10 replies to this topic

[mgamil24]

Dear All;

If i have a methanol tank defined with design pressure (-1 / 9 barg)is this means the tank is designed for full vacuum operations & does not need inert gas blanketing ?

 

Mohamed

[Art Montemayor]

Mohamed:

 

Our members need more information from you.

 

What does (-1 / 9 barg) mean?  Does it mean the following:

 

Design vacuum pressure = -1.0 barg?
Design internal pressure = 9.0 barg?

 

If so, then your methanol tank is probably cylindrical in shape and has a manufacturer’s name plate welded or riveted on its shell that should state the design and fabrication code that it was fabricated under.  Is it the ASME code?

If your tank does not have a manufacturer’s name plate, then where do you obtain the design pressure information from?  I would not assume any design pressure information without detailed engineering calculations done by a professional engineer with the calculations stamped accordingly.

 

If your tank is a conventional API storage tank, then it is not suited nor capable of withstanding a vacuum condition.  Please advise us what are the characteristics and documented calculations of your tank in order to consider whether the tank is capable of vacuum conditions or not.  Most industrial storage tanks are not capable of withstanding a vacuum and must be protected from such an occurrence.

[mgamil24]

Admin; We are still in the Operation readiness plans completion stage. Did not start the construction phase yet. We are reviewing the systems operating guidance for comments.

Attached is the data sheet for the vessel.

The Question is " The tank is not equipped with nitrogen blanket - Is this Ok? with the attached data sheet?"
 

ALL THE BEST

Attached Files

•  methanol vessel.jpg   111.13KB   11 downloads

[breizh]

Hi ,

To me there is no direct link with the construction of the equipment and the need for N2 . Methanol is a flammable material . You need to consider the regulation in force in your country . Here is China we are using N2 blanketing on our CH3OH tank .

Hope this helps

Breizh

[mgamil24]

Sorry Gents; One more question - if the same vessel (Same data sheet) has nitrogen blanketing but NO Pressure vacuum Safety valve PVSV; What will be the case if we lost the blanketing for any shutdown reason during the methanol dispatching process?

 

Sorry for the confusion & thanks in advance for the support.

 

Mohamed

[Art Montemayor]

Mohamed:

 

Breizh, as he accustomed to do, has furnished you with some very specific and important methanol information that you should study and apply to your proposed plan.  I am also enclosing additional information on above ground tank storage for methanol.  Please study the material and note the highlighted sections I have noted that apply to your query on nitrogen blanketing for methanol storage.

 

I don’t know what you mean by “Operation readiness plans completion stage”.  Is this a preliminary engineering design stage prior to forming a complete scope of design?  Your submitted data sheet is lacking in detail.  Was it filled in by a qualified engineer.  You don’t even give a sketch of the tank - or the mechanical design code.  Refer to my data sheet in the attached Excel workbook and use that type of specific data sheet for your specification.  Who filled in the data sheet and where does the data come from?  A design specification for -45 ^oC seems ridiculous (are you located in Siberia?).  The corresponding -1.0 barg (absolute vacuum) specification pressure also seems ridiculous.  Why impose such drastic stresses on a storage tank that contains a flammable fluid?  This is never done with methanol - unless you employ (and can justify) a pressure vessel.

 

You don’t respond to my specific questions and they are left in the air.  Therefore, I can’t supply any specific information on your query.  Your queries can be addressed only generally and not specifically:

 

“The tank is not equipped with nitrogen blanket - Is this Ok?”
Knowing the little we know about your application, I recommend you employ nitrogen blanketing on methanol.  As noted in the literature enclosed, that is a safe way to operate.

 

For your personal safety - as well as that of your workers - I highly recommend you install a conservation vent (PVSV) as is normally done in almost all methanol storage tank designs world-wide.  Why would anyone not install a PVSV on such a tank?  This is also a ridiculous suggestion.  The tank MUST be protected from any failure - that is a common sense, rigid specification.  Please read and study the information supplied for your own benefit and safety.

 

You should also be applying all safety design considerations such as over-fill protection, dike, level alarms, pressure indication and protection, spillage containment, grounding, etc., etc.

 

 Methanol Atm Above Ground Storage Tank.pdf   641.62KB   106 downloads

 Arts Process Spec Sheets.xlsx   685.8KB   94 downloads

[Bobby Strain]

This looks like what I call a bullet. Methanol has a low vapor pressure at normal ambient temperature, so the nitrogen blanketing is appropriate. A vacuum relief is not necessary since the vessel is designed for full vacuum. But you need to equip the vessel with a pressure safety device, sized for fire.

 

Bobby

[mgamil24]

Thanks alot Bobby; so if the design pressure is -1 barg;  this considered as full vacuum case.

The Remaining Question;  if i lost the N2 blanketing and as you said Vacuum relief is not necessary what will be the protection layer then ?

 

Mohamed

[fallah]

Thanks alot Bobby; so if the design pressure is -1 barg;  this considered as full vacuum case.

The Remaining Question;  if i lost the N2 blanketing and as you said Vacuum relief is not necessary what will be the protection layer then ?

 

 

Mohamed,

 

Protection layer against vacuum?

 

No need due to design for full vacuum...

[mgamil24]

Thanks Fallah; the question was just to confirm the answer for final after the discussion.

Thanks to all - it is really clear for me now.

 

ALL THE BEST

Mohamed

[vaibhav]

Mohamed

 again  You are roaming around the same point. As stated in the reply by Mr Art,  vessel shall be protected for vacuum condition.  you can not assume or just consider design data for the tank.  Design code / calculations for the tank , correct product properties including density, viscosity & most important vapor pressure values shall be in place to arrive at correct safeguarding system for the tank. 

Nitrogen blanketing along with PVRV vale is required for the tank to my understanding.  Tank vents ( PVRV ) shall be based on inflow / outflow of liquid to be pumped .

 

Regards

VP