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Fieldbus Cable and Segment Check Procedure
This document is prepared to understand and to detail about Fieldbus segment wiring check, segment diagnostics check and preparation of FF device for loop check. Fieldbus segment wiring check and commissioning is done in 3 parts in the following sequence
a. FF Cable Check.
b. Commissioning FF devices (Preparation for loop check).
c. Segment diagnostics check.
FF CABLE CHECK
As installation of transmitters will be based on construction status (equipment, piping etc), FF cable check will be done in 2 parts
Part 1 : FF cable check for Trunk cable (with transmitters may or may not be connected)
Part 2 : FF cable check for complete segment after all devices (transmitters/valves) of segment are connected. (This check is only for shield cable check)
If all devices in the segment are installed before part 1 check then part 2 check will not be required.
FF FIELD CABLE TEST PROCEDURE
TOOLS REQUIRED
1. Digital Multi-meter with resistance, DC voltage and capacitance measurement capability
2. Small screwdriver
FIELDBUS TERMINATOR
There are 2 FF terminators installed on the segment. One at the FF power supply (power hub) in DCS system cabinet and other at the Segment Protector in Level 2 junction box. Terminator at FF power supply in DCS system cabinet
Terminator at Segment protector in Level 2 Junction Box
PROCEDURE
PART 1 : FF CABLE CHECK FOR TRUNK CABLE FROM DCS CABINET TO LEVEL 2 JUNCTION BOX
Figure below shows the connections of FF segment from DCS cabinet to Transmitter and details about the FF cable checks
1. Ensure that the Trunk cable wiring is properly terminated at DCS System cabinet and at Level1 and Level 2 Junction Box. Spur cables from Level 2 junction box to FF devices (transmitters/DVCs) may or may not be connected.
2. Ensure all all green connectors in Level 2 junction box (Segment Protector) closed.
3. Ensure Terminator at Power hub and at Segment protector is ‘ON’
4. Remove the fieldbus segment cable (+,-, and shield) by opening knife edge terminals at the DCS system cabinet side and measure the resistance and capacitance as per form below
Step 1: Resistance Check
Measure resistance from the: Expected Result
+ signal conductor to – signal conductor > 50 K Ohm
+ signal conductor to drain/shield conductor Open Circuit >20 M Ohm
– signal conductor to drain/shield conductor Open Circuit >20 M Ohm
+ signal conductor to shield ground bar Open Circuit >20 M Ohm
– signal conductor to shield ground bar Open Circuit >20 M Ohm
Shield conductor to safety earth bar Open Circuit >20 M Ohm (Note 1)
Step 2: Capacitance Check
Measure the capacitance at the terminal block in DCS system cabinet coming in from the field.
Measure capacitance from the: Expected Result
+ signal conductor to – signal conductor 1 micro F (0.80 to 1.2 micro F acceptable)
+ signal conductor to drain/shield conductor < 300nF
– signal conductor to drain/shield conductor < 300nF
+ signal conductor to shield ground bar < 300nF
– signal conductor to shield ground bar < 300nF
Note 1: Main Shield cable from Shield bus bar in DCS System cabinet to Earthling cabinet is removed for this check
Note2: Capacitance value will change due to the capacitor charging in the termination RC circuit and the capacitance in the fieldbus cables.
Note3: A reading of <0.5 micro F indicates no terminator on the segment. A reading of a nominal 2 micro F indicates a second terminator on the segment. The acceptable values assume that the power supply terminator is used as the second terminator and only one additional terminator is connected in the field. Otherwise, the expected result would be 2 micro F
Note4: An actual reading that is much greater or varies in a capacitor-charging manner to a high capacitance value (>1 micro F) indicates a poor quality noisy ground on the shield ground bar. Be sure to correct this grounding problem to prevent communication errors on the fieldbus segment. A reading of 300 nF indicates noise on the ground system.
Complete the Fieldbus cable Checkout Form as per form in appendix A.
PART 2 :
FF CABLE CHECK FOR COMPLETE SEGMENT AFTER ALL DEVICES OF SEGMENT ARE CONNECTED
As cable resistance and capacitance already checked for trunk cable in part 1, this part is done only to check proper shielding has been done for all spurs (cable from Level 2 junction box to FF device)
1. Ensure all cables from Level 2 junction box (spur) are properly connected to FF devices.
2. Keep all green connectors in Level 2 junction box (Segment Protector) closed.
3. Remove the fieldbus segment cable (+,-,and shield) by opening knife edge terminals at the DCS system cabinet side and ensure no continuity between +ve and –ve signal conductor with shield conductor and with shield ground bar.
Step 1: Cable Shield Connections Check
Check Continuity from the: Expected Result
+ signal conductor to drain/shield conductor Open Circuit >20 M Ohm
– signal conductor to drain/shield conductor Open Circuit >20 M Ohm
+ signal conductor to shield ground bar Open Circuit >20 M Ohm
– signal conductor to shield ground bar Open Circuit >20 M Ohm
Shield conductor to safety earth bar Open Circuit >20 M Ohm (Note 1)
Note 1: Main Shield cable from Shield bus bar in DCS System cabinet to Earthing cabinet is removed for this check
3 COMMISSIONING FIELDBUS DEVICES (PREPARATION FOR LOOP CHECK)
Fieldbus device requires commissioning of device and download before loop check can begin.Commissioning of field bus devices will be done by MICC at DeltaV engineering station in ITR. All actions required at the field side will be done by construction group.
Commissioning of Field bus devices procedure:
1. Open all connectors of spur in Level 2 junction box (Segment Protector) either by opening
Particular green connector OR removing cable connection of field cable at ‘X2’ terminal strip.
2. Connect spur in Level 2 junction box for FF device, which is ready for loop check. (Correct device, correct cable connection is verified by confirming power to the transmitter at field side and tag name appearing on the DeltaV explorer)
3. Commission the field bus devices. Commissioning of the devices is done as described below in this section.
4. Follow steps 2 and 3 for all remaining devices on the segment.
Commissioning a device assigns it with an address on the segment and makes the device available to the DeltaV system. DeltaV Explorer is used to commission devices. Any differences between the device and the placeholder during the commissioning process can be reconciled.
Please read also : Fieldbus Fundamentals and Difference between fieldbus and HART
Following procedure details the steps for FF device commissioning on DeltaV
1. Attach the device to the segment.
2. Click Start | DeltaV | Engineering | DeltaV Explorer to open the DeltaV Explorer.
3. The device should appear under Decommissioned Fieldbus Devices. It may take a few seconds for
the device to appear. Tip: Press the F5 key to update the list. 
4. The device must be in the Standby state before you can commission it. To determine if a device is in Standby, select Decommissioned Devices, click View | Details from the menu bar, and be sure that the words “Standby Fieldbus Device” appear under Type in the right pane. 
5. If the device is not in Standby, select the device in the right pane, click the right mouse button, and select Standby. It may take a minute or so for the device to transition to Standby.
6. Ensure that the decommissioned device’s properties, Device Type, Manufacturer, and Device Revision, match the placeholder properties. To check the properties, select the item, click the right mouse button, and select Properties. If necessary, edit the placeholder properties to match the device properties. Select the device from the Decommissioned Fieldbus Devices list and drag it to the
placeholder. 
The Device Commissioning Wizard – Start opens.
7. Read the information on the Device Commissioning Wizard – Start dialog and click Next to open the Device Commissioning Wizard – Reconcile Device dialog. 
8. Click the Next button. The parameters in the device will remain as they are and will overwrite the parameters in the placeholder when you commission the device.
9. Click Finish to commission the device
10. It may take a little while to commission the device. Several factors contribute to the time it takes to commission. Among these are the number of function blocks and devices and the time it takes fordevices to move through the various device states. As commissioning and download of device is done through Pro+ (DeltaV Engineering station), device
download may slow down process if multiple teams are working simultaneously. Hence only device commissioning activity is done by all teams as explained above i..e to identify and commission
device. Download is performed at the end of day for all devices with one command.
Once device is downloaded, loop check can be done.
4 LOOP TEST OF FIELDBUS DEVICE
1. After commissioning and download of fieldbus device. It is same as conventional device, connected to DCS system and loop check can be done in the same conventional manner i.e..
2. Simulate Device from DCS or apply process signal to sensor of transmitter
2. Check Range, description, alarms, graphics and simple functional checks
3. Check Local LCD indicator of Transmitter is showing required indication (PV)
5 SEGMENT DIAGONSTICS CHECKOUT PROCEDURE (BY MICC)
Complete segment checkout procedure as per below after loop checking is done for all FF devices of the segment.
5.1 TOOLS REQUIRED
1. Relcom,Inc.FBT – 3 Fieldbus Power and Signal probe
2. Multi meter
3. Small Screwdriver
5.2 PROCEDURE
Figure below details about the segment diagnostics checks
Once all devices are commissioned and downloaded, complete segment diagnostics checkout as per below
1. Ensure that all the devices of the segment are connected and commissioned.
2. Connect multi meter at the TB of DCS system cabinet and measure the voltage.
3. Connect the FBT – 3 Field bus Power and Signal probe (red clip to the positive signal and the black clip to the negative signal.) to the field terminals (TB) in the DCS system cabinet. (Do not open knife edge terminals at the DCS cabinet)
4. There are number of parameters, which can be examined from FBT-3.
These are selected by pressing and releasing ‘MODE’ button. When function is selected, the measurement value shown initially is ‘—-‘ until the needed data gathered by monitor. The indication ‘OK’ is shown if the measured value is within acceptable range. Check for parameters such as Noise Av, Noise Pk and voltage. All should show ‘OK’
Complete the Segment Diagnostics Checkout Form as per form in appendix B.
CABLE TEST FORM
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