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Monday, March 29, 2010




The performance of a control valve is defined by its inherent and installed characteristic curves. The inherent characteristic curve is a plot of the percent of valve opening vs. the percent of maximum flow coefficient (CV). The inherent characteristic curve is determined by measuring the flow rate at various positions of valve travel with a fixed differential pressure across the valve (typically 1 psid) and calculating the CV at each position using a form of the generalized Control Valve CV equation

Thanks to Jeff Sines

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posted by Webworm, 4:08 PM | link | 0 Comments |
Chemical & Process Technology has started blogging since 2007. Subscriber to Chemical & Process Technology increased rapidly. Recently some reader raise a question. How to access previous posts ?

There are several ways you may access previous posts. Several you may access previous posts :
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Hope above features can all reader to maximize usage of Chemical & Process Technology webblog.

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posted by Webworm, 3:42 PM | link | 0 Comments |

Saturday, March 27, 2010

Sulfide -stress cracking is basically a hydrogen-embrittlement phenomenon .Atomic hydrogen enters the steel to cause cracking. The hydrogen is generated on the surface of the steel because of a corrosion reaction. Iron reacts with h2s to form iron sulfide and hydrogen .This hydrogen is generated in atomic form on the steel surface ,where it can either combine to form molecular hydrogen and leave the surface as bubbles or diffuse into steel .This latter process may result in hydrogen embrittlement .Hydrogen sulfide prevents hydrogen recombination & thus promote entry of atomic hydrogen into steel .It is important to note that water must be present for this mechanism to occur ;without it SSC will not be observed ,because the ionization of the hydrogen sulfide is required.

Following is a lecture presentation on NACE Standard MR0175  - Petroleum and Natural Gas Industries – Materials for use in H2S-containing Environments in Oil and Gas Production.
 

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posted by Webworm, 4:33 PM | link | 0 Comments |
Earlier post "API Std 520 Part 1 Dec 2008 is Released" highlighted one of the main  changes was to use of isentropic nozzle flow method and/or ideal gas specific heat ratio for vapor/gas relief flow calculation.

Recommended :
Isentropic nozzle flow method is considering one dimensional homogeneous flow is limiting in Pressure Relief Valve (PRV) nozzle with isentropic (adiabatic and reversible) expansion across the PRV nozzle. Maximum mass flux across the PRV nozzle will be determined follow by mass flow passing the PRV. In determining the maximum mass flux, an integration of specific volume (v) time differential pressure (dP) is required. This integration involve substantial derivation of specific volume (v) which change with pressure (P). If the system can be modelled in HYSYS, you may consider the following tedious and simplified method in determining the specific volume (v) with varies pressure (P).

Tedious method
The detailed method involve the fluid expanded isentropically across multiple expander with fix differential pressure (dP). Entire model is simulated using HYSYS with Isentropic expansion using Expanders. Stream 1 is the feed to PRV nozzle. Stream 1 is expanded isentropically (polytropic efficiency =100%) to stream 2 with fix differential pressure. Stream 2 is further expanded isentropically to stream 3, Stream 4 is further expanded isentropically to stream 4,.............






Mass density is extracted from each stream in order to use for integration of specific volume (v) time differential pressure (dP). Following is the example of specific volume (Inverse of Mass density).




Simple Method
A simple method is proposed hereafter. It basically utilize the capability of Property Table.

Step 1 : Enter stream 1 and open the Property Table Utility in Attachment tab.


Step 2 :From the Connections tab, select Variable 1 as Pressure with Incremental pressure from Outlet (e.g. 1 barg) to Inlet pressure (e.g. 12 barg).

Step 3 :From the Connections tab, select Variable 2 as Entropy with State mode. Enter the Entropy of Stream 1 here.


Step 4 : In Dep. Prop. tab, Add Mass Density. Now the system is ready for calculation. Click the Calculate button.

Now Mass density change according to pressure (with isentropic expansion) is ready.


Above method can be easily adopted for subcooled flashing, two phase flashing flow across the PRV nozzle.

Do you have better idea ?

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posted by Webworm, 2:48 AM | link | 0 Comments |


Let's do it together !

Earth Hour 2010 will drop on March 27th, 2010, 8.30pm Local time. The effort is simple for everyone :

TURN OFF ALL NON-ESSENTIAL ELECTRICAL APPLIANCE FOR 60 MINUTES from 8.30pm to 9.30pm Local time

We in Chemical & Process, Oil and Gas industries known as one of the major "contributor" in global warming is encourage to take this opportunity to take some effort...

See more video clip in "Earth Hour 2010 - You can Help Our Friend... Environment..."

Visit Earth Hour website  : http://www.earthhour.org/


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    posted by Webworm, 1:00 AM | link | 0 Comments |

    Saturday, March 20, 2010

    NACE MR0103 "Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments" was developed by Task Group 231 to provide a standard set of requirements for materials used in sour petroleum refinery equipment. In the past, NACE MR01752, "Sulfide Stress Cracking Resistant Metallic Materials for Oilfield Equipment", was frequently referenced for this equipment, even though refinery applications were outside the scope of MR0175. The process used to develop MR0103 is described, followed by a review of the requirements in the standard accompanied by highlights of the differences between MR0103 and the previous and current versions of MR0175.

    An Overview of NACE International Standard MR0103 and Comparison with MR0175 


    Click here to download the article
    Download #1
    Download #2



    A presentation has been prepared by the author which further summary the differences. You may download via the following link : Download Presentation Handout

    Thanks to Don BUSH, Jeff BROWN & Keith LEWIS


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    posted by Webworm, 2:38 AM | link | 1 Comments |

    Friday, March 19, 2010

    Earth hour is an effort by WWF (World Wide Fund for Nature/World Wildlife Fund) to create awareness on global warming and the need to take action on climate change. All of us can participate in this annual event. Last year 2009, Chemical & Process Technology has participate as well..."Earth Hour - Simple Effort Minimise Global Warming".

    In 2009 hundreds of millions of people around the world showed their support by turning off their lights for one hour. You may see the following video clips showing what happened in 2009.












    Earth Hour 2010 will drop on March 27th, 2010, 8.30pm Local time. The effort is simple for everyone. It is simple :

    TURN OFF ALL NON-ESSENTIAL ELECTRICAL APPLIANCE FOR 60 MINUTES from 8.30pm to 9.30pm Local time

    We in Chemical & Process, Oil and Gas industries known as one of the major "contributor" in global warming is encourage to take this opportunity to take some effort...

    Visit Earth Hour website  : http://www.earthhour.org/




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    posted by Webworm, 4:43 PM | link | 0 Comments |

    Thursday, March 18, 2010

    Atmospheric storage tank normal venting based on API Std 2000 6th edition, Nov 2009 has been discussed in "Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000". Ankur, an experience engineer in Chemical industry, actively involved in CheResource Forum, has take his effort and time to program it in Microsoft Excel spreadsheet. Thanks to Ankur.

    As reminder, the information and methods included within this spreadsheet are presented for common sharing and intended to be used by technically skilled persons at their own discretion. We do not warrant the suitability or accuracy of these methods.



    Insulation type and recommended thermal conductivity have also been included in the spreadsheet for easy reference. The insulation type and thermal conductivity as follow :

    Common Insulation Materials Average Thermal Conductivity, W/m-K 
    Cellular glass  0.05
    Mineral Fiber
    0.04
    Calcium Silicate 0.06
    Perlite 0.07

    Products contain volatile components or dissolved gases or flashing products may result adddtional volatile component / gases / vapor. This amount will increase the outbreathing rate.

    Products stored at temperature above 40 degC or its vapor pressure higher than 5.0 kPa, products evaporation rate shall be added into outbreathing rate.


    Read and download spreadsheet in "Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000".

    * If you find any error or improvement,  please inform us.
    **If you have any useful program and would like to share within our community, please send to me.

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    posted by Webworm, 2:13 PM | link | 0 Comments |

    Wednesday, March 17, 2010

    Liquid in tank truck or storage tank may spill on the ground. Wind blowing, solar and ground surface heating will results evaporation of spilled liquid. The evaporation rate is one of the key information required during design phase for consequence analysis and preparation of emergency handling measures. What is the quick way to estimate evaporation rate ?



    Evaporation rate from spilled liquid subjects to several factors such as :
    • spilled liquid volatility
    • spilled liquid properties
    • spilled liquid surface area expose to wind blowing
    • spilled liquid temperature
    • wind speed
    Evaporation Rate
    Evaporation rate of spilled liquid can be estimated using following equation

    E = (0.284 U0.78.MW2/3.A.VP) / (82.05 T)

    where
    E = Evaporation rate (lb / min)
    U = Wind speed above spilled liquid surface (m/s)
    MW = Spilled liquid molecular weight
    A = Spilled liquid surface area (ft2)
    VP = Spilled liquid vapor pressure at liquid temperature (mmHg)
    T = Spilled liquid temperature (K)

    Spilled Liquid Surface Area
    Spilled liquid surface area is normally fix by the containment itself. Liquid spilled from tank into diked area, the spilled liquid surface area will be the diked area itself  unless the spilled quantity is so small where it will not covers entire diked area. To estimate spilled liquid surface area without any containment, it is assumed that the spilled liquid will have 10mm (or 0.033 ft) thickness. Therefore,

    Spilled liquid surface area (ft2)

    A = V / 0.033

    where
    V = Spilled liquid volume (ft3)


    Example
    Methanol with vapor pressure (VP) of 125 mmHg and MW of 32.04 stored at 25 degC in a 25,000 US gal tank (10 ft diameter). Overfilled methanol results spillage of 1,000 US gal of methanol spread in the diked area (100ft x 40 ft) which contain 8 identical tanks. Assuming wind speed is 1.5 m/s, estimate evaporation rate.

    Spilled volume,
    V = 1000 US gal 
    V = 1000 /  7.48051948 ft3

    [1 ft3 = 7.48051948 US gallons]

    Spilled area (without containment),
    Awc = V / 0.033
    Awc(1000 /  7.48051948) / 0.033
    Awc = 4,050 ft2

    Diked area,
    Adike = Total dike area - tank area
    Adike = 100x40 - 8 x (PI x 10^2)/4
    Adike = 3371.7 ft2

    Since Awc is larger than Adike, entire dike area will be occupied by spilled liquid.


    Inputs

    U =1.5 m/s
    MW =32.04
    A =3371.7 ft2
    VP =125 mmHg
    T =25 + 273.15 = 298.15 K

    Evaporation rate
    E = (0.284 U0.78.MW2/3.A.VP) / (82.05 T)
    E = (0.284x1.50.78.(32.04)2/3.3371.7.125) / (82.05x298.15)
    E =   67.7 lb / min

    Above method is a quick method in determining evaporation rate.


    Ref : "Risk management program guidance for offsite Consequence Analysis", US EPA, Apr 1999

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    posted by Webworm, 3:49 PM | link | 0 Comments |

    Monday, March 15, 2010

    Latitude of a plant is one of the parameter in determining C-factor and Y-factor of Tank normal inbreathing and outbreathing as discussed in "Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000". Simple method to find latitude is using Google Map.



    Another Method
    Lately Google Map has introduced new features. You can view the Latitude and Longitude directly and immediately as you move you mouse along the Google Map. Following are the steps to configure it.

    Step 1 : Goes to Google map (http://maps.google.com/)
    Step 2 : Click "New!" at top right and find . (See below image). Or you can click http://maps.google.com/maps?ftr=0.


    Step 3 : Scroll down and find "LatLng Tooltip" and Click "Enable"



    Step 4 : Click Save Changes at the bottom of page. Now configuration is done.

    Try to find "Ras Laffan, Qatar" again in Google Map. You will get the latitude and longitude immediately from the Google Map. You may also move the mouse and see the effect of latitude and longitude changes...


    Simple ? Let us know if you have even better method...

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    posted by Webworm, 3:50 PM | link | 0 Comments |
    FREE Hydrocarbon Processing for March 2010 is available now...

    Welcome to the March Issue!




    Select Articles from the March Issue
    Fieldbus diagnostics: latest advancements optimize plant asset management
    New field diagnostic profiles will benefit a wide range of automation stakeholders

    Breaking down the silos between energy and asset management
    Having them share a common platform offers several advantages

    Improving data reconciliation and yield accounting
    Here’s how the Mathura Refinery’s data reconciliation and yield accounting project was implemented

    Ensuring safe operations when fulfilling action item requirements
    Consider implementing this criteria to accurately document the process

    Iron sulfides—effect on amine plants
    Amine plants treating gas containing H2S will have iron sulfides in the system. Here’s where they help and hinder plant operation

    Consider new methods for bottom of the barrel processing—Part 2
    New principles of molecule management dictate the best economics when upgrading residuum


    ****************************

    If you yet to be subscriber of Hydrocarbon Processing, requested your FREE subscription via this link (click HERE). Prior to fill-up the form, read "Tips on Succession in FREE Subscription".

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    posted by Webworm, 3:02 PM | link | 0 Comments |
    As discussed in earlier post "3 Most Important & FREE Magazines That I Read..." , Chemical Engineering, Hydrocarbon Processing and Chemical Engineering Progress are three magazines which i will not miss every month. Reason being the contents of these magazines are written by practical engineers for practicing engineers like you and me. The clues, experiences, lesson learnt, new application and new knowledge shared by most practical engineers in our industry, again are practical and educative. I always emphasize to my young engineers consistently read article from these three magazines.

    Out of all three magazines, Chemical Engineering and Hydrocarbon Processing are available FREE for engineer who are eligible. What is eligible ? This really subject to the publisher decision and selection criteria. No one aware including myself. Nevertheless, there are several tips you may try out in order to increase your eligibility  by referring to "Tips on Succession in FREE Subscription". After try to subscribes by clicking Chemical Engineering and Hydrocarbon Processing.


    As for Chemical Engineering Progress, one of the main publication of the American Institute of Chemical Engineers (AIChE), you will be given FREE if you are member of AIChE. If you are not a member of AIChE, try to request your company to purchase it. You will not regret.


    If you success in subscribing Chemical Engineering and Hydrocarbon Processing for FREE. Well...Congratulations to you. You are a step closer to a good and practical engineer. Chemical Engineering and Hydrocarbon Processing offer their subscriber hardcopy and softcopy (view online and downloadable in pdf format). We strongly encourage you to obtain a softcopy.



    There many many benefits by getting a softcopy.

    Green solution
    You will help to minimize world paper consumptions

    No/Minimum storage area
    You will need book rack to keep these magazines. Experiences shows that the magazine may decay and lost wording & color after N years. On the other hand, you can keep softcopy in portable hard disc (which is rather cheap and affordable nowadays)

    Easy Search
    You can easily search article in the PDF file. You may also index, arrange by topic and link it to ease future search. It may be difficult for hardcopy indexing and storing.

    Reproducible 
    If you would like to extract part of the content in some article, you may easily copy and paste into any word editor file. This save you a lot of time.

    Sustainable business 
    Publisher is supported by advertiser and cost in production of these magazine. By delivering a hardcopy, it incurs additional costs like material cost, printing cost, storing cost, transportation cost and etc to publisher. By getting softcopy, above cost is reduced and minimize burden to the publisher. Publisher manage to continue their business and continue to offers FREE magazine for all of us.

    Replaceable 
    If you have hardcopy and once it is damaged, your may find difficulties in replcaing it. Unlike a softcopy. publisher is continuously keeping previous version in their server. You can always make copy from the server.

    Online reading every corner of the worth 
    If you getting softcopy, you can view online anytime, any place and any corner of the world as long as you have internet access and legally allow.

    Obtain Previous Issues
    If you subscribe today, you may get you magazine next month. Next month you can view and download all previous issues by searching the archive section.

    Last but not least, we would like to take this opportunity to thank publishers offering FREE magazines to us. We wish the FREE offers will continue forever.

    Being a Chemical and Process engineers, our "works" have generated a lot of damage to our lovely planet. Why not take simple effort in helping our planet ?

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    posted by Webworm, 2:38 PM | link | 0 Comments |

    Thursday, March 11, 2010

    Recommended :
    Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000 has included a parameter C factor thermal inbreathing calculation and Y-factor in thermal outbreathing calculation. These parameters subject latitude of plant site.This post will introduce a simple method in find Latitude and Longitude of your plant site using Google Map.

    Latitude is line appear horizontal on earth with varying curvature from equator which divides the planet into a Northern Hemisphere, a Southern Hemisphere and has a latitude of 0°. Latitude is ranging from 0° at the equator to +90° at the North poles and -90° at the South Pole.



    Methodology
    Google map is widely used by many engineer to locate longitude and latitude of plant. site Following is simple steps to find longitude and latitude of a plant site.

    Step 1 : Goes to Google map (http://maps.google.com/)
    Step 2 : Type location of your plant site (example Ras Laffan in Qatar)

    (Click image to view larger picture)

    Step 3 : Move mouse and point to A.
    Step 4 : Right click and select "Whats here ?"

    Latitude and longitude of location A will appear in Search Box. (see below)
    Lattitude = 25.924887
    Longitude = 51.575317

    (Click image to view larger picture)

    Simple ? Let us know if you have even better method...

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    posted by Webworm, 1:49 PM | link | 0 Comments |

    Wednesday, March 10, 2010


    FREE Chemical Engineering Digital Issue for March 2010...

    Saving Energy In Regenerative Oxidizers
    Regenerative thermal oxidizers (RTOs) can be retrofitted with catalyst beds to help reduce consumption of auxiliary energy during oxidation of VOCs. Energy savings after such a retrofit can quickly justify the costs of catalysts and installation. Here’s the how-to

    Greenhouse Gases: U.S. Starts Counting
    On January 1, 2010, nearly 10,000 facilities became subject to EPA rules on collecting data on greenhouse gas emissions. This article looks at the rules and how they might impact the CPI’s demand for mitigation solutions

    FAYF - Steam Traps and Tracer Lines
    This one-page guide discusses the selection of steam traps for steam tracer lines



    Agglomeration Technology: Mechanisms
    This review focuses on the mechanisms of agitation (wet granulation) and compression (compaction) methods

    Purifying Coke cooling Wastewater
    A new method for treating coke-cooling wastewater in a delayed coking unit

    Water Solubility in Benzene Derivatives 
    Solubility and Henry’s Law constants for water in benzene derivatives


    Would You Use a Safety PLC for Process Control ?
    Ensure unambiguous independence of the control and safety layers of protection




    ***********************
    TIPS
    If you are subscriber, you may access previous digital releases. Learn more in "How to Access Previous Chemical Engineering Digital Issue".

    If you yet to be subscriber of Chemical Engineering, requested your FREE subscription via this link (click HERE). Prior to fill-up the form, read "Tips on Succession in FREE Subscription".

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    posted by Webworm, 1:32 PM | link | 0 Comments |

    Tuesday, March 9, 2010

    Infor Energy Savings Calculator
    Earlier post "Is Your Company "Green" Enough ?", an Green Assessment using radar chart is introduced by Infor . The Green Assessment tool will allows you to assess how far your company's efforts in achieving a Green organization. This Green Assessment is benchmarked with many other companies and other industries.



    Again Infor introduce another Green Calculator to estimate the potential of energy and costs saving that you can achieve using the EAM Asset Sustainability method. The Infor Energy Savings Calculator is designed to analyze your company’s current power usage and policies, and provide recommendations to help reduce energy costs and drive green initiatives.

    Check out Green Calculator...

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    posted by Webworm, 11:25 AM | link | 0 Comments |
    Recommended :
    - Tips on Succession in FREE Subscription
    - Subscribe FREE - Processing Magazine
     
    Liquid product like Chemical, condensate, etc is commonly stored in fixed roof vertical cylindrical tank. Inert gas blanketing system is provided to avoid air and moisture contact and contaminate liquid product. Liquid movement by content filling (pump-in) or emptying (pump out) and weather changes (ambient heating or cooling) will results internal pressure increase (overpressure) or decrease (vacuum) in the tank. Thus, a protecting system providing inbreathing or outbreathing gas is provided to maintain a constant pressure in the tank.

    Inbreathing
    Emptying (pump-out) and ambient cooling will lead to normal inbreathing. General equation to determine inbreathing flow :

    Vin,air = Vpe + CVtk0.7 Ri

    where
    Vin,air = Total inbreathing in Nm3/h (Air)
    Vpe = Pump-out or emptying in m3/h
    Vtk = Tank capacity in m3
    Ri = Insulation reduction factor
    C = Factor subject to vapor pressure, average temperature and latitude (see Table 1)

    Table 1 : C-factor for Inbreathing
    Latitude Vapor Pressure
    Hexane
    or similar
    Higher than hexane
    or unknown
    Average Storage Temperature  (oC)
    < 25 >=25 < 25 >=25
    Below 42o 4 6.5 6.5 6.5
    42o to 58o 3 5 5 5
    Above 58o 2.5 4 4 4

    Find Latitude & Longitute Using GOOGLE MAP


    Outbreathing
    Filling (pump-out) and ambient heating will lead to normal outbreathing. General equation to determine outbreathing flow :

    Vout,air = Vpf + YVtk0.9 Ri

    where
    Vout,air = Total Outbreathing in Nm3/h (Air)
    Vpf = Pump-out or filling in m3/h
    Vtk = Tank capacity in m3
    Ri = Insulation reduction factor
    Y = Factor subject to latitude (see Table 2)


    Table 2 : Y-factor for Outbreathing
    Latitude Y-factor
    Below 42o 0.32
    42o to 58o
    0.25
    Above 58o 0.2

    Special notes :
    i) If products contain volatile components or dissolved gases or flashing products, perform flashing calculation to estimate quantity of volatile component / gases / vapor. This amount shall be added into outbreathing rate.

    ii) If products stored temperature above 40 degC or its vapor pressure higher than 5.0 kPa, products evaporation rate shall be added into outbreathing rate.

    iii) Quick check on plant latitude, check out in "Find Latitude & Longitute Using GOOGLE MAP"

    Determination of  Ri = Insulation reduction factor

    If no insulation, 
    Ri = 1

    If fully insulated including Shell and roof,
    Ri = Rin = (1 + h x Lin / Lamdain)-1
    If partial insulated,

    Ri = Rinp
    Ri = (Ainp / ATTS).Rin + [1-(Ainp / ATTS)]

     
    Lin = Insulation thickness in m
    Lamdain = Insulation thermal conductivity in w/mK
    h =Inside heat transfer coefficient in w/m2K  [4 w/m2K is commonly assumed]
    Ainp = Insulated surface area of tank in m2
    ATTS = Total tank surface area (shell + roof) in m2

    Concluding remarks
    The following method is the latest method used in API Std 2000, ISO 28300 & EN 14015. Nevertheless, API Std 2000 (6th edition) still maintaining the old method in ANNEX A as an alternative approach in determining normal venting rate. Comparison and recommendation can be found in "Tank Venting - API Std 2000 (Nov 2009) - Revised method and Old Method in ANNEX A".

    In determining normal tank venting rate per ANNEX A, designer can estimate tank venting rate from a table. Siddhartha has presented an equation to predict tank venting based on simple correlation, as discussed in " Tank Normal Venting Rate Estimation Using Siddhartha Equation". JoeWong has further proposed a new correlation as discussed in "Tank Thermal Breathing - Proposed Equation Correlate API Std 2000 Data" with better accuracy.


    Ref :
    i) API Std 2000 "Venting Atmospheric and Low-Pressure Storage Tanks", 6th Edition, Nov. 2009
    ii) ISO 28300 "Petroleum. petrochemical and natural gas industries -  Venting Atmospheric and Low-Pressure Storage Tanks"
    iii) EN 14015 "Specification for the design and manufacture of site built, vertical, cylindrical, flat-bottomed, above ground, welded, steel tanks for the storage of liquids at ambient temperature and above "


    **********************************

    Above equations have been programmed by Ankur, an experience Chemical Engineer, share with readers of Chemical and Process Technology. You may download here.

    Thanks to Ankur
    Download

    *If you have any useful program and would like to share within our community, please send to me.
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    posted by Webworm, 1:59 AM | link | 0 Comments |

    Monday, March 8, 2010

    Liquid product like Chemical, condensate, etc is commonly stored in fixed roof vertical cylindrical tank. Inert gas blanketing system is provided to avoid air and moisture contact and contaminate liquid product. Liquid movement by content filling (pump-in) or emptying (pump out) and weather changes (ambient heating or cooling) will results internal pressure increase (overpressure) or decrease (vacuum) in the tank. Thus, an overpressure and vacuum protecting system providing inbreathing or outbreathing gas is provided to maintain a constant pressure in the tank.



    There are several recommended practice (RP) and standard (STD) are available to guide engineers in designing and specifying venting / relief load from a storage tank.
    • API Std 2000 "Venting Atmospheric and Low-Pressure Storage Tanks"
    • ISO 28300 "Petroleum. petrochemical and natural gas industries -  Venting Atmospheric and Low-Pressure Storage Tanks"
    • EN 14015 "Specification for the design and manufacture of site built, vertical, cylindrical, flat-bottomed, above ground, welded, steel tanks for the storage of liquids at ambient temperature and above "
    Recommended :Tips on Succession in FREE Subscription
    Subscribes to FREE Hydrocarbon Processing

    In determining normal tank venting rate, API STD 2000, (edition 1999) allows designer to estimate tank venting rate from a table. Siddhartha has presented an equation to predict tank venting based on simple correlation, as discussed in " Tank Normal Venting Rate Estimation Using Siddhartha Equation". JoeWong has further proposed a new correlation as discussed in "Tank Thermal Breathing - Proposed Equation Correlate API Std 2000 Data" with better accuracy.

    The methodology in determining normal inbreathing and outbreathing rate are different between API Std 2000 and ISO 28300 / EN14015. Groth Corporation, a well known Pressure-Vaccum relief valve manufacture has conducted a study to compare the API Std 2000 and ISO 28300 / EN14015. A few differences are identified :

     API STD 2000
    • Full vacuum through 1.034 barg
    • Aboveground tanks for liquid petroleum or petroleum products and aboveground and underground refrigerated storage tanks
    • Fixed roof tanks
    • Tank volumes up to 28,618m3
    • No insulation factor considered for regular venting (emergency only)
    EN 14015
    • -20 mbar through 500 mbar
    • Non-refrigerated tanks
    • Fixed roof tanks (with or without internal floating roofs)
    • No limit on tank volume
    • Insulation considered for regular and emergency venting
    ISO 28300
    • Full vacuum through 1.034 barg
    • Aboveground tanks for liquid petroleum or petroleum products and aboveground and underground refrigerated storage tanks
    • Fixed roof tanks
    • No limit on tank volume
    • Insulation considered for regular and emergency venting
    One of the interesting findings in the study was the normal inbreathing and outbreathing comparison betweeen API STD 2000 and ISO 28300/EN 14015.



    (Click image for large image)
    Source : Groth Corporation

    Details can be found in " Introduction and ISO 28300 Presentation". Above study was comparing API STD 2000, revision 1999 and latest ISO 28300 / EN 14015. API has recently released latest API STD 200, last NOV 2009. One of the main changes was synchronizing methodology between API STD 2000 rev. Nov 2009 and latest ISO 28300 / EN 14015. 



    Opinions
    Previous method used in API STD 2000 still maintain in Annex A as "Alternative Calculation of normal venting requirements". This annex provides a calculation approach that may be used to design protection systems for the normal venting requirement of petroleum storage tank.

    Above finding indicates minor difference in outbreathing rate between API STD 2000 and ISO 28300 / EN 14015. Both methods are acceptable for estimating outbreathing (in main text and annex A). However, present inbreathing method (as in annex A) consistently lower compare to revised method. It is always take extra precaution when you used annex A for estimating inbreathing rate.

    You may be working on ongoing project priors to revision of API STD 2000 (NOV 2009). Following standard implementation spirit, you may continue to use old revision. However, it is always advisable to refer to latest API STD 2000 from safety and integrity aspect.

    You may work on revamping or debottlenecking of existing plant, extra precaution shall be  taken. Whenever you have modification or new requirement to existing tank, you may have to comply to latest API STD 2000 (NOV 2009) even thought your existing tank was designed and fabricated to old revision of API STD 2000.

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