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stefanhanoi
ICE Newbee
Joined: Oct 24, 2009
Posts: 3
Location: Hanoi
Status: Offline
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 Posted:
Nov 15, 2009 - 02:42 AM |
 
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| Post subject: Calibration During Commissioning? |
Hi All,
we (gas separation plant) are using pressure Transmitters, dP Transmitters, both with a factory set range, according to our process requirements. They support HART and are connected to the DCS via 2...40 mA interfaces. In addtion to that we use RTDs (3 wire interface).
During commissioning of the plant we plan to do a function check with each sensor, i.e. apply a pressure, temperature change, etc. to each sensor and look that we get a corresponding result in the DCS. This should check the cabling as well as the functioning of the sensor.
My question:
Should we do a full calibration for each sensor (TX, RTD....), i.e. compare the reading with a reference at min. 5 test points, or should it be enough to rely on the factory test that has been done before shipping?
I plan to check that the accuracy within the span where we use the device (i.e. our process range) is acceptable, based on manufacturer's specifications, but think that otherwise we can spare us the lengthy and expensive calibration of each sensor.
What do you think? Experiences? Practices in your industry?
Thank you for any comments.
Stefan |
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Instro
ICE Newbee
Joined: Mar 10, 2009
Posts: 4
Location: New Zealand
Status: Offline
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Nov 22, 2009 - 02:05 AM |
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Stefan - you need to determine the consequences of an incorrectly calibrated instrument. Do you trust the supplier?
In a Gas separation plant I would expect you would have a lot of paper work and cross checks to perform during commissioning - that all have to be signed off by a qualified, experienced and competent engineer. |
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stefanhanoi
ICE Newbee
Joined: Oct 24, 2009
Posts: 3
Location: Hanoi
Status: Offline
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Nov 22, 2009 - 02:56 AM |
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Instro,
thank you for your reply. I was wondering already, whether nobody else has some comments about something basic like calibration.
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you need to determine the consequences of an incorrectly calibrated instrument.
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Well, I think an instrument that is working, but shows completely off readings is unlikely and can be easily detected.
If the readings are outside of manufacturer's specification, but not easily recognizable, then yes ... what are the consequences? I am no process specialist, and will consult with them, but I expect that there are only a few values that have to be measured with high accuracy.
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| Do you trust the supplier? |
I've also come to the conclusion that this is a core question.
Trust is an issue of experience. A group's experience is bigger than that of a single individuum. So, what are the experiences of the members of this forum in regards to
Yokogawa pressure and diff. pressure transmitters?
Do they work ex factory as specified, or are there instances where all the HART tests show "OK", but in fact the readings are off the real value, i.e. outside of the accuracy specifications?
The other sensors are
PT100 (in general, and especially those made in China).
Any experiences that their accuracy ex works is worse than specified?
I assume that many members here did already calibrations. Can you share your experiences?
Thanks a lot!
Stefan |
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sirisha
ICE Student
Joined: June 11, 2007
Posts: 28
Location: Karnataka
Status: Offline
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Jan 20, 2010 - 09:20 AM |
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Hello stephan,
I think u better check the following points.
1. First check up the range and unit of measurement u have asked in ur requirement.
2. Compare it with the transmitters supplied to u. Confirm both are same.
3. If they are not same, u can use ur HART communicator to re-range and configure the transmitter. In this case u need not calibrate.
4. If u are supplied with calibration and test certificates of the transmitters, u need not calibrate the instruments.
Regards,
Sirisha |
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Mike_w
ICE Newbee
Joined: Jan 14, 2010
Posts: 5
Location: CA
Status: Offline
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Feb 08, 2010 - 03:06 PM |
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If you are going to be shooting loops and you have your hart communicator with you, You might as well be saving all the saved configurations from the field devices for reference if there are any kind of issues. Beats trying to track down spec sheets late at night |
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fundu_instru
ICE Expert
Joined: June 20, 2006
Posts: 180
Location: Singapore
Status: Offline
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Feb 15, 2010 - 01:59 PM |
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Above all solutions are well accepted.
However, this is purely client specific.
If client is insisting to have 5 point test during commissioning then it must be followed by physically applying pressure.
Even if the same are not applied, at least at site before erection calibration check has to be done that too physically. You can not escape from that.
And moreover, this is industrial practice as far as almost with all major oil and gas players. |
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Carl_E
ICE Student
Joined: May 30, 2010
Posts: 11
Location: Illinois, USA
Status: Offline
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May 30, 2010 - 08:58 PM |
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| stefanhanoi wrote: |
| PT100 (in general, and especially those made in China). |
A major US instrument manufacturer recently moved its pressure transmitter manufacturing from the US to China.
Whereas previously we had NEVER, in 21 years, had a failure of that brand PT out of the box, we now have problems with everything.
Any time production moves, there's problems. I'm not particularly pointing a finger at China, but that's where this production line went.
Caveat Emptor |
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alexis_sumulong
ICE Newbee
Joined: Nov 17, 2011
Posts: 1
Location: UAE
Status: Offline
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Nov 17, 2011 - 05:11 AM |
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[quote="fundu_instru"]If client is insisting to have 5 point test during commissioning then it must be followed by physically applying pressure.
For the 5 point testing, we need another pressure instruments for comparison. right? do we need a calibrator or tester 4 times higher than the field instruments? Thanks |
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goparaju1171
ICE Newbee
Joined: Nov 16, 2011
Posts: 1
Location: viskhapatnam
Status: Offline
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Nov 17, 2011 - 11:18 AM |
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Dear Stefan,My opinion is covering the normal operating range must include in our loop calibration.One more doubt will you follow temperature loop calibration from sensor to DCS display requires temperature bath to be carried to feild........pl clarify |
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patience |
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