Answer / abdul hameed

Dear Instrumentation Friends,

The Loop checking is defined as pre-Commissioning activity
which is initiated after installation of instruments at x
location to y location instruments or systems.

Loop checking is basically done to ensure the instruments
installed at x and y location has continuity signal with
each other potential's.

If we want to loop check the continuity from instrument to
junction box this is acheieved by laying a cable between
instrument and jounction box.

Normally after installation and cable laying during
construction activity is to be ensured that instrument and
cable and junction termianls and cable which is layed
underground or above ground & is not damaged to confirm this
damage it is mandatory to carry out loop checking between
instruments-junction box- Dcs that is from field to control
room.

Simple Process:- is short the two cores of cable at one end
and check with digital multimeter at other end if the
circuit resistance is ok then the same cores have the cont
unity which means that the cable cores are'nt damaged.

above procedure also helps to identify the particular cable
cores for specific system founction

Above process is called as Cold Loop Checking loop checking
without any external sorce simulation.hencecalled as cold
loop check.

Answer / scheau vlad

Loop check activity is checking entire loop functionality, from field to DCS or Esd or plc or any logical system. It is necesary to check not only continuity of signal, but also range of calibration, alarms, set points and any signal included in the loop folder. For DCS will be tested with hart comunicator or temperature generator, 4-20mA, depends of witch instrument is involved. For Esd (emergency shut down system) loop check will be done with proper instrumentation tools to produce the specific presure or requaired level... For valves you must check all signals as open, close, hi and low limit switch, reset buttons, hand switches , feedback must be check and a lot of other things must be checked .. Loops are direct, revers, split range .. it is not easy and it is not only the continuity check to do.

Answer / bill munz

Loop Check
Definition:
Loop Check: An operational check of the field, controller
and HMI elements of a control loop. A Loop Check is
intended to ensure the integrity of the following.
• The field sensing device is properly installed in
accordance with engineering specifications.
• The field sensing device is calibrated in
accordance with engineering specifications.
• The field sensing device is properly connected to
it’s communication path to the Distributive Control System
Controller. (e.g. Current Loop, Multiple device Bus
Communication Protocol, etc.)
• The field sensing device develops and transmits a
proper analogous signal in response to a variable impressed
upon it or a simulation command issued to it.
• The corresponding logic in the DCS Controller is
ranged accordingly for the field sensing device analog and
engineering units.
• The HMI of the DCS Controller accurately displays
the engineering unit response to the signal of the field
sensing device.
• Alarm points are properly entered into the logic
of the DCS Controller and the HMI displays and logs these
appropriately as they are reached.
• Where control functionality is required, that the
signal from the field sensing device is received by the
control algorithm and generates the appropriate corrective
output signal.
• If present, the field control device, (e.g.
Control Valve, Variable Speed Control etc.), is properly
installed in accordance with engineering specifications.
• The field control device is calibrated in
accordance with engineering specifications.
• The field sensing device is properly connected to
it’s communication path to the Distributive Control System
Controller. (e.g. Current Loop, Multiple device Bus
Communication Protocol, etc.
• The Field control device responds appropriately to
the corrective signal received from the DCS Controller and
that this action is appropriate to the desire process
variable.
• Where specified, the response action of the valve
is correctly transmitted to the DCS Controller and
displayed on the HMI.
• SUMMARY The Loop Check is intended to locate and
identify deficiencies in the Field/Controller/HMI
interface. This includes, but is not limited to, wiring
and cabling issues, engineering issues and mechanical
installation issues. It is not the focus of the Loop Check
to correct any deficiencies found. Full information
concerning the deficiency is captured and passed on to the
appropriate parties for correction. Minor corrections can
be accepted, but this should be limited in scope.


Procedure:
• A list of Loops is collected and identified by Tag
Number.
• Loops are grouped by Location, Availability,
System, Equipment or other criteria. (Note: Locational
Grouping of Loops results in the most efficient execution
of Loop Check. The field team can be routed in a logical
geographical progression of one device to another adjacent
device without time loss for accessing different floors,
buildings, plant sections etc. Loop availability can
prevent this. If at all possible, Loop availability should
be planned to accommodate Locational Grouping)
• Each loop is assigned a separate unique folder.
o Each Loop Folder is populated with either a
comprehensive Loop Sheet, and/or individual elements,
consisting of the following
 Field Device Tag Number
 Field Device Parameters
• Calibrated Zero Process Value and corresponding
Analog (common 4 ma)
• Calibrated Full Process Value and corresponding
Analog (common 20ma)
• Action
 Field Device Accessory List (e.g. Transmitter 3
Valve manifold, Valve Pneumatic Latch etc.)
 Field Device Physical Location
 Field Device instructions as appropriate
 Field Device Wiring connection data. (Terminals,
polarity)
 Wiring Routing information (e.g. Junction Boxes,
Terminals etc)
 DCS I/O Marshalling Information,
(Cabinet,Terminals, Polarity)
 DCS I/O Card or Module information.
 DCS Parameters
• Ranges
• Alarm points
 DCS HMI Graphics assignments
• From the Pending Loops file, the Console Engineer
and the Field Technician draw the Loop Folders to be
checked in that time period.
• The Console Engineer and the Field Technician
review the contents of each Loop Folder in the group to be
checked, comparing parameters for parity and completeness
of data.
• A sequence of Check is agreed to.
• The Console Engineer prepares his record keeping
tool, tracker, for the loops to be checked in the agreed
upon sequence.
• The Field Technician evaluates the test equipment
to be used, collects same and proceeds to the first device
to be checked.
• The Field Technician communicates to the Console
Engineer the Tag of the device he is at
• The Console Engineer calls up the appropriate I/O
channel
• The Console Engineer calls up the appropriate HMI
graphic or graphics
• Transmitters
o The Field Technician reviews the installation and
process connections to ensure they are in accordance with
the specification details and good installation practice.
o Either by impressed signal, (“Pump Up”) or
Communicator command, the Field Technician drives the
transmitter output signal through it’s range. Slowing at
Alarm Points so the Console Engineer can confirm alarm
action. (NOTE: Common is a 0% 25% 50% 75% 100% Check. This
was originally necessary to confirm the linearity of
earlier Pneumatic and ElectroMechanical devices, it no
longer is as critical and becomes a matter of agreed upon
preference.)
o Any wiring and/or piping disturbed to accomplish
signal impression is restored.
o The Field Technician confirms the process
connection line up is as desired. (e.g. For a Differential
Flow Transmitter to be placed in service after check out,
the three valve manifold would have the balance closed and
the process ports open)
• Control Loops
o While the transmitter signal impression is
occurring, the Console Engineer will call up the Control
Algorithm faceplate and by placing the control mode to
Auto, determine that the output action is appropriate.
• Control Valves
o The Field Technician reviews the installation to
ensure it is in accordance with the specification details
and good installation practice.
o If pneumatic, the Field Technician opens the air
source checking for proper pressure adjustment and air
quality.
o If electric, the Field Technician energizes the
proper breaker.
o The Console Engineer adjusts the output signal to
the valve while the Field Technician observes the action of
the valve.
o Jointly, the Field Technician and the Console
Engineer determine if the resultant action is appropriate
for the control signal sent and the previously determined
action of the control algorithm.
o Where present, the Console Engineer observes any
feedback from the valve to be in agreement with the
reported position of the valve action by the Field
Technician.
o Any accessories to the valve are checked for
proper action.
• Switches
o The Field Technician reviews the installation to
ensure it is in accordance with the specification details
and good installation practice.
o Either by Signal Impression, manual toggling, or
conductor manipulation, the Field Technician causes a
change in state of the field device signal.
o The Console Engineer observes the indication of
the signal to be in agreement with the physical state as
impressed on the device by the Field Technician.


• The Console Engineer records the results of the
results of the signal impression, alarm points, ranges,
valve actions, etc.
• If no deficiencies were noted during the Loop
Check, the Loop Folder is placed in the Completed Loops
File. At this point, the client signs for the Loop as being
complete.
• The Console Engineer records and captures any and
all deficiencies noted by either the Field Technician or
the Console Engineer on a sequential uniquely numbered form
for each deficiency noted.
o This deficiency form, or “Kick Back” is logged by
the sequential number assigned to it in a Master Kick Back
Log maintained by the Console Engineer
o The Kick Back form shall include
 Tag number of the deficit device.
 Date
 Reporting Party
 Thorough description of the symptoms noted and any
and all actions taken by the reporting party
o Kick Back form is entered into the Active Kick
Back file.
o The Log Number of the Kick Back is noted in the
Loop Folder and the Loop Folder is moved to the Detained
Loops File.
o The resolution team draws Kick Back forms from the
Active Kick Back file.
o Each time the deficiency is addressed, the Kick
Back form is submitted to the Console Engineer.
 The Kick Back shall include
• Date
• Resolving Party
• Thorough description of the corrective actions
taken
• Recommendations for further actions
• Responsible party assigned to further actions
o When the deficiency is corrected, the Kick Back
form is submitted to the Console Engineer.
 The Completed Kick Back shall include
• Date
• Resolving Party
• Thorough description of the corrective actions
taken

Answer / nachiket dani

Usually used term in Distributed Control System design-
after the logic for the process has been programmed into
the DCS software,the controller cabinet alongwith the IO
modules is interfaced to the server on which the logic
resides.The IOs are assigned as required and circuit
continuity check is carried out-LOOP CHECKING..Outputs are
forced to some value(universal) or forced high(binary) and
the signal level is checked at the output Terminal block of
the IO module.Similarly for Input checks, Voltage/Current
is fed via a calibrator at the Input Terminal Block (1 by
1) and signal is detected via the monitoring mode on the
DCS software..This is to ensure circuit continuity and
scaling(signal limits)-it requires time and usually done as
pre-FAT or FAT procedure.

Answer / sangam surendra

check the continuty,signal and power (depandeng on
instrument) frome fild instrumnet to the control room.

Answer / girish_b_k

checking out whether the reading is coming to the connected txt.

intially d.c.s and field instrument are connected
simulator is used to give mA to txt. and corresponding
readin g is checked in d.c.s whether the o/p is compared
with mA

0- 100 kg 4mA for 0kg and 20mA for 100kg

Answer / dnz_72

In simple terms it is a test starting at the process variable through the controller and back to the control device to see if everything is working properly.

As as example: You have a tank with a water level controlled by an inlet valve that opens or closes as needed to maintain the level.

The signal from a level device (let's say a level transmitter) goes to a controller. A signal then goes from the controller to the level control valve opening or closing it. That is the control loop.

The loop test determines if the proper signal is going from the level transmitter to the controller and then is the correct signal going from the controller to the control valve and is it opening or closing as it should.

Answer / chibuike ibeneme

Loop checking is continuity test from primary elements to marshalling panels, from Marshalling panels to I/O terminals,from I/O module to PLC, from PLC to final elements this is to ensure signal integrity and is carried out during plant commissioning.

Answer / alam

Loop checking is tress of wire in different connection from sensing element to final controlling unit

Answer / hemal

simply loop checking is check of continuty in all wire from
location to location.

what is use single seated and double seated valve?

2 Answers   Doha Petroleum Construction DOPET,

capillary type tranmitter using remote seals and capillary tubes filled with liquid of known of known density so if you wanna callibrate it just close block valve just before capilary @ high side & connect druck apply it's calibrated range pressure as normal calibration ensure low side block valve must be closed & if you asking commissioning so this is not a DP type pressure tx so simple if you wanna put in servie this tx just open high side block valve & than low side block same way i do it but still transmitter showing -13 ma.just tell me what i want to do ?

1 Answers   Gasco,

why most of the DP transmitters using maximum range as 0-2500mmwc?why not 1000 2000 3000 4000mmwc

2 Answers   SPIC, TNPL,

how to caluculate flow by using transmitter?tell me plz I am eagerly waiting for your reply..

2 Answers   Agi Glaspac, Reliance Power,

in my plant 100% feedwater control v/v is air to close but due to instrument air fail,the valve opens but instead of drum level high its get tripped in low low drum level.the urv of level tx is 0 and lrv is -800.pls tell me the reason. for such behaviour.

1 Answers   Sirpur Paper Mill,

what is beta ratio?

3 Answers  

can someone tell me about electronic speed switch &how it conect with proximittyswitch?(with dgm)

0 Answers  

wich is coming the first HAZOP OR SIL

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what should he know if he is an assitent engineer instrumentation in cement industries of experience of 10 - 15 year.

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DCS marshilling Cabinet Power supply can be replace during plant running time?

1 Answers  

why we use impulse line of flow transmitter at 45 deg. angle both side of orifice plate.

0 Answers  

what is different between 2,3&4 wire rtd and how much maximum distance using plc to field.

0 Answers