12 replies to this topic

[Hellmgm]

We have methanol storage tank of 20 m3. Bottom outlet line connected to two Methamol supply pump. Recently we have fire in methanol pump due to heavy seal leak.  By the time operator reached to close pump suction valve, not able to close isolation valve due to wind direction flame was big. Fire continue for long time till all material from tank empty out. 

Pump suction line is not having any remote operated emergency shut down valve. 

 

I would like to know  what is the criteria for provision of emergency shut down valve in pump suction line from Hydrocarbon storage system? is there any standard? It is simply guideline from different licensor of detail design consulting company?

Edited by Hellmgm, 12 December 2014 - 09:23 AM.

[fallah]

Hellmgm,

 

In methanol pump's suction line there is normally a SDV would be closed at LL liquid level in suction drum/tank simulataneous with pump trip to protect the pump and also loss of inventory. Depending on the conditions, in a fire case due to pump seal leakage, such SDV would be closed at LLLL hence at least can prevent the fire extendtion beyond that liquid level. Please upload a sketch of the system along with the additional info to be able to submit more comprehensive response to your query...

[senthil13]

These valves are called SDV or TSV ( Thermally sensitive valve) which is installed in the outlet of any huge hydrocarbon storage in order to eliminate inventory loss. this is dictated by insurance agencies like FM Global or similar companies.

 

These valves are sometimes connected with fusible links which will fail close the valve in case of fire at the pump due to  leakage and fire.

[shekhar dhuri]

Hellmgm,

I also suggest you to provide SDV on pump suction line. In my opinion, SDV needs to be closed on
a) Low Low Liquid Level of the Tank
Emergency Shutdown Scenario (Fire is one of them)

Regards,
Shekhar Dhuri

Edited by shekhar dhuri, 13 December 2014 - 11:36 PM.

[chemsac2]

Hellmgm,

 

ESDVs on pump suction lines are generally provided in following instances:

• a maximum inventory of the process vessel over 8 m3 of light ends (LPG)
• a maximum inventory of the process vessel over 8 m3 and with a product above its autoignition temperature or at a temperature above 250 Deg C
• a maximum inventory of process vessel above 16 m3 and a flammable product

These ESDVs shall be located as close to suction vessel as possible and shall be fire protected. Emergency push button for these ESDVs shall be located 16 m away from zone so that it can be closed in case of emergency.

 

In your case flammable product storage volume is above 16 m3 and hence ESDV shall be considered.

 

Regards,

 

Sachin

[Hellmgm]

Let me thanks for getting good feedback.

 

Size of our methanol storage tank is 19 m3. Location of pump is  five meter away from tank. We have ESDv's on all other LPG or C4 mix stream tanks. Only this two methanol tank we do not have ESDV'S. 

 

SO based on feedback from Mr. Sachin  we shall have ESDv'S on suction line since tank volume larger than 16 m3.

 

Could please give reference of this in which stadnard of best design practice it is available.

[fallah]

Hellmgm,

 

As per good engineering practices, the conditions in which considering a remotely operated ESDV in the suction of a pump is mandatory are as follows:

 

1- When the inventory at normal operating level of the suction vessel is 5 tonnes or greater and will produce in excess of 10% wt flash vapor under leakage conditions.

2- The liquid is toxic.

 

Then you should consider such valve in your methanol's pump suction line.

 

Indeed, it's not a requirement to locate the ESDV as close as possible to the vessel, especially in your case in which heavy seal leak caused having a fire case the primary purpose of the ESDV is to shut off and minimize the liquid leaking through the pump seal; then it's better to locate the ESDV as close as possible to the pump.

Edited by fallah, 14 December 2014 - 07:13 AM.

[chemsac2]

Hellmgm/Fallah,

 

Since purpose of ESDV is to avoid fuel adding to fire, it is preferable to locate ESDV away from fire. Placing ESDV close to pump would make it exposed to fire and susceptible to fire. Although you should fire proof such ESDV and associated cables as well, why take a chance?

 

ESDV located close to pump would at the most help us stop few litres of liquid trapped in piping between vessel and pump from getting emptied, but that may jeopardise entire suction vessel if ESDV fails. I can dig up few P&IDs showing minimum distance between vessel flange and ESDV, but this is plain logic.

 

In your case, its only 5 m and hence not much choice but in refineries/petrochemical installations, all pumps are located around pipe racks for maintenance and are away from suction vessel. ESDV location would be relevant there.

 

As for source of guidelines, these are engineering practices I have seen in standards of few operating/engineering companies. I guess it is based on damage potential of volume and fluid type. It can also be quantified by carrying out Qunatitative Risk Analysis (e.g. PHAST software can do it). 

 

Regards,

 

Sachin 

[fallah]

Sachin,

 

If ESDV failure would be a credible scenario i.e. it might not to be closed when needed in a pump seal leakage case, no matter it is located close to the suction vessel or the pump. Anyway, it could be mentioned that at least in large diameter/long length suction lines ESDV location as close as possible to the pump is highly preferable.

Edited by fallah, 14 December 2014 - 12:21 PM.

[chemsac2]

Fallah,

Here we are not talking about failure of ESDV and it being called to function in event of seal leak.

Here we are talking about ESDV not closing due to fire resulting from seal leak. Thus we want ESDV to close on seal leak, but consequences of seal leak do not let ESDV to perform its intended action. For ESDVs may be possible through Fail Safe action, but at many places MOVs are used which are generally not Fail Safe. Even for ESDVs, operator would prefer not to rely on Fail Safe mode.

I would be intetested in having a look at P&IDs or other documents showing ESDV close to pump. May be I would stand corrected.

Regards,

Sachin

[fallah]

Sachin,

 

Attached you can find my response to your previous post...

 

Attached Files

•  SDV.docx   10.79KB   72 downloads

Edited by fallah, 14 December 2014 - 03:05 PM.

[kiansafaie]

Dear Sachin
Lets talk about real condition instead of practice. Applying ESDV is to avoid spread fire from pump( in leackage condition)to methanol tank as a source of fire due to more inventory, so its reasonable to block the methanol suction pipe in near the pump not near the methanol tank.
Thank you

[shady othman]

I agree with kiansafaie,

you have to keep a safe distance between the tank and the ESD as if the fire reaches the ESD, it will be away from the methanol tank.