Carefully assess information in the web

There are many websites providing FREE information to their users/visitors in recent years. This has made a lot of information available for access and refer with no cost. These websites compile informations and arrange it in the way you can easily access and read. I am sure many of you are more often get information from internet rather than books, journal, etc. Have you ever ask yourself if the provide information is good, correct, reliable, correct and relevant ?

Let take for example, there is a simple Compressed Air Dew Point Chart available HERE for public view. This chart has given a very good tools to the user to convert compressed air dew point @ pressurized condition to dew point @ atmospheric pressure and vice versa. It really a simple but good tools for those process design engineer and plant engineer conversion of compressed air dew point.

However, if you really goes in to details of the ATMOSPHERIC line, take the "0" on X-axis, it mean "0 degC dew point at ATMOSPHERIC pressure". If i draw a line straight-up and touch the ATMOSPHERIC line (diagonal red line) and horizontally reach the Y-axis, you will get "2 degC dew point at ATMOSPHERIC pressure". This does not tally between each and other. These happened to others temperature range from -40 degC to 70 degC. See below image.

This signified that the graph is incorrect for certain temperature range and this also imply that other lines may create some level of error. If you use the curve without careful, you may risk yourself in making mistake.

(This is just an example for continuous education. It does not intended to offense any personal, party and company).

Those anytime you received any new information, first you have to assess how good, correct and reliable of the received information. One of major clue that presently here is use the known facts to verify the information. You may also to cross check with other reliable information e.g Perry Engineering Handbook to verify the information. This way will minimize your risk of making mistake.

If you found some doubt on any information on any website, you are encourage to advise the web owner. With this action, you will avoid more user refer to wrong information if it is really a mistake OR you will learn new knowledge as the web owner will advise you the reasoning behind your doubt.

If you have problem with contacting the web owner, you are always welcome to drop an Email to me.

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12 Features required for Shutdown Valve (SDV)

Shutdown Valves (SDV) are common apply in oil and gas production system for safe and proper isolation purpose to minimize escalation of hazardous from one system to another system. General shutdown valve is controlled by a high integrity Emergency Shutdown System (ESDS).

A shutdown valve shall equipped with the following features :

i) Tie Shut Off (TSO)
- Zero/minimum leakage shall be expected for a device act as shutdown valve. Generally a Shutdown valve seat leakage shall pass the seat leakage testing per API 508 and/or ISO 5208.

ii) Firesafe
- shutdown valve is expected to work promptly even though it expose to external fire attacks. thus, shutdown valve body shall be fire rated according to API 607 for soft seated valve or API 6FA for API 6A & API 6D valves or BS 6755 Part 2.

iii) Fast action (From Full Open - Full Close)
- A shutdown valve shall act fast to minimize the escalation of hazards. Generally a quarter ball valve is the excellent device in quick action. As rule of thumb, shutdown valve shall be capable of begin it closing action within 10 seconds of activation, and time taken from Full open to Full Close is within 1-2 seconds per inch of shutdown valve size. However, this shall be compliant to overall safety philosophy. Proper selection and sizing of actuator to ensure above requirements are fulfilled.

iv) Minimum passing (during closing of shutdown valve)
- The feature is required to minimize the potential of overpressure of Low pressure system and spurious trip. A shutdown valve with equal% characteristic (most ball valve will have this feature. However, this shall be confirmed with valve supplier) is preferred type. With equal% characteristic, it can operate with 10% valve closure give 20% flow reduction, 20% closure give 50% closure...the closure of valve is fast and minimize inventory passing.

v) Minimum disturbance / turbulence to process fluid
- This feature is to minimize unnecessary energy lost. Reduced Bore (RB) ball valve having hole in the middle would minimize flow direction change and turbulence. Full Bore (FB) ball valve virtually like a pipe- significantly minimize energy lost.

vi) Fail-safe
- A shutdown valve actuator shall pneumatic/hydraulic fail-safe spring-return type. Generally a shutdown valve failed to close (FC). Electrical driven type shall not be used.

vii) Manual field reset
- A shutdown valve shall be reset manual at field. The operator shall ensure the system is clear and safe and reset on site. No remote reset is allowed.

viii) Clear physical indicator
- Shutdown valve shall be equipped with visible external valve position indicators to provide clear positioning and status of a shutdown valve.

ix) Position switches
Position switches shall be provided on shutdown valve to provide clear positioning and status of a shutdown valve to control room.

x) Partial Stroke Testing of Shutdown Valve
A shutdown valve in critical service e.g. Pipeline outgoing and incoming shutdown valve (ESDV) will required periodically partial stroke testing in order to maintain / increase it reliability, availability & SIL level.

xi) Accumulator
Some shutdown valve may be equipped with accumulator to facilitate valve stroking and /or reopen in the event maloperation.

xii) Second Solenoid valve
Shutdown valve in critical service may be equipped with second solenoid valve to increase reliability and availability.

Above has presented 12 features of shutdown valve. Some operating company may have their additional requirements and limitation on shutdown valve.

Related topics

• ERRATA - API Std 521, Pressure Relieving and Depressuring Systems
• Requirement of overpressure protection devices on system design to PIPING code
• ESD Selection Guide, Metso Automation, Issue 4/2001
  
• Partial Stroke Testing of Emergency Shutdown Valves, ACM Automation
  
• Achieving High SIL Ratings with Partial Stroke Testing of Valves, ACM Automation

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ERRATA - API Std 521, Pressure Relieving and Depressuring Systems

American Petroleum Petroleum (API) released the API Std 521, Pressure Relieving and Depressuring Systems early of 2007. As usual, there are some mistakes spotted in the this Standard. First errata that i received was dated June 21, 2007. I am a bit outdated. Somehow, i guess there are still many engineers out there (like me...) may not aware of the release of this errata. If you are user of this standard, i strongly urge you to download this errata and make correction to your copy.

API Std 521, Pressure Relieving and Depressuring Systems
ERRATA
June 21, 2007
(Click to download)

If you find anymore mistake or error in this standard, please drop a comments or sent me an Email . I will take the necessary action from there...

Related topics

• Workbook for Chemical Reactor Relief System Sizing
• A must have book...Emergency Relief System Design Using DIERS Technology
• Requirement of overpressure protection devices on system design to PIPING code
• Discussion on ISENTROPIC and ISENTHALPIC process via Relief Valve
• Use of Conventional type PSV with back pressure exceeded 10% set pressure
• Use Ultra-Sonic Flowmeter in FLARE Gas Header for emission monitoring
• Should we consider JET FIRE for Pressure Relief Valve (PSV) load determination ?

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Liquid Slug Stabiliser - Another type of slugcatcher

In earlier post "Slugging and Slucatcher", there are four types of slugcatcher are generally used to handle intermittent transient slug. First three types, horizontal separator, vertical separator and finger type are referred as common type slugcatcher and many engineering companies have the design & engineering capability of these common type slugcatchers. The last type is Slug Stabiliser which is rather different in term of design, operation and slug handling principle.

Those common type slugcatcher are designed to handling gas-liquid separation during normal operation. They are similar to most of the dual phases separator. The only additional feature built in is the slug handling and liquid holdup storage capability.

Slug Stabiliser is operation is slightly different. Normally it don't works as gas-liquid separator. Normal gas and liquid will flow through the bypass and feed the downstream gas-liquid separator. However, in the event transient slug arrive at slug stabiliser, slug with high momentum will flow across the bypass line while gas is taking the easy route flow into the bypass line. Phase separation occur at the bypass branch when slug approaching the slug stabiliser. Liquid (slug) keep in the loop will be handled after slugging event.

OilPro is one of the proprietary technology owner of Innopipe, a patented Slug Stabiliser. The following article is available from OilPro which describe in detail of basic principle, design and operation of Innopipe.

Innopipe Liquid Slug Stabiliser System for Natural Gas Pipelines

Related / References :

• Slugging and Slucatcher

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What you can do to help our friend "Environment" ?

In my earlier post, "Theme for Blog Action Day - ENVIRONEMENT", OCT 15, 2007 is the Blog Action Day and the theme of the day is ENVIRONMENT. Have we ever ask ourself how much damage we have made to our environment ? I m sure many of us (especially within our Chemical & Process , Oil & Gas communities) are aware of the "contribution" by human to environment and nature. If you are one of them who don't ware of this, i am strong requesting you to take a little of your effort... continue reading...

Environmental issue is one of the hot topic recently and a lot of efforts have been taken / are taking to minimize and slowdown the impact and damage to our environment. You can appreciate this by understand the 2007 Noble prize (Chemistry) winning theme is ENVIRONMENT. Many of us may take this issue easy that this type of "biog" things, we leave it to those who has "big" vision, environmentalist, etc, This is just a "politic" topic and enjoy by many politician. Ultimately giving yourself a statement - Nothing much i can do.

Guys !...take a step backward. There are many things we can do although we are just nothing to anything. Following are something you can do :

• Spread the environment awareness - Blog about it, inform you junior / kits, friend around you. Or minimum inform them to read this post. Or Copy contents of this post to forum, etc and create a link to this post.
  
• Practise it - if you have not practised any of measures here, please practise at least ONE. If you have practised some, please practise EXTRA one. If you have practise ALL here. Congratulations ! Please provide ONE more extra measure in the comment.
• Segregation of rubbish - Please segregate rubbish into a few categories such as non-biodegradable type (plastic, polymer, etc), biodegradable type (organic stuff, food, etc), reusable/recyclable bottle / aluminum cans, etc.
• Proper Disposal of Electronic waste - Used batteries collect and sent to licensed disposable unit. NOTE : I would like to collect information on this type of collection center throughout the world so that it can be made known to everyone. If you aware any of this unit within you area, please drop me a note (Email) or leave it in comment column.
• Recycle cellphone - Further reading... cellforcash - Recycle Your- Cellphones
• Use Mechanical watch instead of Electric powered watch
• Minimise consumption of packing paper - When you buy stuff in the store, most store will pack your purchased stuff in a plastic beg. f you only buy some light and small stuff, please do not ask for / return the plastic beg to the store owner (NOTE : remember to keep your receipt as proof of purchase.)
• Use rechargeable battery instead of non-recycle type
  
• Read e-book - Review & comment on the electronic paper instead of hard copy
• Use recycle paper for draft works
  

Guys... Don't just read...lets do it

Related topic

• Theme for Blog Action Day - ENVIRONEMENT

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Why Restriction Orifice is some distance from Blowdown valve ?

Very basic does not imply obvious...i really like this statement. Very often the answer is very fundamental and basic to us, somehow it always does not obvious to us.

Lets look at the above sketch. It is a typical arrangement for a Blowdown Valve (BDV) with Restriction Orifice (RO) , located downstream of the Blowdown valve. This arrangement typically used to depressurized a system inventory to a safe level within a limited time to minimized catastrophic scenario. Between the Blowdown valve and Restriction orifice, there 600 mm spool piece between them. What the main purpose of this 600mm spool piece ?

Is this spool for straightening and smooth flow ?
Is this spool to avoid secondary choke ?
Guess what ?

Reasoning...Major pressure drop will take place at Restriction Orifice, downstream of Blowdown valve during blowdown. Joule-Thompson (JT) effect results fluid temperature downstream of Restriction Orifice drops below subzero (Less than zero degree Celsius). Latent heat in the piping will transfer to cold fluid and slowly approaching this subzero temperature. The "coldness" will travel back to upstream of Restriction orifice and probably reaches Blowdown valve. It potentially cause the upstream Blowdown valve body temperature drops below subzero as well. Moisture from atmosphere will freeze at the Blowdown valve body and potentially cause the stem stuck at position. Operator may not possible to close the Blowdown valve after blowdown activities and may potentially lead to back flow. Those "general good engineering practice is to locate Restriction orifice, 600mm downstream of Blowdown valve.

Related topics

• Workbook for Chemical Reactor Relief System Sizing
• A must have book...Emergency Relief System Design Using DIERS Technology
• Requirement of overpressure protection devices on system design to PIPING code
  

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E-Interview by Chemical Engineering World

Last month, Zaki from Chemical Engineering World conducted an e-Interview with me. Zaki' s blog provides very informative and interesting subject to his readers. He also the owner of Chemical-Engineering-Forum.com. Thanks to Zaki who has spend his valuable time blog / interview / introduce me to reader to his blog and to the world. Appreciate his effort. You may read about me by clicking this LINK.

Chemical/Process Engineering Personality: JoeWong

Related Topics :

• New Concept of Floating Unit - Part 2
• New Concept of Floating Unit-Part 1
  
• Floating Gas Refinery Unit
• Launching of Wilhelm Busch
  
• Gas Processing, NGL Extraction & LPG Fractionation

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