Manhole and Breather valve

[cobraaa]

hi
i hope all of u will be fine and shine....
well i have engaged now a days in modification of a tank. the problem which i faced is that of breather valves.
Existing breather valves are 2Nos. of dia 6" and now requirement increases. Consultant has recommended that intall a new breather of dia 10" to meet the requirment of inbreath and outbreath.

My supervisor asked me to use the Manhole for that breather.i.e. he wish to fabricate a plate/hollow plate for manhole with breather valve, to be welded on that plate.

1. Purpose of Manhole?
2. if i use the manhole for breather purpose wat will be the adverse effect of that?
3. if i use the manhole, how will i acheive the purpose of manhole?
4. can some one share the detail how to fabricate that plate?\



Manhole size is of dia 24"

Thanks and best rgrds

[Nabilia]

The manholes on an external floating roof are for access during out of service, a pressure/vacuum vent can be placed there. A thicker cover plate can be made to the same size/bolt-hole as the existing cover plate and your breather welded to it. Use proper gas monitoring and procedures to change the cover if you are doing it in-service. Fixed roof manways are used for inspection and entry to set internal floating roof legs, as long as the manway to be used is not where the internal ladder is, there would be not problem with using it for a breather.

[superandy]

I think you are speaking about tank roof manhole, probably having a diameter of 18 - 20 ".

You can simply open an hole on the manhole cover and weld a 10" nozzle for the breather valve.

It isn't a the most technical elegant solution but usually it avoids to waste money and time.

Regards
Superandy

[cobraaa]

thanks nabilia

well i need the details of that plate.
i have checked in our warehouse about the breather valve. recently 12" Breather valve with flame arrester is present in our warehouse. 2nd step will surely be to install that breather dia 12" on that manhole plate dia 24"...
can u send the details of how thick the plate must be, so that it can support the breather...
and calculations for that plate thickness..

also
if i use the manhole, how will i acheive the purpose of manhole?
can some one share the detail how to fabricate that plate?

[Nabilia]

Check the existing cover plate and flange, since this will be a vertical load, you don't need a really thick plate to replace it. Like I said before, you need to measure the existing one and make another one that matches for a quick swap out if it is in service or remove the existing cover plate like Superandy suggested and cut a hole in it to mount your now 12" breather. Does the existing manhole have a reinforcing plate? If you are out of service, you should consider the load on the deck if it needs reinforcing with a split reinforcing pad.

[cobraaa]

well thanks a lot.
i think dat vertical load will have effect on the cover plate..

let me check the weight of that breather frm my warehouse and let me check that whether there is a reinforcing plate or not?
thank u again..

Regrds

[ALIRAZA5016]

miss nabila can u give me the detail of external and internal floating roof tank structures and why have the crude tanks have pontone type roof and what is rim seal,why the sides of crude tanks appeared to so clean during the charging or filling instead to appear any mark of crude oil on its internal surface?