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Tank Inlets From Bottom

07/23/2011 2:02 AM

dear sir,

regarding tank inlet nozzles. why tank inlets are given from tank bottom instead from top ?

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Guru
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#1

Re: tank inlets from bottom

07/23/2011 2:18 AM

One reason is to minimize splashing and entrainment of air bubbles into the fluid. Also a (minor) saving in pumping costs, at least while the tank level is low.

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#2

Re: Tank Inlets From Bottom

07/23/2011 11:48 AM

Also it avoids built up of dangerous static charges, especially where the product is a hazardous one like hydrocarbons.

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#3
In reply to #2

Re: Tank Inlets From Bottom

07/24/2011 12:10 AM

Tornado & furio good answers. But sometimes for a certain fluid and as a hydraulically demand, the inlet from the top can avail a constant load at the pump.

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#5
In reply to #2

Re: Tank Inlets From Bottom

07/24/2011 8:51 AM

Dear furio,

I do not understand how static charge builds up for top delivery to tank. Pl. explain how static charge is built up for top delivery to tank.

Thanks,

RAJESWARI

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#7
In reply to #5

Re: Tank Inlets From Bottom

07/24/2011 2:13 PM

Since many organic chemicals are non-polar or have very little polarity (vs. water that is very polar with approx an open surface on the oxygen atom of approx 112 deg and two hydrogen atoms on the other side((sorry but its been many years since I got my degree) with a positive charge concentrations) they build up static electric charge as they go through piping, hoses, etc. unless these are grounded and bonded.

When transferring gasoline, a organic mixture of straight chain and aromatic non-polar chemicals, the delivery truck will attach a bonding wire from the trailer frame to the storage tank. In addition to this they always use hoses that have a bonding wire contained within the hose to prevent the build-up of static. These bonding wires within the hoses are tested periodically to insure they still work. This type of procedure is used in transferring all non-polar chemicals.

Strong to mild acids and strong to mild caustics do not require this type of bonding and grounding since they are polar and therefore any minute static charge within them would be self-dissipated as it contacted another molecule. Water based solutions would also be included. Many sites always use bonding and grounding cable for all material transfers, not because they are always required, but to insure they are always used when needed.

One example of how static charge producing non-polar materials can be added from the top and not create a charge is to: 1) make sure inlet to tank directs the liquid stream directly down such as would be determined by a plumb-bob; 2) from this inlet hang one or more metal chains which go directly down from the inlet to the bottom of the tank with some extra length so it rests on the tank bottom; 3) type of chain is determined by compatibility with material being stored and the material of construction of the tank; 4) as the liquid enters the tank the bonding and grounding of the transfer piping or grounded hose is replaced by the liquid following the bonding and grounding metal chain down to the liquid level, no matter what height it is. I have effectively used this set-up for the transportation/storage of numerous materials such as benzene at flow rates in excess of 200 gpm.

This is the long explanation.

Good Luck, Old Salt

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#10
In reply to #7

Re: Tank Inlets From Bottom

07/25/2011 8:57 AM

GA. old salt for detailed answer. congrats for 40th GA.

We have 1000 cu.m liquid nitrogen tanks with bottom inlet but identical liquid oxygen tanks with top inlet by the same supplier at the same time. Is the explanation given by you also relevant here?

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#4

Re: Tank Inlets From Bottom

07/24/2011 8:04 AM

It all depends on the material being contained in the tank and its properties. Even then it also depends upon what you want to do with the material contained and how you want to do it. There is no universal answer.

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#6

Re: Tank Inlets From Bottom

07/24/2011 10:41 AM

Perhaps better mixing of the incoming fluid with the store fluid.....

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#8

Re: Tank Inlets From Bottom

07/25/2011 1:47 AM

does providing dip pipe inlet serves the same purpose?

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#9
In reply to #8

Re: Tank Inlets From Bottom

07/25/2011 8:22 AM

No.

All dip pipes should have an anti-syphoning hole or holes near the top, so as to prevent, in the absence of a non-return valve in the supply pipework, the tank from syphoning-out to the supply point.

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#11
In reply to #9

Re: Tank Inlets From Bottom

07/25/2011 12:03 PM

Correct! This is also why bottom fills are not used in many situations. A backflow through a bottom inlet is a mechanical problem (if check valves, pumps, seals, etc. fail) that has to be engineered out. If engineering is not all inclusive it has the potential to be a conflagration, environmental disaster, or worse yet the origin of a massive loss of life. If your design engineering uses gravity to your favor, such as the top fill with anti-siphon holes, instead of having to compete with gravity it is almost always a safer situation.

Railroad cars are sometimes an exception to the rule. Compatibility of the material hauled and offloading can sometimes dictate that dip pipes from the dome to the inside bottom of the tank are used to fill and/or unload. A hose from the dip pipe is connected to the storage tank or to a pump which goes to the storage tank. The rail-car is slightly pressurized in order to prime the pump or in the case of direct connection to the storage tank pressure is increased enough to facilitate direct offloading. In either case, check valves are necessary to avoid refilling the rail car from the storage tank in case of transfer pressure loss. Rail cars are an unique breed and have their own set of regulations. There are more exceptions to the rules than there are rules.

Good Luck, Old Salt

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#12

Re: Tank Inlets From Bottom

07/26/2011 12:16 AM

Another reason for bottom fill 'anti-sedimentation' if the material is prone to settling or stratifying.

2ยข added to all above good inputs.

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34point5 (1); Abdel Halim Galala (1); bhalchandra (1); CaptMoosie (1); furio (1); old salt (3); pritam (1); PWSlack (1); rajeswari (1); Tornado (1)

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