Detailed Design: What should be done? 1

[mohtogh]

Hi,
We are going to start detailed engineering phase.
My question is what works shuld be done during this period?
Actually I am looking for a step by step procedure for detaild design. (For example I know that they give us isometric Dwg. and we should re-calculate pressure loss base on those.what other works does need to be done?)

Thanks for all replies.

 

[Montemayor]

mohtogh:

If you are a degreed ChE, then you must have had to pass at least one conventional plant design course in your university curriculum - and in that course, you would forceably be exposed to what a detailed design is and how it is implemented. However, instead of raising questions, I'll just mention the obvious and normal types of detailed process design that is put into effect in this phase of the design schedule:

1) All hydraulic calculations should be finished and checked with all related specification sheets totally filled in, reviewed, and checked. This pertains to all pipe sizes being identified, all pumps sized, all control valves (& piping valves) identified and sized, all fluid transport equipment sized and identified.

2) All major process equipment and vessels should be sized, specified, reviewed, and checked.

3) All off-sites equipment is sized, specified, reviewed and checked.

4) All raw materials, utilities, energy requirements, and services are identified, specified, reviewed, and checked.

5) All safety devices, such as PSVs, safety interlocks, alarms, and other emergency controls and devices are identified, sized, reviewed, and checked.

6) All environmental impact items such as fugitive emissions, waste streams, treatment facilities, exhausts and flues are identified, sized, reviewed, and checked.

7) All startup and shutdown procedures are drafted and reviewed; checking is on-going as well as revisions - all the way up to the initial start-up.

I could get more specific and go into more details, but the above should suffice to give you a good idea of the magnitude and details involved. Forget about being furnished an isometric drawing for the process or plant involved. I don't know where or who you've gotten that idea from, but I can assure you that after 44 years and countless projects, I was never furnished one - nor did I need one. If you don't know everything about the process you are about to detail when you approach the detail design, then you have no business being on the project team.

There is a lot of preliminary engineering and sizing that takes place prior to the detailed phase and project members should know the Scope Of Work intimately and embark directly on the detailed phase. Project members live, breathe, eat, discuss and dream with the preliminary and final details of the design project. It becomes part of you and your nature. The actual, detailed steps required are unique to each specific project and you should not have, use, or require a "recipe" of steps to do the detailed design. You should plan, outline, and implement the specific design for your specific project.

I hope this experience shows you what you are up against and what you will confront.


Art Montemayor
Spring, TX

 

[jsummerfield]

Details.

Basic engineering may not address the plant layout or performance of actual equipment. Fluids may flow from one area to another with changes in elevation not addressed in the basic design. The pump data sheet may indicate the physical properties, flow, hp, etc. The actual pump curve may require a bigger starter, smaller control valve downstream, etc. Major rotating machinery may require auxiliary stuff with vents, drains, etc. that must now be piped. Someone must assign control system I/O points where the P&ID shows a single tag. All "details" from supplier data and the actual physical arrangement must be incorporated. With pressure-safety relief valves sized, the flare and header must accommodate the valve capacity not the basic engineering numbers. The same applies to pressure protection in the low pressure system when sizing the capacity of gas blow-by for a drain valve using the valve selected.

Details.



John

 

[JStephen]

mohtogh, it's not clear to me from your post exactly what it is you're designing. Is this a piece of equipment, or a whole plant or what? More details might help get more specific answers.

 

[mohtogh]

Thanks all.
Montemayor:
Yes, I am a degreed chE, and I passed that course. we designed a whole small plant, but teacher did not say which section is in BASIC and which one is in DETAILED section.(Actually we did that just like a homework.)

JStephen:
It is designing a part of plant.

 

[MJCronin]

mohtogh,

I think that you have asked an extremely important question.

While I respect the informed opinion of Art Montemayer, and have learned much form his posts, over the years, i believe that he has missed a very important element.

The start of detailed design implies that the client is now done with his decision processs and that all major decisions affecting the process and/or the layout are now complete.

I have worked with many large clients that, somehow can never make up thier corporate minds about major issues. If PIDs, layouts ,utilities etc are being changed and revised late into the project, it is a sure sign of disaster.

Nothing strikes terror into the minds of process engineers than a client inspired PID review late in the project where new faces from the maintenance department suddenly appear....

My opinion only

MJC

 

[Montemayor]

MJCronin:

Thank you very, very much for your important contribution. Yes, you are very correct in indentifying this important project milestone. I left it out in my haste and I regret the oversight because it is the "trigger" mechanism that we so identify in any client-related project.

This event of initiating the detailed design, triggers the "freezing" of the scope of work, the PFDs, & the P&IDs. There will be revisions, of course, in the process of achieving the final, detailed design. But any deviation from the Scope Of Work will bring up that dreaded word and form used by all project engineers: "Change Order" - which, in layman's terms means an increase in the project cost.

I qualified my response by stating that "I could get more specific and go into more details, but the above should suffice to give you a good idea of the magnitude and details involved", but you bring up a very good point that I didn't identify until after I had posted. Thanks for your valuable contribution.

Art Montemayor
Spring, TX

 

[MortenA]

Another important thing to remember is: No HOLDS - you cannot have holds when you are finished (OK maybe on a few construction notes but im fan of those either).

Best regards

Morten

 

[OilBoiler]

mohtogh,

I gather from your info you are a mechanical engineer, but then you say you're a degreed ChE, probably I'm overlooking something, but anyway!

If you're a ChE, detailed engineering refers to detailed design of what you will do and that includes: 1)design basis (flowrates, temperatures, pressures, etc), 2)comprehensive process description (what you're going to change), 3)hydraulic calcs, 4)marked up P&IDs, PFDs, and probably plot plans for reference with specific tie-in points. You may have to add more stuff depending on how detailed is your design.

Once you have that, you hand it to Mechanical or Project Engineers. Mechanical Engineers do the construction phase and they receive the design and purchase whatever equipment is needed and ensure that the piping is installed based on the tie-in points given in the design. They also provide estimates.

I hope that helps!

Montemayor: Your posts are very helpful and I've learned much from them because you bring your much needed experience to those of us who need it. I think the comment about being a degreed ChE is out of place. I can speak for myself. I'm a young engineer and I learn as I go and I've found extremely helpful posts here on this site. Anyway that I can I contribute with what little knowledge I have so far. I don't know whether that's motogh's case or he/she has a new assignment, but I think we too have valid questions and that's why engineering is a learned profession. I have learned in the industry that work processes for designs and detailed engineering are out there and may differ for various companies and people with even 40 years of experience are not even well familiar with them, because they don't seem to know how to answer the questions, so it's not a matter of going to school or not.

 

[Samiran]

I agree with OilBoiler: The statement made above about being a degreed ChE is indeed out of place in connection with the post.

I am not sure whether any school goes through what the industry follows as a part of project process. Did any body hear pre-FEED, FEED, Detail Design, EPC in school ?? OR what the hell is FEED HAZOP and EPC HAZOP ? Engineering is like life - we just know by living it.

Samiran

 

[Buwah]

Samiran is correct. Anyone who thinks simply graduating from an accrediated Engineering school makes you fully capable of being a front line process design engineer must have been pushed up to management a long long time ago.

Mohtough, you need to find yourself a design mentor. Yes this site can help, and keep posting your questions, but experience is the only way you can learn how to do full design. If your staff does not have an experienced person on it look around and find someone.

Be safe but have some fun.

Buwah