know
- Shell under internal pressure,
- Shell under external pressure,
- Heads under internal & external pressure
- Cone under internal & external pressure
- Stiffner calculation
- Support calculation - Saddle
- Support calculation - Skirt
- Support calculation - Ring support
- Support calculation - Lug support
- Support - Vessel on Leg (Braced & unbraced)
- Leg Support on Dish & cone
- Vertical & horizontal option
- Cooling Calculations
- Flange Design as per ASME VIII - Div-1 (appendix)
- Surface area calculation
- BOM/ MTO calculation
- Seismic & Wind Loading as per IS/UBC

.. what else?

Cooling - Thermal Calculation

2010-10-13T03:19:00.000-07:00

Lets Start with Diffrent Loading Calculation
Step : 1
1. Heat Loss to Atmosphere : Surface Area m² X Delta (Tavg - Troom)ºC x 0.32 = Q1 kcal/ hr
2. Cooling Load : Volume of liquid (lits) x Delta (Tstart-Tend)ºC/Time (hr) = Q2 kcal/hr
3. Heat evolved during Chemical process/ Fermentation : Q3 kcal/hr

Total Heat to be Removed = Cooling Load = Q = (Q1 + Q2 + Q3) X factor of safety

Please note Unit of Measurement carefully

for Q3, what process do you follow in your vessel, you need to find out the Load.

Step : 2
Calculate LMTD {Log Mean Temperature}
DT1 = TmediaStart - TcoolenEnd
DT2 = TmediaEnd - TcoolentStart
LMTD = (DT1-DT2)/ ln(DT1-DT2)

Step : 3
Calculate Overall heat Transfer co-efficient & Surface Area Required
Q = U A LMTD
Hence, A = Q / (U x LMTD)

U, Over all heat transfer co-efficient : 100-250 Kcal/ hr ºC m², this is mainly depends uppon what type of jacket do you use, limped coil or limped jacket or profile sheets or laser welded jacket etc. you need to have some co-relation to evaluate this if the construction of jacket is non-standard. for standard type of jacket, you can get more info on following link
http://www.cheresources.com/jacketed_vessel_design.shtml

and if nothing works, ask me :)

Step : 4
Calculate amount of Cooling media needed for cooling
Now here is a trick, their are two type of coolent, one, they cool by their latent heat (e.g Ammonia) or two, they cool by dropping their temperature (e.g glycol water)

for First option, we need to consider Enthalpy of latent heat, devide Q by this, and you will get mass flow, for Second type follow following equation
Q = m . cp. DT (Tstartcoolent - TendCoolent)

Make sure you get these enthalpies at the working temperature, refer Perry's handbook, or ask your cooling supplier for detail physical properties, as these properties changes with pressure & temperature, for water mix coolent like glycol, the properties changes with concentation of media

I hope this is sufficient in-sight, in case of help, let me know

Cooling Performance - Overview

2010-09-30T00:48:00.000-07:00

Ok, So you want to design cooling for a vessel.. how to?

Step : 1 : What you should know, and what you should ask
What you should know
a) You should know what type of Vessel Construction your are offering
b) You should know what Jacket for cooling you have
c) You should know your Jacket, Heat transfer co-eff co-releation very well
What you should ask
a) Media to be cooled
b) Media for cooling
c) with agitation or w/o agitation
d) Location (in-house or out-side)
e) Cooling performance needed
Step : 2 : Calculated heat Duty/ Cooling Duty
a) Duty due to Surface Loss
b) Duty due to Fermentation/ Process, i.e to remove heat arising from the process
c) Duty due to Cooling withing given time frame
d) Factor of safety : 10 to 20% depending upon your confidence (prooven history will help to reduce this factor of safety)

Step : 3 : Calculate Amount of cooling media needed

Step : 4 : Calculate Area for Cooling jacket

Step : 5 : Calculate Pressure Drop

Step : 6 : Summary

Next post : How to!

Milk Property fact!

2010-07-08T04:56:00.000-07:00

Just, I got this info & sharing with you
Density of Milk
Whole milk : ρ = 1035.0 − 0.358 T + 0.0049 T^2 − 0.00010 T^3
Skim milk : ρ = 1036.6 − 0.146 T + 0.0023 T^2 − 0.00016 T^3
Buffalo milk : ρ = 923.84 − 0.44 T
Cows’s milk : ρ = 923.51 − 0.43 T

Good, know you know what will be wait of 1 Liter Pouch :)

Cooling of Big tanks

2010-07-02T20:15:00.001-07:00

Dear All,

Recently i was working on designing tanks with cooling jacket.
In brewery in particular, there is lots of need of cooling of tank, to take care of heating load generated out of fermentation, surface losses & to get temperature profile.

and as a motive to open this blog, is to share what i learn, in my next post I'll discuss this in very detail.

See you all soon

PS : if you need any more info ask me, i can add that too in my post!

ERP

2010-05-02T16:35:00.000-07:00

Lately (late in my career), that is for past three years, i'm working on various ERPs. Offcourse i started the work on engineering domain. But thanks to my friends in other domain, who helped me in understanding other modules too. In my recent company i've developed my own ERP. it was made to take care of all engineering needs, and it was now running for past two year. Mean while i've also implemented full fleaeged ERP system. With which my software do seamless communication.

This implementation has given me insight on various aspects of organization, like finance, production, purchase and offcours engineering.

Point is, can i develop an ERP of my own? I think its not a tough target. But can i implement one? Yes for sure.

See you soon.

Earth quake Factors - Why & How

2010-03-11T04:27:00.000-08:00

Whats is Earth quake factor? and how they affect the calculation?

Their are numerous papers on this, and they are equally qualified to tell you what is earthquake factor all about... but what mater to me is.. how do they do it!

As far as India is concern..The earthquake of 26 January 2001 in Gujarat was unprecedented not only for the state of Gujarat but for the entire country in terms of the damages and the casualties. As the state came out of the shock, literally and otherwise, the public learnt for the first time that the scale of disaster could have been far lower had the constructions in the region complied with the codes of practice for earthquake prone regions. Naturally, as Gujarat began to rebuild the houses, infrastructure and the lives of the affected people, it gave due priority to the issues of code compliance for new constructions.

Seismic activity prone countries across the world rely on “codes of practice” to mandate that all constructions fulfill at least a minimum level of safety requirements against future earthquakes. As the subject of earthquake engineering has evolved over the years, the codes have continued to grow more sophisticated.

Liquid storage tanks are commonly used in industries for storing chemicals, petroleum products, etc. and for storing water in public water distribution systems. Importance of ensuring safety of such tanks against seismic loads cannot be overemphasized.

Earthquake loading - Brief

2010-01-28T17:45:00.000-08:00

All designers are accustomed to evaluating moments due to eccentric and wind loads, but there are a few who may not be familiar with the method used for estimating moments due to earthquake. Therefore, the following brief outline is presented because this method is recommended as a design procedure for vessels where dynamic considerations are required. The weight of each vessel element (shell, head, tray, or internal part) is calculated. and then multiplied by the vertical distance from the circumferential seam (or horizontal plane) under
consideration to the center of gravity of the element. The summation of the moments so found ismultiplied by the seismic factor for the area where the vessel is to operate, thereby yielding a moment due to earthquake or seismic disturbance. For vessels, the seismic factor will usually have a value of 0.03 to 0.12, depending upon the geographical location. Expressed mathematically,

Thickness Calculation for Combined loading

2010-01-28T17:37:00.001-08:00

It is customary for most vessel designers to establish the minimum vessel shell and trend thickness according to the pressure temperature conditions and then calculate the thickness required at the bottom head seam due to bending moments imposed by wind or earthquake forces. Stresses in the longitudinal direction are involved nod the following notation may
be used to summarize the thickness required :

Here, The terms within the absolute value signs are positive for tensile stresses and negative for compressive stresses. The first term gives the thickness required for the longitudinal stress resulting from internal pressure and is positive for pressures above atmospheric and negative for pressures below atmospheric. The second term is the thickness required to resist the longitudinal bending stress and both positive and negative values exist at the same time. The third term is the thickness required for the weight of the vessel above the seam being investigated and, since this is a compressive stress, it has a negative value. The combination giving the highest value establishes the thickness required to resist the longitudinal stresses.

This formula hold good when the units are in Psi, ft & lb, if the units are in MPA, mm, N then remove the '48' from the formula.

Design : 2 : Shell (External Pressure)

2010-01-28T17:24:00.000-08:00

External pressure can be due to internal negative Pressure, or external loading like wind, earthquake etc. or live load, snow load etc.

One can design Pressure vessel for either sever combination of various load or for most possible occurrence of load combination.

Load combinations are given in respective 'Building Code' like API, UBC, IS etc.

Yes, If you noticed I've said 'Building Code', why? as most of these loading decides how the pressure vessel, and if it fails, it can harm the occupants. hence design of such loading will be governed by building codes.

These Building code will give su way to calculate loading on tank/vessel, and then our design code like ASME, BS,EN will tell us how to derive the thickness from them.

one should note that, nearly all the design code talks about +ve Internal pressure & -Ve internal pressure & its design rules, but none of the code talk about how to do thickness calculation for the loads specified above.

In latest edition of ASME it does talk about these loading, and ask user to use Engineering practices to calculate loadings (UG-22), loading listed in this sections are
(a) internal or external design pressure (as defined in UG-21);
(b) weight of the vessel and normal contents under operating or test conditions;
(c) superimposed static reactions from weight of attached equipment, such as motors, machinery, other vessels, piping, linings, and insulation;
(d) the attachment of:
(1) internals (see Appendix D);
(2) vessel supports, such as lugs, rings, skirts, saddles, and legs (see Appendix G);
(e) cyclic and dynamic reactions due to pressure or thermal variations, or from equipment mounted on a vessel, and mechanical loadings;
(f) wind, snow, and seismic reactions, where required;
(g) impact reactions such as those due to fluid shock;
(h) temperature gradients and differential thermal expansion;
(i) abnormal pressures, such as those caused by deflagration;
(j) test pressure and coincident static head acting during the test (see UG-99).

In next section, we will discuss how to calculate final thickness of a vessel considering all loadings

Design : 1 : Shell

2010-01-05T20:10:00.000-08:00

We design pressure vessel for longitudinan and circumferencial stresses. Now whats that?
Ok, longitudinal stresses comes on circumferencial joints, where as circumferencial stresses comes on longitudinal joints.
And to add cherry on top circumferencial stresses are twise that of longitudinal stresses.
If you are not yet twisted your tongue, and to avoid that we generally call them c'seam and l'seam and c'stress and l'stress.

In below pictures, one can identify types of Seams and Stress.

here p is design pressure, R is internal Radius, L is Length of shell, t is thickness of shell.

Hence with the basic mechanical formula,
t for Hoop stresses = pL (2R)/2 xStressx L = pR/Allw. Stress
t Longitudinal stresses = px3.14xR^2 / (2x3.14xRxAllw. Stress) = PR/2 Allw. Stress

& what ASME Says..
t for Hoop Stress = PR/(SE - 0.6P)
Where S > All. Stress, E > Joint Eff. or factor of safety
why 0.6 P, because, its factor of safety set by ASME People

&
t for Longitudinal Stress = PR/(2SE+0.4P)

Note the '2' in denominator..

if E remain the same for both cases, then thickness given by Hoop stress will be twice that of by Longitudinal stresses

For Calculation Sheet Visit http://sumitmechsoftware.blogspot.com/

Pressure Vessel catagory (Design Persay)

2010-01-03T20:05:00.000-08:00

OK..

The Billion dollar Question...

Just to make it easy, we will break the pressure vessel in two category..
1. Pressure Vessel without external loading &
2. Pressure Vessel With external Loading

For Category 1, we can use ASME Section VIII Div. 1 directly, where as for Category 2, we need to consider additional loadings. And for additional loading we need to follow the basic engineering practices.

Hence, in future section, 1st we will discuss the Sizing of Pressure vessel as per ASME Section VIII Div. 1, and then we discuss the additional loading part.

"Terms" in Pressure Vessels

2009-12-31T02:06:00.000-08:00

Failure: Failure of a structure is an event, the transition from a normal working state, where the structure meets its intended requirements, to a failed state, where it does not meet its requirements
Limit states: A limit state is a structural condition beyond which the design performance requirements of a component are not satisfied. Limit states are classified into ultimate limit states and serviceability limit states
Elastic limit states: An elastic limit state is a structural condition associated with the onset of plastic deformation. This term is usually used in connection with monotonic actions, and it relates to virtual structures, usually with zero initial stress distribution
OPERATING PRESSURE : The pressure which is required for the process, served by the vessel, at which the vessel is normally operated.
DESIGN PRESSURE : The pressure used in the design of a vessel. It is recommended to design a vessel and its parts for a higher pressure than the operating pressure. A design pressure higher than the operating pressure with 30 psi or 10 percent, whichever is the greater, will satisfy this requirement, The pressure of the fluid and other contents of the vessel should also be taken into consideration.
MAXIMUM ALLOWABLE WORKING PRESSURE : The internal pressure at which the weakest element of the vessel is loaded to the ultimate permissible point
HYDROSTATIC TEST PRESSURE : One and one-half times the maximum allowable working pressure or the design pressure to be marked on the vessel when calculations are not made to determine the maximum allowable working pressure.

There are many more terms than this... but to start with.. these are sufficient.

What is Pressure Vessel?

2009-12-26T07:35:00.000-08:00

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?

2009-12-24T04:30:00.001-08:00

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

2009-12-23T03:20:00.000-08:00

I'm attaching few pictures of Drinktec exhibition..

Visit to Drinktec

2009-09-17T06:12:00.000-07:00

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

2009-04-25T07:40:00.000-07:00

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

2009-04-25T00:35:00.000-07:00

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

2009-01-19T09:18:00.000-08:00

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

2008-06-15T09:33:00.000-07:00

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

2008-04-28T23:00:00.000-07:00

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

2008-04-09T03:32:00.000-07:00

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..

2008-02-21T05:38:00.000-08:00

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

2008-02-20T05:59:00.000-08:00

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

2008-02-16T02:33:00.000-08:00

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

Type of heat exchanger

Fixed Tube Plate
U Tube
Floating head

Classification on Pressure

2.5 kg/cm²(g)
6.3 kg/cm²(g)
10 kg/cm²(g)
16 kg/cm²(g)
25 kg/cm²(g)
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

2008-02-16T02:18:00.000-08:00

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

2008-02-02T02:43:00.000-08:00

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

2008-02-02T02:11:00.000-08:00

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

Parallel Flow
Counter Flow
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

2008-01-05T03:19:00.000-08:00

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

2007-12-10T02:57:00.000-08:00

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

2007-12-05T05:15:00.000-08:00

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

2007-11-30T05:12:00.000-08:00

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

2007-11-29T05:43:00.000-08:00

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!!

2007-11-29T05:37:00.000-08:00

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

2007-06-03T21:39:00.000-07:00

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

2007-06-02T03:39:00.000-07:00

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!

2007-06-01T20:48:00.000-07:00

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...

2007-06-01T20:24:00.000-07:00

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!