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16 comments
Active Contributor

Join Date: Nov 2007
Posts: 22

Sight Glass Reading

05/08/2012 4:00 AM

please check the attached picture

i want to know where is my zero in the sight glass

Is it point # 1 or point # 2

and please explain why

i get confused

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Guru
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#1

Re: sight glass reading

05/08/2012 4:02 AM

2, though it's a false zero on account of the lute between the bottom connection on the vessel and the bottom connection on the sight glass.

One hopes it isn't on a fired boiler.....

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#2

Re: sight glass reading

05/08/2012 4:12 AM

it is an interface level on a settler

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Guru
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#3
In reply to #2

Re: sight glass reading

05/08/2012 4:13 AM

Phew!

What happens when the lute blocks up with settled materials?

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#4

Re: sight glass reading

05/08/2012 4:16 AM

it is gasoline - water settler

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Guru
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#5

Re: sight glass reading

05/08/2012 4:40 AM

Is there anything else the forum needs to know?

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#11
In reply to #5

Re: sight glass reading

05/09/2012 12:03 AM

This part of the forum (yours truly) needs to know what your definition of a 'lute' is! I gather you are referring to the 4-bend offset in the lower line between the vessel and the sight glass.

Then I'd like to know the purpose of the offset. It seems like it would prevent you from seeing the gasoline/water interface in the sight glass until the water reached level 2. ...sort of like a hysteresis in displaying presence/absence of water?

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#6

Re: sight glass reading

05/08/2012 4:43 AM

i want to know why point 2 is the zero?

and what is point 1 represent?

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Guru
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#7
In reply to #6

Re: sight glass reading

05/08/2012 5:04 AM

Because liquids find their own level on the basis of the direction of the gravitational acceleration vector. Once the lute is full, between level 1 and level 2, it cannot drain from there. So point 2 is the indicated zero on the instrument, whereas the true zero is at 1 in the vessel. That is why level 2 is a false zero, and the only zero the instrument can present at this time given the current piping connection at the bottom of both the instrument and the vessel.

It ain't any simpler than that.

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#8
In reply to #7

Re: sight glass reading

05/08/2012 5:12 AM

so in other words if the level become below point 2 i will not know the real level in the settler for that i should make it my zero

am i right?

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#9
In reply to #8

Re: sight glass reading

05/08/2012 5:19 AM

<...if the level become below point 2 i will not know the real level in the settler...>

Correct.

<unsubscribes>

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#10
In reply to #9

Re: sight glass reading

05/08/2012 6:20 AM

thanks

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#14
In reply to #6

Re: sight glass reading

05/09/2012 11:33 AM

Omar,

The "zero" indication depends on the process application and the fluid being measured.

In many applications there is a "minimum" acceptable level established by the process design engineer.

Since the application is a "settler" the solids and heavier fluids will migrate (settle) to the bottom of the vessel.

I am pretty sure that Point 2 would be the design calculated "bottom" of the striated gasoline layer based upon fluid temperature and specific gravity.

Therefore Point 2 would be the "zero" point and everything above that level would be ready for extraction as clean gasoline and anything below that control point level being "unusable" or needing further refining.

Point 1 would be the "bottom" of the settled fluids other than gasoline.

The difference between Point 1 and Point 2 would be the amount of unusable/contaminated fluids and/or fluids needing to be further refined or removed from the process.

Everything below Point 1 to the bottom of the settler would be solids or semi-solids (sludge) needing to be extracted/removed from the settler on a regular time interval or when the level gets above Point 1.

Hope this helps.

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#12

Re: Sight Glass Reading

05/09/2012 8:58 AM

The reason point 2 is the zero is that the level inside the leg going to the bottom of the level gauge is always full, so point 2 is the zero point for reading level in the indicated system, if you want it lower remove the "Dog Leg" and connect directly the bottom connection to the level gauge bottom connection then point 1 would be the zero level indication.

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#13

Re: Sight Glass Reading

05/09/2012 9:18 AM

Good Morning all;

Great answer PWSlack!!!

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#15

Re: Sight Glass Reading

05/12/2012 2:50 AM

thanks all

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Guru
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#16

Re: Sight Glass Reading

05/24/2012 12:20 PM

Dear Mr.Omar Badros,

Undoubtedly at Point No.2 to be taken as basis and seen, but NOT at Point 1. Because if level falls below 2 in the vessel, it cannot reflect the true level in the vessel.

Thanks,

DHAYANANDHAN. S

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Bet Green (1); dhayanandhan (1); dkwarner (1); Omar Badros (6); PWSlack (5); SHOCKISCAN (1); vargaalex (1)

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