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Power-User

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Level Gauge Centre—Centre C-C Distance

12/27/2016 7:14 AM

Dear All,

While selecting level gauges, different C-C distances are provided for level gauges.

With normal level fill, I can extend 50% up from normal & 50% down below normal level (considering the minimum nearest available C-C distance).

So is there any reason to select gauges with higher C-C distance?

Regards,

Jose

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Guru

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#1

Re: Level Gauge Centre- Centre{ C-C} distance

12/27/2016 7:39 AM

50% of what?

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Guru

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#2

Re: Level Gauge Centre—Centre C-C Distance

12/27/2016 1:46 PM

No.

Then again, you might want to, but we can't know the reason for this, nor why you would want to.

Ask your gauge supplier, and tell him why you asked the question.

Do let the forum know what they say. I can't wait to hear your report.

Thanks!

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Guru
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#3

Re: Level Gauge Centre—Centre C-C Distance

12/27/2016 2:20 PM

How can the level be more than 50% higher than 50% or less than 50% by 50% (of the tank)? This sounds a bit off. Do you mean 150% of "normal" is still inside the capacity of the tank, and that 50% below normal is not on the bottom of the tank?

Why are we even dealing in % reading, rather than absolute level?

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Guru
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Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting ["brexit" - ugh] as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
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#6
In reply to #3

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 8:03 AM

Why is there not a "Good Question" button (rhetorical question - NNTR)?

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#4

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 3:17 AM

<...normal...>

The whole idea of a tank is to allow the level to go up and down. If the idea is to maintain constant level, then get rid of the tank: "What you don't have, cannot leak" - with apologies to the late Dr. Trevor Kletz, a globally-recognised process safety guru.

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Associate

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#5

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 7:35 AM

I believe what you are asking for is the distance of travel in the bubble.

Greater (wider) lines indicate Less accuracy. While more lines, mean more accuracy in the distance of measure up to maximum CC-distance. Standard visible length is always less than C-C distance. The maximum operating pressures range, and maximum operating temperatures range.

So the reason for higher C-C is for more accuracy.

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Power-User

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#7

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 8:20 AM

It is often helpful to be able to observe upset conditions, either directly or remotely, if it is instrumented. When something goes wrong, then it is perhaps the only way to know what is going on inside the tank, to help you tune the loop, or diagnose some external problem.

If your level is outside of the sight glass, you have no idea what is going on. Might be OK, though usually the investment in process knowledge pays off easily, sometimes on the first incident.

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#8
In reply to #7

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 9:47 AM

If someone is sitting in the control room, and looking at the RO tank level gauge physically, does he/she know what is going on? No.

If someone is sitting in the control room, and the RO tank level is not being XMT'd to the control room on screen, does he/she know what is going on? No.

If the RO tank level is on screen in the control room, does the operator know what is going on? Maybe, depends on if it is break time. Break time!

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Power-User

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#9

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 11:55 AM

Q ) eg if keep gauge with c-c distance of 470 mm near normal fill level with 235 mm up and down clearance , operator in field still can see normal level

then why ever to consider high c-c distance of eg 1740 mm

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Power-User

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#10
In reply to #9

Re: Level Gauge Centre—Centre C-C Distance

12/28/2016 12:06 PM

How do you troubleshoot the process if you don't know what is going on? Maybe you have other instruments? If so, then this may be a convenience device, and you can produce without it (why install it, as it is a potential failure point?).

Fine when everything is normal, can be costly to operations considering Mean Time To Repair, often the diagnosis of the failure is the bulk of lost production time. Will pay for that longer gauge maybe in the first incident of non-perfect operation.

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Guru
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#11
In reply to #9

Re: Level Gauge Centre—Centre C-C Distance

12/29/2016 3:31 AM

<...then why ever to consider high c-c distance of eg 1740 mm...> Because the visible distance needs to be less than the c-c distance by 2x the distance between the end of the viewing component to the centre line, one at the top and one at the bottom, to allow for the fixings, tees and elbows necessary to mount the equipment onto the vessel. Clearly, the visible distance needs to be sufficient to cater for the expected range of operating levels in the vessel, and different heights of vessel will need different ranges, and therefore different sizes of instruments to be fitted.

This would be self-evident from an image of the equipment in question, which has been withheld from the forum so far.

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#12
In reply to #11

Re: Level Gauge Centre—Centre C-C Distance

12/29/2016 3:48 AM

Thanks

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