When we have to change the field instruments?

[mohdalharbi]

Field instrument we have to change after certain time even if it is working, this due that the maintenace cost after years (say 10) will increase and frequently defect will occured.I heard this time is 10 but i am not sure it is the standard.

 

[jsummerfield]

It is more common to change the field instruments when the technology no longer fits the application than a 10-year routine. I am sure that many Rosemount 1151 series transmitters are still in operation from the 1070's.

If routinely changing the instrument, consider a review of how each loop performs and the problems that the technicians encounter. This permits you to design new installation details that eliminate some process related problems.

Consider routine testing of calibration and settings for the safety shutdown instruments. Offshore applications test most instruments quarterly.

John

 

[IRstuff]

Service life has recently been defined in some military procurements as when the cumulative repair cost equals the cost of a new unit.

TTFN

 

[bmsg]

I do not think that field instruments have to be changed in any particular schedule.
Some field instruments, if they fail, will cause costly plant downtime or create a safety hazard. For such instruments, predictive maintenance technique, if available, may be used (such as, available instrument diagnostics). In such situations, if the instrument itself is very cheap (like an RTD, say), you may like to replace it after a time (depending on your experience) if it has not failed by then.
Otherwise, I do not think, instruments have to be changed, unless they have failed. You only require to have a regular amintenance sechdule (such as, re-calibration, etc.), - at intervals depending on your experience or on the manufacturer's recommendations.

 

[TangoCleveland]

jsummerfield wrote:
I am sure that many Rosemount 1151 series transmitters are still in operation from the 1070's.

That's just after the Battle of Hastings, is it not?

Larry

 

[jsummerfield]

OK, 1970's.

I also saw my typo. A sun dial may last that long. I see MTBF data nearly that long too. Statistics.

John

 

[HCBFlash]

Like many, I'm cursed with having to work with some who feel that replacing something with "a new one" will make everything better. IT JUST AIN'T SO!

1- evaluate performance - current and historic
2- determine if an EXACT replacement is available
3- determine if a replacement unit that will definitely be entirely compatible with the present system is available, and that specifically improves a known current problem.
4- determine the full costs of purchasing AND changing/installing as well as configuration, calibration, and tuning - including "downtime" and other impacted processes.


... or just go ahead and put in a new one

remember: An opinion is only as good as the one who gives it!