Question { 9861 }

How to find out turn down ratio of Pressure transmitter?

Answer

Turndown RATIO= MAXIMUM ALLOWABLE VALUE/ MINIMUM CONTROLABLE
VALUE.... SIMPLY DIVIDING THE UPPER RANGE/ LWER RANGE

Question { Honeywell, 10140 }

What is cold junction compensation in thermocouples? How is
it achieved?

Answer

TC works on the principle of SEEBACK's Effect, which states
the the temperature difference is directly proportional to
induced emf, when two dissimilar metals are twisted together
and heated at end.
its equation states,
hot junction - cold junction = induced emf.
its means hot junction is the temperature measured..
cold junction means the ambient temperature unlessly
considering the compensation. we have keep the cold junction
as constant by giving a constant hot source or ice bath. so
that its easy to find the hot junction values.

Question { Atul, 7318 }

what is exat meaning of compentation in RTD ? what diffrent
between 2 wire,2 wire and 4 wire RTDs?

Answer

In RTD, we are measuring temperature through Resistance
change. Normally we are measuring this parameter in the
field. while transmitting, these signal to control panel
through cable, some additional resistance due to distance
will add upto the RTD resistance value. which shows
incorrect value. in order to overcome these, normally in 2
wire system, we will manual add/subtract some resistance
value with the measured resistance value.but it is no percise
whereas in 3 wire system, a parallely third wire run with
the two polarity wires, but its direction of current flow is
opposite to the other two. so it will cancel the line
resistance and give exact value. similarly, for more precise
and accurate measurement, we mostly use 4 wire system.
In above mentioned description, the addition of resistance
or removal of line resistance through extra wire is called
compensation for RTD

Question { 7770 }

why we require Differential pressure?Why we use Orifice Plate?

Answer

In flow measurement, we require differential pressure.
since because, Flow= Square root(differential pressure).

to create differential pressure in a pipe, we insert orifice
plate inside the pipe. in which upstream pressure will be
higher than the downstream pressure of the orifice plate.
By taking tapping from the upstream and downstream, we can
obtain the differential pressure.

Question { Vedanta, 14876 }

why drum level is increased when one of the running coal
elevations are suddenly tripped?

Answer

This is know swelling effect of the boiler drum.
Due to sudden decrease in steam pressure due to tripping of
coal elevation.

Question { 4607 }

i/p converter always for supply pessure from 3~15 psi
only !! And from where this converter bleed the air.

Answer

I/P converter gets the bleed off air from the Air compressor
unit.
From air compressor unit, air will go to a regulator
from where the Pneumatic air is supplied to the I/P converters.

Question { 7552 }

what is
the
difference
between
flow and
force ,draught
and
vaccum ,tube
and pipe?

Answer

Pipe: mass transfer( ex: only flow)
Tube: mass & heat transfer (ex: heat exchange as well as f

Question { APGenco, 6466 }

why drum level falls when one of the running coal
elevations tripped?

Answer

tripping coal elevator, Reduces the temperature inside the
boiler which incase makes shrinking effect in the boiler drum.

Question { Air Liquide, 11170 }

Why we are using 4-20 mA as Analog signal transmission
other than 3 to 19 or 2 to 18 or 6 to 22 like wise ? What
is the reason behind using 4 & 20 mA? Can anyone give
proper technical reply ?

Answer

the destination of any signal will be a Controller.
Take DCS, its input supply will be 1-5V.
from instruments, across a 250ohm resistor, the value will
reach DCS as desired 1-5V.

expl:
say 4ma is the output of transmitter.
V=IR,
V=4ma * 250 ohm
V= 1V,
say 20ma,
V=20ma*250ohm
V=5V.

Question { Hindalco, 16853 }

Why Flow measurement has to use Square Root

Answer

Normally flow is measured from Differential Pressure.
the equation states,
Flow= Square root( differential pressure).
that's why during flow measurement we are going for square
root extractors.

Question { 18673 }

why IBD Vent is kept at higher elevation than CBD ?

Answer

when water is converted into steam, huge quantity of
dissolved salts are residues of this conversion. They
normally settle down in the bottom of the Boiler drum. In
CBD, we continuously remove this dissolved salts otherwise
it will get carry over with steam and damage the blades of
turbine. Where as IBD is to remove Excess feed water which
crosses the Seperator level inside the boiler drum.so IBD is
to prevent carry over water with steam where CBD is to
prevent carry over of scales with steam.
with above description, we can easily predict why IBD is
in higher elevated than CBD.

Question { OGDCL, 9352 }

why we take 4 to 20 mA as out put of every instrument like
pressure transmittre ?why we cant take 0 to 20mA as output?

Answer

If we use 0 to 20ma, then 0 will be the minimum value and 20
will be maximum value.. In case if there is any problem in
the transmitter or in the cables, we get the value 0 but we
think it as a minimum value..we cant able to know that
there is problem in transmitter.. In order to overcome these
constraints, we went for LIVE ZERO concept as 4ma.
0 ma will be consider as DEAD ZERO.

Question { Emco, 7133 }

what is bms?

Answer

In view of thermal power plant,
BMS- Burner Management system
which is an automated Logical program which governs safe
start up and shutdown of the boiler.
it avoids human error and assures safety of each equipment
in the boiler

Question { EI Electrotechnical Institute, 35142 }

1. what is 3 point calibration & 5 point calibration?
2. If we use hart communicator to set the LRV & URV of a
smart transmitter, did we calibrate the transmitter? why?
3. Make a complet list if meterials needed to properly
connect a pressure gauge to a steam pipe using 1/2 inch
stainless steel tubing. The gauge connections is 1/2 inch
NPT-M and the steam pipe tap has a 1/2 inch female coupling,
compression fittings are use.
4. What are the tools in loop checking?
5. What would the ISA symbol of a square root extractor look
like?
6. What would you do to completely prepare for the
configuration?
7. What safety measures must you undertake when doing
configuration?
8. what are the two most commonly use programming languages
used when we configure a PLC?
9. What would you do if you accidentally skipped a step in
the configuration procedure?
10. How would you know if the configuration were sucessful?
11. Name at least 3 selections available when we configure
the burnout protection of a controller?

Answer

1. 3 POINT CALIBRATION:
Calibration is generally adjusting the output
according to the input ranges.
3 point calibration means calibrating our instruments in 3
ranges- lower, higher and working range
5 POINT CALIBRATION:
in 5 point calibration are very precise calibration
in which we will calibrate our instruments at 5 different
levels to view the response.
0%, 25%, 50% 75%, 100% of the input ranges.

Question { GIPCL, 8659 }

what is actual CAL MODE & cal means?

Answer

CAL MODE, normally during transmitter calibration or
maintenance, we used to put it in CAL mode which give its
last value as a reference value for the controller. So that
we can calibrate or do maintenance for our transmitter
without any disturbance to the process controller