Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

HAZOP meeting and 30% Model Review

HAZOP meeting and 30% Model Review

HAZOP meeting and 30% Model Review

Dear Engineers

Please kindly be informed that our project is Gas treating and sweetening Plant.

In our Contract with client , 30% 3D model review (in PDMS) is the precedence of "HAZOP" study meeting but I can not understand any relation between HAZOP and 30% of 3D Model review meeting. According to your opinion why we can not execute HAZOP study before the said meeting?

P.S. For your information we have three meetings in our project regarding 3D ( 30% , 60% and 90% model review)

RE: HAZOP meeting and 30% Model Review

You have to have a design before you can HAZOP. To some degree the layout will influence the outcome of the HAZOP.

On the other hand if you can argue that this is not the case and that moving up the HAZOP will be a benefit then why should the client object?

Best regards


RE: HAZOP meeting and 30% Model Review

Some design changes result from each process hazard analysis.  Performing an early analysis permits change implementation with less impact on the design hours for rework.  Changes before reaching the IFD stage of P&IDs cause impact some discipline hours.  Changes near the IFC stage impact all discipline hours.

RE: HAZOP meeting and 30% Model Review

JL what you say is common sence - however the HAZOP methodology requires a certain level of the design to be completed - in order to make sence and in order to make sure the meeting dosnt get out of hand and ends up in people stading on their own little soap boxes (just my bias opinion).

Best regards


RE: HAZOP meeting and 30% Model Review

A successful approach to the dilemma of when to do the HAZOP is to do an initial HAZOP as soon as the P&ID is in reasonable shape. Then, when the P&ID is virtually finalized, do a second HAZOP. Parts of the second HAZOP can be run using the "revalidation" methodology to avoid duplication of effort. Recent additions to the P&ID, should be reviewed in full HAZOP mode.

HAZOP at www.curryhydrocarbons.ca

RE: HAZOP meeting and 30% Model Review

Thank you engineering , but I still can not understand why the 3D model is the precedence of HAZOP study.

I know that HAZOP shall perform after reaching P&ID to the proper quality but what is the relation between HAZOP and 3D modeling. Our client insist to perform 30% model review before performing the HAZOP study.

RE: HAZOP meeting and 30% Model Review

Smile and let him pay the bill?

Best regards


RE: HAZOP meeting and 30% Model Review

The HAZOP study should preferably be carried out as early in the design phase as possible - to have influence on the design.
 On the other hand; to carry out a HAZOP we need a rather complete design. As a compromise, the HAZOP is usually carried out as a final check when the detailed design has been completed.


RE: HAZOP meeting and 30% Model Review

We like free draining vapor lines with condensable components or such operating near dew point.  Pocketed lines may be caught during the model review.  An example is the anti-surge valve recycle-line from a compressor discharge back to the suction scrubber.  If pockets exist the line can become liquid full.  If the surge valve opens suddenly the liquid slug can be damaging to pipe supports etc.  The model review may catch such details not observed on a P&ID.

RE: HAZOP meeting and 30% Model Review

Since ur not supposed to solve the areas of concern discussed at the HAZOP strictly speaking this is not a reason for the model - on the other hand you sometime could shut a lengthy idscussion of if's with the model.

Best regards


RE: HAZOP meeting and 30% Model Review

I'll take a small exception to JLSeagull's example.  OSHA doesn't care if you wreck a compressor internals.  or damage piping, they care about catastrophic failures.  Some operators can't seperate PSM from plant/engineering operability questions.  SO, I'd see the OP's answer is that the owner/operator wants the EVOP the process.

RE: HAZOP meeting and 30% Model Review

We would normally have done a HAZAN/QRA we completed FEP or FEEP eg block modelling stage.  

We are going through a project doing hazard studies at 25% design and beyond becuase we are late and unresourced.  It is horrible managing actions and making changes at 25% pipework modelling.  The EPC hates it and so do we.  But , we are making a few observations from the modelling and equipment size that need management.

Good project management would have you completed HAZOP and possibly a QRA or HAZAN, Process hazard REVIEW (IEC61508) type review after FEEP/FEP.  When detailed design starts ideally you should only be implementing the study actions.

There is no point doing a study unless you plan to manage the actions but at the stage of you are at.  Change should be difficult by having robust change management and cost control.

RE: HAZOP meeting and 30% Model Review

Dear Ossareh1352,

I believe that 30% model review prior to the HAZOP study is an arbitrary goal that your contractor set and has little to do with reasoning.  It mostly reflects contractor philosophy.

Purely from an economic perspective, I would like to share my experiences with you.  I have facilitated HAZOP studies prior and after the first model review.  Here are my thoughts:

HAZOP Study conducted prior to first model review:
PROS - Shorter model review duration, reduced man hours.  Model review can focus on 3D shortcomings of the unit instead of process upsets/hazards due to poor design parameters (i.e. lack of safeguards, MAWP/T) - assuming that such issues would be covered in the HAZOP study
CONS - P&IDs lacking detailed information regarding safety features.  Increased number of action items, resulting in more man-hours close out with proper documentation. Increased HAZOP session duration.

HAZOP Study conducted after the first model review:
PROS - Shorter HAZOP review session duration.  
CONS - I can't really think of any...

I hope this was helpful.  I believe that the main point is that the initial HAZOP study should be performed either immediately prior to or shortly after the 30% review to reduce the man-hours associated with follow-up.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close