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Saturday, February 28, 2009

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Simple update to IEM Members or those who are practicing Engineering in MALAYSIA...

It is anticipated that there will be less commercially viable oil & gas fields in the Malaysian shallow water. As such, there is an increased push towards developing fields in the deep (200-1000m water depth) and ultra-deep (more than 1000m water depth) water. In line with this shift, Petronas has set the tone by stating its ambition to make Malaysia as the regional deepwater hub and, along with its Production Sharing Contractors, has set the ball rolling by the successful project execution of and oil production from Kikeh Deepwater Development. The presentation intends to share presentor's general experience in the deepwater projects, which covers background, introduction to technologies, challenges/opportunities, and Kikeh development examples.






A talk on "MALAYSIAN Oil and Gas Deepwater Development", organized by Oil, Gas and Mining Technical Division, IEM has been scheduled.

Date : 19 March 2009 (Thursday)
Time : 5.30 pm to 7.00 pm
CPD : 2 Hours (approved by BEM)
Venue : IEM Conference Hall, Bangunan Ingenieur, Petaling Jaya
Speaker : Ir. Ahmad Sidek

*Any queries, please contact sec@iem.org.my.

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posted by Webworm, 12:58 AM | link | 0 Comments |

Friday, February 27, 2009

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Steam is one of the most commonly use medium to transfer energy from one point another point, room and system heating, power generation, cleaning, etc. Steam also can be used to assist combustion as discussed in "Steam in FIRE...". Steam is clean, easy to manage, predictable properties and engineer is "understand" behavior of steam after few century of experiences.

Steam once give it energy for process fluid heating, conversion to power energy via steam turbine, etc, it will probably form condensate and return to boiler for steam regeneration. Entire heat input, steam generation, heat transfer, condensate formation and finally return back to boiler again form a complete steam-condensate loop. The steam-condensate balance may be conducted using process simulator such as HYSYS, Pro-II, etc. Manual balance may be conducted as in discussed in "Conduct Steam-Water Balance MANUALLY using Water97_v13". Besides there are plenty of useful tools and guideline as listed in "Steam - Condensate Useful Links...". For those new subscriber, check it out.

This post would like to bring to you a very great "movie" about steam asset management, presented by Armstrong. The discussion includes :
  • Becoming "trap active" with steam trap survey
  • Web based data management
  • Common global reporting platform
  • Steam trap diagnosis tools
  • Real time information integration
Click image to download the movie (25.3M) and open with Windows Media Player.


To read FAQ about this presentation, click here.

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posted by Webworm, 12:59 PM | link | 0 Comments |

Wednesday, February 25, 2009

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Pressure relief to protect system from overpressure and emergency depressuring to evacuate system inventory to safe location are common plant safety system. Fluid is discharge in the proper designed collection system will then be send to flare for proper combustion. Different fluid characteristics, pressure available in the collection header, carbon-hydrogen ratio, concentration of toxic component, local requirement, etc will require different type of flare tip for proper flaring.

There are several typical flare type :
  • Pipe flare (subsonic)
  • Sonic flare (single tip & multiple tips)
  • Coanda tip (single & multiple)
  • Steam assisted flare tip
  • Air assisted flare tip
  • Enclosed flare
  • Endothermic flare
  • Liquid burner
  • Other proprietary tip
A process / package engineer will prepare flare tip datasheet and flare tip vendor will base on the provided information and requirement to select a proper tip. It is sometime interesting to know what type of flare tip will typically be selected by vendor. This is to ease preliminary design and plant layout consideration.

A simple flare selection chart has been provided to ease process engineer in flare tip type selection.
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posted by Webworm, 11:08 AM | link | 8 Comments |

Monday, February 23, 2009

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High pressure feedwater pumps are subject to overheating and subsequently very rapid damage if used at low flow as compared to the rated capacity. The minimum flow required for pump protection is specified by the pump manufacturer. It is never less than 15% and can sometimes be 40% or more. When the flow required by the boiler is below this limit, the feedwater pump flow demand is artificially increased by discharging to the deaerator or sometimes to the condenser through a recirculation valve. The recirculation valve is required to operate either on-off within a selected range of values of flow to the boiler, or in modulating service. In this case, the flow through the control valve is equal to the difference between the pump minimum flow and the actual flow to the boiler. Modulating service avoids the waste of energy since the recirculated flow is kept at the minimum acceptable value, but it is more severe in terms of valve service.

Several precautions may have to be taken while selecting this type of recirculation valve :
  1. Cavitation
  2. Pressure drop distribution
  3. Axial / Radial design
  4. Shut-off/ Wire drawing
  5. Clogging
  6. Vibration
  7. Failure position
Read more...
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posted by Webworm, 12:51 PM | link | 1 Comments |

Sunday, February 22, 2009

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American Petroleum Petroleum (API) released the ANSI / API Std 537 / ISO 25457:2008 "Flare Details For General Refinery and Petrochemical Service" Second Edition, Dec. 2008 in December 2008. First important change is it has been upgraded as ISO compliance. User shall remember although it is a standard, it is solely users responsibility to make sound, scientific, engineering, safe, environment friendly judgment. Neither API nor its employee, etc make warranty for the use of this standard. Detail refer to "Special Note" in relevant Standard.

Applicability
User of this standard shall understand the applicability of this standard. This standard specifies requirements and provides guidance for the selection, design, specification, operation and maintenance of flares and related combustion and mechanical components used in pressure relieving and vapour-depressurizing systems for petroleum, petrochemical and natural gas industries. It is primarily intended for new flares and related equipment, it may be used to evaluate existing flare facilities.


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API Std 537 / ISO 25457 is primarily to provide mechanical related information related to flare. For flare system design and related criteria and limitation, user may refer to API Std 521 / ISO 23251 "Pressure Relieving and Depressuring System".

Important information for Process Engineer...
There are several important information that a process engineers may take note :
  • A simple flowchart for Flare Type Selection has been included in this new standard. This flowchart will provide a quick way to understand the potential flare tip type may be selected by the flare vendor. Read more in "Flare Tip Quick Selection Chart"
  • Larger the flare tip diameter, more number of pilots is required. The following table provide minimum requirement of pilots for flare burner diameter. This table presented a minimum pilots per burner, one shall remember there is possibility of pilot, mixer, ignition, etc fail. Thus, redundancy / spare shall be provided.

Flare burner
outlet
diameter
(DN)
Flare burner
outlet
diameter
(NPS)
Minimum
number
of pilots
Note
Up to 200
Up to 8
1
(1)
>200 to 600
>8 to 24
2

>600 to 1050>24 to 42
3

>1050 to 1500
>42 to 604

>1500>60
-
(2)
Note :
(1) For toxic gas, the minimum number shall be two.
(2) To be agreed with the purchaser.
  • Minimum pilot fuel gas consumption is 13.2 kW (45000 btu/h). Knowing the Lower/Net heating value of fuel gas, the minimum pilot gas consumption per pilot can be determined. Together with above information, a process engineer may estimate continuous fuel gas consumption for all pilot
  • This standard recommends a minimum corrosion allowance of 1.6 mm (1/16") to be provided for carbon steel riser contact with relief fluid.
  • Smokeless flaring is normally achieved by utilizing air, steam, water, pressure energy, etc. The requirement of smokeless flaring is determine by local authority or company requirements. Ringlemann number is used for the definition of smokeless level. Read more related to Ringlemann chart in "Flare Smokeless Ringlemann Chart".
  • Minimum LHV of 7450 kJ/Nm3 (200 Btu/scf) for unassisted flare whilst 11175 kJ/Nm3 (300 Btu/scf) for assisted flare (Ref.: 40 CFR PT 60.18). This may be applicable to normal pipe flare. For sonic flare tip, a higher LHV value i.e 800 BTU/scf (subject to vendor) may be required.
  • As highlighted, a steam assisted flare, noise level is the combination of combustion noise and steam jet noise, typically high. Additional attention is required for steam and water assisted flare.
  • For low ambient (subzero during winter), there is potential partial/total blockage of steam/water header due to ice formation. Additional attention is required for steam and water assisted flare.
  • There are typical Flare Tip datasheet available in this standard which assist purchaser, contractor and manufacturer in proper communication of information.
To find details of API Standard 537/ISO 25457, please check out here

For those would like to read more about brief information about the background, intention, contents, structure, etc related to this standard, you may read "New API Standard provides comprehensive information on flares" by R. SCHWARTZ

Download
Source : JohnZink

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posted by Webworm, 12:43 PM | link | 0 Comments |

Saturday, February 21, 2009

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If you have successfully subscribed to FREE Chemical Engineering (CE) magazine, you should have received a note from the publisher requesting you to participate a survey in order to help in better understanding of how people in our industry prefer to receive work related news and technical information. The survey contain 16 simple questions and should only take a few minutes (less than 3 minutes) to complete.

Chemical & Process Technology webblog member (FREE CE subscriber) is encouraged to participate this survey.

Why ?
Reason being
i) to provide your inputs to make Chemical Engineering and so that information can be delivered in effective manners
ii) to serve your commitment to Chemical Engineering magazine as a free magazine subscriber
iii) to increase your "points" so that you qualify again for free Chemical Engineering during next renewal



What to do ?
You as valid FREE CE subscriber, you will receive a message similar to above image. Just click the red button and it will direct you to complete the 3 minutes survey.

FREE Chemical Engineering Subscription Released every month (almost) but limited ! Quick act before they are fully subscribed. Before proceed, get some tips in "Tips on Succession in FREE Subscription". If FREE CE is temporarily unavailable, please try again beginning of the month (tips). Click here to qualify your FREE Chemical Engineering !

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posted by Webworm, 11:57 PM | link | 0 Comments |

Friday, February 20, 2009

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Smokeless flaring
is one of the common requirement for open flare to ensure proper combustion of relief gases and minimize greenhouse effect and pollution. Smokeless flaring may be achieved by direct air blowing, steam injection, water injection, pressure energy to create turbulence, etc. Minimum requirement of smokeless flaring is determined by local authority or company policy. One of the way to quantify smokeless is using Ringlemann number.



The Ringelmann Smoke Chart, giving shades of gray by which the density of columns of smoke rising from stacks may be compared, was developed by Professor Maximilian Ringelmann of Paris. The Ringelmann Chart was used by the engineers in their studies of smokeless combustion. The chart is now used as a device for determining whether emissions of smoke are within limits or standards of permissibility (statutes and ordinances) established and expressed with reference to the chart. It is widely used by law-enforcement or compliance officers in jurisdictions that have adopted standards based upon the chart.

The Ringelmann system is virtually a scheme whereby graduated shades of gray, varying by five equal steps between white and black, may be accurately reproduced by means of a rectangular grill of black lines of definite width and spacing on a white background. The rule given by Professor Ringelmann by which the charts may be reproduced is as follows:

Card 0—All white.
Card 1—Black lines 1 mm thick, 10 mm apart, leaving white spaces 9 mm square.
Card 2—Lines 2.3 mm thick, spaces 7.7 mm square.
Card 3—Lines 3.7 mm thick, spaces 6.3 mm square.
Card 4—Lines 5.5 mm thick, spaces 4.5 mm square.
Card 5—All black.

The chart provides the shades of cards 1, 2, 3, and 4 on a single sheet, which are known as Ringelmann No. 1, 2, 3, and 4, respectively. Refer following samples.



Requirement
Minimum requirement of smokeless flaring is determined by local authority or company policy. Generally onshore plant required Ringlemann 0 (normal operation) and Ringlemann 1 (Emergency) whilst offshore facilities may required Ringlemann 0 (normal operation) and Ringlemann 2 (Emergency).

Download detail report and chart

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posted by Webworm, 3:05 AM | link | 0 Comments |

Wednesday, February 18, 2009

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Mercury is known as one the contaminant present in hydrocarbon oil and gas in the form of elementary, ionic, organic, etc. Release of this component will pollute environment and toxic to human being and creatures. Beside present of mercury in metal i.e. Aluminum will expose the metal to mercury embrittlement which potentially lead cracking. Thus, identifying, tracing, removing and management of mercury contaminated waste is important.

Johnson Matthey Catalyst (JMC), an active mercury removal catalyst supplier in Oil and Gas again will organise it 3rd JMC Mercury Technical Seminar following their successful seminar in 2005 and 2007. The brief report for 2nd JMC Mercury Technical Seminar can be read in "New Findings in 2nd Mercury Technical Seminar".

Those engineers in plant/operational, process design engineers, etc particularly those who involve in mercury rich fields are encouraged to attend this Technical Seminar. This is a technical oriented seminar (non-commercial) intended to share growing problem in mercury in hydrocarbon fluid, new findings & technologies in identifying and removing mercury and great experiences from technical experts.

The key aspects in this 3rd Seminar (subject to changes) include :-
  • The chemistry of mercury and the streams affected in oil and gas processing.
  • Detection and analysis.
  • Mercury removal technology, its application and case studies.
  • Safe handling of materials ("cradle to grave")
  • Research
Expected presentations (may change) are :
  • Understanding Interactions Of Hg On Materials (by M.Wilhelm)
  • Measuring Mercury, (by P.Spitz)
  • Mercury Removal Technology (Part 1) - From Gas Producing and Processing Plants (by JMC expert)
  • Mercury Removal Technology (Part 2) - From Refineries and Petrochemical Plants (by JMC expert)
  • Catalysts Handling (Dialog expert)
  • Cradle To Grave – The "One-Stop-Shop" Approach (by JMC expert)
  • Customer Experiences Of Mercury Removal Technology (TBC)
  • Application Testing & Update On New Technology Developments (by JMC expert)
This seminar will be held in MANDARIN ORIENTAL HOTEL, KUALA LUMPUR, MALAYSIA, 30th APRIL 2009, 8.30am -5.00pm. It is free of charge and only invitee can participate in this seminar. If you are interested, please contact JMC local representative (Click here to find the contact information in your region). The seat may be limited. Please respond by/before Friday 27th March 2009.

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posted by Webworm, 11:44 AM | link | 0 Comments |
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This is a continuous post from "Useful Documentation for UNISIM..."... With the feedback from readers, the original has been updated to include more valuable information.

UNISIM, another most user friendly Process simulator for process system designer. It enables process designer / engineers to create steady-state and dynamic models for plant design, process system performance monitoring, real plant troubleshooting, operational improvement, business planning and asset management.

Following are additional part :
Complete list in Useful Documentation for UNISIM...

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posted by Webworm, 11:04 AM | link | 0 Comments |

Monday, February 16, 2009

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UNISIM, another most user friendly Process simulator for process system designer. It enables process designer / engineers to create steady-state and dynamic models for plant design, process system performance monitoring, real plant troubleshooting, operational improvement, business planning and asset management. UNISIM has almost same display and approach as in HYSYS (from user friendly perspective). If you are familiar with HYSYS, you are certainly know how to operate UNISIM in the 1st attempt to use.




Objective
The mains objective of this post is to compile a complete listing of UNISIM related DOCUMENTATION. This activity intended :

* Educate UNISIM user in operation of UNISIM and making full use of UNISIM via these documentations
* Easy & FREE access to all UNISIM related documentations via a single platform and interface
* Information sharing among the UNISIM user within our community

This post IS NOT intended to share any copyrighted documents and IS NOT host & distribute any documents to the public. It mainly to share the location of documentation available FREE in internet via links.

Benefits to Developer
This post partially and indirectly promote and advertise UNISIM to public and it potentially increase awareness of UNISIM and increase conversion rate. HONEYWELL, the owner of UNISIM is technically support all registered UNISIM user via UNISIM Support team. Nevertheless it only provide support to genuine licensed & registered UNISIM user.

Similar to "Useful Documentation for HYSYS ...", following are compilation of documents related to UNISIM. If you found any documents related to UNISIM and/or available FREE for all, you are encourage to share within our community. You may drop a note via email or comment. Please include your nickname.

****************************
UNISIM Design Tutorials
The Tutorials section of this guide presents you with independent tutorial sessions. Each tutorial guides you step-by-step through the complete construction of a UNISIM Design simulation. The tutorial(s) you choose to work through will likely depend on the simulation topic that is most closely related to your work, your familiarity with UNISIM Design, and the types of simulation cases you anticipate on creating in the future.


UNISIM Tutorial
UNISIM (very similar to HYSYS) is a program used to design chemical plants. It is built around:
  • a library of the physical properties of a large number of chemical species
  • a set of subroutines to estimate the behavior of many types of plant equipment (heat exchangers, reactors, etc.)
  • a graphical user interface to accept specifications for the case, and display results
The user describes the process in terms of pieces of equipment interconnected by process streams, and the program solves all the mass/energy/equilibrium equations, taking into consideration the specified design parameters for the units. In this tutorial, you will be introduced to some of the basic features of UniSim. Once you have completed this tutorial, it is highly recommended that you attempt to work through the advanced tutorial (available for download on the course webpage), as it will introduce you to additional unit operations and features. Upon completion of both tutorials, you will be well-prepared to dig into the plant optimization assignments.

****************************
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Sunday, February 15, 2009

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American Petroleum Petroleum (API) released the API Std 520 Part 1, Sizing, Selection and Installation of Pressure-relieving Devices in Refineries Part 1 - Sizing and Selection Eighth Edition, Dec. 2008 in December 2008. First far most important change is it became a STANDARD, instead RECOMMENDED PRACTICES. User shall remember although it became a standard, it is solely users responsibility to make sound, scientific, engineering, safe, environment friendly judgment. Neither API nor its employee, etc make warranty for the use of this standard. Detail refer to "Special Note" in relevant Standard.

Applicability
User of this standard shall understand the applicability of this standard.
This standard
  • applies to the sizing and selection of pressure relief devices (PRD) used in refineries and related industries for equipment that has maximum allowable working pressure (MAWP) of 15 psig (103 kPag) or greater
  • applicable to PRD protecting unfired pressure vessels and related equipment
  • applicable to steady state flow of Newtonian fluids
  • supplement to ASME Section VIII Pressure Vessel Code
  • is not applicable Atmospheric or Low pressure storage tank (cover under API Std 2000)
  • is not applicable fired vessels (cover under ASME section 1 and ASME B31.1)
Revised/Added Section
Quick glance through this document, several section are revised/added. The updated / added sections are (not limted to) :
  • 3. Terms and Definitions (Revised - all definition are in sorted alphabetically)
  • 4.2.1.3 Balanced PRVs (Revised)
  • 4.2.2.3 Pilot Types (Revised)
  • 4.2.2.5 Pilto-operated PRV Accessories (Added/revised)
  • 4.2.3 Cold Differential Test Pressure (CDTP) (Shifted)
  • 4.4.2.1.1 Buckling pin devices... (revised)
  • 4.4.2.1.3 ASME Code Case 2091-3 defines... (Added)
  • 4.4.2.2.1 The set pressure... (Revised)
  • 4.4.3.2 & 4.4.3.3 Breaking pin... (Revised)
  • 5.3.2.2 ...a) bench set pressure... (Revised)
  • 5.3.4.2 Total backpressure... (Revised)
  • 5.4.1.4 ...(Partly revised)
  • 5.5 Development of Sizing Equations (New)
  • 5.6.1 Applicability (New)
  • 5.6.4.3 Balanced PRVs (New)
  • 5.6.5 Alternate Sizing Procedure (New)
  • Annex B (Revised)
Above are not consolidated changes. If you found any others, please share with us (click here).

Comments
There are several remarks that you may take note (when this standard is apply) :
  • Use of isentropic nozzle flow method and/or ideal gas specific heat ratio for vapor relief estimation
  • Use of Homogeneous Equilibrium Model (HEM) based on thermal and mechanical equilibrium for two phase relief. Nevertheless, the Leung Omega Two point method is still remained as a choice of method.
  • Generally thermal and mechanical equilibrium can be achieved for PRV relief nozzle length more than 100mm. If shorter nozzle is used, Homogeneous Non-equilibrium Model (HNE) may be considered.
  • Additional attention shall be taken when appreciable of non-condensable gas present in the flashing liquid. Leung Omega Two Point method for flashing liquid and non-condensable gas may be referred.
  • Used of HEM method is easy but rigorous. Understanding of the thermal equilibrium for fluid properties is important and required.
  • Two phase Vapor Liquid Relief method presented in Annex B have not been validated by test (accoring to API) and there is no any recognized procedure for certifying the capacity of PRVs in two phase flow service.

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posted by Webworm, 6:23 AM | link | 1 Comments |

Friday, February 13, 2009

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Energy has became one the daily need for human and society. This has lead to many research and developments programs to find and explore new energy sources. Solar cell is one of the product to convert solar (light) energy into electricity and nowadays this technology has been applied in many area i.e. power for satellite, power for parking machine, etc.

Further research and improvement has lead to a new technology called Thermo photovoltaics, invented by Researcher in MIT,. This technology converts heat into light and then into electricity.

Solar Cell : Light --> Electric
Thermophotovaltaics : Heat -->Light --> Electricity

Overall maximum theoretical conversion efficiency of a conventional solar cell is about 30 percent, or 41 percent if the sunlight is first concentrated using a mirror or lens as solar cell selectively convert certain color efficiently. Thermo photovoltaic will concentrate light to heat -up material, then this material will emits light with wavelengths that allow solar cell to convert efficiently. Overall maximum theoretical conversion efficiency of Thermo photovoltaic can be increased upto 85 percent.

This believe to be excellence choice for oil and gas industry as there are many facilities emitting hot waste gases such as gas turbine generator, compressor turbine, fire heater, etc. Besides, this may also great for the car exhaust gas.

Read more in Better Thermal Photovoltaics.
MTPV

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posted by Webworm, 3:15 AM | link | 0 Comments |

Thursday, February 12, 2009

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Conducting overpressure scenario analysis, derivation of relief load, follow by pressure safety valve (PSV) sizing and finally selection of PSV are common activities in oil and gas project. Nowadays, API Std 521 is commonly used for sizing and hence the required API effective discharge area is the result of the calculation. PSV with effective discharge area larger than required API effective discharge area shall be selected. However, many PSVs' certified area are presented in ASME area.

How to relate API effective discharge area and ASME area ?

This is a very common question and problem face by many young engineers. Sometime engineers may wonder why a PSV with ASME "D orifice" is sufficient for a relief scenario required API "E orifice". Reason for the difference between API and ASME is dated back to 1962 when ASME Section VIII Code was changed to derate all certified relieving capacities by 10%. PSV manufacturers have decided to increase PSV flow area by 10%, instead of derating their capacity by 10%. Nevertheless the API "orifice" still remain unchanged.

A PSV with ASME flow area (AASME), ASME discharge coefficient (KASME) and API discharge coefficient (KAPI),

Corrected API effective discharge area, AAPI = KASME x AASME / KAPI

Example,
A calculated effective area based on KAPI = 0.973, AAPI = 0.12 inch2. A API "D orifice" with 0.11 inch2 is insufficient. A "E orifice" with 0.196 inch2 is required.

Let check the National Board published data, a ASME "D orifice" will have KASME = 0.859 and flow area of AASME = 0.15 inch2, the equivalent API effective discharge area would be

AAPI = KASME x AASME / KAPI
AAPI = 0.859 x 0.15 / 0.973
AAPI = 0.132 inch2

The ASME "D orifice" is having API equivalent effective discharge area of 0.132 inch2 is higher than required effective discharge area of 0.12 inch2. Thus an ASME "D orifice"is still sufficient.

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posted by Webworm, 11:48 AM | link | 0 Comments |

Wednesday, February 11, 2009

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Steel picklers have traditionally used carbon block heat exchangers to heat their shallow tank high turbulence pickle baths. The multi-gasketed designs and fragile nature of graphite heat exchangers still require continuous maintenance and repair which results in expensive downtime and spare parts. This has forced the industry to look for alternatives. The use of metal shell and tube heat exchangers virtually eliminates all of the problems associated with carbon block heat exchangers.

As claimed, some of the benefits of metal shell and tube heat exchangers are :
  • Cost competitive with Carbon Block Heat Exchangers
  • Easily retrofittable into existing equipment footprint
  • Elimination of downtime due to equipment failure
  • No spare parts to keep in inventory
  • Superior corrosion resistance
  • High heat transfer
  • High steam pressures to reduce required surface area
  • Fully welded metal design eliminates breakage during handling, installation and operation
  • Elimination of acid leaks into steam condensate
Typical comparison of a Carbon block HEX to a tantalum S&T HEX

Description
Carbon block HEXTantalum S&T HEX
Heat Input(BTU)1,000,0001,000,000
Steam Pressure (PSI)7575
Typical Overall U
(BTU/hrft2.F)
250 650
Surface Area Required
(Sq. Ft.)
29*11.2*
Inventory of Spare
Parts Required
YES NO
Fully Welded
Metal Design
NOYES

Basic heat transfer equation used to calculate required surface area.
*Tantalum heat exchanger surface area required does not take into consideration using a higher pressure steam.

Interested in detail ? Click HERE
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Source : www.titanmf.com

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posted by Webworm, 1:35 PM | link | 0 Comments |

Tuesday, February 10, 2009

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FREE Chemical Engineering Digital Issue for Feb 2009 has just been released !

Chemical Engineering magazine has just released Feb 2009 issue. If you are the subscriber of Chemical Engineering, you should have received similar notification.

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

Interesting articles for this month :

A Primer On Coal-to-Liquids
Converting coal to liquid fuels is one option China and the U.S. are pursing

Selecting a Conveyor
Characteristics of flexible screw, aero-mechanical, vacuum and pneumatic conveyors are discussed here

Facts At Your Fingertips - Pipe Sizing
This one-page guide provides the formulas needed to approximate friction factors, discharge, pressure drop, and pipe diameter.

Plate Heat Exchangers : Avoiding Common Misconceptions
A solid understanding of the critical areas presented here will insure good performance

Compact Heat Exchangers : Improving Heat Recovery
These units offer distinct advantages over shell-and tube heat exchangers, as quantified by the example presented here

Eye-and-Face Personal Protective Equipment
Protecting the eyes and face in the workplace is imperative to preventing the estimated 10–20% of work-related eye injuries that result in temporary or permanent vision loss

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

TIPS
If you are subscriber, you may access previous digital releases (Jan 2008, July 2008 - Jan 2009). 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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Monday, February 9, 2009

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Control valve capacity (Cv) for particular application is determined by the use of recognized valve sizing equations. This valve equation can be found in several handbooks i.e. Fisher, Masoneilan, etc as discussed in "Useful Documents Related to Control Valve".This article presented a simple idea why a control valve is normally operate at around 60-70% valve opening and it associated impact such as increase signal dead band effect and affect optimum controller settings-wider proportional band and faster reset. It recommended a new way to overcome the impacts by introducing VARIMAX. Read more...

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posted by Webworm, 11:28 AM | link | 1 Comments |

Sunday, February 8, 2009

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Dynamic modeling is a common tool for evaluation of plant operating conditions and control strategies. It can be used during design, prior to start-up, campaign changes, normal plant operation and prior to shutdown to understand the performance. It prepare design and operator to understand the potential problem and get ready to handle and manage the situation. High fidelity dynamic simulators has been developed for the process industries provide a solid basis for accurate modeling of the dynamic transitions. Nevertheless, development of custom components (for specific features of the process and measurement system) is often needed to provide a realistic model of the plant.

This paper presents a development approach and application of a dynamic model for the plant off-gas system, characterized by the complex structure and strong interaction of the production units with fast dynamics and sharp unexpected changes of the process pressure.




The model was developed in several phases using a HYSYS dynamic simulator. Initially, the model for the existing plant configuration, in nominal operational mode, was created; i.e. the plant emergency pressure relief devices that required custom modeling were not included. This model was validated using the plant data historian and was used for evaluation of the process dynamics and improvement of the existing control system. Then the model for the thermal oxidizer unit (a redesign option to decrease plant emissions) was added. This model was used in the design of the advanced control strategies for the modified process and thermal oxidizer itself. These strategies were tested for various scenarios of plant events and the expected plant unit interactions were evaluated. Finally, as the confidence of Plant Manufacturing grew, the model was extended with the custom pieces of the pressure relief devices (existing and new projected ones) and was used for development and justification of the plant vent system redesign.

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There is a Dynamic Simulation manual available in ASPEN HYSYS. You may obtain your copy. Read more in "Useful Documentation for HYSYS ...".


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posted by Webworm, 10:41 AM | link | 0 Comments |

Saturday, February 7, 2009

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Product fluid in reactor involve exothermic process is commonly hot. It is then sent to distillation and separation system for catalyst and raw material recovery. Separated product is then cooled by plant wide Cooling Water (CW) before it is sent to storage tank. The product temperature will have to be maintained.

How this temperature is controlled ?


Temperature Control Methods

There are several ways to maintain the product temperature :

(i) Provide a product bypass across the Cooler, control valves on Product bypass line and Outlet line (Split range control) with fixed CW flowrate
(ii) Provide a CW bypass across the Cooler, control valves on CW bypass line and CW inlet to Cooler with full product flow across cooler
(iii) Provide a CW bypass across the Cooler, control valves on CW bypass line and CW outlet to Cooler with full product flow across cooler
(iv) Provide a Control valve at the Cooler inlet with full product flow across cooler
(v) Provide a Control valve at the Cooler outlet with full product flow across cooler

Generally the product flow is fixed by operator based on production plan and the product flow shall not be controlled. Thus, it is always not recommended to provide a control valve at the inlet and outlet of product line for product temperature control.

Disturbance of CW Network Balance
Cooling water is in a network supplying to many heat exchanger through out the plant for cooling purpose. It is normally supplied by a set of centrifugal pump. As centrifugal pump head will be affected flow across, any changes in the CW demand will affect the CW balance in network. This will further affect the pressure in the network and hence the CW flow into other heat exchangers. Thus, it is always recommended not to throttle the CW flow as much as possible to avoid CW balance.

Scaling
Throttling CW flow into heat exchanger would potential lead to low CW flow into heat exchanger, high film temperature at on CW side and promote scaling. The option (ii) and (iii) are always recommended IF throttling on CW side is chosen.

Potential affecting Production
Controlling product fluid temperature with product bypass across the Cooler, control valves on Product bypass line and Outlet line (Split range control) and fixed CW flowrate (option i) is one of the common way in temperature control for product cooling. As it minimize the impact to CW network. Nevertheless, there is still concern about manipulating product fluid or mal-operation (controller failure) of control valves would potentially lead to production lost, the option (ii) and (iii) are always the recommended option.

CW Pressurise or Non-Pressurise
Option (ii) and (iv) compare to option (iii) and (v), the difference is the location of main CW line control valve (either at the inlet or the outlet). Providing a control valve at the outlet will have the following advantages :

a) Maintain high pressure in the heat exchanger and higher pressure will results higher heat transfer

b) CW at high pressure will minimise potential of boiling

c) CW at high pressure will minimise potential release of dissolved gases in CW , trap in heat exchanger and reduce heat transfer

d) In event of Control valve failure (failed to full close position), not further Cooling. CW in the heat exchanger will be heated and potentially lead to heat exchanger overpresure due to thermal expansion and/or boiling. The CW will be relieved via Pressure Relief Device provided on the heat exchanger. Providing control valve at the outlet would allow continue CW feeding into the heat exchanger, this minimise the potential of sudden temperature increase and cause heat exchanger due to thermal shock. The downside is release CW into disposal network.

Considering above advantages, it is always recommended to provide control valve on CW line at the outlet IF throttling CW side is chooses.

CONTROLLING SHELL AND TUBE EXCHANGERS
"Controlling Shell & Tube Heat Exchanger", an excellent article by Walter Driedger discussed about all type of control schemes around heat exchanger. Check out.

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posted by Webworm, 12:20 PM | link | 0 Comments |