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Anonymous Poster #1

Crude Oil Tank Recalibration

12/21/2020 6:36 AM

We need to modified our crude oil storage tank by increasing its height (by about 1.5meter to install new type of Radar gauge)

do we need to re-calibrate this tank and its table

( i.e. is it consider kind of reference gauge point deformation )

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#1

Re: Crude Oil Tank Recalibration

12/21/2020 7:15 AM

You haven't said if you plan on increasing the amount of oil stored, or if the tank addition is just to accommodate the new measurement device....It would depend on the oil level changing or not, and possibly local authority standards for this type of alteration...

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Anonymous Poster #1
#4
In reply to #1

Re: Crude Oil Tank Recalibration

12/22/2020 2:07 AM

stored Oil amount will not increase, only to accommodate the new measurement device

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Guru
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#2

Re: Crude Oil Tank Recalibration

12/21/2020 12:02 PM

Why does the HazOp Study report on the plant modification not say either way?

A HazOp was carried out, wasn’t it?

<...We...> did have a Process Engineer, Operations, Mechanical Engineering and Instrumentation and Controls Engineering represented there together with Operations, didn’t <...We...>?

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Guru

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#3

Re: Crude Oil Tank Recalibration

12/22/2020 1:17 AM

Surely there would be no need to raise the storage tank by 1.5m only install a standpipe to account for the extra distance from the measuring element to the full mark.

Have carried out this modification before. Be aware that the beam angle of the detector does not impact on the bottom of the standpipe else it will give full readings or overfull reading when measuring. This problem can be negated by a larger diameter standpipe or if the radar is configurable by adding blanking to the detected signal at the standpipe/tank interface.

Another trick I have used is to convert the tank depth for non linear tank shapes, conical bottoms into volumetric values by the use of Fx functions if your PLC supports such protocols. By using nested Fx functions any shape of tank can be thus converted to m3, tons, litres.

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Anonymous Poster #1
#5
In reply to #3

Re: Crude Oil Tank Recalibration

12/22/2020 2:26 AM

sorry for mistake

we would install standpipe to install the new radar gauge

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#6
In reply to #5

Re: Crude Oil Tank Recalibration

12/22/2020 6:25 AM

You would only need to set the 0 and 100% values into the radar transmitter for the empty and full tank making sure that the radar beam looks at the bottom of the tank and does not impact on the side of the tank causing scatter.

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Anonymous Poster #2
#7

Re: Crude Oil Tank Recalibration

12/22/2020 6:34 AM

Never mind re-calibration; if you afre installing a new radar gauge you will need to calibrate it period.

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#8

Re: Crude Oil Tank Recalibration

12/22/2020 8:52 AM

As others have pointed out, the tube diameter/height ratio for the new mounting tube must be such that the sensor wave does not impact the tube. All manufacturers clearly detail this in their installation guidelines that are included as part of their instruction manual with most also providing pictures - I assume for the reading challenged ;). If this is a new probe, the sensor and receiving display will need to be set up with a minimum two point level calibration, empty and full (along with the scaling value that full should display on the readout). You did not state if your storage tank is a cylinder (assumed yes) or if it is oriented in a vertical or horizontal position. If vertical, and there is no variation in the diameter as you travel from bottom to top, then a simple two point calibration is all that would be needed. If the tank is mounted horizontally, the hold volume is not linear with height due to the changing geometry. Most manufacturers have software that can automatically calibrate to this given assorted dimensional inputs while others offer a multi point calibration option. Does this new sensor have the same output as the old one? Have you confirmed that input card in the plc (if going into a larger control/monitoring system) or a stand alone display is compatible with the signal from the new sensor?

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#9

Re: Crude Oil Tank Recalibration

12/22/2020 8:01 PM

There is no need to change the tank calibration numbers. They will stay the same, since you are maintaining the original capacity.

You do need to calibrate the sensor to report the same values as the previous sensor reported, height of the oil from the bottom of the tank.

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Anonymous Poster #1
#10

Re: Crude Oil Tank Recalibration

12/23/2020 6:41 AM

Its floating roof oil storage tank,
I'm not worry about the radar accuracy reading only, I'm worry about tank certificate after reference gauge point changed (the measuring level will converted to volume, using the calibration table after being uploaded to the system). also (As per OIML R71 if reference gauge point change, tank should re-calibrate)

(I thought to attach the doc. but it looks this feature omitted )

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#11
In reply to #10

Re: Crude Oil Tank Recalibration

12/23/2020 11:59 AM

The tank reference gauge point doesn’t change, you are just changing the instrument that reports the tank level.

The documentation associated with the instrument needs to relate the installation dimensions to the tank gauge reference point.

This should be no different in concept than the original instrument documentation, where a wire, switch, density sensor uses the gauge point on the side of the tank to report the level.

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Anonymous Poster #1
#12
In reply to #11

Re: Crude Oil Tank Recalibration

12/24/2020 2:56 AM

(The tank reference gauge point doesn’t change) no it's changed

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#14
In reply to #12

Re: Crude Oil Tank Recalibration

12/24/2020 1:02 PM

If you only plan to fill the tank as far as it was filled before, the physical reference point is unchanged. The instrument is calibrated to display the height of the roof as measured from the ground, that does not change. The calibration parameters for the instrument are very specific to the type of instrument, they must conform to the physical reference point, and you must show just how they conform to the reference point. The calibration and setup parameters are NOT the reference point.

Consider a head level gauge on this tank. The reference point is the height of the liquid column above the sensor location, plus the distance to the tank bottom. The calibration parameters are the liquid specific gravity, maybe temperature, and the weight of the roof. These are not the tank gauging reference points, they are instrument calibration parameters to allow the instrument to report according to the tank gauge reference point, which is and always will be the height of the liquid in the tank, converted to volume.

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#13
In reply to #10

Re: Crude Oil Tank Recalibration

12/24/2020 7:45 AM

<...modified...worry about tank certificate...>

Consider it an historical artefact now the tank has been modified.

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#15

Re: Crude Oil Tank Recalibration

12/26/2020 10:13 PM

"do we need to re-calibrate this tank and its table"

Yes, you will need to calibrate (not re-calibrate since the instrument is new).

If I modify a tank and/or use a new instrument, I would calibrate the instrument because the output of level indicators, unlike temperature or pressure, is dependent on the vessel it is attached to.

Radar can be calibrated to read the distance from the instrument but it can't tell you if the level is 0, 100, or whatever percent level the tank has. You have to tell the instrument what distance is 0% and what distance is 100% and the only way to do that accurately is to calibrate.

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Anonymous Poster #1
#16
In reply to #15

Re: Crude Oil Tank Recalibration

12/27/2020 7:43 AM

I'm talking about tank calibration itself and certification .
NOT the radar calibration.
do I need to worry about the tank certificate spoil.
I need reference standard or legislation to what you say

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#17
In reply to #16

Re: Crude Oil Tank Recalibration

12/27/2020 12:08 PM

See #13⇑.

If the <...Tank...> is on the insurance register for the facility, and therefore subject to periodic condition assessment in pursuit of burst/collapse indemnity cover, then these are the sorts of questions needed to have been asked on the topic from the insurance provider before the tank was modified.

If the <...Tank...> is on the insurance register and the modifications have been taken without that party's involvement, then it can in principle walk away from any claim in the event of an incident involving it.

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#18
In reply to #16

Re: Crude Oil Tank Recalibration

12/27/2020 3:16 PM

If you made any modification to the structure of the tank then that needs to be documented, and perhaps evaluated by a professional engineer. Perhaps by the authority that issued the original certification.

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Anonymous Poster #2
#19
In reply to #16

Re: Crude Oil Tank Recalibration

12/27/2020 5:12 PM

How did you calibrate the tank before?

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#20
In reply to #16

Re: Crude Oil Tank Recalibration

12/27/2020 9:38 PM

Okay, let's put it this way.

Previously, your tank 0 and 100% distances were: 2,000 cm (0%) and 500 cm (100%) giving you a tank level height of 1,500 cm.

The new installation will change the distances to: 2,002 cm (0%) and 502 cm (100%) giving you with a tank level height of 1,500 cm.

The tank level height didn't change, right? So, it's still the same. Well, not from the instrument's point of view.

If you copied the configuration of the old transmitter, it will still consider 2,000 cm as 0% and 500 cm as 100% and give you a reading of -0.13% when the tank is empty and 99.87% when the tank is full.

Is 0.13% difference acceptable? I don't know. What's your tank's diameter? How much oil is represented by that 0.13%.

If you'll be very careful with the installation so that the radar distances will not change, then maybe, you can leave after installing the instrument. I don't know what you're company's rules or what the law says about that. All I know is this:

If you change anything in a measuring system, you can assure your auditors that things are as you claim they are by performing a calibration and adjustment.

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#21
In reply to #16

Re: Crude Oil Tank Recalibration

12/28/2020 3:32 AM

Given <...We...>:

How are modifications carried out to other tanks at the facility and why should the procedure for this one differ from those applied to these other tanks?

What do colleagues at the same facility recommend? What documentation is available following their particular modifications?

Why is there no local procedure for modifying tanks available at the facility if this sort of modification has been carried out before? Why did the facility not learn from previous experience, and document it?

What to acquaintances in other facilities in the same country do? What can be learned from these individuals’ experiences?

This forum cannot supply training in the use of the telephone in answering these questions, only the recommendation that this is the tool of choice in finding the solution to this particular problem.

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