chemical engineering: March 2009

Monday, March 30, 2009

Energy Aspect In Industrial Drying

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

Thermal drying operations are found in almost all industrial sectors and are known to consume 10-25% of the national industrial energy in the developed world. With emerging economies rapidly industrializing various economic sectors, the energy consumed for thermal drying and the resulting adverse environmental impact of the greenhouse gas emissions will inevitably rise with time. The most effective solution to this growing problem is to develop and utilize highly energy-efficient drying technologies that will reduce net energy consumption and mitigate the environmental impact.

Over the last three decades much progress has been made in this area. This talk will present an overview of the causes for inefficiency in industrial drying and provide a summary of numerous new attempts to enhance the performance of drying technologies in diverse industries. In particular, advantages of heat pump-assisted drying, superheated steam drying, pulse combustion and pulse combustion-assisted drying, utilization of waste heat and renewable energy for drying etc will be discussed along with selected case studies. In addition, the efficiencies of dryer systems can also be improved by multi staging, combining different types of dryer and by intermittent and multi-mode heat inputs for batch dryers. With over 400 types of dryers used to dry some 50,000 materials at various production scales, it is necessary to examine the problem at the fundamental level of dehydration.

A talk on "Energy Aspect In Industrial Drying", organized by Chemical Engineering Technical Division, IEM has been scheduled.

Date : 23 April 2009 (Thursday)
Time : 5.30 pm to 7.00 pm
CPD : 2 Hours (approved by BEM)
Venue : 2nd Floor, ISM Seminar Hall, Bangunan Jurukur, Petaling Jaya
Speaker : Engr. Assoc. Prof. Dr. Law Chung Lim

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

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Industrial Drying

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

There are over 400 dryer types cited in the technical literature although only about 50 types are commonly found in practice. As such proper selection of dryer is an important topic to industrial drying. Dryer selection has long been practiced as an art rather than science depending more on prior experience and vendors’ recommendations. As drying technologies have evolved and become more diverse and complex, this has become an increasingly difficult and demanding task for the non-expert. Further, the task is exasperated by the need to meet stricter quality specifications, higher production rates, higher energy costs and stringent environmental regulations.

This talk intends to give an introduction to industrial drying and briefly discuss the classification of industrial dryers. The key classification criteria for industrial dryers will be discussed as well as selection criteria. It is important for an engineer responsible for selection of a dryer or a drying system to be aware of what is available in the market, what the key criteria are in the selection process and thus arrive at alternative possibilities before going to vendors of such equipment for comparative quotes. It is time and effort well spent since the cost of incorrect selection can be very high. It was reported that over 80 percent of major chemical companies in Europe – each using over 1000 dryers in their production facilities – made errors in selecting dryers. What is optimal choice in one location at one point in time may be a wrong choice for another geographic location some years later. Prior use is a definite help but not the only criterion to be used in selecting drying systems.

A talk on "Industrial Drying", organized by Chemical Engineering Technical Division, IEM has been scheduled.

Date : 21 April 2009 (Tuesday)
Time : 5.30 pm to 7.00 pm
CPD : 2 Hours (approved by BEM)
Venue : 2nd Floor, ISM Seminar Hall, Bangunan Jurukur, Petaling Jaya
Speaker : Engr. Assoc. Prof. Dr. Law Chung Lim

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

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Sunday, March 29, 2009

Quick Estimate Flare Stack Diameter

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A young engineer asked…He is conducting a flare network studies using ASFA / FLARENET in conceptual stage. He need to allocate pressure drop across flare stack and tip. What is the quickest way ?

Flare tip pressure drop generally subject to flare tip design and only the tip vendor would be able to provide. Quickest way is to obtain vendor advice on similar kind of tip. However, in the absence of vendor information, the flare tip may be estimated according to discussion in earlier posts "Estimate Subsonic Flare Tip Pressure Drop With Graph Derived Correlation" and "Quick Estimate Flare Tip Pressure Drop".

Flare stack is made of vertical pipe in onshore plant and incline pipe (some called it boom) in offshore platform. The height is primarily govern by personnel allowable heat radiation at sterile area. As it is a pipe in nature, gas flow through flare stack during emergency and normal operation will result velocity and pressure drop across the flare stack. Thus, the flare stack diameter is primarily determine by Mach no and pressure drop. The recommended Mach no for flare stack is 0.5 during emergency relief (design capacity) and 0.2 during normal flow. Normal flow could be gas discharge from those pressure control valve (PCV) used to avoid pressure spike in process system.

Mach no here will be the Mach number at downstream of flare stack. One shall remember, the pressure drop across flare tip may be taken into account and it potentially reduce the Mach no and hence the flare stack diameter. The flare tip pressure drop could be estimated according discussion in earlier posts "Estimate Subsonic Flare Tip Pressure Drop With Graph Derived Correlation" and "Quick Estimate Flare Tip Pressure Drop".

Flare stack diameter,

d = [3.23 x 10^-5 ( W / ( P2 x Ma2)) x (z T / MW)^0.5] ^ 0.5

where
W = Mass flow (kg/h)
P2 = Outlet pressure (kPa abs)
Ma2 = Outlet Mach no
z = compressibility factor
T = Temperature (K)
MW = Molecular weight

Select a diameter, D which large or equal to minimum diameter (d) calculated above. Once the D is selected, the pressure drop across the flare stack may be estimated using Isothermal flow equation.

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Friday, March 27, 2009

Acoustic Induced Vibration (AIV) Fatigue

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An oil & gas processing and production facilities may consist of several level of pressure let down station. Typical examples are choke valve between christmas tree and flowline/production header, slugcatcher control valve, onshore pressure reduction station, steam control valve, desuperheating station, etc. Above valves are normally in continuous operation. Besides, there are other valves such as compressor surge / capacity control valve, overpressure dumping control valve, blowdown valve with restriction orifice, pressure relief valve, etc will experience large pressure drop and they are operated intermittently.

There is pressure drop with mass passing through the valve, internal acoustic energy is generated and transmitted to downstream piping and potentially lead to severe piping excitation, vibration and stresses on downstream piping, in particular at discontinuity section i.e fabricated Tee, small bore connection, welded pipe and pipe support, etc. If the downstream piping system is not properly designed, effect of this acoustic excitation would lead to fatigue failure. Above acoustic excitation phenomena is also known as Acoustic Induced Vibration Fatigue. Generally high frequency (more than 1000Hz) acoustic energy contribute to AIV fatigue and once piping expose to AIV, piping can fail in very short period (possibly in several minutes to hours).

Fluid Phase
Generally Acoustic Induced Vibration (AIV) fatigue occur in gaseous system and normally AIV does not occur in liquid system. For two phase gas liquid flow system with high gas flow (i.e. more than 50% gas flow), AIV may starts to be problem and need to be investigated. As two phase flow is complicated in estimating the Acoustic energy, it is always conservative to consider 100% gas flow.

Short & Long Term Operation
AIV fatigue failure of piping downstream of piping is subject to operation time i.e. number of fatigue cycle. A piping in continuous (long term) operation, a design fatigue limit of 80MPa is normally used based on ASME fatigue design limits with suitable safety factors for long term sevice life. A fatigue limit of 185MPa (10^7 cycles) has been used for short-term operation based on published fatigue life data for carbon steel and stainless steel. This fatigue limit represents the maximum acceptable level of stress for 10^7 cycles (12-24 hours of operation) without any safety margin. Those pressure reduction devices has total accumulated service hour within the plant life less than 12 hours, one may consider AIV fatigue may not occur. Pressure relief valve is one of those devices potentially drop in this category.

Experiences has shown that there is high frequency of operation of pressure relief device during plant black start-up and restart-up, AIV fatigue may occur in very short period (minutes to hours), PRV and other pressure reducing device may connect on same downstream pipe, etc, in many event AIV studies for PRV downstream piping to be conducted. Those PRV relief to ATM has very high potential drop in the short term category.

Sound Power Level (PWL)
Sound Power Level (PWL) is the acoustic energy generated by a pressure reduction device. There are several ways to assess the adequacy of the piping to resist AIV fatigue. One of the way to ensure piping downstream of pressure reducing device sufficiently storng to resist AIV fatigue is to ensure the PWL allowable limit of downstream piping higher than the PWL generated by the pressure reducing device. This will be disucssed in coming post.

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Wednesday, March 25, 2009

Earth Hour - Simple Effort Minimise Global Warming

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Earth Hour, an annual international event created by the WWF (World Wide Fund for Nature/World Wildlife Fund) is coming back on March 28, 2009 to create awareness on global warming and the need to take action on climate change. The event has no boundary and is extended from individual to large organization, from households to business. Every living can participate...

The effort is simple for everyone. If you are participating in Earth Hour, what you need to do is :

TURN OFF ALL NON-ESSENTIAL ELECTRICAL APPLIANCE FOR 60 MINUTES
at 8.30pm Local time

We in Chemical & Process, Oil and Gas industries known as one of the major "contributor" in global warming. Why not take this opportunity to do something ?

For more information, visit EarthHour

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Monday, March 23, 2009

Estimate Subsonic Flare Tip Pressure Drop With Graph Derived Correlation

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Earlier post "Quick Estimate Flare Tip Pressure Drop" has presented some clues in obtaining flare tip pressure drop for sonic and subsonic tip. Particularly for subsonic flare tip, a simple pressure drop versus flow curve was presented. This graph may be used for quick estimation during conceptual stage so that it minimize unnecessary time lost. However, the graph has limited to 0.5 - 40 kPa with correspondent minimum and maximum flow. Some conceptual studies may have flaring capacity resultant pressure drop more than 40 kPa, the graph may not be useful. In this post, a simple formula will be presented in order to estimate pressure drop for any flow rate for dedicated flare tip.

dP = 10 ^ (a x Log Q + b)

where
dP = tip pressure drop, kPa
Q = Flow at standard condition, dm3/s (note 1)
a & b = coefficient correspondent to tip size as list in following table

Tip Nom. Dia. (mm)	a	b
250	1.772663	-5.287376
400	1.92372	-6.671917
450	1.948852	-7.034009
500	1.945342	-7.329128
600	1.954552	-7.791866
750	1.968898	-8.24243
900	1.89152	-8.14936
1050	1.722666	-7.781574
1200	1.532001	-7.181798

Note 1 : The standard condition may be different from project to project (read more in "Avoid Confusion In "Standard" Flow Definition". Present standard definition is at 101.325 kPa abs and 15 degC.

Example
Estimate pressure drop of a subsonic flare tip with flow of 30,000 Sm3/h.

Q = 30,000 x 1000 / 3600 =8333.3 dm3/s @ Std

(i) A DN250 tip,
dP = 10 ^ ( 1.772663 x Log Q - 5.287376)
dP = 10 ^ ( 1.772663 x Log 8333.3 - 5.287376)
dP = 46 kPa (outside curve)

(ii) A DN400 tip,
dP = 10 ^ ( 1.92372 x Log Q - 6.671917)
dP = 10 ^ ( 1.92372 x Log 8333.3 - 6.671917)
dP = 7.4 kPa

(iii) A DN450 tip,
dP = 10 ^ ( 1.948852 x Log Q - 7.034009)
dP = 10 ^ ( 1.948852 x Log 8333.3 - 7.034009)
dP = 4.0 kPa

(iv) A DN500 tip,
dP = 10 ^ ( 1.945342 x Log Q - 7.329128)
dP = 10 ^ ( 1.945342 x Log 8333.3 - 7.329128)
dP = 2.0 kPa

You may compare results with chart in "Quick Estimate Flare Tip Pressure Drop".

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Saturday, March 21, 2009

Quick Estimate Flare Tip Pressure Drop

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Previous post "Several Criteria and Constraints for Flare Network - Process" has discussed several major important criteria and constraints related flare system. In particular, back pressure is critical to performance of pressure relief valve (PRV) from capacity and stability aspect. Back pressure at PRV is typically back calculated from flare tip, main header, sub-header and finally tail pipe. Isothermal equation may be used for flare pipe pressure drop calculation for conservatism. AFSA or FLARENET is commonly used for flare network modeling. In calculating back pressure at the PRV, flare tip pressure drop is required. However, the pressure drop of flare is subject to Flare tip vendor design. How shall engineer determine the pressure drop of flare tip without vendor information especially during conceptual design ?

Some simple clues for pressure drop estimation across a sonic flare tip and subsonic flare tip will be discussed. It may be used as first estimate and shall be used for detailed design. As flare tip pressure drop is subject to flare tip design, pressure drop provided by vendor shall always be used during detailed design.

For a sonic flare tip, pressure drop may be in the range of 3 - 5 bar. Pressure drop of upto to 7 bar has also been used. Flare system with sonic flare tip may experience high back pressure, high pressure (HP) system with high set pressure PRV may discharge into flare system with sonic tip.

For a subsonic flare tip, pressure drop is generally very small (possibly lower than 1 bar). Low pressure (LP) system PRV is generally discharge into flare system with subsonic flare tip as low back pressure is expected. Following is a typical flare tip pressure drop versus flow for different flare tip diameter.

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Tuesday, March 17, 2009

Enclosed Flare (SI Unit) Datasheet

In the first release of ANSI / API Std 537 / ISO 25457:2008 "Flare Details For General Refinery and Petrochemical Service", there are few Flare data sheets have been included. The main purpose of these data sheets is to assist plant operator, engineering contractor and flare tip manufacturer in information transfer and communication.

Following are the data sheets for Enclosed Flare (SI Unit) data sheet in Pdf format.

A datasheet in Excel sheet has been generated to ease readers.

Download Enclosed Flare (SI Unit) data sheet in Excel format
Download Enclosed Flare (SI Unit) data sheet in Pdf format

Read also Elevated Flare (SI Unit) Datasheet

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Sunday, March 15, 2009

Several Criteria and Constraints for Flare Network - Piping

In earlier post "Several Criteria and Constraints for Flare Network - Process", several major important criteria and constraints have been discussed. They includes Mach number, back pressure, noise level and two phase flow pattern. This post is the continuation and futher discuss other criteria and constraints for flare networt.

Flow Induced Vibration (FIV)
In a process plant, some of pressure control valves (PCV) may be provided in the process system to release gas into flare network to avoid transient peak pressure in the process system which potentially lead to unnecessary plant shutdown. Besides, this PCV may be used to release off specification gas into flare during plant start-up. Above events will increase the operational time of the PCV and its downstream piping and increase the piping Likelihood of Failure (LOF) due to flow induced vibration (FIV). Typically these PCV would experience low frequency exitation. It is good engineering practice to ensure the

LOF2 < 0.3 + Good engineerng practice for Small Bore Connection (SBC) or;
0.3 <= LOF2 < 0.5 +LOF3 < 0.4

LOF2 is Likelihood of Failure for main pipe assessment
LOF3 is Likelihood of Failure for small bore connection

Acoustic Induced Vibration (AIV)
Pressure control valve (PCV) with choking condition, pressure relief valve (PRV) and Blowdown valve with restriction orifice (BDV/RO) provided in the process and relief to flare network would cause high frequency acoustic exitation to downstream piping and potential results piping failure on Acoustic Induced Vibration (AIV). If the PWL generated by these devices is below PWL lower than 155 dB, the piping downstream of these devices are considered safe from AIV fatigue failure.

Piping downstream of these device may have different wall thickness. Piping with higher wall thickness will be more likely to resist higher PWL. Based on field experiences, table below list the maxmum limit of PWL with increasing ratio of Outside diameter (OD) to wall thickness (wt).

Limit of PWL vs OD/wt
OD / wt	PWL,max
20	174
30	173
40	172
50	170
60	169
70	168
80	167
90	165
100	164
110	163
120	162
130	160
140	159
150	158

Above is the PWL limit , some margin i.e. 3 dB may need to be added.

Maximum and Minimum Design Temperature and Thermal Shock
A flare network maximum and minimum design temperature will be typically determine from fluid discharging into the flare network. The maximum design temperature would typicall determine based on maximum possible fluid temperature with margin (plus) i.e. 10 degC whilst the minimum design temperature would typically determine from minimum fluid temperature with margin (minus) i.e. -10 degC or the fluid minimum depressured temperature with no or lower magin i.e. - 5 degC. The flare network potentially expose to high temeperature fluid during normal plant operaion and follow by cold fluid discharge from process system. Sudden large temeprature decrease in piping may cause thermal shock. Thus, flare piping stress shall analysed base on worst possible and credible temperature different and ensure sufficient expansion loops are provided and proper location of support.

Slug Hammer Elbow
For flare network piping identify potentiall expose to slugging condition, beside provision of necessary support, the slug hammering elbow is potential event and needs to further analyse the impact of the slug hammer.

Solidification, Crystillization, Polymerization, Hydrate and/or Ice Formation
Relief fluid believe to solidify, crystallize and/or polymerize, it potentially plug / block the relief tail pipe and flare network. Further analysis shall be conducted to check should these fluids be discharged in to the flare network. Possible solution is discharge to separate and dedicated disposal drum and vent.

For some flare network receiving wet fluid from high pressure system i.e. slugcatcher, theoretically there is potential of hydrate formation. However, due to high velocity, warm flare piping, intermittent service and non-sustainable discharge flow, field experience shows the likelihood of hydrate formation in flare network is low. Having said that additional measures shall be taken in to consideration. Read more in "Hydrate formed Downstream of PRV ?".

Other issue such as correct material for discharge fluid, corrosion and stress cracking, fluid compatibility studies, etc are those studies have been conducted and decided prior to flare network analysis. Thus, they are not discuss further in this post.

Concluding Remark
Previous post "Several Criteria and Constraints for Flare Network - Process" have discussed those criteria and constraints typically for process aspect whilst this post are typically from piping aspect. All criteria and constrains are listed as follow :

Mach no
Momentum
Back pressure
Noise
Two phase flow pattern
Flow Induced Vibration
Acosutic Induced Vibration
Thermal Shock
Slug Hammering
Hydrate / Ice Formation

These criteria and constraints shall be analysed in detail for flare network studies.

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Saturday, March 14, 2009

FREE Chemical Engineering Digital Issue for March 2009

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

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

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

Interesting articles for this month :

Combining Rupture Disks with Safety Relief Valves
A rupture disk serves as a barrier, protecting the safety relief valve from process media. This barrier extends the life of the relief valve and prevents leakage to the atmosphere

Getting the Most Out of Your Rupture Disc
For optimum rupture-disc performance, pay attention to installation, operation and maintenance

FAYF Membrane Configurations
This one-page guide provides an introduction to tubular, cap-illary, spiral-wound and plate-and-frame membrane configurations, while also detailing the tendency for each to expe-rience fouling

Using Web 2.0 Tools to Increase Your Productivity
Web 2.0 developments can improve an engineer’s productivity at work, as well as his or her professional development

Industrial Gas Applications In the CPI
Technical and specialty gases find use in many synthesis processes and a number of unit operations, in analysis and in plant maintenance

Solar’s Second Coming
Construction of CSP plants is on the rise, bringing jobs and business to equipment suppliers and chemical produc-ers alike

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TIPS
If you are subscriber, you may access previous digital releases (July 2008 - Feb 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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Friday, March 13, 2009

Condensate Pump Recirculation Valve Selection

Recommended :
- Tips on Succession in FREE Subscription

- Subscribe FREE - Control Engineering (Asia )

Condensate Pump Recirculation Valve Selection
Power plant condenser receives exhaust steam from the low pressure turbine and condenses it to liquid for reuse. Condenser back pressure range from 1.0 to 4.5 Hg absolute (3.4 to 15.2 kPa) with higher pressures possible when the cooling water temperature is elevated by using an air-cooled steam condenser. Condensate is collected in the bottom of the condenser in the hot well. The condensate feed pump supplies the subcooled water to the feedwater heaters.

As with most centrifugal pumps, the condensate pump is subject to overheating and cavitation if used at a flow under a minimum value recommendation by the pump manufacturer. When the flow required by the deaerator level control loop falls below this minimum recommended value, additional flow is recirculated back to the condenser by opening a valve installed in a bypass line thus maintaining the minimum flow through the pump at all time. There are problems associate with this valve and its selection. Read more...

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Wednesday, March 11, 2009

Several Criteria and Constraints for Flare Network - Process

Flare system commonly consists of collection networks, liquid Knock-Out drum, knock-out pump and flare stack with tip. Some flare system may includes liquid seal drum, air ingress & purge reduction seal, flare recovery system, liquid heater and/or vaporiser, etc In recent posting, there are several topics related to Flare have been discussed :

If you are dealing with Flare, one of the technical book that you may not missed is John Zink Combustion handbook. Flare network hydraulic simulation may be conducted using Aspen Flare System Analyzer, AFSA (formerly FLARENET). Interesting and useful documents related to AFSA / FLARENET can refer to "Useful Documentation for AFSA / FLARENET...". There are several constraints, parameters and/or criteria that may be considered while carry out Flare network hydraulic studies :

Mach No.
Mach number is the ratio of fluid flowing velocity to fluid sonic velocity. Mach number equation for a fluid may refer to previous post "...Mach No. & Critical Pressure Calculation". For Pressure Relief Valve tail pipe (pipe immediate downstream of PRV), Mach no is commonly limits to 0.7 whilst for collection header, Mach no limit to 0.5. The flow for calculation for tail pipe and header are subject to PRV type. Read more in "Consider Rated flow or Required Relieving Flow ?".

One shall take note, above are common recommendation and good engineering practice. Some engineers may design flare network to Mach no of 1.0, Several concerns related to flare system design to Mach no of 1 may refer to "Is PSV tail pipe & lateral at CHOKED (Mach no = 1) Accpetable ?".

Momentum (density x velocity2)
Momentum is fluid density time fluid flowing velocity power two. For tail pipe, maximum momemtum may be limited to 150,000 Pa whilst for collection header, limited to 100,000 Pa. The flow for calculation for tail pipe and header are subject to PRV type. Read more in "Consider Rated flow or Required Relieving Flow ?". Above value may be increased (not more than 200,000 Pa) provided that the piping support and vibration analysis are healthy.

Back Pressure
Increase (or reduction) in PRV tail pipe or flare header size may affect Mach no. It also decrease (or increase) back pressure to PRV. A conventional Spring loaded pressure relief valve, maximum allowable back pressure (MABP) is typically limited to 10% of PRV set pressure. A balanced bellow (or piston) type pressure relief valve, MABP is typically limited to 30% -50% of PRV set pressure. For pilot operated PRV, MABP of more than 50% of PRV set pressure may be allowed (some previous experience may reach 80% of set pressure). Above are typical value base on Good Engineering practice. Detail and exact MABP is subject to actual PRV and guaranteed by PRV vendor.

Above are typically related to performance (relief capability) and stability of PRV (as discussed in "Several Impact of Backpressure on Conventional PRV". One shall take note that there is Maximum Allowable Backpressure due to mechanical limitation which subject to temperature. Detail may refer to API Std 526.

When discussed about PRV back pressure, correct definition of "back pressure" shall be used in communicating information to PRV vendor. Discussion on confusion about "back pressure" may refer to "PRD Backpressure".

Noise Level
As fluid passing through the PRV (and tail pipe & header), significant noise would be generated and transmitted along the tail pipe and header. The noise may also emitted to atmosphere. One of the common safety requirement is limit the noise level to 115 dBA (Noise level with A-weighted) during intermittent emergency relief scenario. Besides intermittent relief from PRV, some Pressure control valve (PCV) may discharge (continuous or frequent) fluid into flare network. The noise level may limit to 85 dBA for continuous scenario. One shall remember, this noise level should be the mix of noise from device and back ground noise i.e. pump compressor, etc. Acoustic insulation may be considered to minimise noise emission from PRV, tail pipe and headers.

Two Phase Flow Pattern
During common mode relief scenario i.e. total plant power failure, total cooling water failure, etc may leads to multiple PRVs relieve. JT cooling due to pressure reduction, hot fluid mix with cold fluid and composition change may results two phase flow in the tail pipe and header. The flow pattern of this two phase flow shall be analysed and avoid slugging flow pattern as much as possible. Typically may consider to use Taitel-Dukler map to determin flow pattern. Flare network exposing to two phase flow, piping support designer shall make aware and provide sufficient support for piping with two phase flow. If necessary, may consider additional intermediate knock out drum to remove liquid (as discussed in "Provide More than One Flare KOD in SERIES".

[More disucssion about AIV, FIV, Thermal shock, Slug hammering, etc in "Several Criteria and Constraints for Flare Network - Piping"]

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Monday, March 9, 2009

Oil Characterization Method in HYSYS

The petroleum characterization method in Aspen HYSYS converts laboratory analysis of condensates, crude oils, petroleum cuts, and coal-tar liquids into a series of discrete hypothetical components. These petroleum hypo components provide the basis for the property package to predict the remaining thermodynamic and transport properties necessary for fluid modeling. Aspen HYSYS produces a complete set of physical and critical properties for the petroleum hypo components with a minimal amount of information. However, the more information you supply about the fluid, the more accurate these properties will be, and the better Aspen HYSYS will predict the fluid's actual behavior.

In this example, the Oil Characterization option in Aspen HYSYS is used to model a reservoir fluid. The fluid is a combined gas and oil stream. Read more in Oil Characterization.

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Saturday, March 7, 2009

Provide More than One Flare KOD in SERIES

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Flare system commonly consists of collection networks, liquid Knock-Out drum (with liquid retention capability), knock-out pump and flare stack with tip. Some flare system may includes liquid seal drum, air ingress & purge reduction seal, flare recovery system, liquid heater and/or vaporiser, etc. Sometime, two or more flare knock-out drums (KOD) are installed in parallel to reduce KOD size on large flare design flow. However, in some design, two or more flare KODs are installed in series within the flare collection system. What are the common reasons behind providing KODs in series ?

(i) Vapor & Liquid Recover to Source
In a plant, there may consist several production trains with common flare system. This is one of the strategy to minimize capital investment cost. Typical plant with multiple trains and common flare is Liquefied Natural Gas (LNG) and gas processing plant. Example Qatar gas LNG plant has at least 7 trains, Australia North West Shelf has at least 5 trains, etc. Although all trains are located in same place sharing common flare system, however the owner of these train may be different. Probably Train 1, 2 & 3 are owned by company ABC, train 4 & 5 own by company MMM and train 6 & 7 own by company XYZ. Vapor and liquid hydrocarbon leaks or relief from a train, this valuable hydrocarbon may be recovered back to its train process system by same owner. Thus, providing a dedicated KOD for trains belonging to dedicated owner may serve above purpose.

(ii) Design limitation of Main Flare On Operational Non-Smoking Requirement
Common main flare shall be designed for largest load from all trains in any relieving scenario. Common relieve scenario contributes to large relief load are cooling water failure, total power failure, total plant blowdown, etc. This possibly lead to common main flare with large capacity. However, it is also common requirement to have non-smoking flaring during normal operation with low flow. As common main flare with large capacity may have limited turndown and exceeded the minimum normal operational flow, thus a dedicated operational flare may be provided for train(s) with same owner. Providing a dedicated KOD and operational flare for trains belonging to dedicated owner may serve above purpose.

iii) Mixing of Product may not be recoverable in any plant
Some plants with common flare system but relieve different of product. There is potential the mixture of the products may not be recoverable by any of the plant. Thus, a dedicated KOD for dedicated plants are provided so that the product relief from dedicated plant is recoverable in the plant which relieved the fluid.

(iv) Mixing of Fluid Cause Slugging
Common main flare system for plant with hot fluid and cold fluid may lead to condensation and results slugging flow in the flare header. Slugging in flare header potentially results severe erosion, noise and vibration. Providing a dedicated KOD will remove liquid from the relieve fluids and minimise the potential of slugging in the common header. This may only minimise, but not totally avoid as hot vapor may still mix with cold vapor in the common header and condensation/slugging flow may still possibly present. However, providing of dedicated KOD will reduce the slugging flow potential. In the event, severe slugging still possibly present and results problem to flare support, it is always advisable to provide separate flare system.

(v) Reduce Common Header Size
Providing dedicated KOD would possibly reduce relief flow (liquid) to the common header during common relief scenario. Reduction in relief flow will reduce the main flare header size.

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Thursday, March 5, 2009

Elevated Flare (SI Unit) Datasheet

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Following are the data sheets for Elevated Flare (SI Unit) data sheet in Pdf format.

A datasheet in Excel sheet has been generated to ease readers.

Download Elevated Flare (SI Unit) data sheet in Excel format
Download Elevated Flare (SI Unit) data sheet in Pdf format

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Tuesday, March 3, 2009

Pneumatic Test Explosion in Shanghai LNG Terminal

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An explosion occurred in Shanghai LNG Terminal when the construction worker conducting pneumatic test of the equipment on Feb 06 2009. ONE worker was killed and 15 injured in an explosion on a construction site at Shanghai's Yangshan Deep Water Port. The accident happened at a Shanghai LNG Co Ltd work site on Ximentang Isle, north of the Yangshan Deep Water Port, an international shipping center about 45 kilometers from Pudong International Airport. This LNG terminal is expected to receive 3 million tons of the fuel annually after the first phase becomes operational this year. When the facility is online, LNG shipped by sea from Malaysia will be transformed into a gaseous state and sent to downtown Shanghai through pipes.

(Click to view larger image)

The man who died was pierced by a flying steel rod while lying in his dormitory bed. He was pronounced dead at the scene, his co-workers told reporters. The explosion occurred during a pressure test of the equipment, according to the city government media office. Workers were pumping air into a gasifier when some 500 meters of the piping network burst into fragments, buckling cement crossbeams.

Following are collection of article that helps you to educate yourself or your operators related to Pneumatic test :

Pneumatic Test Accident in Singapore
On May 22, 2002, a fatal accident occurred in Singapore involving the failure of a refrigerant receiver during a pneumatic test. In light of this incident, it is appropriate to again remind our readers of the hazards involved in pneumatic tests and to review the precautions that must be taken in conducting such tests.

Hazards of Trapped Pressure and Vacuum
A leak test on a heat exchanger was being conducted using low pressure gas when the tube bundle was ejected with great force striking two employees. One of them died on massive internal injuries...

Pipeline fails under air pressure test - Kills worker
Two workers had completed laying a 30 metre length of 300 mm diameter PVC pipe, in order to connect it to an existing steel pipe, along a suburban roadside. The pipe was then to be pneumatically tested up to a pressure of 690 kPa (100 psi)...

Pneumatic Test Operation Maintenance
This tank is intended for use vented to atmosphere. For outdoor applications, install a weatherproof vent hood or cap on the vent riser pipe and on the interstitial space vent of double wall tanks.

Pneumatic Test - Incident in Brazil
Incident happened in a non-ExxonMobil facility in Brazil during a pneumatic test of the tank associated piping. A blind was NOT installed to isolate the ...
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Pneumatic Test - IncidentASTM A1047 / A1047M - 05
ASTM A1047 / A1047M - 05 Standard Test Method for Pneumatic Leak Testing of Tubing

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Monday, March 2, 2009

Useful Documentation for AFSA / FLARENET...

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Aspen Flare System Analyzer, AFSA (formerly FLARENET) enables engineers to perform steady-state design, rating, or debottlenecking of single or multiple flare and vent systems. AFSA may calculate minimum sizes for new flare systems or evaluate alternatives to remove bottlenecks in existing relief networks and can be used to identify potentially dangerous relief scenarios during design phase or current operational scenarios.

Similar to "Useful Documentation for HYSYS ...", following are compilation of documents related to AFSA or FLARENET. If you found any documents related to AFSA or FLARENET 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.

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