4 replies to this topic

[Neelakantan]

hi all!
my company, (in india) is in the process of finalizing the layout, routing etc of a mini LNG terminal in india (bulk quantum of the LNG shall be stored in a permanently moored LNG FSU and everyday a parcel of app 3000 m3 shall be pumped to the local storage and sent to the regasifier.

the storage is built of 6 x 500 m3 double walled vacuum insulated vessels; we pprovided outlet lines from the bottom of the bullet and connecting to a manifold and then going to a send off pump; since the pump shall be continuous pumping the pump are always in chilled mode and hence the pumps are provided outside the storage.

but when we sent the design to the vetting engineering company in india, they returned the design saying as per oisd 194 the outlet has to be from the top of the bullet; (we have done a design for location abroad and never came across statutory issues)

we tried to reason with them explaining that the general guidelines are for the flatbottom tanks and not for bullet vessels but of no avail. (actually the p&ids went smoothly through HAZOP!)

as per OISD 194, clause 4.5.1 mentions that all nozzles for LNG piping requirement "shall" be from the top of the tank. The word "shall" means a mandatory requirement and we are struck;

any ideas how it is to be done now?

regards
neelakantan

[kkala]

In a local LNG terminal, pumps are submerged and discharge lines come from the top of the tank (see attachment found in Web). But this concerns flat bottom tanks; not bullets of 500 m3, assumed to be slightly pressurized.
Supposing that rejection has been in writing, next step would be to defend your design by sending a memorandum, in an effort to convince that your present design is correct. Before this, you have to study OISD 194 thoroughly and communicate with the responsible person of "vet engineering company", trying to understand what really makes them anxious (beyond formal OISD statement) when exit pipe comes from the bullet bottoms. Some thoughts (among others) to be looked into and included in the memo in their final form (probably differing to what presently expressed) may be as follows.
1. Applicability of OISD 194 concerns flat bottom tanks, not (pressurized) bullets.
Are submerged pumps mandatory per OISD 194? If horizontal pumps are acceptable, suction has not to come from bullet top.
2. Installation quite similar has been operating abroad without accidents or environmental damages.
3. HAZOP study has been elaborated and attached to the memo. Probably Safety Study would help too.
4. References of other installations abroad , consisting of bullets and horizontal pumps would also help. There are horizontal LNG pumps, e.g. http://www.rotatingright.com/pdf/horizontal/Reda%20HPS%20Horizontal%20Pumping%20Systems.pdf.
In case of no consent, you could start a trial, but this is normally time consuming (money for technical arbitrators and lawyers will be spent). It is noted that local statuary authorities (Greece) can need an official legal opinion to approve something not clear to them (not always, but can occur).

Attached Files

•  LNG Terminal Technical Data .pdf   635.56KB   31 downloads

Edited by kkala, 19 November 2012 - 11:30 AM.

[Neelakantan]

dear mr KKALA,
sorry for the delayed response from my end; i was watching this thread for almost a week and gave up as no response was seen; since i have not put any alert for responses, i didnot see it earlier.

the other reason for the delay is work load as of now; because DWVI vessels (double walled vacuum insulated) vessels are costlier and consuming a large lead time, i have managed to convince the owner to go for single walled PUF/PIR insulated (SWPI) bullets, which indian fabricators can do at a competitive cost. Obviously, there are downsides: increased BOG, increased surface area and water requirment for spray and screening, rigididty of the external surface, vapour barrier to avoid water ingress inside the insulation. We are in talk with two major insulating companies both of them are saying that their vapour barriers are quite "tight"; your thoughts on this are welcome. (Rather i should say, your thoughts and suggestions on SWPI vs DWVI are invited!)

coming to the issue of the nozzles, i asked them what is the top and bottome ina horizontal bullet! and since now we are planning SWPI, the issue of puncturing the outer skin is gone. Also i pointed out the whole of OISD -194 is rather dated and need to be revised to accomodate satellite and mini-terminals and their storage requirements. To cap it, PESO gave clearance for our proposed drawings!

Unless the risk analysis committee refuses the design change, we are off with a cheaper and faster SWPI fabrication.

regards
neelakantan

[Bobby Strain]

And problems in the future. I would look to a manufacturer like Chart Industries to supply reliable vacuum insulated vessels.

Bobby

[Neelakantan]

@bobby strain;

from your cryptic reply, i understand, you advocate DWVI and not single skinned vessel with puf/pir insulation.
neelakantan