Golgappa.net | Golgappa.org | BagIndia.net | BodyIndia.Com | CabIndia.net | CarsBikes.net | CarsBikes.org | CashIndia.net | ConsumerIndia.net | CookingIndia.net | DataIndia.net | DealIndia.net | EmailIndia.net | FirstTablet.com | FirstTourist.com | ForsaleIndia.net | IndiaBody.Com | IndiaCab.net | IndiaCash.net | IndiaModel.net | KidForum.net | OfficeIndia.net | PaysIndia.com | RestaurantIndia.net | RestaurantsIndia.net | SaleForum.net | SellForum.net | SoldIndia.com | StarIndia.net | TomatoCab.com | TomatoCabs.com | TownIndia.com
Interested to Buy Any Domain ? << Click Here >> for more details...

hw to calibration a control valve?

Answer Posted / sajid ali khan

In addition to the Calibration, it is also crucial that the
Control Valve (CV) response matches the demands of the
controller.
Normally, the CV is calibrated and checked as already
mentioned in this post, but please appreciate that in real
operation, for most of the time the controller output will
change in very minor amount to counteract the process
upsets or set point changes and the CV need to respond
rapidly and effectively to those changes. Thus if you
observe any CV, or note its trend from the Control System,
you will see movements in fractions of mA/psi etc. Very few
CVs will go to the full close position and valve going to
the full open position is even rarer.
Also, it is necessary that the CV overcomes any stiction,
has minimum hysteresis as well as little dead band.
Therefore, it is important the valve be checked for minor
changes.
How to check that:
1. Move the valve to any position other than at its
extremes, somewhere in the middle.
2. Find a safe spot on the CV stem where you can feel the
minor CV movement against a fixed part of the CV Body. Put
your finger firmly on that spot of the CV Stem. I
repeat “SAFE SPOT,” otherwise if the CV operates suddenly
your finger may be injured.
3. If the CV has a digital positioned with a feedback, the
observation may be simpler and finger feeling may even be
not necessary at all.
4. Now closely observe the CV input signal, preferably the
pneumatic signal on a 6 inch dia pressure gauge of at least
0.5 % accuracy. If digital pressure indicator of similar or
better accuracy is used that would be better.
5. While applying input signal move the CV a small amount,
then apply reverse signal very gently and slowly, and feel
the CV stem movement with your finger, the stem should
move. The numerical value of the input signal against the
minor can be noted from the factory test data of the valve.
In case that is not available it would be known by
experience.
6. Repeat this exercise at two or different CV openings and
always check in forward and reverse directions, till you
are confident of the CV performance.
7. In case valve sticks, shows excessive dead band etc,
then loosening of the stem packing or even CV opening for
inspection to check stem/plug misalignment, or hardened
stem packing may be the culprit.
Regards,
Sajid Ali Khan
engineersajid52@gmail.com

Is This Answer Correct ?    7 Yes 5 No



Post New Answer       View All Answers


Please Help Members By Posting Answers For Below Questions

Capacitance, resistance ( colour coding ), parallel & series circuits.

2216


Tell about your IFFCO plant visit.

2072


Introduce yourself which is not present in your biodata?

2430


how 3 out of 2 Logic/interlocks works? give brief explanation with help of diagram.

2298


how to calibrate Necleuonic level transmitter.?

2104


How do you identify between actual alarm and false alarm in a Temperature Transmitter in SCADA based Control System

1358


which type of filter gives the constant phase characteristics?

1922


Gas equation

1845


whats the abbreviation of IOP? is it instrument of power or input open problem?

1157


what is wave length were using ?

1892


if my flow is 20000 m3/h than which range of DPT i have to use????

1835


hi my name is rakesh patel i just complited my be in instrumentation & control now i am going to working as a validation engineer in a poject department so what is a scope in a future as a validation engginer ? what line is good for me can any bady give me complete solution please? your regard rakesh patel

1964


What is the principle of capacitance type level transmitter?

1074


what is difference between fork type and capacitance type level switch. where it is using

2382


you are on site,the plant trips,you are approached by operations,what do you do?

2241