6 replies to this topic

[thakur]

hello freinds,

presently i am working on the breather valve adequacy check of the tank farm area.during this exercise i came acrross the tanks which dosent have any pvrv or emergency venting.it has the facility of the vent pipe which is connected to the scrubber and then open to atmosphere.
now what i understand that the vent provided to tank is serving as the both emergency and PVRV ( correct me if i m wrong).and secondly such tanks contains chemicals like H2SO4,HCL,NAOH etc.
so can i rule out the fire case for such tanks?
how would i carry out the calculation?
does such type of tanks venting follow the same calculation(in breathing ,out breathing)as mentioned in API 2000?
please help me.

regards
pankaj thakur

[ankur2061]

pankaj,

For normal venting from atmospheric & low pressure storage tanks as per latest`API STD 2000-2009 have a look at the following post:

http://www.cheresour...rd-new-api2000/


Regards,
Ankur.

[thakur]

ankur,

thanks for sharing such valuable information.

However, the post u have linked here tells more about new addition of API 2000. its not answering my above questions.and nevertheless if i follow new additon of the API 2000, probably I'll get all the vent undersize which i cant justify to the management replace older with new one.

So would u please specifically answer my above queations?

And yes, I would love to have ur spread sheet for better understanding. My email id is pankajsinh.thakur@ril.com.

regards
pankaj thakur

[ankur2061]

pankaj,

The spreadsheet is posted on Joe Wong's blog at:

http://webwormcpt.bl...estimation.html


Regards,
Ankur.

[thakur]

hi dear,

Thanks for sharing spread sheet.

But still ankur, u must have the answers of my above questions.
looking forward from u..

regards,
pankaj thakur

[ankur2061]

Pankaj,

For fire case to be considered, certain information needs to be collated & understood in the right context:

1. Volume of the tank under consideration. (For tanks larger then 2780 m³ fire case may not be considered due to the fact that the time required to heat up the tank contents to dangerous pressure levels due to external fire would be so long that adequate time to control/extinguish the fire &/or protect life/property would be available. This is as per recommendation by API 2000).

2. Flashpoint/NBP of the material stored. (Highly volatile & flammable liquid would build up pressures immediately which may require emergency venting. This again needs to be evaluated on a case-to-case basis).

3. Material stored in the tank(s) adjacent to the tank under consideration for fire case. (If the tank ruptures due to overpressurization by external fire, what are the consequences to the adjacent tanks? Will it aggravate the fire by providing fuel to the fire & spread to the adjacent tanks causing further damage & loss? If yes, then a properly sized emergency vent needs to be considered. If the tank is diked properly with a quantitative risk assessment study indicating no further spread of fire due to tank rupture then the requirement of an emergency vent can be debated).

4. Fire-fighting facilities available (sprinkler deluge & foam chambers for rapidly extiinguishing/controlling a fire to prevent dangerous pressure build-up & subsequent rupture of the tank under consideration. Again a quantitative risk assessment is required for the effectiveness of the fire fighting system & whether an emergency vent is required or not).

5. Company policy, guidelines & operating experience for storage tanks (Many companies have formulated policies/guidelines for provision of emergency venting for certain type of bulk liquid stoarge. These guidelines mandate an emergency vent & the designers job is to provide an emergency venting rate without debating the requirement of the emergency vent. No questions are to be asked. Just provide the emergency vent).

Above mentined points need to be thoroughly analyzed before concluding whether an emergency vent due to external fire is required or not.

Hope this helps.

Regards,
Ankur.

[thakur]

thanx ankur,

if i explain you the scheme,the tank for which i am to carry out the calculation is containing the HCL (non flammable material) and it dosent have any emergency vent valve neither it has the breathing valve.its top has simple 1.5" pipe which is connected to the scrubber and then open to atmoshpere.
now the doubt arises that whether this vent pipe is serving as the both emergency valve and breather valve?
if the case is so ,then nothing has mentioned about the tank protection system.

and if at all,that vent pipe is the ultimate protection of this tank ,then calculation(in breathing,out breathing) will be same as the mentioned in API 2000?

REGARDS,
PANKAJ THAKUR