Question { 5819 }

I HAVE GOT TYPICAL PROBLEM WITH THE TEMP.INDICATION.
THE PROBLEM IS THE K-TYPE T/COUPLE OUT PUT IS CONNECTED TO
A INDICATOR.THE INDICATION FLUCTUATES SOME TIMES AND SOME
TIME IT IS STABLE.
WHEN I CHECKED OUT PUT OF T/COUPLE THE MV WILL NOT VARY.
WHERE AS INDICATION FLUCTUATES.
WHEN I GIVE MV SOURCE TO T/COUPLE EXTENSIONCABLE FROM THE
FIELD IT INDICATION IS STABLE.
WHEN GIVE MV SORCE TO INDICATOR ITS INDICATION IS STABLE.
PLEASE CLARIFY.

Answer

I agree with Mr. Satyendra Bhai Patel suggestions.
More over please check followings:
1. May be some electric motor starts and its cable routing
is near to your extension cable.
2. Also get check thermocouple,some time,its hot juction
got open and close with the passage of time. Replace
thermocouple.
3. Check loose connections.
4. Check thermocouple any wire being grounded at some time.
5. Any how, do not megger thermocouple extension wire.
Check it with normal multimeter.
aftabmazari@yahoo.com

Question { 13952 }

how to calibrate differential pressure switch

Answer

Differential pressure switch has two sensing ports. Hi and
Lo, Suppose set point of differential pressure switch is
30 PSI. Connect the pressure source at hi side of switch.
Leave Lo side (No any connection or any supply to low side)
Connect multimeter at switch terminals. Apply pressure at
high side. When pressure will reach 30 PSI, Switch will
operate and will change its contacts and also will be
indication at meter.
Suppose switch Low side is faulty, then apply 30 PSI at
High side and also apply low side pressure (5 to 10 PSI),
switch contacts should change, which indicate switch is
working.
aftabmazari@yahoo.com

Question { 4689 }

Control valve question
what is the meaning of cauge.?what is the use of cauge?

Answer

Cages are used in control valves for following purposes:
1. To determine chracteristics of flow.(Equal percentage,
Linear, Quick opening)
2. To avoid flashing and cavitation in control valve.
aftabmazari@yahoo.com

Question { C2C, 7807 }

what happen if i install my pressure transmitter below the elevation of pipe in natural gas service. Also support your answer

Answer

Pressure will be added up a bit more, see its detail:
1. Suppose,you want to install a pressure transmitter 10
meter below of pipe line.
2. Density of methane (Examlpe) 0.656 kg/m3 at 25C.
3. your pressure transmitter will show (10 x 1000 x0.656 =
6560mm) 6569 mm of water pressure more.
4. Suppose gas pressure is 20Kg/cm2, then due to this
elevation, transmitter will show 20.66Kg/cm2
aftabmazari@yahoo.com

Question { 24610 }

hw to calibration a control valve?

Answer

Following procedure should be done for control valve
calibration.
Suppose it is spring loaded and direct action.(Direct
action means at top of diapgargm signal and with the
increase of signal, stem will move downwards or the stem
will extend).Also valve is signal to close. Check its Bench
Set. Suppose it is 6 to 21 PSI.
1. Set pressure regulator of positioner at about 30 PSI.
2. Apply 3 PSI (4 mA if positioner is smart or electronics)
signal to Positioner.Gradullay increase signal. Note the
movement of stem.
3. Apply 6 (8 mA),9 PSI (12 mA), 12 PSI (16 mA) and 15 PSI
(20 mA) signal. Valve stem should move accordingly and
indicator must show 25%,50%,75% and 100%.
4. If error, remove it from zero and span of positioner.
5. If facing any error problem, give signal 50% and then
remove error. Rest will be ok automatically.
6. Suppose valve is normally closed and at any vent service
and signal to close as I mentioned earlier, then make shut
close of valve at 14.5, or 14.7 PSI. Valve may start
closing at 2.75PSI.
7. If valve is at control operation, like level, pressure
etc, then calibrate it accurately.No need to calibrate it
at 2.75 and 14.5 PSI.
aftabmazari@yahoo.com

Question { 8420 }

i have height of stem drum level 1000mm.how i calculate the
DP transmitter

Answer

1. Never use any one one port of transmitter at boiler
point and other to atmosphere. Never. It will make a
serious accident and also transmitter will never work.
2. Connect Hi side of DP transmitter at bottom point of
outlet from boiler and LO side of DP tranmitter at top side
of boiler point.
3. Also use condensation bottle at lo side of tranmitter
(top side of boiler point)
4. Suppose transmitter is almost same level of bottom point.
Now there are two methods of calibration:
Method No. 1
a. Do not open valves of boilers side.(Very Important).
just open both hi to atmosphere and fill water at low side
from top of dp transmitter.
b. Transmitter will show less mA as compare to 4 mA.
Suppose its showing 2 mA. Tranmitter zero elevated. Get
adjust 4 mA from HART.
c. Your range is 1000 mm. Usually specific gravity of
boiler water under temperature and pressure is 0.45. (It
depends upon boiler pressure and temperature).
d. So get range = 1000 x 0.45 = 450 mm of H2O. It is that
type of transmitter which did its zero by HART.So adjust 20
mA by feeding pressure of 450 mm of H2O.
e. Get connect piping of transmitter to sensing lines and
put in service the transmitter.
Another method is, you want to calibrate it at work shop
without using HART.
a. Usually water specific density/gravity at upper side
after getting out from boiler drum and being condensated in
pipe of transmitter is 0.99.
4 mA = 1000 x 0.99 = 990 mm H2O
It will be written as - 990 mm H2O.
b. Give pressure at lower side of dp transmitter 990 mm H2O
and transmitter Hi side must be opened to atmosphere.
c. Get adjust transmitter 4 mA.
d. 20 mA range = 1000 x .45 = 450 mm H2O
e. Apply 450 mm H2O pressure at Hi side of transmitter and
adjust 20 mA signal from range knob. Remember not to
disconnect lo side pressure.
Suppose, you want to calibrate from lo side only.
a. At 990 mm of H2O low side = 4 mA
b. Decrease the pressure from 990 to 540 mm of H2O (990 -
450 = 540) from low side, you will get 20 mA.
Note: If you put transmitter hi side connected to boiler
and low side to atmmsphere, DP transmitter will burst.
Becareful.

aftabmazari@yahoo.com

Question { Carlo Gavazzi, 6539 }

what is differences between singal acting and double action
valve

Answer

Single Acting means, in one direction,(Open or close) the
valve will move with signal and other direction will move
with spring force.
Double Acting means, valve will move (Open or close) in
both directions with signals.
aftabmazari@yahoo.com

Question { Shell, 11930 }

If a control valve is hunting means means if we are giving
50% to the cv, the cv will open at 51% then slowly slwoly
it will reaches 49% , then it will reaches again 50%, this
type of action occured frequntly.. so what to do for solve
this problem. The possible cause is in volume booster or
positioner's relay.. positioner is double acting .. and
make siemens..sipart.The cv is double acting and mounted
for anti surge operation, it having 4 nos. volume booster,
one sov, one positioner, etc..?

Answer

Check the following items:
1. Any loose connection or leakage of pneumatic signal.
Check all tube fittings with soap solution.
2.Check the gland packing should not be so tight. If feel
tight, get loose them a bit.
3. Check the pneumatic relays of Postioner. Get clean its
ports, nozzle, flapper etc.
4. Also check, that linkage, feed back mechanical link
should not have any dent, grove, burs etc.
aftabmazari@yahoo.com

Question { Wipro, 8441 }

what is the difference between earthing and grounding?

Answer

There is no difference. In American system, it is called
Grounding and in British system, it called Earthing.
aftabmazari@yahoo.com

Question { 3864 }

What is seismic transducer?Where it is used?

Answer

seismic transducers are that which do not need any power
supply. But usually seismic transducer are called vibration
velocometer or earth quake seismic probes. These
transducers generate mv by vibration. More vibration, more
mv.
aftabmazari@yahoo.com

Question { 3957 }

draw a loop drawing of vibration beginning to end

Answer

1. Monitor's 3 wires should be connected to Proximitor.
2. Monitor's 3 wire means (a). Power supply for Proximitor wire (b). Common wire (c). Input wire to Monitor.
Now I am connecting from probe (sensor) end.
3. Install probe at fixture.
4. Connect probe connector to extension cable connector
5. Connect Extension cable other end to Proximitor.
Let I explain another way: Probe -> Extension Cable -> Proximitor -> Monitor
aftabmazari@yahoo.com

Question { 4148 }

Somebody ask me how many size of
control valve what is mean of control
valve size?

Answer

Control Valve size means, size of control valve body.
In a simple way, you may understand the size of control valve connections like 4" X 3". This 4" is inlet and 3" is outlet of control valve.
aftabmazari@yahoo.com

Question { SMH, 7477 }

What is input and output of vaiberation transmitter and what is its unit.

Answer

your question has different parts. Let I explain you a bit in detail:
1. Input of a vibration transmitter (Proximitor or Oscillator De-modulator) is in shape of frequency which feeds probe or sensor.
2. supply of a Bently Nevada Proximitor is -24 Volts DC. (But now many manufacturers made simple 2 wire vibration transmitters which required +24 Volt DC).
3. Out put of a Proximitor is AC volts and DC volts.
4. AC volts tell us how much is vibration in a shaft/casing, bearing etc where sensor is installed
5. Where as DC voltage indicates how much sensor is away from target. (Target means shaft/bearing etc).
6. These ac volts output of a proximitor is converted at an indicator/equipment to micron Peak to peak or mil Peak to Peak which is units of vibration.(Remember, velocimeter and accelerometer has different units even those also used for vibration sensors)
7. Suppose you have a proximitor with a scale factor
8 volt/mm.
8. Your proximitor output ac voltage is 0.232.
9. Multiply this 0.232 by 353.6, you will get direct microns P-P.
10. Look, 0.232 x 353.6 = 82 microns p-p.
(This all method of proximitor/sensor is called non contact system)
aftabmazari@yahoo.com

Question { Sabic, 4413 }

What is meant by cold float of compressor shaft.

Answer

Basically its machinery related question.
Cold float of shaft of any compressor/turbine means free movement of shaft without running and without any oil / process temperature.
Suppose at running bearing/shaft oil temperature is 60C. Its float of shaft may be different. Let compressor stop and allow to cold at ambient temperature.Its float movement will be different.
This is called cold float of compressor shaft.
aftabmazari@yahoo.com

Question { ADMA OPCO, 28863 }

What is meant by GAP VOLTAGE, in vibration measurement.
Normally how much GAP VOLTAGE is set and state the reason.

Answer

Gap voltage of Bently Nevada vibration probe is usually set at -10V. Reason for setting at -10 volt is as we know, proximitor allows probe to work -2 volt to -18 volt. So voltage difference of 2 to 10 and 10 to 18 is 8 volt. When setting at -10 volt, probe can equally measures vibration at both sides(I mean when shaft is going away from probe or towards probe).
Suppose we adjust probe at -9 volt. Probe can detect vibration?
Yes, it can can detect vibration but its one side will be margin of 7 volt and other side margin of 11 volt. At 11 volt margin, probe will detect vibration excellent but at other side,7 volt side, it has limitation, when more vibration it may not detect.
(Old system, when proximitor supply was 18 volt, setting were at -8 volt, now such proximitor almost obsoleted)
aftabmazari@yahoo.com