Calibration

February 20, 2019 | Author: Bhegz Escalona | Category: Observational Error, Calibration, Accuracy And Precision, Uncertainty, Metrology
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Calibration...

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Instrumentation Calibration, Design and Techniques

Instrumentation and instrument What is instrumentation?  In general defnition this can be defned as the art  and  and science o measurement and/or control. Is

achieved by using an “instrument” .

Instrumentation based on industrial application: “It is the application o instrument or the purpose o measuring, observing, transmitting, indicating, recording, monitoring, and controlling any industrial process variable”.

What is an instrument?  Is

any device used directly or indirectly in order to accomplish an objective or task.   In Instrumentation, an instrument is any sensing, measuring, transmitting, indicating, or controlling device associated with a process or system. E. !easuring a body temperature using a thermometer.

Instrument application categories and functional divisions. Factory

automation instruments Plant safety or safeguarding instruments Product Quality monitoring/control instruments Environmental condition monitoring /control instruments. Process variable measurement and control instruments.

Implementing instrumentation •

o! is instrumentation implemented?

". #ingle or #tand alone #ystem. $. %omple #ystem

Instrumentation system "nstrumentation system # is an arrangement o two or more instruments connected together to perorm a unifed task.  Each instrument operates independently according to its specifc task. &ailure rom one member o instrument, means ailure o the entire instrument system.  #implest orm o instrumentation

Automation  Is

a system concept that utili'es instrumentation system to perorm a certain task or se(uences o operations in an automatic manner or without human intervention.  )oth maimi'ing (uantity o production and (uality and durability o produced goods is greatly improved.

AUTOMAT! "#O$%%  Is

a process or se(uence o production activities done in an automatic manner. %&PE' (F )*%(+)%E P-($E''  *ighly !echani'ed +rocess  %hemical

and +hysical +rocess

Maintenance

What is Maintenance? ll

actions necessary or retaining an item, or restoring to it, a serviceable condition, include servicing, repair, modifcation, overhaul, inspection and condition verifcation.  -eep systems e(uipment in working order.  o repair the e(uipment ater &I012E.

&uestion? 3hy

do we need maintenance4 3hat are the costs o doing maintenance4 3hat are the costs o not doing maintenance4 3hat are the benefts o maintenance4 *ow can maintenance increase proftability o company4

"urpose of Maintenance •

• • •

ttempt to maimi'e perormance o production e(uipment e5ciently and regularly +revent breakdown or ailures !inimi'e production loss rom ailures Increase reliability o the operating systems

"rinciple Ob'ectives in Maintenance •

 o achieve product (uality and customer satisaction through adjusted and serviced e(uipment • !aimi'e useul lie o e(uipment • -eep e(uipment sae and prevent saety ha'ards • !inimi'e re(uency and severity o interruptions • !aimi'e production capacity 6 through high utili'ation o acility

Maintenance Ob'ectives •



!ust be consistent with the goals o production 7cost, (uality, delivery, saety8 !ust be comprehensive and include specifc responsibilities

Maintenance $osts • • • •

%ost to replace or repair 0osses o output 9elayed shipment #crap and rework

(ailure &ailure

6 inability to produce work in appropriate manner E(uipment / machine ailure on production :oor 6 worn out bearing, pump, pressure leaks, broken shat, overheated machine etc. E(uipment ailure in o5ce 6 ailure o power supply, air;conditioned system, computer network, photocopy machine .

  %ontinue troubleshooting by applying Elimination by Input / Output Test method.

?.

 pply Root Cause Analysis 72%8.

limination by /!eductive Approach0  roubleshooting by eliminating one component rom the other component in a loop by deduction or logical thinking method.

limination by !eductive Approach ".

1nderstand properly the etent o the problem based on given acts, data and symptoms.

$.

#tart troubleshooting by frst using Elimination by Deduction   method. I the cause o the problem is highly identifed, perorm corrective action at once to solve the problem.

>.

  %ontinue troubleshooting by applying Elimination by Input / Output Test  method.

?.

 pply Root Cause Analysis 72%8.

1uidelines in using !eductive Approach: ".naly'e

the etent o the problem based on given acts or symptoms.

$.%ome

up with a probability per element based on given acts and decide which element most likely to cause the problem.

>.2ectiy ?.pply

problem i already possible.

2oot %ause nalysis 72%8.

limination by /Input2Output Test0 or /$ause 3 ffect Method0  roubleshooting by applying an input and monitoring the output per loop component based on elements input/output relationship table.

1uidelines in using Input2Output Test: ".

$.

>.

?.

Established the details o each loop component o a given control loop. 1sing the degree o probability based on the result o your “9eductive [email protected], perorm “Input/[email protected]  est. 2ectiy problem encountered while doing input/output test. pply 2oot %ause nalysis 72%8.

%ignificant use of /Input2Output Test0 or /$ause 3 ffect0 Input/Autput est i properly administered is a very e=ective tool in identiying e(uipment unctional, potential and hidden ailures. ny ailure identifed during the test could trigger appropriate maintenance action/s.

Applying #oot $ause Analysis ,#$A-

What is a /#oot $ause Analysis0 It is a systematic approach to maintenance problem analysis. It emphasi'e mainly on the main cause or root cause o the problem not just the temporary solution.  his concept could be well implemented by considering the = (uestionsB  Is

the problem clearly identifed and understood based on given symptoms4  Is the corrective action done really corrects the problem4

Other factors need to be considered in troubleshooting instrumentation system problem: • •



 0oop confguration / system integrity.  Instrument type, installation, calibration C physical conditions.  Environmental conditions.

In general4 the follo+ing simple guide 5uestions +ill help an Instrument Technician perform effective maintenance: • • • • •

3hat is the problem4 3hat do we think caused the problem4  3hat evidence do we have about the causes4  3hat solution7s8 do you have in mind4  *ow will the solution7s8 eliminate the cause o the problem4

$orrecting Instrument Output response: 3hat do you think will be your courses o actions i ater doing an input/output test, the actual measured values are signifcantly di=erent rom the desired values4

Do Adjustment

Why Instrument $alibration is 6ecessary?  he successul operation o any automated industrial process depends on the accuracy  and perormance  o each instrument in the measurement and control loop. Instrument calibration helps to ensure that a process operates e!ciently and saely  within plant specifcations and produces a product o optimum quality"

7ample n Instrument technician is conducting an Input/Autput test o an I/+ converter shown in the fgure. Input is ?;$D m rom 2% and output is >;" psi.  he resulting s &ound I/A  able is shown belowB

(indings )ased on the s &oundB I/A test able below, the I/+ shows an error o D.$psi in every test point. In;order to eliminate the error, the instrument sensitivity was adjusted. ter adjustment, another Input/Autput test was conducted, and the result is shown on the I/A able on the right. his time the error in psi per test point is D. the process o adjusting the error is what is called %0I)2IAF.  he able that contains the data ater calibration is called s 0etB I/A est As 8eft: I2O Test Table As (ound: I2O Test Table  able.

$alibration

$alibration “Calibration is an insurance policy that verifies the accuracy of test instruments.”  %alibration is the act o checking and veriying the accuracy o a measurement instrument by comparison with a reerence standard. +roperly calibrated instruments perorm to manuacturers published specifcations. 2egularly calibrating measurement instruments ensures the accuracy o measurements that are relied upon during design and manuacturing test.

Why $alibrate? 3hile most instruments that are evaluated and calibrated normally pass the test, instrument perormance can change over time. here are several actors that can contribute to this change including drit, normal wear and tear, lack o proper maintenance, user error, and improper use and abuse o e(uipment. 2egular calibration ensures that test and measurement instruments are operating at a known perormance level.

Why is $alibration #e5uired? )y doing proper calibration procedure and through proper interpretation o the calibration results, instrument error/s can be identifed and be corrected.

%alibration is re(uired by law.

Instrument $alibration $ycles   %alibration is not a one;time occurrence. Instruments must be calibrated periodically to ensure specifed perormance. Each instrument re(uires a specifc interval between calibrations. his interval is determined by the instruments owner and is oten based on the manuacturers recommendations.  he original e(uipment manuacturers 7AE!8 calibration intervals are typically based on conservative perormance or the average user. &or best results, the instrument owner should use several additional actors in determining the optimal calibration interval, includingB he re(uired accuracy or the application vs. the instruments specifed accuracy. he business impact o using AA

$alibration &uality %ystem  he International Argani'ation or #tandardi'ation 7I#A8 is comprised o representatives rom various national organi'ations and has "G$ member countries. I#A develops standards or industry and trade. +artnering with I#A registered calibration providers ensures that the provider ollows standard practices. I#A HDDD is a amily o standards that provide a ramework or managing an organi'ations processes and a set o standardi'ed re(uirements or a (uality management system. I#A/IE%"JD$ is a standard used by testing and calibration laboratories. 0aboratories implement the

$alibration according to 8egal Metrology %alibration according to 2.. H$>G o $DD> 72E+1)0I% % FA. H$>G *E FIAF0 !E2A0AKL % A& $DD>8, is a set o operations establishing under specifed condition, relationship between values indicated by a measuring instrument or measuring system, or values represented by material measure, and its corresponding known values o

Instrument $alibration )loc* !iagram *nput Measurement "tandard (*M")

7nit 7nder Test (77T)

9utput Measurement "tandard (9M")

b-ac 8ote: *M"  9M" are commonly !nown as C35*43T94"+

When is $alibration #e5uired? ".Aver a period o time $.%hange in process parameters >.%hange in environmental conditions ?.%hange in instrument mounting position .)eore .)eore installation o new n ew instrument G.ter any instrument repair J.3hen process verifcation is re(uired M.Kovernmental 2egulation 7i.e.2 H$>G8 H.Ather reasons deemed necessary

9o+ often instrument is calibrated? )y practice, the re(uency o calibration depends upon the classifcation o the instrumentsB

Critical# n instrument which, i not conorming to specifcation, could potentially compromise product or process (uality and saety. 7ypical is twice yearly8 $on%critical# n instrument whose unction is not critical to product or process (uality, but whose unction is more o an operational signifcance. 7ypical is yearly8 Reerence Only#  n instrument whose unction is not critical to product (uality, not

$ost and #is* of 6ot $alibrating %alibration can be easily ignored or cycles etended beyond their recommended time rame, which may increase operational risk or regulatory compliance. Feglecting routine calibration schedules can lead to (uality and regulatory issues, increasing downtime, and increase epenses. I a company is unable to meet its customer or regulatory re(uirements, they introduce signifcant risk o business interruption, loss o operating privileges, or compromised public saety. 3hen compared with the signifcant business risks associated with non;compliance, calibration

Types of $alibration

Wor*shop4 8aboratory or )ench $alibration %alibration utili'ing deal conditions such as room temperature, humidity, room pressure, vibration C etc.  )ench %alibration is perormed in the shop on the bench with power supplied rom an eternal source. It may be perormed upon receipts o new instruments prior to installation. his provides an assurance that the instrument received is undamaged. his also allows confguration and calibration in a avourable environment. Advantages !isadvantages ;+ *nstrument is removed, cleaned and inspected+

;+ #roblem may encounter during pullout and installation+

? )ased on defnition under $.$ o the I#A Kuide to the Epression o 1ncertainty in !easurement 7K1!8, the word “[email protected] means 9A1), and thus in its broadest sense “uncertainty o [email protected] means doubt about the validity o the result o a measurement.

Measurement Uncertainty $oncept

Measured alue @ .B m)ar C Uncertainty of measurement

$ommon %ources of Uncertainty  Environmental conditions  +ersonal bias in reading values  &inite instrument resolution %alibration o standards  2ounding o measurement   !ethods C procedures o measurement  #tability o power supply and etc. 

Ishi*a+a ,fishbone diagram-: nvironment

5uipment

Temperature

Man

 3ccuracy

#ressure ibration  others

ias

4esolution

rror 

"tability  others

'irect or *nferred

9thers

Connection  wire resistance

"tability of utilities

9thers 9thers

Measurement method 3 procedure

Measurement system 3 utilities

Uncertainty can be e7pressed in terms of the follo+ing: ". $. >.

#tandard 1ncertaintyB ui %ombined 1ncertaintyB uc Epanded 1ncertaintyB # $ uc %k&

Methods of valuating %tandard Uncertainty ui $omponents: ". ype  Evaluation 7o uncertainty8 6 is the method o evaluating uncertainty by the statistical analysis o a series o observations. In this case, the standard uncertainty is the eperimental standard deviation o the mean that ollows rom an averaging procedure.

$. ype ) Evaluation 7o uncertainty8 6 method o evaluation o uncertainty by means other than the statistical analysis o series o observations. In this case the evaluation o the standard uncertainty is based on some pool o inormation such asB •

previous measurement dataO



eperience with or general knowledge o the behavior and properties o relevant materials and instrument



manuacturers specifcations



data provided in calibration and other certifcates other relevant inormation

%ample: $alculating %tandard Uncertainty ,ui) of (lo+meter and "roving Tan* in terms of %tandard !eviation ,%T!-:  "D;validation runs were conducted on a :owmeter calibration system using >DDD batch si'e. 2esults were tabulated and #9< o the :owmeter and the proving tank were calculated. 2esults shown on the let table. ui o &lowmeter is >."> ui o +roving tank is ".D

The $ombined %tandard Uncertainty ,u c-  :

 he combined standard uncertainty o a measurement result, suggested symbol uc, is taken to represent the estimated standard deviation o the result. It is obtained by combining the individual standard uncertainties ui, whether arising rom ype  or a ype ) evaluation, using the usual method or combining standard deviations.

$alculating the $ombine %tandard Uncertainty ,u c - of (lo+meter and "roving tan*: ui  of Flowmeter is >+;> and ui of #roving Tan! is ;[email protected]?

Combine 7ncertainty

(uc   ) = (ui of Flowmeter)D E (ui of #roving Tan! )D (>+;>)D E (;.0 )D

Combine 7ncertainty

(uc   )

= !.!

7panded Uncertainty ,U -:  (uantity defning an interval about the result o a measurement that may be epected to encompass a large raction o the distribution o values that could reasonably be attributed to the measurand. he epanded uncertainty denoted by * is obtained by multiplying the combined standard uncertainty uc by a coverage actor k. husO #Puc7k8 T47 Measurement  9bserved measurement E2-7

$alculating the 7panded Uncertainty ,U - of (lo+meter and "roving tan*: (") = uc (#) = !.! ($) = %&' . 

xpanded 7ncertainty

here: uc = Combine standard uncertainty # = Coverage Factor 

%tatement of Uncertainty of Measurement in $ertificates In calibration certifcates , the complete result o the measurement consisting o the estimate y  o the measurand and the associated epanded uncertainty *  shall be given in the orm 7y /# *.  o this an eplanatory note must be added he reported e*panded uncertainty of measurement is stated which in the general case should have the as the standard uncertainty of measurement multiplied by the ollowB covera+e factor #=$, -hich for a normal distribution corresponds to a covera+e probability of appro*imately / level of confidence.

8evel of $onfidence: !ost o epanded uncertainty calculations are based on coverage actor 7kP$8 and confdence level o HQ 7" chance in $D that the value o the measurand lies outside the interval8.

D. $ompliance to I%OEF;G %alibration technical re(uirements per +F# I#A/EI% "JD$B$DDD  *uman &actors 7+ersonnel8  Environmental %onditions  est C %alibration !ethods and !ethod . 1ncertainty o !easurements ?. %ompliance to I#A;"JD$ " Acceptable Tolerance

G. Acceptable Tolerance Every
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