Answer / aftab ahmed mazari

For DP type flow transmitter, suppose hp side valve No. 1, LP side Valve No.2, and Equalizer Valve No.1,
Close HP.No.1 Valve
Open Equalizer Valve 3. and then close LP side Valve No. 2

Answer / mithilesh kumar

i am agree with above answer.
but here on of the important thing that
1st this transmitter is connected in process(DCS) or not,
if connected then 1st this tag must put in CALibration mode.
this facility in YOKOGAWA DCS.
without this action if this tag has been taken in
protection then plant will be trip.
then we can follow above answer.
any comment u most welcome.
good luck

Answer / sajid

if its a orifice type flow transmitter it must have a 3 way
or way manifold..
in 3 way manifold 2 isolation valve and 1 equlisation valv
will be there..
open the equalisation valve and make sure that DP is 0..
then close low pressure and highpressure valve

Answer / mohammed abbas

If it is dp type of flow tx,
first if is the 5 way manifold means 2 is isolation
valve,2 is drain valve and 1 is equilizing valve,open the
equilizing valve to make presuure both in HP & LP same and
close the process root valves,then open the darin valves
for flushing it.

Answer / aswin

First job is to zero check of Tx.
If it will show zero meanns, Tx is ok on its 0 value.
Now u hav to close both isolatoin valve of Tx manifold.
Now open the drain plug of Transmitter.Tx show 0 value.
Next to open drain valave of both H.P AND L.P.(LIR).
The total water will drain out from impulse pipe.
If still u r not getting any flow of water in drain line it means ur lines are severely choked.
After jamming cleared again u hav to charged Tx by some step by step procedure.If condensing pot is there then u v to carefully charge the line.

Answer / abu khaled

1-close the high side valve from manifold
2- open the equalising valve
3- close the low side valve
4- close the equalising valve
5- be careful do not open the three valve in the same time
to avoid damage sensore or cabsoule .sometimes the prosses high temperture or cmical can damege cabsoule>
or maybe there is seale liqude in the high and low side
6- open the vent for low side to zerw check and be sure the equalier valve is closed .
7- if need calibration use high side connections
8- after being sure the TX is oky go to next step
9- make flashing to both sides high and low if they are blugged aske operator to isolate from orfice plate and aske piping group to flash tow lines
10-to return the TX to servse
11- open equalising
12- open the low side
13- close the equalsing
14- open the high side

Answer / amjad sohail

1. There is no any problem if open the equalizing valve
first. just dp become zero after equalizing valve
opening. so we can open 1st equalizing valve. and
then isolate both process isolation valves at
manifold one by one.
And keep it in your mind at orifice or any other dp
creating device the pressure difference b/w both
sides of transmitter is not high, in fact its a minor
difference b/w both sides.usually minimum 500 ~
2500mmh2o to maximum 10000mmh2o for flow
measurements. and LP side & HP side diaphragms are
designed for bear the same MWP value.(Which is given
at name plate of TX) so there is no matter if high
pressure side process comes to LP side diaphragm. So
if we open equalizing valve 1st then minor difference
of pressure b/w both sides will also become zero.
then we isolate the LP & HP valves one by one.

2. If we 1st isolate high pressure side of tx then pressure will be trapped B/W transmitter and isolation valve of manifold. so there is no any problem if we isolate the high pressure side 1st. (But do not open the drain of HP side. Because its very harmful for TX due to transmitter will come to its maximum & out of range dp value before isolate the LP side and open the equalizing valve.) So do not operate the drain valve and open the equalizing valve & then isolate the low pressure side. Now we can drain the LP & HP side respectively. And usually this practice is adopted by all instrument technician and engineers.

Answer / suresh agravat

First close root valve
second isolate manifold valve
open equaliser valve it was zero check procedure
open root valve
open manifold isolated valve
close equaliser valve it was taken in line procedure.

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